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African Environmental Development Portion 129 of the farm Sterkfontein 173 IQ Mogale City Republic of South Africa African Environmental Development PO Box 1588 Rant-en-Dal 1751 Tel & Fax: - (+27) 11 956 6537 or 083 657 0560 E-mail: - [email protected] http://www.aed.co.za African Environmental Development THE "GEM" MINI SEWAGE TREATMENT PLANT Direction of flow Introduction: For many centuries, a septic tank coupled to a French drain soak-away has been the only choice of sewage and wastewater treatment and disposal in areas not connected to a municipal sewerage system. This has worked fine in many areas for many years. However, an increase in the incidence of groundwater contamination and restrictions on the use of French drains within certain municipal areas and in regions located on certain rock types prone to the development of sinkholes (such as dolomite) and in certain other environmentally sensitive areas, has prompted us to look at more modern alternatives to the conventional septic tank / French drain combination. Furthermore, the shortage of water in many regions in Africa has made it necessary to re-use water as far as practical. We are therefore proud to announce a modern-day alternative to the septic tank / French drain, the “GEM” Mini Sewage Treatment Plant manufactured by Ballam-Waterslot (Pty) Ltd. The “GEM” Mini Sewage Treatment Plant is an on-site sewage treatment plant capable of producing an effluent, which complies with the General Effluent Standard (as promulgated in Government Notice 991/9225 of 18/05/1984), the current standard for sewage effluent for most areas in South Africa. In essence, the “GEM” Mini Sewage Treatment Plant is a compact sewage treatment plant employing principles of anaerobic and aerobic (activated sludge) biological sewage treatment used by all municipal sewage treatment plants in South Africa. The “GEM” Mini Sewage Treatment Plant is merely a miniature version of a municipal sewage treatment plant. 148090894 Page 1 of 8 Created on 11/06/2004 08:38:00 African Environmental Development Portion 129 of the farm Sterkfontein 173 IQ Mogale City Republic of South Africa African Environmental Development PO Box 1588 Rant-en-Dal 1751 Tel & Fax: - (+27) 11 956 6537 or 083 657 0560 E-mail: - [email protected] http://www.aed.co.za African Environmental Development Advantages of the “GEM” Mini Sewage Treatment Plant The biological processes used have been proven and have been used in all types of sewage treatment plants for many years. Low cost, low maintenance, hygienic solution. Prevents groundwater pollution, as there is no need for a French drain soak-away. Prevents the spread of waterborne diseases. Installation and commissioning is relatively simple. It produces an effluent free of odours and can be installed close to dwellings/buildings. No need for a 2-pipe system as is the case with septic tanks. The unit treats all wastewater from toilets, baths, wash-hand basins, washing machines and dishwashers. The unit is designed for a normal household of up to 6 people (calculated at 200 litres per person per day). The ultimate solution in replacing pit latrines and/or bucket systems, subject to a water supply and a 220V power supply being made available. The effluent water produced by the unit is safe to use for irrigation under controlled conditions. Ideally suited for single households, caravan parks, clinics, schools, game reserves, lodges, offices, coastal chalets, public toilets, ablution blocks, etc. where a municipal sewer connection is not available. Any application where the General Effluent Standard for sewage effluent is applicable and a compact unit is required. Ideally suited in areas where the soil and/or geological formations exclude the use of French drains due to the potential risk of groundwater contamination or sinkhole formation or in environmentally sensitive areas such as the Cradle of Humankind World Heritage Site, located almost exclusively on dolomitic limestone. 148090894 Page 2 of 8 Created on 11/06/2004 08:38:00 African Environmental Development Portion 129 of the farm Sterkfontein 173 IQ Mogale City Republic of South Africa African Environmental Development PO Box 1588 Rant-en-Dal 1751 Tel & Fax: - (+27) 11 956 6537 or 083 657 0560 E-mail: - [email protected] http://www.aed.co.za African Environmental Development Technical Data and Operating Principles The “GEM” Mini Sewage Treatment Plant makes use of natural biological processes to purify the sewage water and it does this in three stages. The First Stage (Anaerobic Digestion) The first stage of the plant makes use of anaerobic bacteria to break down the complex organic material in the sewage to simpler organic molecules. This phase is similar to a septic tank where anaerobic bacteria (bacteria that live in the absence of oxygen) are used to break down the complex organic molecules. The by-products produced by these bacteria are mostly gases such as methane, hydrogen sulphide and carbon dioxide. These gases are vented off through the normal ventilation system of a building’s sewage pipe system. Using anaerobic digestion, around 40% of the organic substances found in sewage can be broken down. To remove the rest of the organic substances to a concentration that complies with the General Effluent Standards, a further aerobic process is required. The Second Stage (Aerobic or Activated Sludge Section) The second stage of the “GEM” Mini Sewage Treatment Plant is the aerobic treatment section. Here a different type of bacteria is grown, aerobic bacteria (bacteria that requires oxygen to break down organic substances found in sewage). Aerobic bacteria are much more efficient than anaerobic bacteria in the breakdown of organic matter found in sewage, but require excessive amounts