Abattoir layout and construction.pdf

ABATTOIR LAYOUT AND CONSTRUCTION 1. 2. 3. 4. 5. 6. 7. 8. 9. 10 11. 12.

INTRODUCTION LAYOUT FLOW DIAGRAM OF A RED MEAT ABATTOIR CLEAN AND DIRTY PRODUCTS PLANNING FACTORS TO BE CONSIDERED WHEN CHOOSING A SITE ABATTOIR DESIGN GRADES OF AND REQUIREMENTS FOR ABATTOIRS STANDARD DESIGN DRAWINGS FOR RED MEAT ABATTOIRS THE USE OF WATER IN THE ABATTOIR DISPOSAL OF ABATTOIR EFFLUENT SEPTIC TANK SYSTEMS

2

ABATTOIR LAYOUT AND CONSTRUCTION 1.

INTRODUCTION An abattoir is a food factory and its primary aim is to produce a healthy, wholesome and clean product, which is safe for consumption. A well-designed and constructed structure is needed to systematically “break” down the animal that is slaughtered. The further the process progress, the greater the risk of contaminating the product. Prevention thereof is determined by the layout and the flow patterns, which the product follows. Hygiene is the prevention of contamination of the product Each function in the slaughter process has a fixed status in terms of “Clean” or “Dirty”. In choosing the premises, this important aspect must be taken into consideration. “Clean” and “Dirty” areas are separated by distance, physical barriers and in certain cases by time.

2.

LAYOUT The layout of the premises and building must be designed so that the production process moved in one direction without any crossflow of products, which may adversely affect the hygiene of the product. Live slaughter animals are received at the “dirty” end of the abattoir and meat is out loaded from the clean side of the abattoir. “Dirty” area • Livestock entrance. • Vehicle wash bay for trucks that transported animals. • Offloading platforms and facilities for marking animals. • Lairage where animals are kept until they are slaughtered (shade for pigs and sheep). • Ante mortem inspection. • Isolation lairage for animals that are or might be sick. • Emergency slaughter facilities for hurt animals. • A post mortem inspection area for animals which arrive dead or die in the lairage. • Facilities where animals can be restricted and efficiently stunned. • Bleeding area. • Area for electrical stimulation of ruminant carcasses. • Facilities where condemned products are handled. • Areas/rooms where inedible products are handled e.g. hides/pelts horns etc. • Including facilities for sorting grading and weigh. • Room for the cleaning and sometimes processing of rough offal. • Disposal of solid waste such as paunch and intestinal contents. • Areas where rough offal is packed and cartoned.

3 • Chiller or freezer facilities for rough offal. • Dispatch area for rough offal. • Effluent pre-purification plant and holding tanks. • Facilities for the processing of condemned products to by-products such as blood/carcass meal and tallow • Cloakrooms, toilets, showers, washing facilities and dining room where only workers of the dirty areas have access. • Store rooms for dirty area. • Maintenance workshops. “Clean” area: • Slaughter hall for the dressing of animals under hygienic conditions with facilities for separating the different components. • Area for inspection of the carcass and other edible portions in order to determine in fitness for human consumption and to prevent the spread of disease to humans and animals. • Facilities for the retention for secondary inspection of carcasses which are suspect. • Grading and weighing of carcasses as part of the marketing function. • Chilling of carcasses to ensure that the quality of the product is maintained and the optimal shelf life ensured. • Freezer facilities for storing provisionally approved carcasses with slight measles contamination. • Sorting and loading of carcasses in a cooled area to ensure that the cold chain is not broken. • Dispatch facilities. • Washing bay for meat trucks. • Office accommodation and ablution facilities for meat inspectors. • Office for management. • Laundry facilities. • Laboratories. • Cloakrooms, toilets, showers, wash facilities and dining room where only workers in the clean area have access. • Store rooms.

3.

FLOW DIAGRAM OF A RED MEAT ABATTOIR The diagram below gives some idea of the working of a larger red meat abattoir. Personnel movements are however not shown.

