Biological filter beds usually consist of a mineral media over which effluent to be treated percolates. The media becomes host to a biomass which is grazed by a series of more complex organisms. If the growth of the biomass is greater than the rate at which the grazing occurs then the biomass film will accumulate in the bed. This will block the interstices of the media and restrict effluent drainage and ventilation of the bed. Under these conditions ammonia oxidation (nitrification) is usually the first to suffer however reduction in BOD removal can also be frequently observed.

Greener Waste Ltd is a Process Engineering and Environmental Consultancy specialising in the Municipal sector. Following several years of extensive research Greener Waste Ltd has advanced the unique bio-augmentation technology which has been successfully introduced to a number of water companies. The concepts are being successfully used in wastewater treatment to optimise processes which suffer from excess FOG, BOD overload, poor nitrification, and poor sludge quality.

A small works treating a DWF of 848m³/day and a FFT of 27l/sec. The works comprises screening and grit removal, conventional primary settlement, Two high-rate plastic filter media primary filters(4.5 m deep) followed by humus settlement, and a conventional single blast furnace slag media secondary filter(1.8m deep) followed by humus settlement.