of oxygen. For this reason, the “GEM” Mini Sewage Treatment Plant is fitted with a small compressor, which uses only 180W of power. The compressed air is diffused into very small bubbles through a stainless steel diffuser at the bottom of the aerobic section of the “GEM” Mini Sewage Treatment Plant and apart from keeping the bacteria in suspension, also provides oxygen for the bacteria. The type of aerobic bacteria grown in the second stage of the “GEM” Mini Sewage Treatment Plant tends to group together in the form of “flocks”. The second part of the aerobic section of the “GEM” Mini Sewage Treatment Plant is used to separate the aerobic bacterial 148090894 Page 3 of 8 Created on 11/06/2004 08:38:00 African Environmental Development Portion 129 of the farm Sterkfontein 173 IQ Mogale City Republic of South Africa African Environmental Development PO Box 1588 Rant-en-Dal 1751 Tel & Fax: - (+27) 11 956 6537 or 083 657 0560 E-mail: - [email protected] http://www.aed.co.za African Environmental Development flocks from the purified water. The clean water then flows to the third stage of the “GEM” Mini Sewage Treatment Plant, while the bacterial flocks are re-circulated to the aerated section of the plant so that they can continue to perform their water purifying work. In order to recirculate the bacterial flocks, an airlift pump is used. The airlift pump is powered by compressed air from the same compressor that provides air for the aerobic bacteria in the second (aerobic) section of the plant. After a while, the population of bacteria in the second section of the “GEM” Mini Sewage Treatment Plant will become too large. Provision has therefore been made to continuously “waste” small amounts of these bacteria to the first (anaerobic) section of the plant. Here the anaerobic bacteria consume the “wasted” aerobic bacteria in a similar manner as the way they “consume” organic matter in the raw sewage entering the system. The Third Section – Disinfection By the time the treated water (effluent) leaves the second (aerobic) stage of the plant, the organic load in the sewage that entered the “GEM” Mini Sewage Treatment Plant has been brought down to acceptable levels. There may, however, still be pathogenic bacteria left in the effluent water from the second aerobic stage of the plant. For this reason a disinfection section is provided as the final stage of the sewage water treatment process. The disinfection section of the “GEM” Mini Sewage Treatment Plant comprises of a chlorinator that uses a cartridge of chlorine tablets. The type of chlorinator used on the “GEM” Mini Sewage Treatment Plant is simple to use and to adjust. The grey top of the chlorinator is simply removed; the old chlorine cartridge is removed and replaced with a new one. To adjust the amount of chlorine dosed, the grey cap is merely screwed in deeper. Calibration marks on the side of the chlorinator indicates the dosage. One cartridge of chlorine tablets should last between 6 and 12 months, depending on the number of people occupying the house/premises. What to do with the effluent? Although the effluent is not purified to a drinking standard, it is nevertheless safe and may be used in a variety of applications. There are many ways the 148090894 Page 4 of 8 Created on 11/06/2004 08:38:00 African Environmental Development Portion 129 of the farm Sterkfontein 173 IQ Mogale City Republic of South Africa African Environmental Development PO Box 1588 Rant-en-Dal 1751 Tel & Fax: - (+27) 11 956 6537 or 083 657 0560 E-mail: - [email protected] http://www.aed.co.za African Environmental Development final effluent produced by the “GEM” Mini Sewage Treatment Plant may be utilised. The most useful application of the effluent is to irrigate it onto lawns, gardens or crops. In this case, effluent will have to be stored in some form of reservoir until enough effluent has accumulated for irrigation. Please also adhere to the safety principles discussed hereunder. In general, a plastic lined reservoir is the simplest method of storing effluent water produced by the “GEM” Mini Sewage Treatment Plant. It can also be turned into an attractive water feature by installing a water fountain in the reservoir. When sufficient water has been accumulated, a centrifugal pump may be employed to spray the effluent onto gardens, etc. If enough of a slope is present, the water could be gravitated onto the crops intended for irrigation. A second alternative to storage is to direct the effluent into an artificial wetland. This wetland could ultimately discharge into a pond or it could be constructed in such a manner that it would use all the water within the wetland through evapotranspiration. Please always keep the environmental considerations, discussed hereunder, in mind when designing and constructing such a wetland. There are many other industrial and domestic uses for sewage effluent not discussed in this pamphlet. 148090894 Page 5 of 8 Created on 11/06/2004 08:38:00 African Environmental Development Portion 129 of the farm Sterkfontein 173 IQ Mogale City Republic of South Africa African Environmental Development PO Box 1588 Rant-en-Dal 1751 Tel & Fax: - (+27) 11 956 6537 or 083 657 0560 E-mail: - [email protected] http://www.aed.co.za African Environmental Development Product Specifications From the outside, both of the units look identical. Internally, however, they differ considerably. The unit specifications of the housings are as follows: Construction continuous injection moulding Height: 1.4 m (base to manhole lid) Diameter: 1.2 m Length: 1.5 m per unit Approximate dimensions of excavation for installation: 1.5m deep x 1.5m wide x 4.5m length Construction cylindrical ribbed with dome ends Weight 40 Kg Chambers 2 (both units) Total capacity 1200 litres Fluid working capacity 1000 litres Wall