Design Construction And Performance Evaluation Of A Model Waste Stabilization Pond

The study aimed at the design, construction and performance evaluation of a model Waste Stabilization Pond (WSP). The WSP comprised of one facultative pond and three maturation ponds all in series. The influent of the WSP after filtration through the lined sandy loam media (obtained from the premises of Federal University of Technology, Owerri, Nigeria) had the BOD reduced to 22 mg/L from 356 mg/L indicating a 93.8% removal level. A faecal coli form count (fc) of the influent sample gave 1×108 fc/100 mL, whereas the effluent gave 10 fc/100 mL which was 99.9% fc removal. The value of 150 mg/L of the Total Suspended Solids (TSS) for the influent was reduced to 26 mg/L for the effluent after treatment. It was concluded that the effluent from the WSP was within the limits of Federal Environmental Protection Agency (FEPA) standard of 30 mg/L for TSS, 30 mg/L for BOD 5 and 400 fc/100 mL for faecal coli form thus making the waste water safe for discharge into surface water as well as its use for irrigation after treatment. The sandy loam soil media was found to be non-promising earlier in the removal process until it was lined with polyethylene material. A clay media was therefore recommended.

As urban and industrial development increases, the quantity of waste/water generated also increases. These wastes pose a serious threat to public health when they are not treated and not readily disposed of.

Waste Stabilization Ponds (WSP) often referred to as oxidation ponds or lagoons is a method of wastewater treatment, suitable for use in hot climates. It consists of series of shallow lakes (ponds namely anaerobic, facultative and maturation) through which waste water flows. Treatment occurs through natural, physical, chemical and biological processes and no energy or machinery is required except sun light energy. According to Arthur (1983), stabilization ponds are the preferred waste water treatment process in developing countries where land is often available at reasonable cost and skilled labour is in short supply.

Usually, anaerobic and facultative ponds are designed for BOD removal and maturation ponds for pathogen removal although some BOD removal occurs in maturation ponds and some pathogen removal in anaerobic and facultative ponds (Mara et al., 1998).

The most appropriate wastewater treatment is that which will produce an effluent meeting the recommended microbiological and chemical quality guidelines both at low cost and with minimum operational and maintenance requirements (Arar, 1988).

A World Bank report (Shuval et al., 1986) endorsed the concept of stabilization as the most suitable wastewater treatment system for effluent use in agriculture.

The choice of a site to construct a pond system requires an area where the water table is deep and the soil is heavy and impermeable. Silt or clay soils are ideal for pond foundations and construction. Building ponds over coarse sands, gravels, fractured rock or other materials, that will allow effluent to seep out of the pond or allow groundwater to enter in, should be avoided (Agunwamba, 2000).

Generally, ponds should be located at least 200 m (preferably 500 m) downwind from the community they serve and away from any likely area of future expansion (Mara et al., 1998).

Therefore, the objectives of the study are to design and construct a model waste stabilization Pond and to evaluate its performance.