design of drinking water treatment plant

DESIGN OF DRINKING WATER TREATMENT PLANT FOR ARNI UNIVERSITY A PROJECT REPORT Submitted by SUKHSHAM SHARMA VIPUL KERNI AMAN SHARMA AJAY VERMA TARUN PURI

AACI0044A/09 AACI0046A/09 AACI0047A/09 AACI0048A/09 AACI0050A/09

in partial fulfillment for the award of the degree of

BACHELOR OF TECHNOLOGY in

CIVIL ENGINEERING

ARNI SCHOOL OF TECHNOLOGY

ARNI UNIVERSITY:: KANGRA JUNE 2013

ARNI UNIVERSITY: KANGRA BONAFIDE CERTIFICATE Certified that this project report “DESIGN OF DRINKING WATER PLANT FOR ARNI UNIVERSITY” is the bonafide work of

“SUKHSHAM

SHARMA (AACI0044A/09), VIPUL KENRI (AACI0046A/09), AMAN SHARMA (AACI0047A/09), AJAY VERMA (AACI0048A/09) and TARUN PURI (AACI0050A/09)” who carried out the major project work under my supervision.

SIGNATURE

SIGNATURE

Mr. BHARANIDHARAN B

Mr. DAVINDER SINGH

HEAD OF THE DEPARTMENT

ASSOCIATE DEAN

EXTERNAL EXAMINER

INTERNAL EXAMINER

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SUPERVISOR

ABSTRACT

This project presents a review on design of drinking water treatment plant including the design of for sedimentation, filtration, chlorination, aeration etc. The main work of this project is to check the WHO standards for drinking water, to check whether water is suitable for drinking purposes or not. If it is not so then various treatment methods are used for maintaining the standards of water. The application of modern water treatment processes had a major impact on water-transmitted diseases, and these processes provide barriers or lines of defense between the consumer and waterborne disease. This project provides an overview of the drinking water treatment processes. The most common treatment process train for surface water supplies is conventional treatment, which consists of disinfection, coagulation, flocculation, sedimentation, filtration, and disinfection. The safe drinking water requires a holistic approach that considers the source of water and treatment processes. Depending on water quality influent, each unit can be optimized to achieve the desired water quality effluent, both in design and operation stages. A typical water treatment plant has the combination of processes needed to treat the contaminants in the source water treated by facility. The presence of unbeatable organic or mineral substance causes some problems in obtaining drinking water. Understanding these phenomena requires taking into account the physical and chemical natures of the water to be treated.

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ACKNOWLEDGEMENT

We express our sincere and heartfelt thanks to the MANAGEMENT and the CHANCELLOR and PRO CHANCELLOR for providing all the necessary facilities and support required for carrying out this project successfully. We thank our Vice Chancellor Dr. S.K. KAUSHAL for his care and guidance which helped us in completing this project in time. We express our sincere thanks to our Associate Dean Mr. DAVINDER SINGH and Head of the Department Mr. B.BHARANIDHARAN for their valuable suggestions and encouragement throughout this project. We also express our sincere thanks to the TEACHING and NONTEACHING STAFF of our department, who had showed a keen interest at all stages of our work and provided us with the required help. We gratefully acknowledge the help rendered by our UNIVERSITY LIBRARIAN and his Staff for providing us with the necessary books and references. Finally our unfailing gratitude is to our PARENTS and FRIENDS for their love and affection, which kept us on wheels to do the work energetically and successfully.

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TABLE OF CONTENTS

CHAPTER NO.

1.

TITLE ABSTRACT

iii

LIST OF TABLES

ix

LIST OF FIGURES

x

LIST OF ABBREVATIONS

xi

INTRODUCTION

1

1.1 GENERAL

1

1.2 WATER SOURCES

3

1.2.1 Hydrological cycle terms

3

1.3 SOURCES OF DRINKING WATER

4

1.4 WATER QUALITY

5

1.5 POTABLE WATER

7

1.6 REQUIREMENT FOR WATER

7

1.7 NEED FOR TREATMENT

8

1.7.1 Water borne diseases 2.

LITRATURE REVIEW 2.1 OBJECTIVES OF PROJECT

3.

PAGE NO.

WATER QUALITY ANALYSIS

8 10 18 19

3.1 CHARACTERISTICS OF WATER

19

3.2 PHYSICAL CHARACTERISTICS

20

3.2.1 Turbidity

20

3.2.2 Colour

21

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3.2.3 Taste and odour

21

3.2.4 Temperature

21

3.3 CHEMICAL CHARACTERISTICS

22

3.3.1 PH

22

3.3.2 Acidity

22

3.3.3 Alkalinity

22

3.3.4 Hardness

23

3.3.5 Chlorides

23

3.3.6 Sulphates

23

3.3.7 Iron

24

3.3.8 Solids

24

3.3.9 Nitrate

24

3.4 WATER TREATMENT METHODS

26

3.4.1 Aeration

27

3.4.2 Types of aerators

27

3.5 SETTLING

28

3.5.1 Purpose of settling

28

3.5.2 Principle of settling

29

3.5.3 Types of settling

29

3.5.4 Types of settling tanks

29

3.6 COAGULATION AND FLOCCULATION

30

3.6.1 Flocculation

30

3.6.2 Mechanism of flocculation

31

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3.6.3 Coagulation in water treatment 3.7 FILTRATION

5.