4

FLOW DIAGRAM FOR A RED MEAT ABATTOIR RECEP TION - OFFLOADING

ANTE-MORTEM

POST-MORTEM AREA DEAD ON ARRIVAL

DESTROY

INJURED/UNFIT ANIMALS

KILL & DESTROY

INSPECTION LAIRAGE

ISOLATION PEN

STUNNING HOISTING BLEEDING

EMERGENCY SLAUGHTER

Dirty area

Dirty area Clean area REMOVAL OF HEADS AND FEET

HEADS AND FEET ROOM

OUTLOADING

HIDES AND SKINS ROOM

OUTLOADING

ROUGH OFFAL CLEANING ROOM

OUTLOADING

REMOVAL OF HIDES/SKINS

EVISCERATION CARCASS SPLIT

CONDEMNED TRIMMINGS/ORGANS (LOCKABLE CONTAINERS)

Dirty area

PRIMARY MEAT INSPECTION DETAIN AREA CARCASSES PASSED

SECONDARY MEAT INSPECTION:

CONDEMNATION ROOM OUTLOADING

FINAL WASH

CARCASSES PASSED CARCASSES CONDEMNED

HANGING HALL

CHILLING

DEBONING BONES TO RENDERING

QUARTERING / MARSHALING

CHILLED / FROZEN PACKED PRODUCTS

OR PROCESSING

(CONDEMNATIONS)

RENDERING PLANT (DIRTY SIDE)

RENDERING PLANT (CLEAN SIDE)

Clean area

OUTLOADING

OUTLOADING

OUTLOADING

(CARCASSES)

(PACKAGED MEAT)

(CARCASS MEAL)

5

4.

CLEAN AND DIRTY PRODUCTS Clean products: • Dressed carcass (includes head and feet in pigs) • Red offal: Lungs Pancreas Diaphragm Kidneys if removed Heart Diaphragm if removed Tongues Heifer udders if removed Liver Sweetbreads (Thymus) Tail Clean fat (omentum) Spleen Testes Dirty products: Edible: • Rough offal: Paunch and oesophagus Intestines Head – skin on Feet – skin on Inedible: • • •

Hides skins Horns Hair hooves snout

Condemned products: • •

5.

Blood, male/female reproductive organs including lactating udders/penis, gall bladder. Carcasses and portions of meat condemned by the meat inspector/veterinarian which poses a possible health threat. Such material must be held under secure conditions until disposed of in accordance with legislation.

PLANNING Anyone intending to erect an abattoir must pay attention to the following during the preliminary viability study rather than spend money to no purpose on actual planning: (i)

Make sure that a meat inspection service can be provided. A written undertaking by the provider of this service must accompany the application.

(ii)

Obtain approval in writing for the project from the local authority in whose area the abattoir is to be erected. This might be any one of the following: (a) (b) (c)

(iii)

6.

Municipality Local Government Board Department of Health

Make sure at this stage whether the site has the necessary zoning for abattoir use.

FACTORS TO BE CONSIDERED WHEN CHOOSING A SITE The choice of a suitable site for an abattoir is most important. The factors listed below must therefore be taken into account when selecting a premises:

6.1

ENVIRONMENT No source of contamination should occur in the environment in which we place an abattoir: examples are a paint factory, foundry, sewage farm, river or residential area. Abattoirs are classified as light industries. Because water pollution does occur, the abattoir should be a reasonable distance away from any river.

6 6.2

GEOLOGICAL STRUCTURE AND FEATURES Drainage is affected by the nature of the soil - sandy or loam, by the water table and the natural slope of the surface.

6.3

SITE DIMENSIONS The site must be large enough to allow the abattoir and allied activities to be correctly situated and oriented. Provide also for future extensions. Lairages must not be situated on higher ground than the buildings, nor must they be closer than six metres to them.

6.4

SERVICES Water – An adequate supply of potable water must be available. Consideration should also be given to the storage and treatment of water should this be necessary. Effluent disposal – An effective system for the disposal or removal of effluent must be provided where necessary. Electricity – There must be a reliable source of power for heating water as well as to provide for the partial or total mechanisation of the abattoir.

7.

ABATTOIR DESIGN

7.1

PREMISES (a)

Must be fenced with lockable gates in order to control the unauthorised entry of vehicles, persons and animals.

(b)

The layout of the site should be such that a linear flow pattern can be maintained with live bird reception on one side and the removal of products on the other.

(c)

"Clean" and "dirty" areas must be separated according to their functions as previously mentioned.

