Keywords: contaminants, manure, organic fertiliser, organic pollutants, pathogens, treatment option, urine, faeces, waste, wastewater.
The existing handling of biodegradable waste, wastewater and some animal manure is not organised in a sustainable manner that includes the reuse of the constituent nutrients. As our natural resources of phosphorus and potassium are finite and there is a high energy input (based mostly on fossil energy) for production of nitrogen fertilisers, a rethinking of the nutrient management procedure is essential. However recycling returns not only the nutrients but also potentially hazardous substances such as pathogens and organic pollutants to agricultural fields.
This work provides a review of current knowledge on the loads and types of pollutants to be dealt with in biodegradable waste, the different wastewater streams and manures, and describes the potential hazards, such as antibiotic resistance, contamination and uptake in agricultural plants, effects on soil-dwelling organisms, and ecotoxicological impacts. It also describes the treatment options available to reduce these compounds to an acceptable level, e.g. anaerobic digestion, composting, membrane technologies and oxidation processes. There are three options regarding the handling of these potential fertiliser sources: to continue with business as usual; to head towards a zero emissions policy that would lead to a large increase in incineration and other high-tech solutions; or to re-use these nutrient streams while taking into account the potential hazards included and addressing them by defining appropriate treatment techniques. The main non-metallic pollutants that need to be dealt with are pathogenic microorganisms. Even though organic pollutants have to be taken into account e.g. antibiotic residues can lead to major problems with resistance developing in soils. The major conclusion is that treated wastes should be regarded as a valuable fertiliser. This involves using them to replace mineral fertiliser in appropriate amounts. It is easier to handle the different pollutants separately at source rather than mixing the different fractions before treatment. Thus by source-separating into yellow, brown, and grey water, it is easier to recycle nutrients and to sanitise the different wastewater fractions according to their specific composition.
Dr Björn VinnerÃƒÂ¥s, Swedish University of Agricultural Sciences, Department of Energy and Technology, Box 7032, SE-750 07 Uppsala, Sweden and National Veterinary Institute, SE-751 89 Uppsala, Sweden.
Dr Joachim Clemens, University of Bonn, INRES – Plant Nutrition, Karlrobert-Kreiten-Strasse 13, D-53115 Bonn, Germany.
Martina Winker MSc, Hamburg University of Technology, Institute of Wastewater Management and Water Protection, EiÃƒÅ¸endorfer Str. 42, D-21073 Hamburg-Harburg, Germany.
32 pages, 4 figures, 1 table, 91 references.