A REVIEW OF THE SUSTAINABLE VALUE OF EFFLUENTS AND SLUDGES FROM WASTE-WATER STABILIZATION PONDS

Sludges and liquids from wastewater stabilization ponds are cost effec tive by-products useful for agriculture, aquaculture and for manufactu ring building materials. They represent valuable sustainable resources as raw materials to support fisheries for human consumption, to produ ce animal feed derived from single cell algal proteins and aquatic wee ds. Biogas from waste fermentation represents a significant tertiary p roduct. Stabilization ponds are dynamic, low-cost waste recycling ecos ystems comprising complex communities of algae, virus, protozoa, rotif ers, insects, crustaceans and fungi. These organisms interact and modi fy the organic content of the waste to produce effluents which need li ttle further investment in treatment. The economic, societal and susta inable value of stabilization ponds is governed by the management regi me and the use for which the sludge and effluent is intended. Fish, du cks, prawn and algal protein production rely upon adequately treated e ffluent. This is particularly valuable for irrigation in arid and semi -arid climates, where natural waters are insufficient and nutrient dep leted. Oxidation ponds provide sustainable mechanisms for dealing with sewage and for reducing the risk of infection from parasites and the effects of toxins. The resulting sludges can be used as fertilizer or be composted with local vegetation. Aerobic and anaerobic digestion, l ime treatment and pasteurisation are used to improve sludge acceptabil ity and utility to enhance its value as a sustainable resource.