Effect of Acti-zyme loading and retention time on sewage physicochemical properties during anaerobic treatment

Abstract

Acti-zyme, an enzyme bio-catalyst was used for anaerobic sewage treatment. The sewage total Kjeldahl nitrogen (TKN), biochemical; oxygen demand (BOD5 )total suspended solids (TSS), total dissolved solids (TDS), electrical conductivity (EC), pH, chloride ions concentration (CI- ), total phosphorous (TP), sulphate ions concentration (SO 42-), dissolved oxygen (DO) and the chemical oxygen demand (COD) were measured. All other parameters were measured by titrimetric methods; the pH and EC were measured by electrodes whereas the SO42- ions were measured by the gravimetric method. Effects of the Acti-zyme loading, retention time and their interaction on sewage physicochemical properties were determined using 22 factorial designs. Samples were incubated at 37°C under anaerobic conditions at agitation of 60 rpm. Acti-zyme loading was varied between 35-50 g/m3 whilst residence time was varied between 7-40 days. The sewage effluent TKN, BOD5, TSS, EC, CI-, TP, SO42-and COD decreased linearly >18% on increased Acti-zyme loading and residence time as well as their interactions unlike in Acti-zyme free effluent. The sewage pH changed from being alkaline to neutral and the DO increased by >200%. In overall, sewage treatment using Acti-zyme resulted in >90% decrease of the sewage contaminants. Highest sewage treatment conditions to meet the set guideline for disposal were obtained at 50 g/m3 Acti-zyme loading and retention time of 40 days.