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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”. [ABSTRACT FROM AUTHOR]

To obtain the contact parameters of livestock and poultry manure accurately and quickly, this study calibrated the contact parameters of pig manure by physical stacking test and simulation method. A stacking angle measurement test bench was designed, and the contour of the stacking slope was obtained by the image-digital simulation method, and a linear fitting was performed. Through the natural air-drying and the deionized water adjustment methods, the pig manure accumulation angle under different water content was measured, and a polynomial fitting model between the water content and the pig manure accumulation angle under different water contents was established. To obtain the actual stacking angle, the Hertz-Mindlin with JKR sphere bonding model was used, and the discrete element simulation of the physical stacking test was performed by EDEM2.7 Screening experiment design (Plackett-Burman Design, P-BD) was used to screen 10 initial parameters. It was found that JKR (Johnso-Kendall-Roberts) surface energy, particle-particle rolling friction coefficient, and particle-particle collision recovery coefficient had significant effects on the swine manure accumulation angle, and the other 7 factors had no significant effect on the accumulation angle. The best range of three significant influencing factors was determined by the steepest climbing test. The 7 non-significant influencing factors in this test were the intermediate values of the initial range, and the 3 significant parameters gradually were increased until the relative error between the simulated value and the physical test value reached the minimum. Based on the results of the response surface experiment design (Box-Behnken Design, B-BD), a quadratic polynomial model between the stacking angle and the three significant parameters was created. The analysis of the quadratic polynomial model variance showed that the model was meaningful. Under the condition that the model was significant and the miss-fit terms were not significant, the terms that did not significantly affect the results were removed, and the regression model was optimized to obtain a new quadratic polynomial regression model. The coefficient of variation of the optimized model dropped to 0.81%, indicating that the reliability of the model had been further increased. The determination coefficient R² =0.994 1 and the correction determination coefficient R² adj=0.986 1 were both close to 1, indicating the model fitted better. The precision (precision) was 37.023, improved before optimization, which could be used to predict the particle accumulation angle. Through the optimization of the optimized quadratic polynomial regression model, the best parameter combination of 3 significant influencing factors were obtained. The results illustrated that the surface energy of JKR was 0.03 J/m2, the coefficient of rolling friction between pig manure and pig manure was 0.27, and the coefficient of recovery of the collision between pig manure and pig manure particles was 0.54. The discrete element stacking test simulation was carried out based on the calibrated optimal values of the discrete element parameters of pig manure, and the error between the simulated stacking angle result and the actual test result was 4.27%, which showed that the calibration results were credible. The results could provide a reference for the selection and calibration of discrete element model parameters to other agricultural livestock and poultry manure. [ABSTRACT FROM AUTHOR]

The harmless treatment of night soil in rural toilets is significant for the“Toilet Revolution”and the strategy of rural vitalization in China, owing to the prevention of fecal-oral transmitted diseases and controlling night soil pollution. This paper summarizes the development of a technology for night soil treatment worldwide and analyzes the advantages and disadvantages of the technology and the influencing factors. Combined with the present situation and the demand for night soil treatment in China, this paper puts forward a research direction that should pay attention to the source separation of urine and feces, strengthening the research and development of water-saving toilets and providing a prerequisite for rapid reduction and resource utilization of night soil. At the same time, combined with combing the characteristics of night soil, it is suggested that the research on agricultural verification and environmental risk assessment by the application of night soil should be strengthened, aiming at providing a reference for the selection of rural toilet improvement technology products and the treatment and utilization of night soil. [ABSTRACT FROM AUTHOR]