32

3.7.1 Filtration mechanism

32

3.7.2 Filter material

32

3.7.3 Types of filter

33

3.7.4 Principle of slow sand filter

34

3.7.5 Slow sand Vs rapid sand filter

35

3.8 DISINFECTION

4.

31

36

3.8.1 Methods of disinfection

36

3.8.2 Forms of application of chlorine

37

EXPERIMENTAL PROCEDURE

39

4.1 TO DETRMINE TOTAL HARDNESS OF WATER SAMPLE

39

4.2 TO DETERMINE ALKALINITY OF WATER SAMPLE

40

4.3 TO DETRMINE PH VALUE OF WATER SAMPLE

40

4.4 TO DETEMINE CHLORIDE CONTENT IN WATER SAMPLE

41

4.5 TO DETRMINE THE TOTAL DISSOLVED SOLIDS IN WATER SAMPLE

42

4.6 TO DETERMINE DISSOLVED OXYGEN IN WATER

43

RESULTS AND DISCUSSION 5.1 RESULTS OF CHEMICAL TEST

vii

45 50

6.

7.

5.2 DISCUSSION OF RESULTS

53

DESIGN OF DRINKING WATER TREATMENT PLANT

54

6.1 WATER QUANTITY ESTIMATION

54

6.2 FLUCTUATIONS IN RATE OF DEMAND

54

6.3 DESIGN PERIOD AND POPULATION FORECAST

55

6.4 DESIGN DETAILS

56

6.5 DESIGN OF SEDIMENTATION TANK

58

6.6 DESIGN OF RAPID SAND FILTER

59

6.7 DESIGN FOR CHLORINATION

60

6.8 DESIGN OF COAGULATION TANK

60

CONCLUSION

62

REFERENCES

63

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LIST OF TABLES

TABLE NO.

TITLE

PAGE NO.

3.1

PHYSICAL STANDARADS OF DRINKING WATER

25

3.2

CHEMICAL STANDARDS FOR DRINKING WATER

25

3.3

FUNCTIONS OF WATER TREATMENT UNIT

26

4.1

DETERMINATION OF PH

41

ix

LIST OF FIGURES

FIGURE NO.

TITLE OF FIGURE

PAGE NO.

1.1

HYDROLOGICAL CYCLE IN NATURE

4

3.1

CROSS SECTIONAL VIEW OF RAPID SAND FILTER

34

3.2

OPERATION OF RAPID SAND FILTER

36

3.3

WATER TREATMENT STEPS

38

3.4

WATER TREATMENT PLANT

38

x

LIST OF ABBREVATIONS

BCM

Billion cubic meter

CPCB

Central pollution control board

WHO

World health organization

GIGO

Garbage in garbage out

NTU

Nephelometric turbidity unit

JTU

Jackson turbidity unit

DBP

Disinfection by product

ETSW

Extended terminal sub fluidization wash filter

FPA

Flavor profile analysis

TDS

Total dissolved solids

EDTA

Ethylene diamine tetra acetic acid

SSF

Slow sand filter

EBT

Erichrome black T

BOD

Biological oxygen demand

DI

Deionization

RO

Reverse osmosis

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CHAPTER 1 INTRODUCTION 1.1 GENERAL Water is a precious commodity. Most of the earth water is sea water. About 2.5% of the water is fresh water that does not contain significant levels of dissolved minerals or salt and two third of that is frozen in ice caps and glaciers. In total only 0.01% of the total water of the planet is accessible for consumption. Clean drinking water is a basic human need. Unfortunately, more than one in six people still lack reliable access to this precious resource in developing world. India accounts for 2.45% of land area and 4% of water resources of the world but represents 16% of the world population. With the present population growth-rate (1.9 per cent per year), the population is expected to cross the 1.5 billion mark by 2050. The Planning Commission, Government of India has estimated the water demand increase from 710 BCM (Billion Cubic Meters) in 2010 to almost 1180 BCM in 2050 with domestic and industrial water consumption expected to increase almost 2.5 times. The trend of urbanization in India is exerting stress on civic authorities to provide basic requirement such as safe drinking water, sanitation and infrastructure. The rapid growth of population has exerted the portable water demand, which requires exploration of raw water sources, developing treatment and distribution systems.

