[Start-up of high solid anaerobic digestion process for treating straw with sludge cake as nitrogen additive]

Straw co-digestion with sludge cake as nitrogen additive from wastewater treatment plant (WWTP) can solve the pollution problems of improper treatment of straw and sludge. Moreover the products, including biogas and organic manures, can relieve the problems of energy supply and soil infertility in countryside. The properties of the start-up periods of two anaerobic digestors were studied. The result showed that the efficiency of the anaerobic digestors rose after pre-treating the straw by NaOH and adjusting C/N by adding 5% sludge. The start-up period lasted 930 h. The anaerobic bacteria activity has recovered and was acclimated in the start-up period. The solid content of the feeding was 12%-16% and the biogas-production rate was 0.15-0.18 L/h at the end of start-up period. The total solid and volatile solid degradation rates were 54% and 65% in the 1st reactor, and 67% and 75% in the 2nd reactor, respectively. During the start-up period, COD concentration and NH4+ -N concentration were rather low, which were 1000-6000 mg/L and 200-600 mg/L, respectively.