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While the pilot projects confirmed that the ASAS concept and the theoretical design were sound, a number of modifications were needed. For example, unforseen quantities of soil entered the system through the showers and laundry troughs, so we decided to connect these drains directly to the septic tank. Furthermore, the presence of odours indicated the need to 'inoculate' or 'seed' the tanks. Dry horse manure gave good results. In addition a ventilation pipe was installed as a precaution. It also became clear that it would be convenient to insert a cleaning access junction or control box with a screen in the septic tank discharge pipeline to the sewers. |
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Observations on the use of the sanitary units and fixtures, water consumption and operation of tanks and sewers were made. Measurements of sludge and sullage were taken, and analysis of BOD5, pH and suspended, dissolved and total solids were made on samples of the septic tank effluents and the final sewer effluent. The BOD5 ranged between 72 and 184 mg/1, with an average of 140 mg/1. The suspended solids results in the tank effluents when only toilets and kitchen sinks were connected to the tanks ranged between 130 and 160 mg/1. At the sewer outlet, when the showers and laundry troughs were included, the readings were very close to 40 mg/1. Compared with the sewage of the city, which had an average of 250 mg/1 for both BOD5 and suspended solids, reductions of 4060 per cent for BOD5 and about 84 per cent for suspended solids were obtained. For sludge accumulation rates, the calculated average was 10.2 litres per person per year. Scum formation was erratic. In those tanks where scum was detected, the average was 3.5 litres per person per year. |
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Based on these results, adjustments were made to the ASAS design for the Southeast Zone and Pasacaballos, and were presented in the final report of the study presented in September 1982. |
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10.2.7
Subsequent Observations and Adjustments. |
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During 1983 measurements of sludge and scum were made in the pilot projects. These indicated very little formation of scum and |
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