The raw water quality available in India varies significantly, resulting in modifications to the conventional water treatment scheme consisting of aeration, chemical coagulation, flocculation, sedimentation, filtration and disinfection. The backwash water and sludge generation from water treatment plants are of environment concern in terms of disposal. Therefore, optimization 1

of chemical dosing and filter runs carries importance to reduce the rejects from the water treatment plants. Also there is a need to study the water treatment plants for their operational status and to explore the best feasible mechanism to ensure proper drinking water production with least possible rejects and its management. With this backdrop, the Central Pollution Control Board (CPCB), studied water treatment plants located across the country, for prevailing raw water quality, water treatment technologies, operational practices, chemical consumption and rejects management.

Water to be supplied for public use must be potable i.e., satisfactory for drinking purposes from the standpoint of its chemical, physical and biological characteristics. Drinking water should, preferably, be obtained from a source free from pollution. The raw water normally Available from surface water sources is, however, not directly suitable for drinking purposes. The objective of water treatment is to produce safe and potable drinking water. Some of the common treatment processes used in the past includes Plain sedimentation, Slow Sand filtration, and Rapid Sand filtration with Coagulation-flocculation units as essential pretreatment units. Pressure filters and diatomaceous filters have been used though very rarely. Roughing filters are used, under certain circumstances, as pretreatment units for the conventional filters. The treatment processes may need pretreatment like pre-chlorination and aeration prior to conventional treatment. The pretreatment processes comprising of Coagulation and Flocculation have been discussed under the main title of Rapid Sand filters. Detailed discussion on all such aspects as well a recommended unit operations, is given in the Manual on Water Supply and Treatment (1999 Edition) Ministry of Urban Development.

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1.2 WATER SOURCES Before we discuss the types of treatment it is easier to first understand how the source of water arrives.

1.2.1 HYDROLOGICAL CYCLE TERMS  Precipitation: The process by which atmospheric moisture falls on to the land or water surface as rain, snow, hail or other forms of moisture.  Infiltration: The gradual flow or movement of water into and through the pores of the soil.  Runoff: Water that drains from a saturated or impermeable surface into stream channels or other surface water areas. Most lakes and rivers are formed this way.  Evaporation: The process by which the water or other liquids become a gas.  Transpiration: Moisture that will come from plants as a byproduct of photosynthesis.  Condensation: The collection of the evaporated water in the atmosphere.

Once the precipitation begins water is no longer in its purest form. Water will be collected as surface supplies or circulate to form in the ground. As it becomes rain or snow it may be polluted with organisms, organic compounds, and inorganic compounds. Because of this, we must treat the water for human consumption.

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Fig 1.1 Hydrological cycle in nature

1.3 SOURCES OF DRINKING WATER A clean, constant supply of drinking water is essential to every community. People in large cities frequently drink water that comes from surface water sources, such as lakes, rivers, and reservoirs. Sometimes these sources are close to the community. Other times, drinking water suppliers get their water from sources many miles away. In either case, when you think about where your drinking water comes from, it's important to consider not just the part of the river or lake that you can see, but the entire watershed. The watershed is the land area over which water flows into the river, lake, or reservoir. In rural areas, people are more likely to drink ground water that was pumped from a well. These wells tap into aquifers--the natural reservoirs under the earth's surface that may be only a few miles wide, or may span the borders of many states. As with surface water, it is important to remember that activities many miles away from you may affect the quality of ground water. Your annual drinking water 4

quality report will tell you where your water supplier gets your water. Your water will normally contain chlorine and varying amounts of dissolved minerals including calcium, magnesium and sodium, chlorides, sulphates and bicarbonates, depending on its source. It is also not uncommon to find traces of iron, manganese, copper, aluminium, nitrates, insecticides and herbicides although the maximum amounts of all these substances are strictly limited by the regulations. These are usually referred to as 'contaminants'. Most of these substances are of natural origin and are picked up as water passes round the water cycle. Some are present due to the treatment processes which are used make the water suitable for drinking and cooking. The water will also contain a relatively low level of bacteria which is not generally a risk to health.

1.4 WATER QUALITY Samples of raw and treated water will be taken at regular intervals for analysis. In a large Waterworks with its own laboratory, sampling will almost certainly be carried out daily, since the effluent analysis constitutes the only certain check that the filter is operating satisfactorily and the raw water analysis provides what is possibly the only indication of a change in quality that might adversely affect the efficiency of treatment. In case of small plants with no laboratory facilities, an attempt should be made to conduct sampling on regular basis. Field testing equipment may be used to measure water quality.

