Over a period of three months two filtration methods, i.e. cross flow microfiltration and continuous sand filtrations were tested for their capacity to improve the quality of the effluent from a waste water treatment plant. The removal capacity of both methods was explored for suspended solids, COD, Kjeldahl nitrogen phosphorus, copper and zinc with and without iron flocculation. Without iron flocculation only the suspended solids can be removed. Iron has to be added prior to removal so that suspended solids and phosphorus can be removed in sufficient quantities. In that case, total P can be removed for 70% by means of continuous sand filtration, and for 90 % when microfiltration is being applied. The removal of COD, nitrogen Kjeldahl, copper and zinc is confined to 10 or 20%.
From a technical point of view, microfiltration is preferred because of its high removal efficiency for all the components. On the other hand, from a financial point of view, microfiltration is not feasible. Treatment costs for sand filtration and microfiltration are calculated at f 0.15 and f 2.07 respectively per m3 water treated.