(d)

Other factors affecting the placing of the abattoir and allied operations on a site are:

(e)

(i)

Prevailing winds – Must blow from the "clean" side to the "dirty" side.

(ii)

Natural slope – Rainwater and runoff from the dirty area must not flow into the abattoir, nor must they flow from the dirty to the clean side of the premises. Tanks for the collection of effluent and pre-purification plants must be situated at the lowest point of the site, on the dirty side.

(iii)

Water supply – There is often a need for storage tanks, chlorination tanks and pressure tanks. These must be on the clean side, preferably at the highest point.

(iv)

Access roads and staff separation – If this is required for the relevant grade, the "clean" and "dirty" areas of the premises must be physically separated. Vehicles which offload live animals, loads intestines heads and feet as well as vehicles removing paunch contents, condemned material and refuse are restricted to the "dirty" area and may not enter areas where meat vehicles and staff who handle meat are to be found.

Surfaces on the site must be paved or grassed. Traffic areas in the smaller abattoirs must have a surface that is dust and mud free, readily cleanable and well drained. The traffic zones of larger abattoirs must have a permanent surface. The planting of grass and shrubs creates a pleasant environment and gives the impression that the premises are well managed and cared for. From the point of view of industrial psychology it has been found that the more attractively a site is maintained, the easier it is for the workers to accept and adjust to the high standards of hygiene expected of them; they are also more likely to do so.

7

7.2

(f)

All paved areas must provide for stormwater drainage.

(g)

Vehicle parking areas where birds are offloaded or meat is loaded must have kerbstones and be drained so that they can be cleaned every day. Dirt that is washed onto grass is impossible to remove.

(h)

Walkways for staff between the ablution block and the abattoir must preferably be roofed.

(i)

Specific areas such as collection points for manure from holding pens and paunch contents must also be paved, drained and provided with kerbstones.

ABATTOIR WORK AREAS In designing an abattoir the principle of a linear flow pattern, is of utmost importance to prevent the contamination of carcasses and meat. This aim can be achieved by correct internal abattoir design. patterns of people and products.

The layout must eliminate cross-flow

General guidelines:

7.3

(a)

During processing, product flow must be from dirtier to cleaner areas, zones or rooms. These products must not come into contact with the floor or walls, or even with equipment like platforms, and must remain within the building until dispatched.

(b)

Drainage must be from clean to dirty.

(c)

The airflow must be from clean to dirty.

(d)

Product flow lines must not intersect or cross.

(e)

Backtracking must be avoided.

(f)

Products derived from slaughtering and dressing must be removed from the slaughter area as quickly as possible. Heads and skins must not be carried or passed under or around dressed carcasses on route to the exit point.

(g)

"Warm" and "cold" working areas must be distinguished.

(h)

Staff must take the shortest routes when moving to their workstations.

(i)

Hand washbasins must be readily accessible to all workers, at a distance not exceeding three metres from any workstation, which handles products. Hand washbasins must be available at raised platforms. Where manual equipment is in use, sterilisers must be provided in combination with the hand basins. Taps must be operated with the foot or knee.

FACILITIES FOR STAFF (a)

Cloakroom facilities, toilets, showers and dining room facilities sufficient for the number of workers on the premises must be provided.

(b)

From C- Grade physical separation is required for the various categories of workers.

(c)

Staff facilities must be planned so that total separation is achieved between cloakroom/ shower and toilet/urinal areas. Hand basins or wash troughs with taps controlled not by hand but preferably with the foot or knee must be provided at the exit of these facilities.

(d)

A storeroom for overalls, equipment and clean manual implements, normally required for the work, must be provided.

(e)

Cleaning agents, soap and chemicals must be stored separately.

8

8.

GRADES OF AND REQUIREMENTS FOR ABATTOIRS All abattoirs must comply with statutory grading requirements. The higher the grade of the abattoir, the higher the requirements, because a higher throughput enlarges the risk of contamination The throughput determines the basis for the grade of the abattoir. It is regulated as follows: Grade E Grade D Grade C Grade B Grade A

-

1-8 slaughter units 9-15 slaughter units 16-50 slaughter units 51-100 slaughter units More than 100 slaughter units

Definitions: 1 slaughter unit:

1 Cold room unit:

1 Bovine (cattle) 1 Horse 15 Pigs 15 Sheep

1 Bovine (cattle) 1 Horse 2 Pigs 6 Sheep

Government Gazette R.1028 of 26 May 1989 fully spells out the specific requirements laid down for the different grades of abattoirs: Requirements for Grade E red meat abattoirs 1.