Water is colorless, tasteless, and odorless. It is an excellent solvent that can dissolve most minerals that come in contact with it. Therefore, in nature, water always contains chemicals and biological impurities i.e. suspended and dissolved inorganic and organic compounds and micro organisms. These compounds may come from natural sources and leaching of waste deposits. However, Municipal and Industrial wastes also contribute to a wide spectrum of both organic and inorganic impurities. Inorganic compounds, in general, 5

originate from weathering and leaching of rocks, soils, and sediments, which principally are calcium, magnesium, sodium and potassium salts of bicarbonate, chloride, sulfate, nitrate, and phosphate. Besides, lead, copper, arsenic, iron and manganese may also be present in trace amounts. Organic compounds originate from decaying plants and animal matters and from agricultural runoffs, which constitute natural humic material to synthetic organics used as detergents, pesticides, herbicides, and solvents. These constituents and their concentrations influence the quality and use of the natural water resource. Primary water quality criteria for designated best classes (for drinking water, outdoor bathing, propagation of wildlife & fisheries, irrigation, industrial cooling) have been developed by the Central Pollution Control Board. The presence of contaminants and the characteristics of water are used to indicate the quality of water. These water quality indicators can be categorized as:  Biological: bacteria, algae  Physical: temperature, turbidity and clarity, color, salinity, suspended solids, dissolved solids  Chemical: pH, dissolved oxygen, biological oxygen demand, nutrients (including nitrogen and phosphorus), organic and inorganic compounds (including toxicants)  Aesthetic: odors, taints, color, floating matter  Radioactive: alpha, beta and gamma radiation emitters Groundwater is often high in mineral content and can contain dissolved gases such as methane and hydrogen sulphide. Surface water comes from two very different sources: rivers, and lakes. Surface waters in their natural state are potentially unsafe for human consumption because they are constantly exposed to contamination from human, animal, industrial wastes, and from natural sources such as soil, vegetation, and algae. Rivers can be a difficult source of water to treat as the turbidity can change rapidly and dramatically. Lakes are 6

less prone to changes in turbidity as suspended matter tends to settle to the bottom, however, ice cover can cause degradation along with taste and odor problems in water quality. All natural waters contain some turbidity and color. Turbidity is caused by very finely divided particles held in suspension. This gives the water a cloudy appearance. Color is caused by dissolved and colloidal particles, a result of organic or inorganic material in the water.

1.5 DEFINITION OF POTABLE WATER Potable or drinking water can be defined as the water delivered to the consumers that can be safely used for drinking, cooking, and washing. A certification by licensed professional engineer specialized in the field is no longer sufficient. The public health aspects are of such importance and complexity that the health authority having jurisdiction in the community now reviews inspects, samples, monitors, and evaluates on continuing basis the water supplied to the community using constantly updated drinking water standards. Such public health control helps to guarantee a continuous supply of water maintained within safe limits.

1.6 REQUIREMENTS OF WATER FOR DOMESTIC USE  It should be colourless and sparkling clear. It must be free from solid in suspension and must not deposit a sediment on standing.  It should be of good taste, free from odour.  It should be reasonable soft  It should be plentiful and cheap.  It should be free from disease producing bacteria.  It should be free from objectionable dissolved gases, such as sulphuretted hydrogen.  It should be free from harmful salts. 7

 It should be free from objectionable minerals such as iron, manganese, lead, arsenic, and other poisonous material.  It should not lead to scale formation.  It should be free from radioactive substances such as radium, stronsium etc.

1.7 NEED FOR WATER TREATMENT Due to increased number of micro-organisms, pathogens and harmful bacterias, There is a need of water treatment which includes many water treatment methods for purification purposes. These harmful micro-organisms leads to many water borne diseases.

1.7.1 WATER BORNE DISEASES Water borne diseases are those diseases which are caused due to ingestion of water contaminated by human or animal excrement, which contain pathogenic microorganisms. Water borne diseases include cholera, typhoid, amoebic and bacillary dysentery and other diarrheal diseases. In addition, water borne diseases can be caused by the pollution of water with chemicals that have an adverse effect on health. The chemicals included are  Arsenic  Fluoride  Nitrates from fertilizers  Carcinogenic pesticides (DDT)  Lead (from pipes)  Heavy Metals Various water borne diseases are listed below  Cholera 8

 Typhoid  Bacillary dysentery  Infectious hepatitis  Giardiasis To make water free from these harmful bacteria and pathogens we need to treat water for drinking purposes.

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CHAPTER 2 LITERATURE REVIEW The main aim of water treatment and drinking water distribution is the protection of health. Another important aim is to ensure access to the highquality drinking water. Epidemiological studies also suggest that drinking water can be significant source of calcium. Calcium rich mineral water provides over one-third of the recommended dietary of this mineral in adults. However receiving calcium is important at all ages, but the need for Ca2+ is higher during childhood, fetal growth, pregnancy and lactation (Azoulay et al., 2001). Upwards of 99 % of total calcium is found in bones and teeth, where operate like important structural component. Others calcium´s functions belong to metabolic processes, where serve as signal for basic physiological processes, for example vascular contraction. It influences on blood coagulation, because cooperation in transformation fibrinogen on fibrin. Calcium ions influence muscles contractions and nervous transmission. Calcium ions also are very important on activation and elimination of various hormones secretion (e.g. insulin), as well various enzymes (Melicherčík and Melicherčíková, 2010). Based on the World Health Organization (WHO) findings, next to fluoride, for calcium and magnesium are evident the strongest health benefits associated with their presence in drinking-water (Cotruvo et al., 2009, Nordin 2010). Japanese chemist Kobayashi described the relationship between water hardness and the incidence of vascular diseases in 1957. His claims were based on epidemiological analysis. Higher mortality rates from cerebrovascular diseases in the areas of Japanese rivers with more acid (i.e. softer) water were compared to those with more alkaline (i.e. harder) water used for drinking purposes (Kožíšek, 2000). 10

