The development of biological methods for utilisation and treatment of diluted manure streams

One possible solution for sustainable utilisation and treatment of diluted manure streams is preliminary separation of the solid and liquid fractions followed by separate biological treatment of both fractions. This approach was the starting point of a joint Russian-Dutch project: “The Development of Biotechnological Methods for Utilisation and Treatment of Diluted Manure Streams” (1996-1998). This paper describes the most important results of the project. The UASB process was found to be suitable for the pre-treatment of the liquid fraction of various types of manure using a lab-scale experimental set-up. The maximum organic loading rate (OLR) applied was approximately 12 g COD/1/day for hen or pig manure and 6 g COD/1/day for cattle manure using a hydraulic retention time (HRT) of about 1 day. The total COD reduction under these conditions was about 75% for the hen or pig manure and 42% for the cattle manure. The effluents obtained in this step can be used as liquid fertilisers (if possible) or should be post-treated to meet standards for discharge or reuse. Intensive composting can efficiently treat the solid manure fraction. Experiments at a pilot scale level with the solid fraction of hen manure showed that various amendments (peat, straw, sawdust) could be used for the production of composts having an elevated NPK content, reduced levels of Clostridia and faecal coliforms, vital weed seeds and the absence of Salmonella and helminth eggs.