A red meat abattoir may be graded as a Grade E red meat abattoir if it complies with the following requirements: (a)

The throughput thereof shall not exceed eight slaughter units.

(b)

Roads on the premises thereof shall be so surfaced to be dust and mud free.

(c)

Lairage facilities shall be available, and shall (i) be sufficient to keep at least the number of slaughter units to be slaughtered there in the course of four hours: Provided that if animals stay overnight in an adjacent grazing paddock and can be brought quietly from there immediately prior to slaughter, lairage facilities need not be provided; (ii) be provided with concrete floors with an adequate slope to ensure the drainage of water; and (iii) be located at a lower level than the abattoir building.

(c)

Facilities shall be available to restrain and stun animals in a humane manner prior to slaughter.

(d)

A slaughter hall, which may also serve as a dry landing area and bleeding area where animals are bled in a hanging position, shall be available.

(f)

A solid partition of at least three metres high, behind which rough offal is emptied, cleansed and kept prior to removal, shall be available within the abattoir building.

(g)

Such partitioned area shall have an exterior door for the removal of unskinned heads, feet, stomachs and intestines. Hanging facilities, calculated at 0,75 metre length of rail per chiller unit, shall be available for carcasses and red offal.

(h)

(i)

A door, which is used exclusively for the removal of carcasses and red offal, shall be available.

(i) Covered loading facilities for the removal of carcasses and red offal shall be available.

9 (k)

Suitable equipment (excluding a scalding tank for pigs) shall be available for the efficient performance of all functions required in terms of the Act in connection with the slaughter and dressing of animals and the inspection of meat.

(l)

Theft proof containers and facilities shall be available for the collecting and disposing of meat and animal products which have been condemned in terms of section 27 (b) (i) of the Act.

(m)

Change-rooms, toilets and shower and wash facilities shall be available for all persons who perform functions at such abattoir.

(m)

An efficient drainage system and facilities for handling effluent shall be available.

(o)

Facilities for the storage of supplies needed for the effective operation thereof shall be available.

Requirements for Grade D red meat abattoirs 2.

A red meat abattoir may be graded as a Grade D red meat abattoir if it complies with the following requirements: (a)

The throughput thereof shall not exceed 15 slaughter units.

(b)

Unless otherwise determined in this clause, it shall comply with the requirements set out in clause 1.

(c)

Roads on the premises thereof shall be provided with a suitable surface in order to render it dust and mud free.

(d)

Lairage facilities shall be available, and shall be sufficient to keep at least the number of slaughter units to be slaughtered there in the course of four hours.

(e)

Suitably equipped stunning areas shall be available for all the kinds of animals that are slaughtered there: Provided that if different kinds of animals are not slaughtered simultaneously, the same stunning area may be used for different kinds of animals.

(f)

A dry landing area and bleeding area that are separated from the dressing area shall be available for each kind of animal slaughtered there: Provided that if different kinds of animals are not slaughtered simultaneously, the same dry landing area and bleeding area may be used for different kinds of animals.

(g)

Separate rooms shall be available in which -

(h)

(i)

rough offal such as unskinned heads, feet and trotters, as well as inedible offal such as hides, skins, hair, horns, hooves and feathers in the case of ostriches are kept prior to removal;

(ii)

rough offal such as stomachs and intestines are emptied, cleansed and kept prior to removal; and

(iii)

red offal such as thyme, pancreases, livers, spleens, kidneys, hearts, lungs, tails, oesophagi, diaphragms, omenta and, in the case of heifers, udders are handled and kept if it is not conveyed with the carcasses.

Facilities, including a side rail, shall be available for the keeping of meat and animal products detained in terms of section 27 (b) (ii) of the Act and condemned in terms of section 27 (b) (I) of the Act.

Requirements for Grade C red meat abattoirs 3.