thickness 5 mm Inlet and outlet diameter standard 110 mm, both fitted with screw-in inspection eyes Manhole diameter 450 mm Manhole lid design provision for filling with concrete ballast Manhole access extension 500 mm No metallic components used in tank construction Stainless steel aeration diffusers used in aeration tank Manufacturer of compressor Becker Manufacturer of chlorinator Klorman Time between de-sludging 5 to 10 years, depending on the amount of inorganic matter, such as sand, allowed into the sewer ahead of the plant. Environmental Management and Safety Considerations Although the “GEM” Mini Sewage Treatment Plant is intended to replace the septic tank / French drain entirely in all areas not serviced by a municipal sewer, it was primarily designed to be used in environmentally sensitive areas or in areas where the geology is such that septic tanks / French drains are not permitted, i.e. where groundwater contamination or sinkhole formation may result from French drains. As described above, an anaerobic septic tank does not purify sewage water to nearly the same quality as an aerobic process. The following items are therefore listed as an environmental/safety guide when installing or operating the “GEM” Mini Sewage Treatment Plant. 148090894 Page 6 of 8 Created on 11/06/2004 08:38:00 African Environmental Development Portion 129 of the farm Sterkfontein 173 IQ Mogale City Republic of South Africa African Environmental Development PO Box 1588 Rant-en-Dal 1751 Tel & Fax: - (+27) 11 956 6537 or 083 657 0560 E-mail: - [email protected] http://www.aed.co.za African Environmental Development Safety Considerations Never drink the treated effluent. It has not been treated to a drinking water standard. Mark any taps with effluent water with a clear “nondrinking water” sign. Always treat raw sewage water with respect. It may contain pathogenic bacteria (bacteria that could transmit diseases to people coming into contact with the water). Always wear protective clothing and gloves and wash your hands with disinfectant soap immediately after handling any untreated sewage or sanitary fittings. Although chlorine is one of the most efficient disinfectants used in the water treatment industry, do not assume that the effluent is safe. The chlorinator may not be adjusted correctly. Always treat effluent as if it may contain pathogenic bacteria. When irrigating the effluent, never allow it to be sprayed directly onto people or animals. Do not irrigate treated effluent onto vegetables or fruit that are normally eaten raw. When irrigated onto the lawns of sports fields, always allow for at least two days of drying in the sun before any sports activities are allowed on the field, especially in the case of sports where people may fall and come into direct contact with the lawn. Adhere to open dam safety principles, especially when there are children around that cannot swim. Always protect all open dams with some type of barrier similar to that used around swimming pools. When there are children around, ensure that concrete ballast is cast in the lids of the two manholes to prevent them from opening the manholes. If a person falls into one of the units drowning could result. Environmental Considerations Never allow effluent to be discharged directly onto ground near a drinking water borehole. This is of particular importance if the underlying geology is dolomite. As a rule of thumb, provide for a distance of at least 100m from any borehole. In dolomite, however, there may be preferential access routes directly into the groundwater from much further distances. Also keep the distance from your neighbours’ boreholes in mind! If effluent water is discharged into an artificial wetland, always ensure that the wetland is constructed on impermeable soil or alternatively, construct such a wetland using an impermeable lining. Never allow water to stand in a permanent un-lined pond in areas underlain with dolomite. This practice may lead to the formation of sinkholes and could also contaminate the groundwater. 148090894 Page 7 of 8 Created on 11/06/2004 08:38:00 African Environmental Development Portion 129 of the farm Sterkfontein 173 IQ Mogale City Republic of South Africa African Environmental Development PO Box 1588 Rant-en-Dal 1751 Tel & Fax: - (+27) 11 956 6537 or 083 657 0560 E-mail: - [email protected] http://www.aed.co.za African Environmental Development Ensure that there are no leaking pipes/couplings, especially pipes containing raw sewage en route to the sewage treatment plant. This may lead to groundwater contamination. Do not discharge the effluent produced by any sewage treatment plant directly into any public stream without a water license from the Department of Water Affairs and Forestry. Under normal circumstances, a sand trap or grease trap is not fitted ahead of the plant. Under conditions where there may be excessive grease or sand/gravel entering the plant, it is recommended to install these in order to protect the plant from premature siltation. African Environmental Development is the distributor for the “GEM” Mini Sewage Treatment Plant in East, Central and West Rand and, more importantly, in the Cradle of Humankind World Heritage Site. One of the very first units installed in South Africa was installed at our offices in the World Heritage site in an environmentally sensitive area, with dolomitic caves, including the world-famous Sterkfontein Caves, within a stone’s throw from our premises. Customers are welcome to visit us to view the unit at our offices first hand. We also install units in whichever configuration most suits your location, environment, effluent application and budget. Please contact us at any time for more information relating to the product and its installation. 148090894 Page 8 of 8 Created on 11/06/2004 08:38:00