The contributions of drinking water to nutritional status also depend on water consumption. It is highly variable depending on behavioural factors and environmental conditions. Individuals with the greatest relative consumption of water include infants, residents in hot climates, and individuals engaged in strenuous physical activity. Consumption of moderately hard water containing typical amounts of calcium and magnesium (1.6—2.2 mmol.l–1) provides an important incremental percentage of their daily intake. Moreover, hard water (>2.2 mmol.l–1) can reduce the losses of calcium, magnesium and other essential minerals from food during cooking. If low mineralized (0—1.6 mmol.l–1) water is used for food and beverage production, reduced concentrations of Ca and Mg, and other essential elements would also occur in those products (Monarca et al., 2009, Poláček et al., 2010). The reason of low mineral content in source water is that water is formed in the poor soluble mineral geological structures. If the content of dissolved inorganic salts in nature water is very low, it is necessary to supplement them in the process of water treatment technology. Water treatment can affect the content of minerals, and thus the total intake of calcium and magnesium. Recarbonization process aims to increase water hardness (calcium and manesium content increases) and is appropriate for very soft water treatment. Very soft water is corrosive to plumbing resulting in the damage of the systems and potentially increases content of metals such as copper and lead in drinking water. Endurance of water facilities is determined by their resistance to corrosion. In order to limit the corrosion of steel and concrete pipes, it is desirable to acid neutralizing capacity must be reached 1.4 to 2.1 mmol.l–1. In this value is applied inhibitory effect of calcium, bicarbonate and carbonate ions, which means that the inner surface of the pipe begins to create protective carbonate layer (Cotruvo et al., 2005; Yang et al., 2002; Olejko, 1999).

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The main aim of this contribution was to analyze raw surface source water quality and prepared drinking water quality. The procedure of lab-scale verification of recarbonization process using lime and carbon dioxide was chosen. The lime reacts with CO2 to form calcium bicarbonate. Another aim was to investigate the influence of recarbonization process on efficiency of water treatment processes in lab-scale. Rietveld et al. and Bookslooper et al. reported that although drinking water treatment plants are already functioning for more than a century and in the last decades the operation has become more complex. Because of more stringent regulations, the plants efficient or effective use of” your water treatment plant have to produce water of a better quality and, therefore different treatment processes are placed in series to meet the guidelines. Because of frequent job rotation and increased automation, experienced operators who are able to interact with the processes are nowadays scared. Therefore, it is impossible to compensate with the complexity of the operation. Optimization of Conventional Drinking Water Treatment Plant: As a “treatment train”, conventional drinking water Optimization of conventional drinking water treatment plant compounds of many series stages and units (coagulation-flocculation, sedimentation, filtration and disinfection), which on each unit should be optimized on its design, process and operation. Banff et al. defined optimization of conventional drinking water treatment plant means “to attain the most efficient or effective use of” your water treatment plant which consist of some principles, there are; achievement of consistently high quality finished water on a continuous basis; and the importance to focus on overall to interact with the process of plant performance, instead of focusing too much on individual processes. Approaches to conventional drinking water treatment plant optimization should be mostly common sensed, be organized 12

and get into the facts first. Systematic gathering of information about plant performance are need, such as: data trending and analysis, check plant design criteria against actual track chemical dosing versus performance, field measurements and visual observations. The data trending and analysis should remind of the “GIGO” (Garbage In Garbage Out) principles and also correlate to plant operating parameters trends against each other to look for valuable information. Rietveld et al. reported that in drinking water pumps, it is particular importance to determine the water quality indicators for good operation. In the reported research the objective was to focus on the instantaneous mixing and static mixers which can lose target water quality parameters and direct indicators for the performance. In the operational practice of drinking water treatment, however, derived indicators are often used. In softening, for example, pH is measured in the effluent as an indicator for performance, while the main purpose of softening is to decrease the calcium concentration. Specific questions and issues to be addressed by the model were linked to the different interest group. Optimization of Coagulation and Flocculation: Water is treated with compounds that make small suspended particles stick together and settle out of the water. Flocculation refers to water treatment processes that combine or coagulate small particles into larger particles, which settle out of the water as sediment. Banff et al. also presented that optimization of coagulation and flocculation should be have many considerations, such as: chemical dosing trends, coagulation and flash mixing, colloid stability, selecting coagulant, operational and design

