atv_m_269_e

GERMAN ATV STANDARDS W A S T E W A T E R

-

W A S T E

ADVISORY LEAFLET ATV-M 269E

Requirements on On-line Process Analysis Equipment for N and P December 1995 ISBN 3-934984-58-4

Publishing Company for Wastewater, Waste and Water Pollution Control Theodor-Heuß-Allee 17 D-53773 Hennef Postfach 11 65 . D-53758 Hennef

ATV-M 269E

Preparation This Advisory has been elaborated by the ATV Working Group 2.13.3 "Requirements on On-line Process Analysis Equipment for N and P", within the ATV Specialist Committee 2.13 "Automation of Sewage Treatment Plants", to which the following members belong: Dr.-Ing. Peter Baumann, Stuttgart Dipl.-Ing. Franz Douda, München Dr. rer nat. Dieter te Heesen , Dinslaken Dipl.-Ing. Jörg Maschlanka, Karlsruhe Dr.-Ing. Viktor Mertsch, Düsseldorf Dipl.-Ing. Eberhard Michel, Waldbronn (Chairman) Klaus Pfeiffer, Berlin Dipl.-Ing. Klaus Werner, Norderstedt Dipl.-Ing. Werner Worringen, Düsseldorf

All rights, in particular those of translation into other languages, are reserved. No part of this Advisory Leaflet may be reproduced in any form by photocopy, microfilm or any other process or transferred or translated into a language usable in machines, in particular data processing machines, without the written approval of the publisher.  GFA -Publishing Company for Wastewater, Waste and Water Pollution Control, Hennef 1995 Original German Edition produced by: J. F CARTHAUS GmbH & Co, Bonn

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ATV-M 269E Contents Notes for Users

5

1.

Objective

5

2.

Employment requirements

6

3. 3.1 3.2

Sample preparation General Notes on the installation and on the operation of sample preparation systems Technique of ultrafiltration Function and notes on installation Operation and maintenance Practical example - cleaning an ultrafilter Other techniques of sample preparation Drum sieves Paper strip filters Sieve filtration using ultrasonic cleaning Pre-coated filters Comparative assessment of sample preparation systems Advantages and disadvantages of the operation of on-line analysis equipment without special sample preparation

7 7

3.3 3.3.1 3.3.2 3.3.3 3.4 3.4.1 3.4.2 3.4.3 3.4.4 3.4.5 3.5

8 9 9 11 12 12 12 13 13 13 14 14

4. 4.1 4.2 4.3 4.4 4.5 4.6

Measuring Procedures General Ammonium Nitrate/nitrite Total nitrogen Orthophosphate Total phosphate

15 15 15 17 18 19 20

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7

General requirements on process analysers Equipment design Characteristics and outfitting Operation Operating instructions Availability Monitoring of quality Certification

20 20 21 23 24 25 25 25

6 6.1 6.2 6.3

Chemical materials Employment Work safety with handling and with storage Disposal

26 26 26 26

7 7.1

Requirements/notes on training, maintenance and product care Training of personnel

27 27

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ATV-M 269E 7.2 7.3

Care and maintenance of analysers Product care

27 28

8

Costs

28

8.1 8.2 8.3

General Investments Operating costs

28 28 30

9

Ordinances, standard specifications, standards

31

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ATV-M 269E

Notes for Users This ATV Advisory Leaflet is the result of honorary, technical-scientific/economic collaboration which has been achieved in accordance with the principles applicable for this (statutes, Rules of Procedure of the ATV and ATV Standard ATV-A 400). Here, according to precedents, there exists an actual presumption that it is textually and technically correct and also generally recognised. The application of this Advisory Leaflet is open to everyone. However, an obligation for application can arise from legal or administrative regulations, a contract or other legal reason. This Advisory Leaflet is an important, however, not the sole source of information for correct solutions. With its application no one avoids responsibility for his own action or for the correct application in specific cases; this applies in particular for the correct handling of the margins described in the Advisory Leaflet.

1.

Objective

This Advisory Leaflet is concerned with the requirements on on-line analysis equipment for nitrogen and phosphorus compounds. As basis for decision making the planners, operators and authorities are to be given information for the planning and the reliable operation of on-line analysers and the associated peripheral equipment. The treatment performance of a wastewater treatment system can be monitored using the already for some time increasingly employed measuring facilities for the continuous measurement of ammonium (NH4), nitrate (NO3) and orthophosphate (PO4). The daily curves determined, allow conclusions to be drawn about necessary changes in operational management or process technology. The employment of continuous or discontinuous operating measuring equipment is authorised and, in individual cases, depending on the size of a sewage treatment plant, also required in the self or own monitoring ordinances promulgated by the Federal States. However, although the MSR technique remains unconsidered with the dimensioning of sewage treatment plants, potential savings result with materials and thus operating costs through regulation or control of units. Thus, for example, the employment of an on-line phosphate measurement for the regulation or control of the addition of flocculants (other than with lime) is a proven method of reducing the costs for chemicals and for preventing an unnecessary increased sludge yield (comp. ATV Advisory Leaflet ATV-M 206). The regulation of the oxygen transfer according to the ammonium content in the effluent of the biological reactor stage leads also to a significant saving of energy costs and to the improvement of the efficiency of an upstream denitrification. The regulation of the internal circulation with upstream denitrification using a continuous NO3-N measurement in the effluent of the denitrification zone represents a further possibility for operational optimisation (comp. ATV Advisory Leaflet ATV-M 268).

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ATV-M 269E A possible connection with treatment performance is to be observed with regard to possible savings with operating costs. Effluent quality and operating costs are therefore, as a rule, not capable of optimisation separately from one another.

2.

Employment Requirements

The employment requirements for on-line measuring facilities are to be oriented according to the application purpose. The units for sample conveyance are to be determined taking into account the medium to be conveyed (e.g. raw wastewater or activated sludge) (see also Chap. 3).The employment of on-line measuring facilities for regulation and control tasks demands a rapid provision of measured values and as short as possible calibration times. With process analysers the following criteria are to be observed:

• Rapid information i.e. -

short analysis times automated operation

• Reliable information -

reproducibility of measured values sufficient sensitivity high availability self-diagnosis

• Expense -

investment costs operating costs maintenance and personnel assignment

Diagram 1 shows the inclusion of such a measuring facility in the process. The wastewater sample is transported to the sample pretreatment using a suitable pump. The analysers, as a rule, require a continuous and solids-free sample flow. The employment of on-line measuring facilities requires suitable output equipment in order to be able to evaluate the determined measured values. If the output signals of the measuring facility are also used for regulation or control purposes then the appropriate actuator (e.g. dosing pump, blower) is influenced by the regulator or control system. Measuring facilities for N and P with associated peripheral equipment are to be installed in an area protected from the weather. In addition, the installation of a heating system, possibly an outside ventilation system and a water connection is necessary. Basically as many individual units can be operated as there is filtrate available using the sample flow from one sample preparation facility. In particular, if two or three units are supplied from one sample preparation facility, the flow time is to be kept as short as possible in order to minimise a delay to the output of measured values.