A red meat abattoir may be graded as a Grade C red meat abattoir if it complies with the following requirements: (a)

The throughput thereof shall not exceed 50 slaughter units.

10 (b)

Unless otherwise determined in this clause, it shall comply with the requirements set out in clause 2.

(c)

It shall be designed and erected in such a manner that “dirty” and “clean” parts and functions at the abattoir are separated, and for this purpose (i)

(d)

(e)

“dirty” parts shall include a l irages, washing facilities for conveyances of animals (if provided), stunning areas, dry landing areas, bleeding areas, a de-haring room, areas and rooms where inedible offal is handled on rough offal is handled, chilled and frozen, as well as eating areas, change-rooms, toilets and shower and wash facilities for persons employed in said parts, and entrances to such facilities, rooms and areas; and (ii) “clean” parts shall include the slaughter hall, areas and rooms where carcasses and red offal are handled, chilled and frozen, loading facilities for carcasses and red offal and washing facilities for conveyances or meat (if provided), as well as office accommodation and eating areas, change-rooms, toilets and shower and wash facilities for persons employed in said parts, and entrances to such facilities, rooms, parts and accommodation. Separate rooms shall be available for the handling of (i) Unskinned head and feet; and (ii) hides, skins, hair, horns, hooves, and feathers in case of ostriches. A room shall be available for the keeping of meat and animal products, detained in terms of section 27 (b) (ii) of the Act, and has been condemned in terms of section 27 (i) of the Act, and such room shall be equipped in such manner that such meat and animal products can be sorted and re-arranged within that room.

(f)

Hanging facilities shall be adequate for the carcasses and red offal of the slaughter units that are slaughtered and dressed there in the course of two hours.

(g)

Refrigeration facilities shall be available for the carcasses and edible offal of the throughput thereof: Provided that if edible offal is removed from the abattoir within four hours after an animal has been slaughtered, refrigeration facilities for the edible offal of such animal need not be provided.

(h)

An area for the quartering, sorting and marking of carcasses and meat shall be available between the refrigeration facilities and the covered loading facilities.

Requirements for Grade B red meat abattoirs 4.

A red meat abattoir may be graded as a Grade B red meat abattoir if it complies with the following requirements: (a)

The throughput thereof shall not exceed 100 slaughter units.

(b)

Unless otherwise determined in this clause, it shall comply with the requirements set out in clause 3.

(c)

The air temperature within the area for the quartering, sorting and marking of carcasses and meat shall be maintained at not more than 10 degrees Celsius while meat is being handled.

(d)

Washing facilities shall be available for the conveyances in which animals are brought there.

(e)

Separate office accommodation and change-rooms shall be available for meat inspection personnel.

Requirements for Grade A red meat abattoirs 5.

A red meat abattoir may be graded as a Grade A red meat abattoir if it complies with the following requirements:

11 (a)

The throughput thereof may exceed 100 slaughter units.

(b)

Unless otherwise determined in this clause, it shall comply with the requirements set out in clause 4.

(c)

Separate rooms shall be available for the keeping of meat and animal products detained in terms of section 27 (b) (ii) of the Act, and for the keeping of meat and animal products condemned in terms of section 27 (b) (I) of the Act.

(d)

Separate change-rooms, toilets and showers and wash facilities shall be available for the persons who dispose of condemned meat and animal products referred to in paragraph (c).

(e)

It shall have ante mortem, isolation and post mortem facilities available, and shall have access to laboratory facilities.

Requirements for export abattoirs 6.

An abattoir from which meat or animal products are exported shall at least comply with the requirements for a Grade C, Grade CP or Grade CH abattoir, as the case may be, as well as any additional requirements as determined by the appropriate authority in the country to which such meat of animal products are to be exported.

Exceeding of throughput Provincial Director: Veterinary Services may on application grant written authority that the throughput of an abattoir may exceed the maximum determined in this notice: It is suggested that the of llowing throughputs will be regarded as the maximum allowed for that specific grade of abattoir. Red meat: E D C B A

15 30 80 150 >150

The following criteria should be considered when assessing an application for a higher throughput.

9.

(a)

Available facilities i.e. hanging space, cold room capacity, water supply, capacity of the effluent disposal system etc.

(b)

Proven managerial ability.

(c)

Ability of applicant to maintain hygiene standards at the abattoir concerned.

