THE INFLUENCE OF WASTE-WATER TYPE AND ORGANIC LOADING ON THE PROTOZOAN AND METAZOAN POPULATION OF A PEAT BED FILTER

Three peat bed filters treating wastewaters with differing proportions of industrial input were compared experimentally by analysis of their population structure. The plants were all full scale and served villa ge communities around Madrid, Spain. All three plants showed a high ci liated protozoan population density (>10(5)/l), but the least loaded s ystem, which received only domestic wastewater, exhibited a 10 fold gr eater abundance and a predominance of Paramecium. The plants with an i ndustrial input performed less well and showed a population structure predominated by Chilodonella and Colpidium as well as having substanti al populations of nematodes and rotifers. Protozoans may contribute to wards an enhanced BOD and COD removal efficiency and can be used as in dicators of optimum oxygenation conditions with the peat bed.