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ATV-M 269E

Registration Sample pre-treatment

Monitoring

Pump

Sample flow

Measuring facility Regulation/ control unit

Regulation/ control

Actuator

Nitrification/denitrification phosphate elimination

WASTEWATER FLOW

Diag. 1:

On-line measuring system with peripheral facilities (schematic)

Design, operation and maintenance of individual equipment have a decisive influence on the availability of the complete measuring system. Faulty installation, incorrect operation as well as lacking maintenance and care lead to short service lives, interruption of measured values and thus to interference to the monitoring, control and regulation of the wastewater treatment systems. With the inclusion of analysis equipment in control and regulation systems the appropriate ATV Advisory Leaflets (e.g. ATV-M 206, ATV-M 208 and ATV-M 268) are to be observed.

3.

Sample Preparation

3.1

General

The on-line measuring facilities employed today function according to complex physicalchemical measuring processes. Due also to the substances contained in the wastewater they require not insignificant maintenance resources and often the employment of chemicals. The desire for a small usage of chemicals with on-line analysis leads to equipment with small pipeline profiles and, with optical measuring procedures, possibly to small measuring cells. In order to prevent a blockage of the analysers, as a rule, the wastewater sample must be prepared free of turbid substances. For this, in the majority of sewage treatment plants today, a membrane procedure, so-called ultrafiltration (UF), is employed, however, increasingly other methods. The employment of drum sieves, paper strip filters and so-called subfiltration with ultrasonic cleaning are chosen, in December 1995

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ATV-M 269E particular in the effluent of secondary sedimentation. Pre-coated filters can also be employed with high solid contents in the sample to be filtered. With the employment of paper strip filters or sieve devices an agreement on the on-line measuring equipment is absolutely necessary at the forefront of planning. Recently, analysis equipment has appeared on the market which has only an equipment internal coarse filtration or even completely dispenses with a sample preparation. Basically it applies for all equipment which is employed for the analysis of Ntot or Ptot that, with an upstream sieving or filtration, not all nitrogen and/or phosphorus compounds can be recorded. The measured value can therefore deviate considerably from the actual content of Ntot or Ptot. Accordingly, with these measuring systems, attention is to be paid that the permitted particle size is selected to be as large as possible. The user of on-line systems must therefore evaluate the applicability and expressiveness of the thus obtained measured results dependent on the respectively applied sampling preparation. 3.2

Notes on the Installation and on the Operation of Sample Preparation Systems

The installation point of the pump for sample feed must be easily accessible. For the feed pump, if required, a lifting device is to be provisioned at the sampling site. The connection between pump and ultrafiltration is to be kept as short as possible, free of kinks and protected from the light, in order to prevent false measured values due to fouling, deposits or blockages. The sample feed pipeline is possible in two variants:

• Plastic pipeline (e.g. LDPE pipe) • Plastic hose, laid in cladding tube. If a plastic hose is laid in a cladding tube then an exchange of hose (e.g. with heavy fouling) can be carried out without earthworks. For this the tube is to be provided with a wire pull to draw in the hose. The sample feed pipeline should be laid with constant gradient and safe from frost. Through this the pipeline can be completely emptied during idle periods. In any case care is to be taken for satisfactory frost protection of the sample feed pipeline. The same also applies, for example, for filtrate runoffs, flushing water connections etc. The prevent deposits and blockages fittings are to be designed as ball valves. Filtrate pipelines are to be laid short and protected from the light. If several analysers are arranged in series, then the employment of a filtrate pump can be sensible. In this case a pressure switch is to be provided in order to pre-empt the creation of a vacuum. With the operation of several on-line measuring devices with one sample preparation attention is to be paid, that only the original permeate flow gets into the equipment units. Particularly suitable in this case are therefore devices which require only a partial flow of the supplied filtrate for analysis and the remaining filtrate is available to further analysis equipment via an overflow vessel. Devices which use the complete filtrate flow provided for analysis are to be arranged as the respectively last equipment December 1995

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ATV-M 269E unit. Through this it is prevented that flushing solutions or chemically altered wastewater samples lead to false analysis or damage to equipment in a downstream unit. For periodic monitoring of several wastewater streams it can be practical to use only one measuring device consecutively for several measuring points. With this, the switching of the filtrate streams should take place automatically, e.g. using a solenoid valve and time switch), and the hosepipe between switching point and measuring device inlet kept very short. With the evaluation it is to be noted that, following switching, no assessable measured values can be produced for a transitional period due to the mixing of the filtrate streams. This is to be taken into account with the further processing of measured values. The on-line measuring devices should be installed as near as possible to the sampling points. Operation is made more difficult with increasing length of the sample pipeline: the maintenance expense (cleaning) becomes greater, the danger of falsification of measured values increases and the dead time of a control loop grows. Measurement in a central measuring house can therefore not be recommended with feed pipes over 50 m in length despite the organisational advantages for maintenance of the analysers. Installation of analysers should be in a man-accessible container or a measuring house. If, for example for reasons of space or due to large distances from the sampling point, this is not possible, sample preparation and analyser can also be accommodated in a protective cabinet. Sample preparation and analyser should be as close as possible to each other in order to avoid delays. This point has particular significance with regulation. In the vicinity of sample preparation one has to reckon with splash water. Therefore a collection trough with floor drain is to be provided under the device. 3.3

Technique of Ultrafiltration

3.3.1

Function and Notes on Installation

For sample preparation normally tube shaped ultrafiltration modules are employed. These are fed axially; the permeate is removed radially (see Diag. 2). So-called plate modules, by which the membrane lies between two screwed plates, are currently under trial. To avoid blockages mainly filtration modules with, for example, 1" internal diameter are used. With a recommended feeding of the tube module of 6 - 8 m3/h velocities of ca. 3 4 m/s are achieved. The permeate yield lies in the per thousand range (up to ca. 5 l/h). The high turbulence prevents the formation of a filter cake and causes a self-cleaning effect. The pore width of the membranes is normally 0.01 to 0.02 µm.

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ATV-M 269E The outer membrane carrier is capable of accepting only an extensively constant internal pressure. Therefore pressure surges, in particular, underpressure, are to be avoided. For continuous operation suitable rotary pumps, if required with cutter, have proved to be suitable for feeding. The protection of the pump from coarse materials should be through suitable measures such as, for example, strainer baskets or basket protectors (e.g. basket protectors made from stainless steel perforated plate, Ø 8 - 10 mm). In the simplest case sample preparation consists of only one ultrafiltration module. If an extensively interruption-free sample stream preparation is required, one must work using two alternately operated closable ultrafiltration modules, whereby one functions as standby module. The latter must be kept wet as the ultrafiltration modules are irreversibly damaged on drying out. With high requirements on automation the automatic switching to the standby module and the subsequent cleaning of the up to then operated module can be realised.

