Technical investigation and evaluation of rural sanitary dry toilets in cold and arid regions of China

Abstract: The toilet environment is closely related to human health and is an important benchmark for the progress of human spiritual civilization. With the continuous enhancement of the improvement of the rural living environment in China, the rural toilet environment has been greatly improved. However, the cold and arid areas of our country are limited by geographical and climatic conditions, which makes the traditional "flush toilet + sewage treatment plant" treatment mode unable to be used on a large scale, and traditional dry toilets are difficult to meet the current sanitation and non-toxicity of manure treatment. It is urgent to develop and construct sanitary dry toilets suitable for arid and cold regions.From May 2020 to August 2021, this study organized more than 150 investigators to conduct surveys in 57 counties (cities, districts) across the country, and the survey objects were mainly farmers, enterprises, governments and other rural toilet improvement processes. The key objects involved in the participation process are based on a combination of field research and discussion, focusing on the technical mode of toilet modification, construction, operation and maintenance, sanitation effects and economic costs as the main research contents, and a total of 29 provincial research reports have been formed.In this study, combined with research reports and literature, the sanitary dry toilets are divided into two manure treatment technologies. One is sanitary toilets using aerobic fermentation technology, including compost toilets and microbial degradation toilets; the other is facultative aerobic toilets. Sanitary toilets with storage technology, including the urine-diverting household toilet, double-pit alternating household toilet, and solar drying toilet. It also summarizes and analyzes the technical principles, application scenarios, advantages and disadvantages.Through the evaluation and analysis of 5 types of toilets from the perspectives of hygiene and economics, the results show that compared with the other three types of sanitary toilets using facultative storage technology, the microbial degradation toilet and composting toilet using aerobic fermentation technology. The treatment effect is remarkable, especially in the treatment effect of fecal pathogenic microorganisms, with the advantages of significant inactivation effect and short treatment time. At the same time, in terms of toilet environment and toilet odor intensity, the qualified rate of adult flies and fly maggots in compostable and microbial degradable toilets can reach more than 90%, and the qualified rate of microbial degradable toilet odor intensity can reach 100%. The three types of toilets adopting facultative oxygen storage technology have obvious advantages in procurement cost, operation cost and economic benefit. The procurement cost does not exceed 4 100 yuan per year, and the operating cost does not exceed 400 yuan per year. At the same time, it can generate economic benefits of 50-100 yuan per year.Finally, this study analyzes the future development trend of the technical level and operation effect of sanitary dry toilets, and puts forward different technical choices and optimization suggestions for different regions in cold and regions. The relevant standards that are urgently needed and the standard system should be improved. In the research and development of technical equipment, efforts are made to improve the performance and quality of products, and to optimize the research and development of new technical processes. The study results can provide reference for the selection, optimization and improvement of sanitary dry toilets in the next stage of toilet renovation in China's rural "toilet revolution".