Open access publications in the SLU publication database

Abstract

To successfully recirculate organic wastes from densely populated areas back to agriculture, changes in the handling of toilet wastes are needed. A urine separation system facilitates the handling and spreading of these wastes. 70-90% of the nitrogen in toilet waste is found in the urine. Urine normally contains low counts of pathogenic microorganisms. There is, however, a risk of contamination of the urine by faecal material. The hygenic quality of stored urine was investigated by collecting urine samples from seven urine-separating constructions in October-94 and in May-95. Faecal indicator bacteria in the samples were enumerated. The content of Escherichia coli was low in all the samples, while faecal streptococci were present in amounts between 7 and 13000 cfu/ml. No coliphages could be detected. The pH in the stored urine ranged from 7.7 to 9.2. The die-off of E. coli faecal streptococci, Salmonella typhimurium SH 4809, Campylobacter jejuni S201/94 and bacteriophage S. typhimurium 28B was tested by adding these strains to urine in amounts of ca 10^6 cells/ml. Samples were incubated at 4 and 20°C. The die-off of E. coli, S. typhimurium and C. jejuni in urine was rapid. C. jejuni could not be recovered at all. After two days, S. typhimurium could not be detected in the urine incubated at 4°C, or at 20°C. E. coli could not be detected after three days in urine stored at 20°C or after seven days in 4°C. The persistence of faecal streptococci was considerably better. After 35 days the counts in urine incubated at 20°C were reduced to less than 1 cfu/ml while these at 4°C were ca 3000 cfu/ml. No significant reduction was observed for bacteriophage S. typhimurium 28B in urine incubated 42 days at 4 or 20°C. The chemical composition of the stored urine was also investigated. Samples were collected in December -94 and in May -95. Nitrogen content varied depending upon many other things, the dilution with flashwater. Analyses showed that the urea in the urine during storage had been decomposed to ammonia, which led to high pH values.