Permeate

Membrane Membrane carrier

Module housing

Wastewater

Diag. 2:

Principle of ultrafiltration

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ATV-M 269E 3.3.2

Operation and Maintenance

The very turbulent flow in the ultrafiltration module extensively prevents the formation of deposits; bacterial fouling must, however, be removed regularly. For cleaning, the ultrafiltration module is filled with diluted sodium hypochlorite solution (chlorine bleach), with possibly the addition of sodium hydroxide solution. This can take place when removed or via a fitting provided for this. In the second case direct contact of operating personnel with chemicals is ruled out. The ultrafiltration membrane is permeable to active chlorine, i.e. bacterial fouling is destroyed on both sides of the membrane. Alkaline cleaning agents are not in a position to dissolve deposits containing lime or hydroxide coatings which, for example, can occur with simultaneous precipitation. It is then sensible to carry out cleaning cyclically using diluted hydrochloric acid. As alternative, alkaline cleaning agents containing chlorine with lime dissolving additives are on offer. This agent should not get into the analysers (coordination with the manufacturers). If both chlorine bleach and hydrochloric acid are used, there has to be an intermediate flushing in order to avoid a mixing of the two chemicals. The cleaning of ultrafiltration modules must take place regularly. In the normal case a reduced permeate yield is the criterion for cleaning. In particular with measuring in the sewage treatment plant effluent the service life of the filter should also be noted in order to prevent false measured values due to biological fouling. The shortest cleaning cycles occur with ultrafiltration of wastewater from sewage treatment plant influent. In the individual case, a daily cleaning can be necessary. With measurements in the area of the biological reactor the service lives are considerably greater. Here the modules should be cleaned in good time (e.g. weekly). In the outfall of a sewage treatment plant cleaning cycles of 2 - 6 weeks can suffice. With the service lives given here one is concerned with reference values, the achievable service lives can deviate considerably from these, depending on employment conditions. The durability of ultrafiltration modules is essentially determined by the type and frequency of cleaning and, inter alia, can be extended thorough the observation of the following basic rules:

• Continuous operation of the system • Avoidance of a vacuum in the system • The membranes may never dry out • Cleaning with a permeate flow of, from experience, less than 0.8 l/h. For the monitoring of the quantity of permeate a flow control instrument and actuator should be provided

• It is not practical to increase the pressure in the module for an increase in permeate as this can lead to damage of the membrane and blockage of the module.

• With longer idle periods the membrane must be conserved using a suitable means (according to manufacturer's details).

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ATV-M 269E 3.3.3

Practical Example - Cleaning an Ultrafilter

After removal the ultrafilter is first cleaned mechanically using an intense water jet and a soft bottle brush. The end of the ultrafilter which is opposite to the filtrate removal connecting pipes is then closed with a plug and the filter is placed vertically. Now cleaning solution (50 ml sodium hypochlorite with 13 % active chlorine topped up to 1 litre using distilled water) is poured in. The cleaning solution flows through the membrane, fills the inner space between supporting fabric and outer jacket and again exits through the filtrate removal connecting pipes. There is repeated topping up with fresh cleaning solution. At the start the exiting cleaning solution is brown to yellowish in colour depending on the contamination of the filter. With advancing cleaning this remains finally colourless. This treatment can stretch over several days. If the cleaning solution remains colourless and flows rapidly through the filter, regeneration is successfully concluded. Until next employment the filter remains filled with diluted sodium hypochlorite solution (20 ml sodium hypochlorite with 13 % active chlorine topped up to 1 litre using distilled water). This prevents biological fouling of the filter during storage. Should the filter then be employed the diluted cleaning solution is allowed to run out through the membrane (close filter and reverse), it is rinsed briefly with drinking water and filled with a ca. 5 % hydrochloric acid which is then also allowed to run out through the membrane. This is to prevent components of the filtrate being precipitated by residual lye in the membrane or the supporting fabric and blocking of the membrane. The filter is again flushed briefly using drinking water and can then be used. The filtrate flow during the first 10 minutes is to be thrown away. For removal, cleaning and assembly of an ultrafilter one has to reckon with in total a maximum of 1 hour. If several ultrafilters have to be exchanged at the same time during continuous operation, the amount of time per filter decreases accordingly. The handling of chemicals required for cleaning must take place according to the applicable safety regulations. 3.4

Other Techniques of Sample Preparation

3.4.1

Drum Sieves

Drum sieves make available very simply a relatively large sample stream of wastewater with few solids. The wastewater flows over the upper side of the horizontally placed drum, whereby it penetrates the perforated drum jacket and is trapped at the sample outlet. Excess water flows over the rotating drum and runs out through a separate outlet. Particles adhering to the drum are removed by a scraper plate. Sticking particles can be removed from the drum by back-flushing using process water. Current mesh widths are 1000, 250, 100, 50 and 20 µm. The employment of drum sieves is problematic in a biological reactor due to high solid contents. A considerable advantage of this method is, however, the small maintenance requirement, which is limited to the back-flushing of the drum for cleaning purposes. Back-flushing should take place daily. If the drum tends to blockages, then the cleaning should take place automatically with time allowance for the flushing cycle and the duration of flushing. The weak point of such sieve devices, in most cases, is the scraper. If this does not function optimally then there is a possibility that fibres stick in cracks and lead to blockage of the filter, or that particles which are not removed get into the filtrate. Therefore a satisfactory quality of the filtrate cannot always be guaranteed. December 1995

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ATV-M 269E 3.4.2

Paper Strip Filters

With paper strip filters the wastewater flows tangentially to the paper filter. The filtrate is sucked through the paper by means of a hose pump and fed to the measuring device. The tangential flow against the filter effects a surface flushing of the paper and reduces the danger of blockage. Additionally, the exchange of the paper used for filtration is achieved via a selectable continuous forward feed. The filter papers can be obtained with different pore diameters (e.g. 2, 2-3, 4, 5-7, 10-12 µm). Filtrate flows of up to 2 litre/hour are possible. Paper strip filters are, above all, suitable for the sample preparation in the effluent of the secondary settling tank or following a filtration (e.g. flocculation filtration). Maintenance tasks on the strip filter equipment are, as a rule, limited to the replacement of the used paper rolls. This, depending on the advance feed rate of the paper, is necessary once to twice a week. The exchange of filter rolls is simple and can be carried out in less than 10 minutes. The minimal maintenance resources is a significant plus point of strip filters. The reliability of the equipment is high. Impurities in the filtrate can only occur with too high feed flow. With this the paper lifts from the guide surface and unfiltered wastewater can get into the filtrate stream. Disadvantage is the low filter performance which cannot be significantly increased even with suction using a hose pump. 3.4.3

Sieve Filtration Using Ultrasonic Cleaning

With this method a slotted hole screen serves as filtering element. As a result of tangential feed flow a good flushing of the screen is guaranteed. With heavily contaminated water, however, this self-cleaning is not sufficient. The slotted hole screen is therefore subjected (periodically) to ultrasonics (ca. 40 kHz); thereby the stuck particles are loosened through the pressure peaks occurring on the slotted hole screen. In the long-term, the organic material adhering to the filter cannot be loosened using ultrasonics alone. Therefore an additional manual cleaning depending on the operating conditions is necessary. 3.4.4

Pre-coated Filter

This filtration method of microfiltration with stabiliser material is particularly suitable for raw wastewater and other wastewater rich in solids. To relieve the filtration membrane (carrier layer) and to form a protective layer, a stabiliser material (usually silicate powder or powdered cellulose) is pre-coated. If a pre-selected maximum pressure is achieved during operation, back-flushing using compressed air takes place automatically. The covering layer is blown through and new stabiliser material is pre-coated. The service life of the filter here is dependent on the medium to be filtered as well as on the requirement for filtrate. With activated sludge one should reckon with a useful life of 10 to 30 minutes. As a result of the short back-flushing time the filtrate flow is, in practice, not interrupted. With this method a high-grade filtrate can be created completely automatically over long periods.