factors affecting

and evaluating

trends

optimization

consist of; understand how chemical dosing impacts plant performance and 13

look for over-or under-dosing, which it track to relation between; raw water turbidity versus coagulant dose, raw and coagulated water pH and alkalinity versus. Insufficient air loading is set 15 min total. Fourth, maximum coagulant dose and clarified water turbidity versus coagulant dosage. Franceschiet al. and Zularizam et al. reported that in some cases, the addition of mineral salts or organic compounds causes the agglomeration of these particles, allowing their elimination by decantation or filtration in most water treatment plants, the minimal coagulant concentration and the residual turbidity of the water are determined by the Jar-Test technique. In their paper a systematic study of the influence of raw water quality and operating conditions on the effectiveness of the coagulation-flocculation process using aluminum sulphate is presented. In the other research, Husseinet al. reported that the main possible applications of ozone are preoxidation, intermediate oxidation and final oxidation. Generally pre-ozonation decreases color, turbidity, tastes and odors. This treatment is generally used to enhance the coagulation. Preozonation and coagulation processes were optimized for total organic carbon removal and bromate control. Optimization of Sedimentation/Clarifier: Water is passed through a settling basin or clarifier allowing time for mud, sand, metals and other sediment to settle out. This particle conglomerate is removed from the water prior to filtration. Banff et al. presented that optimization of sedimentation/clarifier

it

should

be presented by many conditions, there are; consistently result less than 2 NTU, stable when faced with rapidly changing water quality conditions, produces sludge of consistent quality, sedimentation: 0.5-1% of Total Solid (TS). Common causes for poor clarifier performance are: density currents due to 14

temperature variation within basins, excessive operating loading rates, entrained air-incidental flotation, poor hydraulics due to uneven inlet flow splitting. Optimization of Filtration: Water is passed through a dual media (sand and anthracite) filter, which removes many remaining pollutants. Many water treatment facilities use filtration to remove all particles from the water. Banff et al. presented that a “good” filter performance should be presented by many conditions, such as; consistently less than 0.3 NTU, particle counts less than 50 particles/mL, long and predictable filter runs (24+hours), minimal premature particle breakthrough. Poor performance can be difficult to rectify, but many issues can be resolved with simple fixes. He also presented that “good” filter design should be presented by many conditions, most efficient media design has largest media at the top and the finest at the bottom, however, backwashing immediately re-classifies bed to place the finest grains at the surface, therefore use multi-media to mimic this effect, with coarse grains in the top layer to trap solid sand finer layer below for polishing. In the other research James reported that the increased passage of particles and microorganisms through granular media filters immediately following backwashing is a common problem known to the water treatment community as filter ‘‘ripening’’ or maturation. While several strategies have been developed over the years to reduce the impact of this vulnerable period of the filtration cycle on finished water quality, this research involves a recently developed filter backwashing strategy called the Extended Terminal Sub fluidization Wash Filter (ETSW). Their research concludes that optimality of the coagulation process was also shown to influence magnitude of filter ripening particle passage. Extended Wash, generally falling out of favour, but common in Terminal Sub fluidization Wash on filtration is a method of terminating the backwash cycle with a sub fluidization. 15

Optimization of Disinfection: Chlorine is added to the water to kill and/or inactivate any remaining pathogens. Fluoride is added to prevent tooth decay and a rust inhibitor is added to preserve the pipes that deliver the water to homes and businesses. Water is often disinfected before it enters the distribution system to ensure that potentially dangerous microbes are killed. Nikolaou et al. and Chaiket et al. reported that occurrence of disinfection byproducts (DBPs) in drinking water has been an issue of major concern due to their adverse health effects. Application of disinfection processes during water treatment leads to the formation of disinfection by-products. The development and optimization of analytical methods for the determination of Disinfection by Products in water are key points in order to estimate human exposure after water treatment. In the other research Huseyin et al. reported that much attention that

the

purpose of intermediate oxidation is to degrade toxic micro pollutants and to remove chlorinated by-product precursors. Remarks for Optimization of Water Treatment Plant: Based on many articles which discuss about optimization of particles of water treatment plant, their researches have given us the basic scientific informations. From Franceschi et al, we could conclude on flocculation-coagulation process that; optimization of the residual turbidity needs to retain only a few parameters as opposed to the optimization of minimally added Aluminium Sulfate concentration.; there is an antagonistic influence of the different parameters on the two studied responses turbidity and aluminium sulfate so it is impossible to simultaneously optimize both of them. We also could conclude from Huseyin et al. that after pre-ozonation, alum coagulation was applied and it was found that pre-ozonation enhanced the efficiency of alum coagulation; however Bromate removal was insignificant at the optimum alum concentration. 16

