Peat Bed Filters for On-site Treatment of Septic Tank Effluent

The addition of a bed of peat, approximately 600 mm deep, as a treatment mechanism for reducing the impact of septic tank effluent (STE) on the receiving environment (land or water) has been shown to be significant. By regular dosing of a Biogreen peat filter through a pressurised distribution system to maintain an aerobic environment, reductions in typical STE contaminants can be achieved. At Tingha, on the Northern Tablelands of New South Wales, seven on-site systems have had biological filters installed, each comprising a blended peat product from Biogreen’s peat resource in Colac, Victoria. Five of these on-site systems are being monitored to evaluate the treatment of STE through the peat filter. By sampling from both the septic tanks and the peat beds, direct comparisons for each system are being made. To date, the monitoring program has shown the success of the peat filtering systems in providing beneficial treatment of the STE by removing much of the potentially contaminating components from the effluent, prior to its ultimate treatment in the soil. Results show that faecal coliforms (FC) have been reduced by 99.46%, total nitrogen (TN) by 44.2% and total phosphorus by 83.6%. Of similar significance is the oxidation of ammonia to nitrate and the beneficial loss of odour nuisance from the effluent. The predictions, based upon the above results, are that there will be a likely improvement in nitrogen removal, ongoing reduction in FC and a gradual increase in phosphorus levels moving through the peat until it is life-expired in relation to peat. Overall the results confirm Biogreen peat’s reduction in contamination of highly permeable soils in a system that is almost maintenance free and does not rely upon any change in the behaviour of residents.