1.Rural Sewage 

The amount of water in rural sewage is small, but the total amount is large; water quality and water volume vary greatly and water discharge is irregular; distribution is scattered, the collection ,construction and the management all are difficult. 

.Specific Performance: 

1) The Coefficient of Variation is Large:  

The quality of rural sewage water fluctuates greatly, and the climate and temperature change in different parts of the north and south are also large. Because of the large-scale sewage plants’ large volume and good regulation function, the coefficient of variation of water quality and quantity is relatively small.However, rural sewage has become a difficult problem because of its small volume.

2) Construction and Supervision are difficult: 

Rural sewage is small, multi-distributed, and its supervision is a difficult problem. The construction quality is uneven, and many of them have quality problems such as leakage, which directly affects the collection of sewage. It is very typical that the amount of water in the rainy day becomes larger, the biochemical efficiency is greatly reduced after the sewage is diluted.Thereby further affecting the effluent results. 

3) Operation and Management are difficult:  

Many places only considered the cost of pre-construction and equipment, but did not consider the operating costs in the later period, resulting in the situation that the sewage treatment devices will be put into production and at the same time will be discontinued. Thousands of sites, few professional managers, so who manages? If you delegate to a third party, how should the third party manage it? How do supervision department monitor and manage the effect and a series of other issues? 

4) Costs of Investment, Operation and Maintenance are High:  

The basic characteristics of rural sewage, if the average cost to tons of water, whether its construction or maintenance costs both are higher than urban sewage treatment plants. It is also a difficult point to come up with a best solution which can balance the investment and the effect. 

5) Construction Mode:  

For many rural areas’ sewage are adopted PPP mode, the investors need to ensure the effect of 20-30 years. These all put forward higher requirements for the planning, construction ,operation and maintenance of sewage treatment. 

.How to solve these problems? 

There are many rural sewage points, wide areas and large quantities, and operation management has always been a big problem. Wisdom Water took the lead in applying Internet technology to the management of sewage devices, effectively solving this problem. On-site personnel use mobile phones for daily management, remote monitoring and command transmission. One person can manage hundreds of sites,which can improve management efficiency and significantly reduce management costs, forming an integrated management network of terminal sites, operation and maintenance personnel, monitoring centers and regulatory units. 

2. Municipal Sewage Main Indicators of Pollutants in Domestic Sewage: 

Chemical oxygen demand, biological oxygen demand, suspended solids, total amount of phosphorus, total amount of nitrogen, and escherichia coli.

.Influences: 

Domestic sewage generally contains more nutrients such as protein, sugar, fat and other organic matter and its decomposition products, as well as inorganic substances such as chloride, phosphorus, potassium, sulfate and sediment. These pollutants make the surface water turbid, resulting in the proliferation of aquatic plants such as algae, and the oxidative decomposition of organic matter can also consume dissolved oxygen in water. If such pollutants are discharged into the water too much, it will easily cause the lack of dissolved oxygen in the water and affect the growth of fish and other organisms. After the dissolved oxygen in the water is exhausted，the organic matter will undergo anaerobic decomposition to produce substances such as hydrogen sulfide and ammonia, which will make the water smelly and make the water quality further deteriorated . 

.How to solve these problems? 

Oxidation ditch process, anaerobic---aerobic sewage treatment process (A/O method), Sequencing batch reactor (SBR process),biological aerated filter process (BAF process), membrane bio-reactor process (MBR process) 

3.Industrial Sewage 

.Indicators of major pollutants in industrial sewage: 

The composition of industrial sewage is complex and the pollution is serious. Different chemical sewage have large differences in water quality. Some chemical sewage contains toxic or highly toxic substances such as cyanide, phenol, arsenic, mercury, cadmium and lead. The organic matter has high concentration, unstable PH value, more nutrient substances, and higher phosphorus and nitrogen content. .Influences:  Chemical sewage directly flows into channels, rivers and lakes to pollute surface water. If it is toxic, it will lead to the death or even extinction of aquatic plants and animals; chemical sewage may also penetrate into groundwater and pollute groundwater; if surrounding residents adopt contaminated surface water or groundwater as living water, it will endanger the health of their body and cause serious death. 

