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The inhibitory effect of ozone and hydrogen peroxide (HP) on urea hydrolysis in stored urine was investigated and compared. Ozone showed less effect on urea hydrolysis due to the complicated composition of urine (including a large amount of urease-producing bacteria) and bacteria regeneration. Ozone concentration and total heterotrophic bacteria analysis demonstrated that residual ozone concentration decreased by 43% within 15 hr from 13.50 to 7.72 mg/L in the one-time ozonation urine test, and finally completely decomposed within 4 days. In addition, bacteria regenerated quickly after ozone completely decomposed. However, HP showed a significant effect on inhibiting urea hydrolysis not only in stored urine but also in fecal-contaminated urine. The suitable doses of applied HP to inhibit urea hydrolysis in stored urine, concentrations of 0.5 and 1.0 g feces per liter of fecal-contaminated urine, were 0.03, 0.16 and 0.23 mol/L, respectively. The urea concentrations after 2 months stored were 7,145, 7,109 and 7,234 mg/L, respectively.

This study examines a closed-loop sanitation system (CLSS) in the ger areas (informal peri-urban settlements) of Ulaanbaatar, Mongolia in order to evaluate system feasibility and to identify the future prospects of CLSS as an alternative to conventional sanitation and drainage options. Results show that the CLSS concept is well understood and accepted by users and that services are being scaled up. Over 50 per cent of respondents used CLSS technologies during both winter and summer, testifying to the potential for scaling up these technologies and services. Moreover, all users responded positively in their evaluation of the emptying services. Despite some problems and challenges, the system proved to be feasible, replicable and acceptable in the study area. It is recommended that the entire CLSS approach be tested through scientific validation to convince more communities, government and other stakeholders about scaling up the system beyond the study area for better health, environmental conservation and resource recovery.KEywords closed-loop sanitation system / cold climate / composting / emptying services / ger areas / urine-diverting toilets sayed Mohammad nazim uddin is a phd researcher and project Manager, university of science and technology beijing.Address: school of civil and Environmental Engineering, university of science and technology beijing,

Sanitation is one of the most pressing issues faced by the population in the peri-urban Ger areas of Ulaanbaatar, Mongolia. Poorly constructed pit latrines have caused environmental, socioeconomic and health problems especially Hepatitis A, among the residents, which is predominant among children less than 5 years old. This research aimed to investigate the feasibility of co-composting fecal matter with different recipes using two different technologies, i.e. composting facility and greenhouse (GH) technology. All the trials conducted met the international sanitary requirements for compost, i.e. World Health Organization (50 °C ≥ 1 week). Conclusively, GH technology with the addition of food waste allowed the temperature to increase up to 70 °C, which proved to be a better option for co-composting of fecal matter under specific local conditions.