(d)

Effectivity of meat inspection and the correct method of disposing of condemned and not used material.

STANDARD DESIGN DRAWINGS FOR RED MEAT ABATTOIRS The following floor plan drawings serve to give some insight into the lay out of smaller animals.

12

GRADE-E RED MEAT ABATTOIR

13 GRADE-D ABATTOIR

14 GRADE-C (PART 1)

15 GRADE-C (PART 2)

16

10

THE USE OF WATER IN THE ABATTOIR The average water consumption of an A grade abattoir can be analysed as follows: 1. 2. 3. 4. 5. 6. 7.

Lairage Slaughter and dressing Offal processing Heating water Creating steam Cooling Ablution, laundry, etc.

10% 20% 25% 25% 5% 8% 7%

LEGAL ASPECTS REGARDING THE USE OF WATER IN ABATTOIRS Three Acts in particular have relevance to the application of water in an abattoir: The Abattoir Hygiene Act 1992 (Act 121 of 1992) and the Standing Regulations in terms of this Act The Act and Regulations prescribe the availability and quality of the water used in abattoirs: Regulations 2 and 6 of Part III of the Standing Regulations prescribe the following: A water supply of at least 900 litres per slaughter unit must be available under pressure and protected against contamination. The water must be clean, potable and free of suspended material and substances which could put health at risk. The water must be subjected to flocculation, filtration, chlorination or other treatment to ensure that: (a)

there are no coliform organisms present;

(b)

it contains not more than 100 viable micro-organisms per millilitre.

An adequate supply of hot water at 60°C and of cold water under pressure must be available during working hours in convenient places. The water must also meet any other standards and conditions which the Director: Veterinary Services may lay down from time to time. The Water Act 1956 (Act 54 of 1956), as amended by the Water Amendment Act 1984 (Act 96 of 1984) This Act and its Amendment regulate the use of water for industrial purposes, and abattoir owners are advised to obtain a copy of this Act and to study it carefully, especially the Amendment. Bye-laws issued by local authorities Abattoir owners must familiarise themselves with the bye-laws issued by their local authority. GUIDELINES FOR THE TESTING OF WATER The following guidelines have been laid down by the Director: Veterinary Public Health in respect of bacteriological and chemical tests on water used in abattoirs. A, B and C grade red meat abattoirs (a)

Bacteriological testing every month.

(b)

Chemical testing every six months.

17 D and E grade red meat abattoirs (a)

Bacteriological testing once a year.

(b)

Chemical testing once a year, except where water comes from a borehole in which case it must be tested twice a year, in the wet and the dry season.

The aim of regular water testing is to ensure that water used in abattoirs complies with the requirements laid down in Regulation 2 of Part III of the Standing Regulations. User code, SABS 241 - 1984 "Specifications for water for domestic use" is a guideline (a)

Physical requirements Colour - The colour must not exceed the following: Recommended limit: Maximum permissible limit:

20 mg/1 platinum Not specified

Smell and taste - The smell and taste must not be objectionable. (b)

Chemical requirements: The pH-value must be within the following limits: Recommended limit: Permissible limit:

6,0 min.9,0 max. 5,5 min.9,5 max.

The conductivity of water must not exceed the following: Recommended limit Permissible limit:

: 70 mS/m 300 mS/m

The macrodeterminants (macroconstituents) of water must meet the requirements laid down in column 2 or 3 as applicable. TABLE 1 - MACRODETERMINANTS 1 Determinant, mg/l Total hardness Magnesium Sodium Chloride Sulphate Nitrate + Nitrite Fluoride Zinc

2 Recommended limit 300 max. 70 max. 100 max. 250 max. 200 max. 6 max. 1,0 max. 1,0 max.

3 Maximum permissible limit 650 100 400 600 600 10 1,5 5,0

The microdeterminants (microcomponents) of the water must meet the requirements laid down in column 2 or 3 as applicable.