James found that Extended Terminal Sub fluidization Wash (ETSW) on filtration was shown to remove significantly greater quantities of backwash remnant particles thereby reducing the magnitude of filter ripening turbidity and particle count spikes. Optimum Extended Terminal Sub fluidization Wash flow rates were determined for deep-bed anthracite and granular activated carbon filters herein by monitoring filter effluent turbidities. Extended Terminal Sub fluidization Wash was found to be equally effective for biological and conventional deep-bed anthracite filters. This paper discusses dissolved air flotation (DAF) applied to drinking water treatment. It was first applied to drinking water treatment in the late 1960s in Scandinavia and South Africa. The process is particularly efficient in removing low density particles and flocs. DAF is a good clarification process for treating supplies of low to moderate turbidity, and those containing algae and natural color. It has found increasing favor over sedimentation processes for treating these type supplies, and it is now widely used world-wide. The DAF reactor has two functions, to provide collisions or contact opportunities between air bubbles and flocs, and to provide removal of the floc-bubble aggregates. The paper describes bubble properties, bubble suspension concentrations, and bubble characteristics, and contact zone model. Model variables are discussed beginning with the role of pretreatment coagulation chemistry and flocculation for successful bubble attachment and collisions of flocs with bubbles. The importance of bubble size and concentrations is addressed and the separation zone modeling is also summarized. Rise velocities of floc-bubble aggregates are compared to separation zone theory and hydraulics. Some applications are presented on the removals of algae and protozoa pathogens by DAF, and on recent trends of designing DAF plants with short flocculation times and high hydraulic loadings.

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2.1 OBJECTIVES OF PROJECT 1. Water must be distributed in sufficient quantity and pressure at all times. 2. Storage capacity at the source as well as at intermediate points of the distribution system, should maintain the water pressure and flow within the conventional limits. 3. Maintenance of distribution system must be planned, implemented and controlled at the same optimum level contemplated for the design, construction and operation of the treatment facilities and the projection of the water source. 4. Contaminants must be eliminated or reduced to safe level to minimize menacing waterborne diseases and formation of long-term or chronic injurious health effects. 5. Water quality cannot be monitored without adequate laboratories facilities.

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CHAPTER 3 WATER QUALITY ANALYSIS

3.1 CHRACTERTICS OF WATER The raw or treated water is analyzed by testing their physical, chemical and bacteriological characteristics: 1. Physical Characteristics  Turbidity  Colour  Taste and odour  Temperature

2. Chemical characteristics  pH  Acidity  Alkalinity  Hardness  Chlorides  Sulphates  Iron  Solids  Nitrates

3. Bacteriological Characteristics: Bacterial examination of water is very important, since it indicates the degree of pollution. Water polluted by sewage contains one or more species 19

of disease producing pathogenic bacteria. Pathogenic organisms cause water borne diseases, and many non pathogenic bacteria such as E.Coli, a member of coliform group, also live in the intestinal tract of human beings. Coliform itself is not a harmful group but it has more resistance to adverse condition than any other group. So, if it is ensured to minimize the number of coliforms, the harmful species will be very less. So, coliform group serves as indicator of contamination of water with sewage and presence of pathogens. The methods to estimate the bacterial quality of water are:  Standard Plate Count Test  Most Probable Number  Membrane Filter Technique 3.2 PHYSICAL CHARACTERISTICS OF WATER Various physical properties of water are discussed below 3.2.1 Turbidity If a large amount of suspended solids are present in water, it will appear turbid in appearance. The turbidity depends upon fineness and concentration of particles present in water. Originally turbidity was determined by measuring the depth of column of liquid required to cause the image of a candle flame at the bottom to diffuse into a uniform glow. This was measured by Jackson candle turbidity meter. The calibration was done based on suspensions of silica from Fuller's earth. The depth of sample in the tube was read against the part per million (ppm) silica scales with one ppm of suspended silica called one Jackson Turbidity unit (JTU). Because standards were prepared from materials found in nature such as Fuller's earth, consistency in standard formulation was difficult to achieve. These days turbidity is measured by applying Nephelometry, a 20

technique to measure level of light scattered by the particles at right angles to the incident light beam. The scattered light level is proportional to the particle concentration in the sample. The unit of expression is Nephelometric Turbidity Unit (NTU). The IS values for drinking water is 10 to 25 NTU. 3.2.2 Colour Dissolved organic matter from decaying vegetation or some inorganic materials may impart colour to the water. It can be measured by comparing the colour of water sample with other standard glass tubes containing solutions of different standard colour intensities. The standard unit of colour is that which is produced by one milligram of platinum cobalt dissolved in one litre of distilled water. The IS value for treated water is 5 to 25 cobalt units. 3.2.3 Taste and odour Odour depends on the contact of a stimulating substance with the appropriate human receptor cell. Most organic and some inorganic chemicals, originating from municipal or industrial wastes, contribute taste and odour to the water. Taste and odour can be expressed in terms of odour intensity or threshold values. A new method to estimate taste of water sample has been developed based on flavour known as 'Flavour Profile Analysis' (FPA). The character and intensity of taste and odour discloses the nature of pollution or the presence of microorganisms. 3.2.4 Temperature The increase in temperature decreases palatability, because at elevated temperatures carbon dioxide and some other volatile gases are expelled. The

