Whereas hygienic measures deal with the operational aspects of slaughter or the creation of conditions under which animals, activities and personnel can be secured from contaminating the product, sanitation is focussed on the establishment and maintenance of healthy environmental and appropriate physical conditions congenial to the attainment of a wholesome product. In essence, the two concepts are identical, culminating in the same end-result, but differing in targets.
In this connection, the scope of sanitation may be identified broadly with structures and facilities, i.e. the premises, installation and equipment, that is their disposition and maintenance. Additionally, sanitation covers specific slaughter operations that are likely to cause contamination, e.g. offal cleaning, waste disposal and infestation by pests, etc. This chapter, like the previous one, will collate aspects of the subject already touched upon as well as add new information.
The influence of siting, design and construction of slaughter premises on sanitation has been dealt with at length in Chapter 2. In summary, the following guidelines are offered.
The ideal site for a slaughterhouse should be fairly airy, outside built up areas and possibly close to the coast, if such a location is available. Established townships if close to the premises could easily be the source of air-borne contaminants from households or industries. The area must be open, preferably on high ground, to keep drainage from stagnating in the surroundings. Alternatively, the area must be dry and not waterlogged or puddled as these could cause mosquito breeding. River, lake and lagoon sites must be avoided partly for the above reason, but chiefly to prevent livestock from drinking from them if polluted as well as to eliminate the temptation of discharging slaughter wastes into the waters, which could be drinking sources for humans.
Finally, the site must be large enough to accommodate auxiliary slaughter functions or structures such as holding pens (kraals), an emergency slaughterslab and a byproducts plant. The immediate vicinity should be cleared of all bush, and roadways leading to and from the premises must be well laid out and paved.
Materials used in constructing and equipping the plant (Chapter 3) must be durable. Specifically they must be impervious to water, easy to clean and to sanitize, non-corroding and not attractive to insects or termites.
Demarcation must be made of the slaughter/dressing zone from the offal/waste handling areas, and these areas from personnel places of convenience such as bathrooms and toilets. The interior of all rooms and chambers should have ample lighting and ventilation: lighting to facilitate the work and ventilation to flush out stagnant air and enhance the keeping of the product.
Of operational facilities needed, water is most important. Standards in industrialized countries stipulate the use of ample potable water from the public or municipal supply system. The water must be colourless, odourless and free from organic matter. It must also be well conditioned to eliminate, for instance, ‘hardness’ and be properly distributed in the plant such as at strategic points with hosing where necessary. Hot as well as cold water is necessary.
In the developing countries, these conditions may be difficult to attain especially in rural areas. Some municipalities can only clarify water, but not treat, sterilize or condition it; consequently in some towns pipe-borne water is boiled prior to drinking.
Many rural slaughter outlets draw their water supplies from the same source, river or lake, which may serve also for washing, bathing and even drinking, not to mention occasional waste disposal. Even where dug-outs and wells are available, the quality of water can still not be guaranteed unless a treatment plant is available to assure safety for use in slaughter operations.
Large quantities of clean water are required in the cleaning of floors, walls, equipment and tools. The operation should begin with removal of solid waste such as meat and fat trimmings, bone chips, blood clots and so on by brushing them off the floor. High pressure hosing is then applied, starting from the walls and other rigid facilities and ending with the floors. Hot hosing under pressure is more ideal as it melts down fat and removes sticky waste from corners and drains.
For scrubbing of tables, working surfaces and tools, hard fibre brushes and detergents are recommended. Liquid detergents are more useful than ordinary soaps, because they dissolve more easily in water by reducing the hardness while absorbing dirt or attaching themselves to it for removal by flushing with water. If liquid detergents are not available, powdered soap may be dissolved in water and used. After rinsing the washed items should be disinfected. Knives must be sharpened and sterilized or boiled in water.
(a) Large Slaughterhouse
The wastes from a large slaughterhouse are a heavy polluter of any recipient. The waste water from a meat plant should be allowed into a municipal drainage system without previous thorough treatment in a waste water treatment plant. The details of such treatment are outside the scope of this manual. An outline is however given in order to show the size of the problem.
In the slaughter premises, the general principle regarding waste disposal is that initially, the solids and sweepings from operational waste (of the dressing chamber and offal floors) must be removed from the liquid. Secondly, the operational Liquid must be separated from the conventional drainage, namely that of toilets and bathrooms. The two lines should be kept apart within the premises well to the outside before being joined together.
The purpose of this is to prevent contamination of the premises in the event of a back-up of conventional sewage in the early stages of discharge. A catch-basin must be provided to collect residual solids, especially fat to prevent clogging of the system. Clogging can also result from discharge and coagulation of blood in the drainage and create further back-up problems. Thus by collecting blood in special containers, much inconvenience is avoided and valuable raw material provided for byproduct processing (Chapter 10).
The principle of handling liquid waste from the common outside drainage system is first to screen out, collect and cart off solid matter. The rest is then let into a basin in which the finer and lighter particles settle while fat is skimmed off, including suspended organic matter which is sedimented from the water phase. (A sludge is formed which can be collected and added to manure and processed together (Chapter 10).)
In the second phase of the treatment, bacterial breakdown of dissolved substances in the water phase takes place. This process requires oxygen to convert organic matter into simple inorganic substances. The latter are removed by physical treatment or by chemical means. At this stage the water is considered treated, though not recommended for human use. It can be used for agricultural purposes or discharged into water bodies.
(b) Rural Slaughter Premises
These premises pose a problem as investment in waste treatment plants is too high in comparison with the low work load. Far easier and safer is to bury all solid and semi-solid waste along with manure in pits to make compost. Blood should, however, be collected separately and dried into blood meal. Both processes are described in Chapter 10.
The liquid effluents can be spread out on the ground at some distance from the plant for quick drying as they empty on a slope from deep concrete drains away from the plant. Straw bedding should be placed on the ground initially to absorb the liquid and re-layered at each time of disposal. The site should be constantly maintained to ward off vermin (see below).
The term “vermin” is applied to creatures which by nature like living close to man, scavenging on food and filth. In slaughter premises, the commonest vermin are rats, mice, flies and cockroaches. All multiply in great numbers within a short time.
The dangers posed by these creatures is that they live in hidden places such as splits, holes and crevices in floors and walls gathering dirt on their skin, appendages, mouth or mouthparts with which they contaminate food, sometimes destroying the food outright. Furthermore, by their contamination of food, they are capable of transmitting disease mechanically to man. In the case of rats, they can cause food poisoning, rabies, typhus fever and bubonic plague among other diseases.
Cleanliness and general environmental sanitation basically keeps them away, as accumulation of waste, refuse, manure etc. soon attracts them to slaughter premises. Doors and windows should be secured against all possible openings to ward off vermin. The insect group are usually kept off by flyproof and fly trap devices as well as gauze screenings, while rodents are at best exterminated by chemical poisons. However, caution should be exercised in the use of chemical exterminators as some of them often have harmful effects on man.