18 TABLE 2 – MICRODETERMINANTS 1

2

3

Determinant ìg/l

Recommended maximum limit

Maximum permissible limit

100 10 500 200 100 50 50 5 5 20

300 20 1000 300 1000 100 1000 10 10 50

Arsenic Cadmium Copper Cyanide Iron Lead Manganese Mercury Phenol compounds Selenium

The water must not contain any other substances in concentrations which make it unsuitable for domestic use. If radio-activity is present, it must be within the limits laid down by the International Commission for Radiological Protection. The abattoir owner must keep meticulous records of the results of bacteriological and chemical tests. All expenses incurred are the responsibility of each individual abattoir owner. (c)

Bacteriological requirements When tested according to the methods in Column 4 of Table 3, the water must satisfy the requirements in column 2 or 3 as applicable.

TABLE 3 - BACTERIOLOGICAL LIMITS 1 Property

2 Recommended maximum limit

3 Maximum permissible limit

4 Test method subdivision

Nil*

5

5,2

Count of faecal coliform bacteria per 100 ml

Nil

Nil

5,3

Standard plate count per millilitre

100

Not specified

5,4

Total count of coliform bacteria Per 100 ml

* (a)

If any coliform bacteria are found in a sample, take a second sample immediately after the tests on the first one have been completed; this sample must be free from coliform bacteria; and

(b)

a maximum of 5% of the total number of water samples from a given network tested per year may contain coliform bacteria.

19

11. DISPOSAL OF ABATTOIR EFFLUENT The volume of waste water from abattoirs is 80 – 85% of the water intake. This waste water typically contains the following contaminated waste material: blood, bits of meat, fat, paunch contents, urine and dung. Each of these waste materials contributes to a high organic load as well as a considerable amount of suspended material in the waste water. The management and treatment of waste water is a specialised subject and professional advice from consulting engineers is essential. Most abattoirs including large ones make use of municipal sewerage systems. Where these facilities are not available alternative arrangements must be made in consultation with officers of the Department of Water Affairs. Care must in all cases be taken to avoid contamination of natural streams and water sources. Removal of as much of the solid waste in the effluent is essential in making further processing of effluent more manageable. Excessive amounts of solids in affluent may lead to exorbitant levies by municipalities or the overloading of systems on the abattoir premises. In a system where solids are removed effectively, the remaining fluid may be disposed of percolation system (French drain)or used to irrigate lands.

in a

It is important that sewerage from toilets are not mixed with abattoir effluent but is channelled to a septic tank system associated with a French Drain.

12. SEPT IC TANK SYSTEMS Based on a CSIR technical guide K86 of the Institute for Water Research A septic tank system usually consists of two main components: 1. 2.

the septic tank the final disposal system, that is usually an underground seepage furrow.

Each of these components has specific functions and should be designed accordingly The functions of the components Raw sewerage will clog the soil, causing ineffective absorption by the sub-soil. The septic tank, however, will condition the incoming sewerage, separating the solids from the liquid phase by either setting to the bottom or collecting at the surface (float). This results in the formation of three distinct layers : • Layer of sludge on the bottom, • A floating layer of scum on top and • A relatively clear liquid layer in the middle. Bacterial digestion of organic material will cause liquefaction of the solids with associated gas formation – thus reducing the solids volume. The only function of a soil disposal system is to get rid of the effluent from the septic tank in a safe and inoffensive manner. Designing requirements 1.

Septic tank (a) (b) (c) (d) (e)

The tank must function both as a sedimentation tank as well as a digester. The capacity of the tank should be large enough to provide ample retention time for inflowing sew erage. Possible clogging of the in- and outlet and internal pipes must be limited to a minimum. Provision should be made for ventilation for gasses to escape. The possibility of passage of sludge and scum to the soil percolation system must be avoided as far as possible.

20 2.

Sub-soil percolation system (a) (b) (c) (d)

The nature of the soil to a large extent determines the shape and size of the system. Locations should be such that it does not create a danger for public health or pollute either ground- of surface water. The clogging effect of the effluent on the surface soil must be avoided Facilitate full use of the available infiltration area.

Public Health aspects of septic tank systems In built up areas, this system should be seen as a temporary measure. There is practically no difference between the effluent from a septic tank and raw sewerage as far as potential danger for public health is concerned. Organisms causing disease can be present in the effluent of the septic tanks. In communities where drinking water is derived from boreholes, it is usually unwise to make use of a septic tanks system. Combined and separate disposal systems Two types of disposal systems are in use: 1.