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ideal temperature of water for drinking purposes is 5 to 12 °C - above 25 °C, water is not recommended for drinking. 3.3CHEMICAL CHARACTERISTICS OF WATER Various chemical characteristics of water are discussed below 3.3.1 pH pH value denotes the acidic or alkaline condition of water. It is expressed on a scale ranging from 0 to 14, which is the common logarithm of the reciprocal of the hydrogen ion concentration. The recommended pH range for treated drinking waters is 6.5 to 8.5. 3.3.2 Acidity The acidity of water is a measure of its capacity to neutralize bases. Acidity of water may be caused by the presence of uncombined carbon dioxide, mineral acids and salts of strong acids and weak bases. It is expressed as mg/L in terms of calcium carbonate. Acidity is nothing but representation of carbon dioxide or carbonic acids. Carbon dioxide causes corrosion in public water supply systems. 3.3.3 Alkalinity The alkalinity of water is a measure of its capacity to neutralise acids. It is expressed as mg/L in terms of calcium carbonate. The various forms of alkalinity are (a) hydroxide alkalinity, (b) carbonate alkalinity, (c) hydroxide plus carbonate alkalinity, (d) carbonate plus bicarbonate alkalinity, and (e) bicarbonate alkalinity, which is useful mainly in water softening and boiler feed water processes. Alkalinity is an important parameter in evaluating the optimum coagulant dosage.

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3.3.4 Hardness If water consumes excessive soap to produce lather, it is said to be hard. Hardness is caused by divalent metallic cations. The principal hardness causing cations are calcium, magnesium, strontium, ferrous and manganese ions. The major anions associated with these cations are sulphates, carbonates, bicarbonates, chlorides and nitrates. The total hardness of water is defined as the sum of calcium and magnesium concentrations, both expressed as calcium carbonate, in mg/L. Hardness are of two types, temporary or carbonate hardness and permanent or non carbonate hardness. Temporary hardness is one in which bicarbonate and carbonate ion can be precipitated by prolonged boiling. Noncarbonate ions cannot be precipitated or removed by boiling, hence the term permanent hardness. IS value for drinking water is 300 mg/L as CaCO3. 3.3.5 Chlorides Chloride ion may be present in combination with one or more of the cations of calcium, magnesium, iron and sodium. Chlorides of these minerals are present in water because of their high solubility in water. Each human being consumes about six to eight grams of sodium chloride per day, a part of which is discharged through urine and night soil. Thus, excessive presence of chloride in water indicates sewage pollution. IS value for drinking water is 250 to 1000 mg/L. 3.3.6 Sulphates Sulphates occur in water due to leaching from sulphate mineral and oxidation of sulphides. Sulphates are associated generally with calcium, magnesium and sodium ions. Sulphate in drinking water causes a laxative effect and leads to scale formation in boilers. It also causes odour and corrosion problems under aerobic conditions. Sulphate should be less than 50 mg/L, for some industries. 23

Desirable limit for drinking water is 150 mg/L. May be extended upto 400 mg/L. 3.3.7 Iron Iron is found on earth mainly as insoluble ferric oxide. When it comes in contact with water, it dissolves to form ferrous bicarbonate under favourable conditions. This ferrous bicarbonate is oxidised into ferric hydroxide, which is a precipitate. Under anaerobic conditions, ferric ion is reduced to soluble ferrous ion. Iron can impart bad taste to the water, causes discolouration in clothes and incrustations in water mains. IS value for drinking water is 0.3 to 1.0 mg/L. 3.3.8 Solids The sum total of foreign matter present in water is termed as 'total solids'. Total solids are the matter that remains as residue after evaporation of the sample and its subsequent drying at a defined temperature (103 to 105 °C).Total solids consist of volatile (organic) and non-volatile (inorganic or fixed) solids. Further, solids are divided into suspended and dissolved solids. Solids that can settle by gravity are settleable solids. The others are non-settleable solids. IS acceptable limit for total solids is 500 mg/L and tolerable limit is 3000 mg/L of dissolved limits. 3.3.9 Nitrates Nitrates in surface waters occur by the leaching of fertilizers from soil during surface run-off and also nitrification of organic matter. Presence of high concentration of nitrates is an indication of pollution. Concentration of nitrates above 45 mg/L causes a disease methemoglobinemia. IS value is 45 mg/L.

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Table 3.1 Physical Indian standards for drinking water

Desirable–tolerable

If no alternative source

limits

available, limits extends upto

Turbidity (NTU unit)