International Conference on Water Reclamation and Reuse, June 2015

Krobinian Kätzl was invited to present „Biochar and woodchips as alternative filter materials for pre-treatment of wastewater with roughing filter“ at the 10th IWA International Conference on Water Reclamation and Reuse, in Harbin, China, 5th to 9th of June, 2015.

Filtration system for safer irrigation water completed, May 2015

During May 2015 a low cost filtration system was constructed next to the central field experiment in Tamale. The major aim of the pilot wastewater treatment plant is the reduction of pathogenic bacteria by multi-stage filtration for production of safer irrigation water. Multi-stage filtration means the combination of a roughing filter as pre-treatment followed by a slow sand filter for further treatment. For roughing filtration, a coarse filter material is used to remove suspended solids from wastewater. This is important to prevent rapid clogging of the slow sand filter. For slow sand filtration, a finer filter material and a low hydraulic loading rate is used. This treatment step is mainly accountable for the reduction of pathogens. Different phenomena take place in the purification process. After some time a dirt layer, the so called Schmutzdecke, will develop at the boundary phase of filter material and supernatant water layer. This is a very active biological layer and mainly responsible for pathogen removal. The biofilm will also start growing all over the filter material and serves as a hostile habitat for microbes. The predation within the biofilm and adsorption of the bacteria by the filter material and biofilm lead to a significant reduction of pathogens.

For the comparison of different locally available filter materials, two treatment lines were build out of oil barrels. A polytank on top of a platform of 2.5 m height supplies the system with sufficient pressure and acts as a storage reservoir. In the next weeks two different filter materials will be examined to test their suitability for wastewater treatment. Therefore one treatment line was filled with Biochar and the other one with the natural feedstock of the same (corn cobs and rice husks - see pictures below). Preliminary results from laboratory experiments in Bochum, Germany indicates the suitability of biochar as filter material. The focus is now on the implementation and adaptation of this technology at local conditions in West Africa.

Filtration system
Rice husks as filter medium; carbonized and un-carbonized
Corn cobs as filter medium; carbonized and un-carbonized