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ATV-M 269E 3.4.5

Comparative Assessment of Sample Preparation Systems

For the filtration of all wastewater and sludge streams, filtration using pre-coated filters, subject to high investment costs, can be employed. With this even very solid rich wastewater (e.g. return sludge or raw wastewater) can be filtered to a large extent without problem. The employment of ultrafiltration modules for the filtration of wastewater streams in the area of biological reactors and secondary settling stages is a very widely and successfully employed method. The investment costs are, as a rule, lower than with precoated filtration; however, with thread-shaped micro-organisms, greases and oils or high solid contents, short useful lives complicate operation. The method of filtration using drum sieves, paper strip filters and sieve filters are often suitable only for employment in the effluent of secondary settling stages or following a filtration. Higher solid contents in the medium to be filtered often lead to blockages or to uneconomically short useful lives. 3.5

Advantages and Disadvantages of the Operation of On-line Analysis Equipment without Special Sample Preparation

With process measuring equipment without special sample preparation the investment costs otherwise arising for this and also the resources for monitoring, control and maintenance are dispensed with. The delay with measured value output is shortened by the period which is otherwise occasioned by the filtration. This period, with the employment of ultrafiltration is ca. 4 - 8 minutes. The missing sample preparation, as rule, leads to increased use of chemicals and to a larger dimensioning of equipment components, but should not, however, lengthen the T90 time of the measuring device (see Chap. 5.2). As a rule, these process devices require greater maintenance resources, which arise from the necessity for manual cleaning and the increased cleaning requirement of the measuring sensors, e.g. the electrodes with nitrate and ammonium analysers. Thus, for example, grease in the sample can cause a blockage of membrane perforations of electrodes and can lead to higher personnel resources and wear (membranes). The disadvantages mentioned do not apply for special systems which are submerged in the medium to be measured as here, as a rule, measurement is free of chemicals and without great use of expendable parts. The following listing shows the advantages and disadvantages of analysers without sample preparation:

• Costs:

+ no investment costs for a filtration + no maintenance resources for filtration + no requirement for chemicals for the cleaning of filtration units - increased requirement for chemicals due to larger sample volumes, in part also for cleaning the system - increased maintenance resources (cleaning) - increased use of expendable parts (membranes) December 1995

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ATV-M 269E • Process technology

+ shortening of reaction time of the complete measuring facility by the time delay of filtration + exclusion of faults caused by filtration (e.g. insufficient filtrate flow) - current limitation of methods to electrode measurement a UV absorption with determination of NOX-N

4.

Measuring Procedures

4.1

General

For the determination of nitrogen and phosphorus compounds there are various measurement methods with different characteristics which, with the selection of employment location and, with regard to the content substance of the sample, are to be taken into account. In particular, measuring accuracy and reaction times are to be assessed. As a rule, measuring devices show the measured value as NH4-N, NO3-N or PO4-P. The following conversions apply: 1 mg/l NH4-N = 1.29 mg/l NH4 1 mg/l NH3-N = 1.21 mg/l NH3 1 mg/l NO3-N = 4.43 mg/l NO3 1 mg/l PO4-P = 3.06 mg/l PO4 4.2

Ammonium

The continuous determination of ammonium can take place potentiometrically (Diag. 3) or photometrically (Diag. 4). Essentially two methods have been propagated:

• Measurement using gas sensitive electrode (potentiometric) With measurement using a gas sensitive electrode the sample is thermostated and is treated with complexing agents (e.g. EDTA) against lime precipitation as well as for the avoidance of false measured values through the combination of ammoniac with metal ions. The sample is dosed with lye in order to create a pH value > 11, through this ammonium is converted to ammoniac. The ammoniac diffuses through the electrode membrane and causes a change of the pH value of the internal electrolyte. This change is measured and passed to the indicator. For "adjustment", a two-point calibration is necessary. With this measuring method measurement ranges are possible, graduated from, for example, 0.1 - 2 mg/l to 0.1 1000 mg/l NH4-N,. The T90 time is < 5 min. The service life of the electrode is, according to manufacturer's details, ca 1½ to 2 years. The membrane and the electrolyte should be replaced at least every 3 months. Cross-sensitivities, for example with regard to volatile amines exist, however, in practice are barely of significance.

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ATV-M 269E

Evaluation Mixer

Sample

Electrode

Overflow

Calibration solutions

Reagent

Outflow

Diag. 3: Schematic representation of a potentiometric measuring process (ammonium or nitrate analysers)

Mixers

Sample

Signal

Lamp Cuvette Overflow

Calibration solution

Reagents

Photocell Outlet

Diag: 4 Schematic representation of a photometric measuring procedure

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ATV-M 269E • Indophenol blue method (photometric) The indophenol blue method is derived from the standardised procedure according to DIN 38406 E5. In the presence of sodium nitroprusside as catalyst, ammonium ions react, with a pH value of 12.6, with hypochlorite and salicylate ions to form an indophenol blue dye. The rate of reaction is dependent on temperature. Therefore the sample is to be tempered or the sample temperature is to be taken into account with analysis. The colour intensity of the indophenol complex formed is measured in a photometer at ca. 655 nm. Through measurement using another suitable wavelength the disturbances can, under certain conditions, be compensated. Measurement ranges of the undiluted sample can be realised graduated from, for example, 0.01 - 2 mg/l NH4-N to 0.1 to 100 mg/l NH4-N. The equipment is calibrated using a standard solution. Depending on equipment type the T90 time lies between 5 and 20 minutes. 4.3

Nitrate/Nitrite

For the determination of the concentration of oxidised nitrogen compounds there are various processes available which either determine the sum of nitrate and nitrite (NOX-N) or record the individual components. Continuously functioning measuring equipment for the determination of nitrite are on the market but, due to the very small necessity for application, are not dealt with in these notes. For the continuous determination of NOX-N the following measuring methods are common:

• UV absorption (photometric) The UV absorption method is based on the property of nitrate and nitrite ions of absorbing ultraviolet light. The UV radiation penetrates the water sample found in a flow cell. The intensity attenuation at ca. 210 nm is a measure for the concentration of nitrate and nitrite, which is shown in mg/l NOX-N. The measurement range with this method is 0.1 mg/l to 100 mg/l NOX-N. A single point calibration is carried out. The T90 time lies at < 5 min. Cross-sensitivities occur with UV absorbing content substances (such as, for example, humic substances and dyes). Through a suitable, equipment internal comparative measurement, these cross-sensitivities with biologically treated municipal wastewater can, as a rule, be compensated. In individual cases, multiple results can occur in the inflow (before biological treatment) with an increased COD content. The pure physical measurement principle makes possible a reactive and delay-free measurement and a low maintenance operation of the measuring device.