A separate system for the ablution facilities (cloakrooms, toilets and kitchens) utilising a septic tank and a separate or common soil percolation system

2.

A second system for the abattoir effluent incorporating the necessary solids/fat traps and sedimentation tanks to remove solids (pieces of meat and fat). Effluent from this system can be discharged in a separate of the same common soil percolation system

Designing criteria 1.

Volume sewerage water

Abattoirs require a water supply of at least 900 litre per slaughter unit. The water must be available at an effective pressure and be protected against pollution Average water consumption at a A-grade abattoir can be subdivided into: Holding pens Slaughter and dress Offal area Warm water Steam Chilling Ablution

10% 20% 25% 25% 5% 8% 7%

The volume of effluent in approximately 80 – 85% of water required Typical abattoir effluent contains blood, pieces of meat, fat and gut. Constant urine and dung in suspension. Each of these contributes to a very high organic load. 2.

Septic tanks

(a)

Location: Local authorities usually have by-laws determining the minimum distances for the placing of septic tanks from buildings and boundaries. It is recommended that the tank be located near to a driveway to facilitate cleansing by means of a vacuum tanker. From a health point of view it is sufficient to have a soil cover of 150 to 200 mm over the system.

21 (b)

Capacity: Calculation of capacity is based on usage per person per day with a retention period of 24 hours in the septic tank to provide for separation of scum and sludge thus providing for a relatively clear effluent.

(c)

Shape proportions and compartmentation: For tanks of a given capacity and depth, the shape of the tank is relatively unimportant. The liquid depth should be between 1 and 2 meters. Single compartment tanks usually give acceptable performance but if a tank is divided vertically into two compartments with the first compartment half to two thirds of the total volume, the amount of suspended solids removed from the effluent is greater

(d)

Inlet, outlet and inter-compartment arrangements: The illustration indicates the positioning of the above in terms of the water level. To accommodate the scum accumulation, the distance between the waterline and the roof of the tank should at least 20 percent of the water depth.

(e)

Access and ventilation: The different compartments/components should be accessible for inspection and maintenance. The location of man holes should be as such that admission is easily obtained to pipes that could block. Ventilation is usually through the inlet sewer to the vent pipe against the wall of the building.

(f)

Materials: Septic tanks should be constructed of materials such as concrete, bricks, coated steel or any other materials which are not subject to excessive corrosion.

Design and construction of soil percolation system (a)

Location : Percolation trenches should be located where dangerous pollution of ground water is least likely to occur.

(b)

Suitability of the soil : There is no simple test to accurately determine if soil is suitable to absorb the effluent. standard SABS-test gives an indication and can be used as a guide-line.

The

The relative proportion of sand, silt and clay determine the texture of the soil and influences the absorbing ability. The larger and more unifo rm the particles, the faster the percolation rate. Yellow and reddish-brown soils usually have good absorption quality, whereas a dull-grey (high clay content) has not (c)

Trench design: The bulk of the effluent enters the soil through the side walls of th e trench. Deep narrow trenches are therefor preferable to wide shallow trenches. A permeable layer, covered with impervious strata will require a deep trench, while the permeable topsoil, with permeable sub-soil will call for shallow trenches.

(d)

Trench construction: Trenches should be constructed along the contours. Where two more trenches are adjacent to each other the distance in between should be twice the depth. After excavation the sides of the trenches should be roughened to restore the natural surface. Filling material should be clean and free of dust or silt.

22 The size of the filling material is not critical and can be from 6 mm to 75 mm or more. It is advisable to have a layer of fine gravel or coarse sand against the infiltration surfaces. The trench should be filled with gravel to about 100 to 150 mm from the top. Prior to back-filling, a layer of finer gravel should be placed on top to prevent soil from entering the trench. If the length of the trench is in excess of 6 m it will become necessary to provide an open jointed distribution pipe. The trench should be approximately 4 m in length for every 1000 litres given average absorption of the soil Maintenance Septic tanks require effective maintenance. When scum and sludge gets discharged into the percolation trenches, the septic tank should be emptied and the silt and foam should be removed. If this is not done, the seepage system can be damaged permanently. When a ground seepage system starts clogging, there is little to be done, but proper usage of the septic tank can extend the life time of the furrows considerably.

23

24