.How to solve these problems? 

The pollutants in industrial sewage are various, so the treatment process must be highly targeted and high-tech. It is necessary to use a combination of various methods to achieve the desired effect.The main technologies in the treatment process include oil separation, air flotation, coagulation, sedimentation, oxidation, ion exchange, electrolysis, activated carbon and other technologies to separate and reduce oil, color and heavy metals, toxic and harmful substances in industrial sewage. Biochemical techniques such as hydrolysis acidification, contact oxidation, oxidation, and aerobic activated sludge process are also used. 

4.Hospital Sewage 

.Main pollutants indicators of hospital sewage:  

Chemical oxygen demand, biological oxygen demand, suspended solids, ammonia nitrogen, escherichia coli .Influences: The source and composition of sewage in hospitals are complex, contain pathogenic microorganisms, and have the characteristics of space infection, acute infection and latent infection. Without effective treatment, it will become an important way for the spread of disease and induce diseases and cause serious environmental pollution.

.How to solve these problems? 

Bar screen+ regulating pool + hydrolysis acidification tank + biological contact oxidation tank + inclined tube sedimentation tank + chlorine dioxide disinfection ----- Discharge on Standard. 

5.Pharmaceutical Sewage 

.The main pollutants of pharmaceutical sewage includes:  

Suspended matter (SS), chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia nitrogen (NH3-N) and phenolic toxic substances. .Influences:  After the pollutants that are difficult to be degraded in the pharmaceutical sewage enter the water body, they can not only remain in the water for a long time, but also have strong toxicity and carcinogenic, teratogenic and mutagenic effects.Through food chain, they constant accumulate and eventually enter the animal or human body to produce toxicity or other hazards. 

.How to solve? 

1) Physicochemical Treatment: a. coagulation, b air flotation, c adsorption, d ammonia stripping, e ion exchange, f membrane separation method, etc. 

2) Chemical Treatment: a iron carbon method, b chemical redox method (fenton reagent, H2O2, O3) c. deep oxidation 

3) Biochemical treatment: a aerobic biological method, b anaerobic biological method, c aerobic + anaerobic  

6.Papermaking and Dyeing Sewage 

.Contaminants in papermaking and dyeing sewage:  

Mainly because COD, Ss, alkali, and  chroma are high. 

.Influences:  

Papermaking and dyeing sewage are very harmful. The black water problem is the biggest,and its pollutants account for more than 90% of the total pollution discharge of the paper industry. Because black water is alkaline, dark in color, heavy in odor, foamy, and a large amount of dissolved oxygen in small water, the water source is seriously polluted, which brings harm to the environment and human health. 

.How to solve? 

1) Air floatation or precipitation method  

2) Combination of physicochemical and biochemical treatment

7. Heavy Metal Sewage 

.Heavy metals belong to a wide range of industries including: 

Metallurgy, mineral processing, electroplating and other industries. The water quality of heavy metal sewage is complex and the composition is difficult to control. It contains heavy metal ions such as chromium, nickel, copper, zinc, gold and silver. 

.Influences:  

Heavy metal sewage has serious harm to industrial and agricultural production and people's health. Acid-base sewage will corrode pipes and buildings, affect the growth of crops and poison fish.Cyanide and chromium are toxic substances, among which cyanide is more toxic and its damage is more serious. Cyanide can cause acute poisoning and even death in humans and animals, and long-term effects at low concentrations can also cause chronic poisoning. Cadmium can cause kidney disease and can cause pain. Hexavalent chromium can cause lung cancer, gastrointestinal diseases and anemia, and it accumulates in bone, spleen and liver. 

.How to solve? 

Heavy metal sewage treatment technology is relatively mature. At present, it is generally treated by physicochemical method, including electrolyzer air flotation, redox flocculation sedimentation, filtration adsorption, ion exchange method and so on.