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ATV-M 269E • Ion selective electrodes (potentiometric) The potentiometric measurement takes place using an ion sensitive nitrate electrode. This reacts directly to nitrate ions in the wastewater sample. The measurement device requires a two-point calibration. Reproducibility of measured values is, as a rule, however, impaired by cross-sensitivities to other substances such as, for example, humic matter, nitrite and high salt contents. Employment location and conditions are therefore to be examined accurately beforehand. Ion sensitive electrodes can be "poisoned" by disruptive wastewater content substances. Nitrate electrodes are to be exchanged after a certain operating time; service life is, according to manufacturer's details, ca. 1 - 1½ years.

• Griess method with reductor (photometric) With NOX-N determination using the Griess method, nitrate is first reduced to nitrite (e.g. via a cadmium column). Through reaction of the nitrite with sulphanilamide and N-(1naphthyl) ethylenediamine a red azo dye is formed, whose intensity at 530 nm is measured photometrically. This method corresponds with EN 26777. With the Griess method one has to reckon with a time delay of ca. 10 min. The selection of the reduction process is to be assessed particularly critically under the aspect of environmental pollution through cadmium or hydrazine. 4.4

Total Nitrogen

The importance of the TNb measurement (total bound nitrogen) is documented through acceptance in the German Unit Process (DIN 38409, Part H 27) as well as the EG Directive (91/271 EEC of 1991) on the treatment of municipal wastewater. Various manufacturers in the meantime offer on-line analysers; practical experience with these is still outstanding. For TNb determination the total nitrogen in the sample is measured independent of the type of chemical compound (nitrate-N, nitrite-N, ammonium-N or organic N). Beforehand the bonded nitrogen compounds have to be converted through hot catalysis into nitrogen monoxide (NO), whose concentration is then determined. Elementary nitrogen (N2) is not recorded. The influence of other combustion products on the measured value is, in general, constant and capable of compensation. Due to the practically identical design of the equipment TOC (Total Organic Carbon, DIN 38409, Part H 3) and TNb can be determined using one device. The conversion in particular of ammonium nitrogen to nitrogen monoxide is no longer complete with higher concentrations; the optimum measurement range therefore lies with 0 - 50 mg/l nitrogen. With higher concentrations one should work with an automatic dilution. As, in any case, unvapourable compounds (salts) remain in the reactor, an automatic dilution can, in addition, extend the maintenance cycle for the reactor considerably. Prerequisite for the measurement on diluted samples is a sufficiently sensitive detector. The "salting" of the reactor should be monitored (e.g. by pressure measurement).

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ATV-M 269E The measurement cell must be sufficiently resistant due to the high corrosiveness of the measurement gas. Of advantage are devices with internal processing of the carrier gases. Standards of potassium nitrate/ammonium sulphate or ammonium chloride are used for calibration. Here the ammonium/nitrate ratio should be as close as possible to that of the sample. Robust on-line analysers, depending on the measured medium, make do with monthly maintenance intervals; intermediate(automatic) calibration is, in general, unnecessary. Depending on the type of sample (measurement location) this must be additionally processed before catalytic treatment. The equipment internal hose layout must be designed for a particle size of ca. 300 µm, as with advanced filtration only the dissolved nitrogen component is determined. 4.5

Orthophosphate

To date, two procedures have achieved a position of importance in continuous orthophosphate analysis:

• Molybdenum blue procedure (colorimetric) With the molybdenum blue procedure, orthophosphate converts with ammonium molybdate in the acid medium into complex phosphorus molybdic acid. This is subsequently converted using reduction agents into phosphorus molybdenum blue. The intensity of the dye is measured photometrically at ca. 800 nm. This method covers the range from 0.01 to 5 mg/l PO4-P, it is thus particularly suitable for low concentrations (sewage treatment plant effluent). The stability of the reagents used is limited to 2 - 3 weeks.

• Vanadate-molybdate procedure (colorimetric) With the vanadate-molybdate procedure (yellow procedure) orthophosphate ions react in the acid medium with molybdenum molybdate and ammonium vanadate to yellow ammonium phosphate vanadomolybdate. Its intensity is measured photometrically at ca. 380 nm. Yellow content substances in the water influence the measured value. This effect can, as a rule, be compensated through special automatic calibration procedures. The yellow procedure requires reagent with long stability This method covers a range in steps from 0.01 to 20 mg/l PO4-P. Depending on the application purpose, the operator has to decide whether the yellow procedure, which is more economical for higher PO4-P concentrations, or the blue procedure, which is more accurate in the lower range, is more practical. The T90 time for the procedure is ca. 5 - 12 min. 4.6

Total Phosphate

The content of hydrolysable phosphate - following decomposition through at least 30 minutes boiling using sulphuric acid - can be determined together with orthophosphate December 1995

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ATV-M 269E (DIN 38405-D11-3). The determination of the total phosphate content requires the decomposition of the unfiltered sample using potassium peroxide sulphate and sulphuric acid (DIN 38405-D11-4). In both cases the subsequent measurement is carried out according to the blue method (comp. Chap. 4.5). The previously known on-line measuring devices function according to these DIN procedures. Prerequisite for the measurement of the content of total phosphate is the inclusion of all solids in the decomposition, as the majority of the polyphosphate is bonded to the solids. It must therefore be ensured that an unfiltered sample is analysed; otherwise only the dissolved phosphate and an unknown part of the undissolved phosphate is detected. The decomposition of completely unfiltered samples is, however, in the main, not practical using currently available on-line measuring devices

5.

General Requirements on Process Analysers

5.1

Equipment Design

The conditions of employment and the desire for simple and safe operation lead to minimum requirements on equipment design.

• Housing The housing is to be robust and enclosed all sides and must at least meet the protective system IP 54 according to EN 60 529. The analysis part must be resistant to chemicals. An advantage is a housing that is suitable for both placing on a table and for a space saving mounting on the wall. Should the analysis equipment be delivered in a protective box instead of a housing, then the former is to be equipped with a 220 V socket and made lockable.

• Component grouping The grouping of the components is to be well arranged and offer sufficient space to enable easy working on all parts (important for control, maintenance and servicing tasks). The electronic component must be arranged above the wet part. All parts, including the hoses should be easily capable of removal manually. Internal lighting is practical. The flow path of the liquids is to be clearly recognisable and marked.; an appropriate schematic diagram belongs to the equipment. Reagents and calibration solutions must be capable of being secured in the equipment at the protected position provided for this. The measured valued as well as the alarm and status reporting system (e.g. calibrations) are to be displayed via an anti-glare, illuminated and large size display.

