Physical and chemical characteristics of anaerobically digested slurry from large-scale biogas project in Jiangsu Province

Biogas plant in the intensive livestock and poultry farm is a large potential biomass energy project, which could provide clean energy and reduce the stress on environment. However, studies about nutrient management of biogas by-product (i.e. anaerobically digested slurry (DS)) were few. Characteristics and nitrogen (N), phosphorus (P) and potassium (K) contents in DS from 21 large-scale biogas projects were investigated in intensive piggery and dairy farms in Jiangsu Province. The results showed that the investigated DS from digested reactors was reductive and pH values were neutral and weak alkaline. Total N of DS in piggery farms and dairy farms were concentrated on 400 to 900 mg/L and 200 to 400 mg/L, respectively, and 30 to 100 mg/L and >300 mg/L for total P, 100 to 500 mg/L and >500 mg/L for total K. More than 70% of N was ammonium N. Total and dissolved P varied greatly among the investigated sites. Anaerobic reactor became more steady with running time, which significantly influenced on the physical and chemical properties and nutrient characteristics of DS. Oxidation pond (OP) could significantly cripple the suspended solid, N and P in DS. Compared with the primary OP, multi-stage of OP had better crippling effect.