Biogas slurry contains a high concentration of organic matter and nutrients, with a total solid content of 1%-2% and a slightly alkaline pH. It is rich in a large amount of nitrogen, phosphorus, potassium and many trace elements, hydrolytic enzymes, amino acids, organic acids, humic acids, auxins, gibberellins, B vitamins, cytokinins and some antibiotics, and other bioactive substances for crops. The application of biogas slurry can improve the yield and quality of melon, vegetable, tea and fruit.
The contents of heavy metals in biogas are different with the use of feed and veterinary drugs. Some feedstuffs and veterinary drugs used in livestock and poultry farming add heavy metal additives, such as copper and zinc, and most of them are discharged through feces and urine, resulting in heavy metals in Biogas of some farms. It is beyond the standard. The enrichment of heavy metal elements in soil leads to vegetable pollution, and then enters the human body through the food chain, resulting in chronic poisoning, seriously affecting people's health.
Under the condition of satisfying the application conditions, the best way to deal with biogas slurry is field fertilization. However, there is not enough land for biogas digestion around most farms, and the biogas slurry BOD5 / COD is low, the biodegradability is poor, C/N / P is unreasonable, the concentration of ammonia nitrogen and TP is high, and some of the heavy metals in the biogas slurry exceed the standard, which increases the difficulty of biogas treatment. Therefore, it is urgent to explore efficient technology for biogas slurry treatment.