In 3 out of 4 Polar Breweries in Venezuela, waste water is purified by the activated sludge method. About 5 million litres/day are treated yielding about 25 metric tons/brewery/day of waste thickened by decantation. This sludge contains nitrogenous substances, phosphorus, calcium, potassium and trace metals, copper, iron, manganese and zinc as well as organic matter. The high contents of salts and trace metals have a toxic effect on plants when the wastes are applied to certain soils hence a region of sandy, permeable soil of poor nutrient content called ultisoil in Guanipa in eastern Venezuela was selected for the field trials. Dry sludge was applied to the soil at levels between 1 and 35 tons/ha (0.4 and 14 tons/acre) and mixed. Maize, sorghum and peanuts were cultivated on the soils and gave much higher yields than controls. Maximum yields were obtained with between 10 and 20 tons/ha. Horticultural trials with sludge added to soil showed that asparagus, chili, cucumber, tomatoes and watermelons first sown in plastic cups then transferred to soil mixed with sludge showed faster and stronger growth than controls. Compost from waste sludge, spent grains and garden waste produced by the aerated stationary pile method gave high yields of vegetables and fruits when mixed with poor soils.
Keywords : activated sludge agriculture brewery disposal effluent sludge waste