Interaction between suspended and settled solid particles in cassava wastewater

摘要

Cassava (Manihot Esculenta, Crantz) is a very important staple food in most developing countries. During its processing into cassava flour or garri, wastewaters are generated and are indiscriminately discharged into the public sewers or into the environment and in some cases; the fermented wastewater is usually poured into latrines with the aim of degrading sewage. This study is aimed at finding out the interaction between the suspended solids and settled solids of cassava wastewater. Cassava wastewater was collected from a cassava processing plant at Ogige main market in Nsukka town and monitored for 14 days. Half of the samples collected were left unstirred and the other halves were continuously stirred. The parameters monitored include biochemical oxygen demand (BOD5), suspended solids, coliform, cyanide and pH. Results showed that there was a 73.4, 27.5 and 99.9% reduction in the settled solids for BOD5, suspended solids and coliform bacteria respectively, for the stirred samples while there was a 97.8, 44 and 99.9% reduction in the settled solids for BOD5, suspended solids and coliform bacteria respectively, for the unstirred samples. Overall, the unstirred samples performed better than the stirred samples with respect to BOD5 and SS removal. The result of this work will guide sanitary engineers in the selection of influent parameters for the effective design of treatment units.