# Mathematical Modelling for Bio-nutrient Removal in Sewage Treatment using Acti-zyme as Bio-catalyst

## Authors

• Musaida Manyuchi* Harare Institute of Technology
• Daniel Ikhu-Omoregbe Cape Peninsula University of Technology
• Oluwaseun Oyekola Cape Peninsula University of Technology
• Willard Zvarevashe Department of Mathematical Sciences Harare Institute of Technology
• Zororo Makunbe Department of Chemical and Process Systems Engineering, Harare Institute of Technology

## Abstract

Alternative biological sewage treatment methods have received atten-tion lately in developing countries. The present study presents the mathe-matical modeling for bio-nutrient removal in sewage after applying Acti-zyme a biocatalyst at various retention times and loadings. The bio-nutrient removal was measured through the removal of the sewage bio-contaminants i.e. chemical oxygen demand to the biochemical demand ratio(COD/BOD5), the BOD5 to the total Kjeldahl nitrogen ratio (BOD5/TKN),the COD/TKN ratio and the COD to the total phosphates ratio (COD/TP).In addition, all the other sewage physicochemical parameters were mea-sured to determine the quality of the sewage. Experiments were carriedout in 250 mLВ asks with a 75% working volume anaerobically incubatedat 37C and agitation of 60 rpm. The Acti-zyme loading was varied be-tween 35-70 g/m3 whilst the residence time was varied between 0-60 days.The COD/BOD5, BOD5/TKN, COD/TKN and COD/TP ratios obtainedwere greater than 1.2, 4, 8 and 15, respectively. COD/BOD5, BOD5/TKN,COD/TKN and COD/TP models with R2 > 0.9 in the form: Bionutrientremoval ratio=K+ X1 TKN +X2 BOD+X3 TP +X4 COD at a p value of0.05 were developed. Validation of the models using p-plots indicated thatthe predicted values and the measured values were correlated. The modelsare ideal for application in measuring the bio-nutrient removal in sewagetreatment using Acti-zyme.