Integrated mechanical, biological and physico-chemical treatment of liquidmanure streams

The results obtained during the first year of execution of a joint Russian- Dutch project "The development of integrated anaerobic-aerobic treatment of liquid manure streams with maximisation of production of valuable by-produ cts (fertilisers, biogas) and re-utilisation of water" (1999-2001) are disc ussed. The application of a straw filter was an effective means to separate the solid and liquid fractions of diluted pig manure wastewater and result ed in the removal of a significant part of the dry matter, total nitrogen a nd phosphorus (65, 27 and 32%, respectively). From the filtrate generated, 60-80 % of the COD was removed in a UASB reactor operating at 20-30 degrees C. Up to 66% of phosphate was precipitated after air stripping of the CO2 from the anaerobic effluents. Ammonia was efficiently removed (>99%) from t he anaerobic effluents using zeolite (Ural laumantite) as an ion exchanger However, the N-content of the resulting zeolite was too low to be used as a fertiliser. A feasible alternative for nitrogen elimination involved nitri fication of the anaerobic affluent followed by denitrification in a UASB re actor using the COD of the filtrated manure wastewater as carbon source.