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ATV-M 269E • Outlets/interfaces There must be at least one 0/4 to 20 mA analogue output available. Potential-free threshold contacts (1 x minimum, 1 x maximum, for example for two-point control) can minimise the expenditure for control and regulation. Potential-free contacts should also be available for status and fault reporting. A standardised serial interface (e.g. RS 232 or similar) is very practical. The data structure and the transmission protocol of the interface is to be left open as additional software has to be produced for coupling to the process control level. The status signal can, for example, be used to activate an alternative value strategy with the absence of measured values; the possibility must at least exist that the last measured value is maintained. For certain operational purposes the storage of certain data, such as, for example, 24 hour, 2 hour average, minimum and maximum values and the measured value deviation before and after calibration, in the measuring facility is sensible. 5.2

Characteristics and Outfitting

The requirements on characteristics and outfitting are determined by the operational purpose and the technical environment of the equipment. Due to the significance of the terms "accuracy" and "reaction time" these points are explained in somewhat more detail.

• EMC (Electromagnetic Compatibility) The EMC behaviour of the equipment is to be based on the requirements according to IEC 801. The equipment may not be magnetically influenced by the surroundings; in accordance with prEN 50 082-2. The interference transmission must be according to EN 50 081-2 and the radio interference level N according to EN 55 011. The equipment must meet the requirements of the EC Directive 89/336/EEC.

• Electrical safety The electrical safety is to be based on the requirements according to DIN 31 000/VDE 1000, VDE 0410, EN 61 010/VDE 0411 or VDE 0106, Part 101. The appropriate EC Directive is 73/23/EEC. [VDE = Association of German Engineers].

• Measurement range The measurement range must be matched to the terms of reference and be oriented on operational values. It is important that the measurement is not selected too large in order that a high resolution and measurement accuracy is achieved. Insofar as measurement range switching takes place automatically due to actual measured values, this must be taken into account in the measured value processing.

• Accuracy Accuracy is a qualitative term to designate the total deviations of the analysis results. December 1995

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ATV-M 269E The total deviation (DIN 55 350-13) is made up from system and random errors of measurement. Although system deviations can, in the individual case, be minimised by calibration, they can finally, however, only be determined quantitatively in comparison with the results of other measurement procedures. Details on random errors of measurement through the process variation coefficient allow the comparison of the precision of analysis procedures, as its determination is standardised (DIN 38 402-51). The error of measurement to standard solutions is, however, only then visible from the process variation coefficient if a calibration function is also determined. For operational practice this is complicated. The normal detail of the random error of measurement in percent of the end scale value or indicated value is simple and confirmed in practice. Details are, however, not uniform and the determination of their relevant values are carried out by manufacturers in different ways; an immediate comparability of the details for different measuring devices therefore does not always exist. At least the detail of static certainty is required (which part of all measured values lie within the given range). This can, for example, take place through the application of the standard deviation or the relative standard deviation - of the variation coefficient - based on the mean of the measurements, in each case under repeat conditions. These values refer to deviations to standard solutions within the given working range with calibrated equipment. The determination of these values is, however, not laid down uniformly. Equipment for the determination of N and P compounds should maintain a variation coefficient of ≤ 5 % or a process variation coefficient of ≤ 3 %. It is necessary to observe the manufacturer's details on the carrying out of calibration, on the chemicals and aids (standard solutions) to be employed as well as the calibration intervals. These intervals must be so selected, that the drift compared with the random errors of measurement is negligible. Great linearity in the selected measurement range and high calibration constancy are significant.

• Reaction time The time response of process analysers, which measure continuously, should be described by detail of the reaction time (also response time). This is made up together from the dead time (= time between a concentration discontinuity at the input of the measuring device and the first reaction at the output) and the subsequent period in which the output signal duplicates a defined part of the concentration discontinuity. The reaction time is normally given as T90 time (also indicator delay, 90 % time). With this it understood to be the time which passes between a concentration discontinuity at the input to the equipment and indication or output change, which represents 90 % of the concentration discontinuity. With quasi-continuous systems, that is measuring at intervals, a stored measured value is issued which is respectively replaced by the current measured value. Dead time and reaction time are then identical.

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ATV-M 269E Decisive for the overall time response is, in this case, the duration of the analysis procedure (= minimum reaction time) or the time interval duration - in many cases selectable - of analysis. Duration of analysis is understood to be the period of time between sampling by the measurement device at its input and the jump of the indicator to the measured value. As the output of measured values takes place discontinuously, the detail of the duration of analysis represents a T100 time. The duration of analysis and the possible analysis interval are to be given. For regulation tasks the reaction time should be as short as possible. A considerable portion of measured value delay can, however, result from the necessary sample preparation.

• Behaviour with abnormal occurrences Following a power failure return to operation is to take place automatically without renewed adjustment. With faults which can lead to damage an automatic switching off is necessary; the equipment should produce an (adjustable) alternative value. The last measured value before an equipment failure is to be stored.

• Environmental conditions The equipment must be so designed that it functions correctly from 2° C to 40° C.

• Reagent consumption The equipment should have an as low as possible reagent consumption; in this connection equipment functioning quasi-continuously can have an advantage over those functioning continuously.

• Sample volumes The sampling requirement should be kept as small as possible in order to keep reagent consumption low.

• Self-monitoring The equipment is to be self-monitoring for possible malfunctions (self-test). 5.3

Operation

For reasons of operational safety and security against incorrect operation minimum requirements with regard to the operation of the equipment have to be set.

• Calibration The complete system is to be delivered with factory calibration. Calibration in operation should take place automatically, whereby the intervals and the point in time must be selectable, in order to schedule calibration in periods of low measurement requirement. The calibration status should be controllable via the indicator and/or via a protocol. There must be a possibility of calibrating the equipment manually. Notes on manual calibration must be included in operating instructions. In order not to interrupt measurement too long, calibration time should be kept as short as possible. December 1995

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ATV-M 269E During calibration the measured value indicated and the output signals must be selectable (measured value during calibration, fixed value, last measured value), so that regulation and control processes are not disrupted by zero or standard signals. With manual calibration a warning signal is to be produced after exceeding a freely selectable period from the start of calibration.

• Operational messages Messages for functional readiness and the operational status (calibration phase, flush cycle, measurement) are required.

• Error messages Messages on a "collective fault" in the equipment display and on a standardised interface and/or on a potential-free contact (slight expense with evaluation) are required. In addition selective error messages in the display and on the interfaces should also be produced, for example operating errors or leakage. With faults, messages in clear text are an advantage.

• Operation Operation of the equipment should be in dialogue. Operation of essential functions must be possible without use of a manual. Operating errors may not lead to damage. It can be practical to protect certain equipment functions through a code. Implausible operating conditions or the absence of measured values must result in an error message with defined adjustable output signals.

