LAUSR

In this study a green waste rye grass was added as the co-substrate for petroleum wastewater (PWW) fermentation with different mixing ratios for enhancing methane production. First order modified process model was employed to methane production from co-digestion of PWW with different ratio of rye grass. The results showed that the highest methane yield was 204.8 mL/g-VS added /h − 1 and total solids 41.6% and volatile solids (VS) 29.6% removal ratio reached at the ratio of 30–70 PWW-rye grass. Which were 98.7, 61.9 and 34.5 times higher than that from sole PWW fermentation, respectively. The first order modified process model best fitted the actual evolution of methane yields, as evidenced by low root mean square prediction error as well as high correlation difference between the predicted and actual values. The utilization of carbohydrate and protein were also improved by co-digestion of PWW with rye grass. After methane fermentation, acetate was the dominant soluble metabolites in all groups. The SMA activity results showed that more active microorganisms in the co-digestion system contributed to higher methane production and waste utilization.