Efficacy of fluidised bedbiofilm bioreactor in bioremediating dairy wastewater

Abstract

Industrial effluents such as that from dairy factories are known to cause major pollution in water bodies which the effluent is discharged into. Nitrogen and phosphorous levels increase and cause eutrophication which results in the death of aquatic life, as well as causing disease in terrestrial animals, and humans. Dairy effluent is rich in organic wastes, and have variable pH due to fluctuations caused by sanitation chemicals. This study served to use an aerobic fluidised bed biofilm bioreactor to treat a synthetic dairy wastewater by utilizing 2 different types of consortia as a bioaugmentation tool. Dairy spoilage isolates were isolated from dairy products, and identified using 16S rDNA identification. Isolates were then evaluated for proteolytic and lipolytic ability using milk agar and lipolytic agar. Isolates exhibiting both proteolytic and lipolytic ability were evaluated for its effect in a synthetic dairy wastewater in flask cultures, each isolate both independently and in combination. Two consortia were chosen which degraded the synthetic medium most efficiently. One consortium contained a Gramnegative and Gram-positive bacteria, while the other consortium contained Grampositive only bacteria. An appropriate carrier material was then chosen from 5 different types, a 4mm pellet carrier sourced from coal. The aerobic fluidized bed biofilm bioreactor was then set-up, and bioaugmentation was used to degrade the total organic carbon in the synthetic wastewater using first the Gram-positive consortium, then the Gram-positive and –negative consortium, while the pH and flow rate was varied to simulate real dairy wastewaters. Total organic carbon reduction was evaluated, as well as attached and planktonic growth in the bioreactor. The Gram-positive and –negative consortium was successful in depleting TOC in the synthetic wastewater, while the other consortium although degrading TOC, did not degrade it completely. Biofilm growth was sustained when both consortia were used. Each experiment was done in triplicate and statistically evaluated using multiple variable analysis (P< 0.05).