Anaerobes, aerobes and phototrophs (A winning team for wastewater management)

Abstract

Current mainstream technologies for wastewater treatment, such as activated sludge and tertiary nutrient removal, are too costly to provide a satisfactory solution for the increasing wastewater problems in developing regions. Besides, these technologies do not allow for re-use of valuable energy and nutrients contained in the wastewater. In light of these limitations, it is important to reconsider the technology and strategic approaches in wastewater management. This paper introduces the ‘Cleaner Production’ concept to sewage management, which combines two approaches: pollution prevention and re-use. Pollution prevention includes a shift towards low water use sanitation technology. The more concentrated wastewater, becomes more attractive for re-use oriented treatment schemes. A combination of anaerobic pre-treatment followed by macrophyte-covered stabilisation ponds is proposed for the effective recovery of energy and nutrients from sewage. By selecting optimal applications of the plant biomass and pond effluent, nutrients will end up as fish and crop protein. This contrasts favourably to tertiary nitrogen removal in activated sludge systems, which recycles ammonia through molecular nitrogen at the expense of energy and high costs. Macrophyte ponds are proposed as a key step in waste recycling, because these form the central unit of a recycling engine, driven by photosynthesis. The process is energy efficient, cost effective and applicable under a wide variety of rural and urban conditions.