Toilet revolution has become one important part of a rural revitalization strategy in China, aiming to effectively reduce the incidence rate of fecal oral diseases, while to ensure the health-care level and quality of human beings. Since 2018, the Ministry of Agriculture and Rural Affairs, together with relevant departments, has taken active actions to vigorously promote the rural toilet revolution and achieved positive effects. However, some situation, like “poor construction, not working well and improper use” of rural toilets, still occurs in some rural areas. The main reason is a lack of a standard system for the toilet modernization and utilization of excrement, further to improve the hygiene of toilets facilities in rural areas. Therefore, this study first summarized the 22 national and industry standards system that were directly related to rural toilet construction and excrement disposal in China. It was found that the number of existing standards was seriously insufficient, indicating the standard system has not been well-established for the rural toilet construction and excrement disposal in China. As such, this study aims to establish a three-dimensional structure diagram of rural toilet construction and excrement disposal, using the system engineering technology method, including levels (basic standards, general standards, special standards), sequence (product equipment standards, engineering construction standards, technical method standards, operation management standards, safety and health standards), category (rural household toilet standards, fecal sewage centralized treatment center standards, other standards). An optimal level of special standard was further determined, according to the basic established principles of a standard system for rural toilet construction and excrement disposal. The key content of a standard system construction was proposed to fill the research gaps in the basic national standards, and the general standards system, as well as in the special standards. Four recommendations were also proposed during this time: 1) To organize a special standardization working group or professional committee as soon as possible to systematically implement the policy of the toilet revolution; 2) To strengthen the fundamental research on the various advanced international standards systems; 3) To speed up the preparation of urgently needed standards systems; 4) To encourage the local governments to actively prepare the local standards system, in order to provide for the rural toilet revolution in China. The standard system of toilet modernization and utilization of excrement in rural areas can provide an important means to guide the renovation of toilet and the utilization of excrement as resources, further to standardize development of the modern industry. [ABSTRACT FROM AUTHOR]

Toilet waste composting is one of the main ways of rural toilet sewage resource utilization, which plays an important role in promoting the rural toilet revolution. In order to solve the problems of difficult disposal of rural toilet manure and poor environmental sanitation in rural toilets, a 110 L rural household composting reactor with negative pressure suction, spiral feeding- spiral coil aeration-membrane auxiliary heating was designed in this paper. The reactor structure included manure collection unit, aerobic fermentation unit, heat preservation unit and aeration unit. According to the principle of biological and thermodynamic, the negative pressure fan suction was used to collect manure automatically. In order to reduce the pressure loss of aeration fan, the aeration pipe was arranged Archimedean spiral structure, and the timer and aeration fan were used to realize controllable ventilation in composting process and improve composting quality. Insulation cotton membrane heating structure was adopted to achieve the heating and insulation of the reactor. The power of the reactor was 1.29 kW, the composting cycle was 15 d, the aeration frequency was 4 min per 26 min interval, the aeration rate was 1.75 L/min. The performance tests of composting reactor were conducted in September 2019. The manure and corn stalks with 1-2 cm particle size were placed in the reactor layer by layer according to the mass ratio of 4:1, and the samples were taken at 0, 3, 6, 9, 12 and 15 d after composting, respectively. The physical and chemical properties, such as temperature, water content, volatile solids, reliable content, seed germination index, the number of worm eggs and fecal coliforms of the samples during the aerobic fermentation process were tested, respectively. The results showed that the stalks and manure were layered with a strong odor during the first 2 d of aerobic fermentation. With the progress of aerobic fermentation, the manure gradually integrated into the gap between stalks and mixed with stalk. The color of the manure turned progressively dark brown and the odor faded. After 10 d of aerobic fermentation, the pile was dark brown, odorless, fluffier and moister with white filaments distributed on the surface. The high-temperature period lasted for 5 d. After 15 d of continuous fermentation, the fecal coliform bacteria was 46 MPN/g (≤100 MPN/g), the mortality rate of worm egg was 100%, and the seed germination index was 88.4%, which met the sanitary standard of harmless manure. The annual maintenance cost was saving 16% compared to the three-slot septic tank and 44% compared to biological purification tank household toilets. [ABSTRACT FROM AUTHOR]