• Handling of reagents, standard and cleaning solutions Regulation containers, which ensure a safe exchange, must be available for reagents, standard and cleaning solutions. Safety data sheets must be available in accordance with EC Directive 91/155/EEC. 5.4

Operating Instructions

Operating instructions for analysers must be comprehensive, easily understood and produced in the language(s) of the operator. Documentation must cover: equipment construction, equipment characteristics, requirements for employment, dimensioned diagrams and functional description, taking into service, operation, control and maintenance (incl. cleaning). There must be clear details on error detection and correction. Brief waterproof instructions are required in or on the analyser. They should also contain details on the ordering of materials and spare parts as well as on addresses and telephone numbers of contacts for advice and service. 5.5

Availability

Optimal availability exists only with regular care, control and maintenance. It is essential to observe details laid down by manufacturers. The presence of the manufacturer for service, maintenance and spare parts is of considerable significance for availability.

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ATV-M 269E Expense items and spare parts should, if possible, be held by the user. An alternative is to take account of appropriate manufacturer's service (e.g. 24 hour service). Availability is particularly significant for employment in control and regulation cycles. The reliability of controlled or regulated systems should be ensured through appropriate measuring systems and, additionally, through alternative value strategies and limiting values of other parameters. 5.6

Monitoring of Quality

The examination of measuring facilities using standard solutions takes place regularly within the framework of automatic calibration. Here the measured values before and after calibration are to be compared with each other. With deviations the measured values of process equipment are to be checked for plausibility through control measurements using other suitable procedures in the laboratory, if required also using wastewater samples. With sampling attention is to be paid to comparable conditions. A further possibility of quality monitoring is the examination of equipment using standard solutions, which the user makes up himself or obtains from the equipment manufacturer. If reagents are self-made the manufacturer's recipe must always be observed. With maintenance contracts the examination of the technical part of the equipment should be included within the scope of quality monitoring. 5.7

Certification

Certification is a system of examination which the manufacturer organises in order to guarantee the quality of his product.

• Certification refers to the complete business and its quality management system. • The quality management system of the business carrying out certification concerns

not only the products but also all performance, in particular all services (e.g. advice, tasking, service).

• ISO 9001, other than production, also concerns design, development, assembly and customer service. Even the development of new products or services are carried out on the basis of the quality management system.

The equipment must carry the CE marking (CE = Communautés Européennes = European Community); here, attention is to be paid to applicable transition times for marking obligations. With the CE marking the manufacturer declares the observation of all applicable legal requirements for the equipment. These are the EU Directives converted into national law.

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ATV-M 269E

6.

Chemical Materials

6.1

Employment

As far as possible environmentally damaging reagents are to be avoided. For all necessary reagents the manufacturer must keep a verification of delivery. The complete recipe must be part of the technical documentation. 6.2

Work Safety with Handling and with Storage

There are two possible routes for the supply of reagents:

• Self-made Safety with handling can only be ensured through specialist personnel. The plant operator is responsible for safety.

• Use of ready-made reagents With the use of ready-made reagents in containers, which are solely exchanged, the manufacturer's safety information must be observed. To the reagents belong safety data sheets in accordance with EC Directive 91/155/EEC from which, inter alia, details on handling and storage, protective and first-aid measures, marking and hazard potential (e.g. classification in accordance with the ordinance for inflammable liquids [in Germany VbF] or water hazard class) must be taken. Depending on the substance and quantity the requirements of the hazardous substance ordinance applies. If water hazardous substances are employed then the requirement catalogue for HBV systems (German catalogue of the requirements to be placed on the manufacture, handling and employment of water hazardous substances) is to be observed. The handling of reagents must be a part of the instruction of user personnel. For reasons of safety there should be a freely accessible connection for drinking water available at the location of the measurement facility. This can additionally be used to wash prepared samples. Regenerants for the components for sample pre-treatment are, as a rule, corrosive and, with handling, require special protection for eyes, skin and clothing. Furthermore eye douche must be available. Automatic facilities for the regeneration of the sample preparation reduce the hazard considerably with the handling of these substances. 6.3

Disposal

The quantities of reagent used for the analyses are usually very small. In practice, therefore, the liquids produced at the measurement facility are currently discharged again into the sewage treatment plant. In special cases (e.g. hydrazine) and with the employment in lakes and rivers, a disposal of the used chemicals is to be carried out. Empty containers and packaging must, equipment taken out of service should, be taken back by the suppliers.

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ATV-M 269E

7

Requirements/Notes Product Care

7.1

Training of Personnel

on

Training,

Maintenance

and

The manufacturer must so train and instruct the user that he can operate and look after the equipment under his own responsibility. A personal instruction in operation, handling, care and maintenance of the analysis equipment by the manufacturer is fundamentally necessary and must therefore be part of the scope of delivery. Training of personnel should include basic instruction and follow-up service:

• Basic instruction covers the explanation of the parameters to be analysed and the

handling of the equipment (also fault finding) on the basis of the operating instructions. Basic instruction must, in addition, include information on the respective hazards with the handling of chemicals taking into account the use of personal protective equipment such as, for example, gloves and protective glasses.

• Effectively, for the follow-up service, the manufacturer must be available at short

notice for further enquiries following the taking into service of the equipment. Further training at suitable intervals should be offered by the manufacturer.

7.2

Care and Maintenance of Analysers

Analysis equipment requires a higher level of care and maintenance than, for example, process measuring equipment for pH value or conductivity. A daily visual inspection should be carried out with all process analysers. The level of care can, depending on the equipment and operating conditions, be up to 1.5 hours per day. However, in the normal case, it should be significantly lower. In general one has to reckon with ca. 20 min. per equipment per day (plus setting-up times) incl. sample pre-treatment. If process analysers are to be employed in one plant for various measured variables, then settling on only one manufacturer offers not only organisational but also other advantages as a result of more cost effective supply of materials, spare parts, maintenance and services. This applies even more for common equipment families which, in addition, are characterised by the same type of operation. On the other hand, different technologies can be particularly well suited for the respective tasks. Thus it should be decided in each individual case which advantage has the greater significance. Maintenance is to be carried out with regard to interval and scope according to the manufacturer's details. As a rule, it consists of plausibility control, checking of measured values, functional checks as well as of the exchange of expense items such as, for example, hoses, and of cleaning tasks. The members of staff responsible for the analysis equipment carry out the above given control tasks which, together with maintenance tasks and important comments on the process analysis equipment, are recorded in a maintenance log. Through this the user achieves a continuous documentation on the measuring facilities.

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ATV-M 269E Depending on the number of personnel and operational conditions, it can be practical to hand over the maintenance to a specialist firm (maintenance contract). It is recommended, in particular in large wastewater treatment plants, to employ ones own specialists for care and maintenance. 7.3

Product Care

The equipment manufacturer should operate a product care such that operational experience and technical improvements also flow into existing product lines, if the technical expense is justifiable. Representative and practical improvements are, for example: increase of accuracy, decrease of the use of reagents, reduction of the maintenance expense, increased service life and the updating of software. Furthermore, it is desirable that product care measures are also available to all operators who already employ equipment so that they also can make use of the technical and economic further developments. For this, however, the technical and economic expense is to be examined.

