Effect of Saline Sludge on Anaerobic Digestion of Kitchen Waste for Methane Generation: Modeling and Fertilizer Recovery.

A comparative study of methane recovery by co‐digesting kitchen waste and saline sewage sludge is performed to evaluate its feasibility for waste minimization. The experiment is performed at 37 °C having a mixing speed of 100 rpm and pH of 6.49–7.5 in anaerobic mixed batch reactors. The higher salinity level of the saline sewage sludge reduces the degradation rate of kitchen waste causing an enhancement in soluble chemical oxygen demand by 133% compared with 280% when co‐digesting with the non‐saline sample. The inhibitory behavior is in line with the low volatile solid elimination efficiency of 31% of saline against 55% of non‐saline sludge. The Gompertz modeling, based on the outcomes, fits the cumulative methane generation trends quite well, with a strong correlation coefficient (>0.994). Besides, use of the non‐saline sludge results in three times more methane production than the saline sample digestion. Sludge recovery is 0.07 m3 sludge m−3 wastewater, and water recovery is 0.84 m3 m−3 wastewater. The liquid produced from the fermentation of the slurry can be used for irrigation as well as fertilization. Kitchen waste co‐digestion with both sludge samples has been proven to be a practical method for exploiting the extra digestion capacity of wastewater treatment plants currently in operation, but it is more practical for non‐saline sludge. [ABSTRACT FROM AUTHOR]