Absrtact: With the prosperity of China’s economy and the improvement of people’s living standards, average water consumption and sewage production are increasing. These domestic sewage discharged without treatment not only aggravates the pollution of water and environment, but also seriously threatens the rural drinking water safety and farmers ‘health. Therefore, the technical methods of rural domestic sewage treatment are analyzed in this article.
Key words: rural areas; domestic sewage; treatment technology and methods
1. Characteristics of Rural Domestic Sewage
1.1 Water Quality Characteristics
(1) Dispersed sewage distribution; imperfect pipeline network collection system; extensive discharge; Few sewage treatment facilities; (2)Rural domestic sewage concentration is low and varies greatly; (3)The characteristics of most rural domestic sewage are similar, water quality fluctuates greatly and biodegradability is strong; (4) The quality of toilet sewage is poor, but it can be used as fertilizer in septic tank.
1.2 Water Characteristic
(1) The amount of domestic sewage in general rural areas is relatively small, except for small towns. General rural population are spread out, but the amount of water and sewage production is small; (2) the coefficient of change is large, and the living rules of residents are similar, which results in the discharge of rural domestic sewage greater in the morning and evening than in the daytime. Waste water discharge gets smaller in the night, and may even stop. The change of water volume is obvious.
2. Several Treatment Technologies of Rural Domestic Sewage
2.1 Treatment of biogas digester for domestic sewage purification
Domestic sewage purification biogas digester treatment can adapt to rural domestic sewage treatment, with a thrifty treatment method which can reflect the combination of environmental and social benefits. Biogas digester produces biogas after anaerobic fermentation of organic matter in sewage. Human beings use biogas for cooking and power generation. After treatment of domestic sewage, most of the organic matter is removed to achieve the purpose of purification. The treated water can be used for watering flowers or as a fountain. Domestic sewage purification biogas digester has replaced the traditional septic digester. At present, the technology of domestic sewage purification biogas digester has been greatly improved. The technical perfection is relatively formed, and the treatment level of rural domestic sewage will also be improved.
2.2 Treatment of Land Infiltration Treatment System
Land infiltration treatment technology utilizes the automatic purification ability of nature to adsorb organic matter in sewage through soil or vegetation and reuse organic matter in sewage by physical, chemical and biological functions, so it could allow vegetation grow more flourishing and degrade organic matter in sewage.
In the process of sewage treatment, we often imitate the effect of nature to filter, degrade and separate the organic matter in the sewage, which is suitable for the treatment of rural domestic sewage.
2.3 Constructed Wetland Treatment System
Constructed wetland is a technology which imitates nature’s wetland system to treat rural domestic sewage. At the bottom of the constructed structure, sewage treatment is carried out by filling materials according to a certain technical plan. These fillers include stones, sand and so on. Some vegetation adapted to the living conditions of domestic sewage is planted on the surface. Through the synergistic effect of microorganisms or plants in the ecosystem, the treatment and purification of pollutants are achieved. Constructed wetlands are economical and practical, and suitable for the treatment of rural domestic sewage. The mechanism of its utilization is complex, and the purification from vegetation plays a crucial role. This sewage treatment technology has been widely used and is more suitable for rural areas.
2.4 Biofilter Technology
There are fillers made of crushed stone and plastic products in the biofilter. Microorganisms attach to the fillers and grow into biological communities. When sewage enters the biofilter, a reactor is formed instantaneously to decompose the organic matter in the sewage. Fillers intercept large particles and suspended solids in filtered sewage and act as filters. Microorganisms in the filter can hydrolyze the insoluble substances of macromolecules into soluble substances of small molecules and play a role in hydrolysis. The microorganisms in the process pool absorb the organic pollutants in the water, part of which is transformed into their own growth, reproduction and metabolism, and part of which decomposes the organic pollutants to produce biogas emissions.
2.5 Solar/Wind Micropower Wastewater Treatment Technology
Based on the traditional “A2/O” process, the solar/wind micropower wastewater treatment technology is composed of solar photovoltaic panels, small wind turbines, storage batteries, aeration systems, reflux systems, micro-computer control systems and remote communication systems. Solar energy is converted into electricity through solar photovoltaic panels, and combined with small wind turbines as aeration facilities and reflux facilities. The power and surplus energy are stored in the battery. According to the optimized debugging data, automatic control is completed through the microcomputer control system, and the aeration facilities, reflux facilities and mixing facilities are automatically operated. After water accumulation, anaerobic biological treatment, contact oxidation and precipitation, it can meet the discharge standards.
Solar energy and wind energy as energy resources in sewage treatment applications, is not only for micro-power energy. In the north, it is also for the pool to play a thermal insulation role, improving the efficiency of sewage treatment in winter. The wastewater treatment technology has the advantages of cleanliness, convenience, safety and energy conservation. Solar/wind micro-power wastewater treatment technology makes rational use of heat and climate conditions, making the whole process more environmentally friendly and energy-saving; its operating cost is zero, which is incomparable with other treatment processes. However, it also has some shortcomings such as lack of professional and technical personnel, and difficulties in the later operation and maintenance process.
The treatment technology of rural domestic sewage should be implemented and managed according to the geographical status of rural areas, taking full account of local rural climate, temperature, humidity and other conditions. Using domestic sewage purification biogas digester, Land Infiltration Treatment system, constructed wetland treatment system, biological filter, solar/wind energy micro-power sewage treatment and other technical methods to select the corresponding treatment technology for rural domestic sewage, and introduce appropriate sewage treatment technology in this area according to local conditions.