8

Costs

8.1

General

For the assessment of costs the complete measuring system is to be considered. In addition to analyser costs there are, inter alia, costs for analysis equipment space, for sample preparation, sample flow feed and follow-on costs are to be included. Depreciation times of a max. of 5 years should be assumed for analysers. With the comparison of different offers the total costs for at least two operational years are to be assessed, that is costs for:

• • • • • • 8.2

Investment Reagents Taking into service Training /instruction Maintenance Spare parts/expense items Investments

With the procurement of a measuring station the investment costs are, in general determined by the following components:

• Pumps and ancillaries • Ultrafilter station with two filters (manual, semi-automatic, automatic) or alternative • • •

sample preparation Measuring facility(-ies) Building/container with heating and ventilation Sample inflow and outflow

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ATV-M 269E • Installation material and tasks, energy and water connections, measured value • •

processing (datalink) Security arrangements Instruction and taking into service

Possibilities for savings:

• Sample preparation: layout as manual, semi-automatic or as automatic station has a very great influence on the investment costs. The higher investment costs for automatic operation are to be offset against the higher operational costs for a manual system. A decisive cost factor is the sample requirement for the analysis equipment. With small requirements and the same sampling point, several devices can be supplied using a single sample preparation.

• Building/container: here the special conditions on site decide the necessary investment. Buildings in the vicinity of the measuring point could possibly be utilised.

• Instruction and taking into service: depending on the manufacturer these costs are included in the system price or are additionally calculated. These are to be indicated separately in requests for tender and offers. The distribution of investment costs is shown as an example in Table 1. Table 1:

Investment costs for measurement facilities Costs in % of the total costs

1. Sampling incl. mounting for pump pump electrical connection wastewater connection protective basket

4

2. Measuring house incl. foundation measuring house, ca. 10 m2 base line voltage distribution assembly

18 - 38

3. Filtrate production

0 - 32

4. Measuring equipment incl. instruction

25 - 45

5. Cable laying 6. Drinking water connection

- 14

1 -20 1

The cost shares attributed to the total investment can only represent a guide. To determine the cost shares the details of various sewage treatment plant operators were December 1995

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ATV-M 269E evaluated and the respective minimum and maximum values adopted. By taking on own efforts with the production of peripheral facilities, the investment costs can be reduced significantly. This applies also if existing structural facilities (rooms, empty pipes) are utilised. The actual on-line measuring equipment, as a rule, has only a share of 25 - 45 % of the total costs. The peripheral equipment costs may therefore not be underestimated. 8.3

Operating Costs

Essential factors influencing the operating costs are:

• Costs for chemicals With the usage and prices of chemical materials all means such as reagents, calibration solutions and cleaning agents are to be taken into account. Depending on the procedure different quantities and a different number of chemicals are required. Some procedures require no reagents or calibration solutions. Costs can be saved using made-up solutions, however, the resources of personnel and material are to be taken into account as are the costs for the analytical quality assurance (inter alia laboratory analysis) and disposal.

• Energy costs (load on the equipment, lighting and, in particular, heating and pumps) • Sample preparation • Maintenance costs It is essential to obtain details on maintenance and care by the user in advance from the manufacturer. It is recommended that the experience of other operators are investigated. If maintenance and service is to come from outside then the offer with regard to scope of the performance, number of hours, service and reaction times and travel costs are to be examined.

• Expense items Disposal costs result for used chemicals and sample mixtures, chemical residues and containers, packaging as well as through peripheral equipment. With the purchase of ready-made chemicals it is to be checked in advance whether a free disposal of chemical residues and containers takes place via the manufacturer.

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ATV-M 269E 9

Ordinances,

Standard

Specifications,

Standards

[Known translations into English are given as such otherwise a courtesy translation is included in square brackets]

73/23/EEC Low voltage 89/336/EEC Electromagnetic Compatibility 91/155/EEC Directive of the Commission of 05 March 1991 on the determination of details of a special information system for hazardous preparations in accordance with Article 10 of Directive 88/379/EEC of the Council DEV Allgemeine Angaben (Gruppe A); Anwendung statistischer Methoden zur Beurteilung von Analysenergebnissen in der Wasseranalytik [General Details (Group A) Application of statistic methods for the evaluation results from water analysis] DIN 1319-3 Grundbegriffe der Meßtechnik; Begriffe für die Meßunsicherheit und für die Beurteilung von Meßgeräten und Meßeinrichtungen [Basic concepts in metrology; terminology for measuring uncertainty and for the assessment of measuring equipment and measuring facilities] DIN 31000/VDE1000 Allgemeine Leitsätze für das sicherheitsgerechte Gestalten technischer Erzeugnisse [General guidelines for the safe design of technical products] DIN 38 402-51 General information (Group A); calibration of analytical methods, evaluation of analytical results and linear calibration functions used to determine the performance characteristics of analytical methods DIN 38 409-3 Bestimmung des gesamten organisch gebundenen Kohlenstoffs (TOC) [Determination of Total Organic Carbon (TOC)] DIN 38 409-27 Determination of Total Bound Nitrogen TNb DIN 55 350-13 Begriffe der Qualitätssicherung und Statistik; Begriffe zur Genauigkeit von Ermittlungsverfahren und Ermittlungsergebnissen [Terminology of quality assurance and statistics; terminology for the accuracy of investigative procedures and results] EN 29 001 Quality assurance systems; model demonstration of quality assurance in design/development, production, assembly and customer service

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ATV-M 269E EN 55 011 Radio interference suppression of electrical resources and systems; limiting values and measurement procedures for radio interference from industrial, scientific and medical high frequency equipment prEN 55 082-2 Electromagnetic compatibility (EMC), generic specification resistance to jamming, Part 2: industrial area, draft EN 60 529 Protective systems using housings EN 61 000 Electromagnetic compatibility EN 61 010/VDE 0411 Safety regulations for electrical measuring, control, regulation and laboratory equipment GefStoffV Verordnung zum Schutz vor gefährlichen Stoffen (Gefahrstoffverordnung) [German Ordinance on protection against hazardous substances (Hazardous Substance Ordinance)] IEC 801 Electromagnetic compatibility of measuring, control and regulation facilities in industrial process technology EN 55 081-2 Electromagnetic compatibility (EMC); generic specification resistance to interference transmission, Part 2: industrial area VDE 0410 Sicherheitsbestimmungen für anzeigende und schreibende Meßgeräte und ihr Zubehör [Safety regulations for indicating and recording measurement equipment and its ancillaries] VDE 0106, Part 101 Schutz gegen gefährliche Körperströme [Protection against hazardous field currents] VDI/VDE 2600* Metrologie (Meßtechnik) Metrology (Measuring technology)] VDI/VDE 3516-2 Flüssigkeitsanalytische Betriebsmeßeinrichtungen und -anlagen [Operational measuring devices and systems for analysis of fluids]

* VDI = Association of German Electrical Engineers; VDE = Association of German Engineers

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