Health Risk Assessment Associated With The Reuse Of Source-separated Human Urine

Human excretion in the urine contains large amounts of nitrogen, phosphorus and potassium and other nutrients. By using of urine-separated technique, it can reduce the pollution in the sewage, recycle the nutrients, and form the loop of nutrients in the fields, crops, food and human. In order to aviod human health risks and ensure the source-separation system safety, the risks caused by the use of source-separeted urine were calculated and analyzed.By searching the literature, the content of pharmaceutical residues in domestic sewage and the content of common pharmaceuticals in human urine were analyzed. German researchers survey124kinds of pharmaceuticals in urine, the range is0.1-103μg/L, and Chinese researchers monitored the8kinds of pharmaceutical, the concentration is in the range of50-4500ng/L, the level of common pharmaceuticals in human urine is in the range of60ng/L-73.26ug/L. Pharmaceutical residues in urine can not impact crops growth. Even if the plants are exposed to high concentrations of drugs (mg/kg soil), the drug content in different parts of plants is very low (ng/kg dry matter). Pharmaceutical residues will not cause serious problems when source-separated urine is used for agriculture fertilizer,By Collectting the existing research results, the level of the pathogen concentration and the probability distribution function in urine were figured out, pathogenic health risk associatied with different urine exposure situation was calculated with the Monte-carlo method.When accidental ingestion of unstored fresh urine, the risk caused by viruses is0.02-0.87/a with an average risk of0.08/a, this risk is unacceptable high. The mean risk caused by Campylobacter jejuni is4.70x10-4/a with a standard deviation of6.67x10-4/a. The mean risk caused by Cryptosporidium parvum is3.81x10-5/a, and standard deviation is5.44x10"5/a. Compared with the acceptable health risk of10-4/a suggested by US EPA. The cumulative probability of risk caused by Campylobacter jejuni less than10-4/a and10-3/a is17.3%and89.4%respectivliy. The cumulative probability of risk caused by Cryptosporidium parvum less than10-4/a is92.56%.The risk caused by inhalation of aerosols depends on urine storage time. The risk caused by bacteria and protozoa is very low under any conditions of storage. But the infection risk of rotavirus is at the level of10-1/a for the urine stored after6months at5℃or after1month at20℃, if urine is stored after6months at20℃before irrigation, the average risk will be reduced to4.02×10-5/a.The risk caused by consumption of vegetables fertilized with urine such as lettuce and cucumber after two weeks is at the level of10-9/a, which can be negligible.