The effect of biomass acclimation on the co-digestion of toxic organic effluents in anaerobic digesters

Abstract

Currently KwaZulu-Natal (KZN) province is populated with textile industry, which produces wastewater, some of which is not biodegradable. Due to the stringent environmental regulations the wastewater cannot be discharged into the rivers or public owned treatment systems. The alternative solution is to co-dispose this wastewater with easily biodegradable waste (labile effluent). The aim of this investigation was to develop a process protocol for the codigestion of high strength and toxic organic effluents under mesophilic conditions (35°C ± 2°C), with emphasis on the effect of biomass acclimation. A total of four effluents were chosen for this study, two labile (distillery and size) and two recalcitrant (scour dye and reactive dye). Two anaerobic batch experiments and two pilot scale trials were performed. The first batch anaerobic experiment investigated the influence of biomass source in anaerobic treatability. The second batch test investigated, whether biomass acclimation enhanced the biodegradability of pollutants. The pilot scale trials were the scale up version of the biomass acclimation test. The results showed sludge from Umbilo Wastewater Treatment Works was a superior biomass source, producing more gas and methane compared to Mpumalanga waste. For the high strength organic waste, the acclimated size and distillery samples produced 50% more biogas and methane compared to non-acclimated samples. This confirms that the biomass acclimation enhances the biodegradability. The biomass acclimation did not enhance the biodegradability of the recalcitrant effluent (scour dye). The pilot scale trials did not yield meaningful data; therefore it could not be proven if acclimation works on a larger scale.