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Effect of acti-zyme loading, Retention time and their interactionon sewage physicochemical propertiesduring anaerobic treatment

M.M.Manyuchi, D.Ikhu-Omoregbe, O.O.Oyekola

Acti-zyme, an enzyme biocatalyst was used for anaerobic sewage treatment as a biological means. The sewage total Kjeldahl nitrogen (TKN), biochemical; oxygen demand (BOD), total suspended solids (TSS), total dissolved solids (TDS), electrical conductivity (EC), pH, chloride ions concentration (CI-), total phosphates (TP), sulphate ions concentration (SO4 2-), dissolved oxygen (DO) and the chemical oxygen demand (COD) were measured. All other parameters were measured by titrimetricmethods; the pH and EC were measured by electrodes whereas the SO4 2- ions were measured by the gravimetric method. Effects of the acti-zyme loading, retention timeand their interaction on sewage physicochemical properties were determined using 22 factorial designs. All samples were incubated at 37°C under anaerobic conditions at agitation rate of 60 rpm. Acti-zyme was varied between 35-50 g/m3 whilst the residence time was varied between 7-40 days. The TKN, BOD, TSS, EC, CI-, TP, SO4 2- and COD decreased linearly by more than 18% on increased acti-zyme loading and residence time as well as their interactions. The sewage pH changed from being alkaline to neutral and the DO increased by >200%. Optimum sewage treatment conditions to meet set guideline for disposal were obtained at 50g/m3 acti-zyme loading and retention time of 40 days.