Urban Black-odor River Treatment

In 2015, the State Council formally released the " The Actiong plan of  for Prevention and Treatment of Water Pollution " (referred to as the "Water Ten Measures"), which put forward clear requirements for the treatment of black and odorous water bodies: "By the end of 2017, the built-up areas of municipalities, provincial capitals, and municipalities with independent planning status under the national social and economic development should basically eliminate black and odorous water bodies; by 2020, the black and odorous water bodies in the built-up areas of prefecture-level and above cities in China will be controlled within 10%;By 2030, the proportion of excellent and good water quality in seven major river basins in China will reach more than 75%, and the black and odorous water bodies in urban built-up areas will be eliminated.

1. What is urban black and odorous water body?

Urban black and odorous water bodies refer to water bodies that exhibit unpleasant colors and/or emit uncomfortable odors in urban built-up areas.

2. What is formation mechanism of black and odorous water body?

Causes of black and smelly water pollution: the direct cause of black and odorous water is due to insufficient DO, and the discharge of pollutants is the source of black and odorous water;

• Water body organic matter and ammonia nitrogen pollution
• Humus adsorption and chelation of black substances and resuspension of substrates
• Mass propagation of actinomycetes in sediment
• Mass propagation of eutrophic algae
• Other factors: heavy metals (iron and manganese), random stacking of domestic and industrial wastes, urban storm runoff, tributary drainage or upstream sewage, water thermal pollution, etc.

3.Ideas and technologies for the treatment of black and odorous water bodies

3.1 External source control

3.1.1 Sewage interception by pipes
The sewage interception by pipes is the most direct and effective engineering measure for the treatment of black and smelly water bodies, and it is also a premise for other technical measures. By laying sewage interception pipelines along rivers and lakes, and reasonably setting up lifting (transportation) pump rooms, the sewage is intercepted and incorporated into the urban sewage collection and treatment system.
Scope of application: Sewage discharge outlets along the coast of urban water bodies, initial rainwater or dry flow discharge outlets of diversion rainwater pipes, and coastal discharge outlets of combined sewage systems.
Restrictive factors: large engineering volume and one-time investment, difficult project implementation, and long period.

3.1.2 Area source control
Urban non-point source pollution mainly comes from the pollutants contained in rainwater runoff, and its control technologies mainly include various urban low-impact development (such as sponge city) technologies, initial rainwater control technologies, and ecological bank protection technologies.
Scope of application: It is mainly used for the control and treatment of pollution sources such as initial rainwater, melting water from ice and snow, sewage from livestock and poultry breeding, and surface solid waste.
Restrictive factors: large amount of work, wide range of influence, strong system, long construction period, etc.

3.2 Internal source control

3.2.1 Garbage disposal
The garbage disposal along the urban water body is an important measure for pollution control, and the cleaning of the temporary garbage stacking point is a one-time engineering measure, which should be cleaned up in place at one time.
Scope of application: It is mainly used for cleaning up the temporary dumping point of garbage along the urban water body.
Limiting factors: in areas with a long history of garbage storage along urban water bodies, incomplete garbage removal and transportation may accelerate water pollution.

3.2.2 Removal of biological and floating debris
Aquatic plants, riparian plants and fallen leaves are seasonal source pollutants in the water and need to be cleaned up before drying up; floating objects on the water surface mainly include various fallen leaves, plastic bags, and other domestic garbage, which require long-term cleaning and maintenance.
Scope of application: It is mainly used for the seasonal harvesting of aquatic plants and riparian plants in urban water bodies, and the cleaning of seasonal falling leaves and floating objects on the water surface.
Limiting factors: The cost of cleaning up seasonal biological debris and floating debris is high, and it is difficult to supervise and maintain.

3.2.3 Dredging
Dredging Including mechanical dredging and hydraulic dredging, etc., the storage and purification measures of the original black and odorous water in urban water bodies should be considered in the project.
Scope of application: Generally speaking, it is suitable for all black and odorous water bodies, especially the cleaning of sediment pollutants in severe black and odorous water bodies.
Limiting factors: expensive treatment costs, high dredging precision and accuracy requirements, silt treatment problems, etc.

3.3 Ecological restoration technology

3.3.1 Ecological purification
It mainly adopts technical methods such as artificial wetlands, ecological floating islands, and aquatic plant cultivation, and uses the soil-microbe-plant ecosystem to effectively remove organic matter, nitrogen, phosphorus and other pollutants in the water body.

Scope of application: It can be widely used in the long-term maintenance of the water quality of urban water bodies. Through the restoration and system construction of the ecosystem, it can continuously remove water pollutants and improve the ecological environment and landscape.
Limiting factors: Control of external and internal pollutants is the premise, ecological purification measures must not conflict with other functions of the water body; ecological purification measures have insignificant improvement effects on severely polluted rivers; plant harvesting, treatment and disposal costs are high.

3.3.2 Rehabilitation Technique
Taking the form of planting ditch, ecological revetment and permeable brick, the original hardened river bank (lakeshore) is reconstructed. By restoring the natural purification function of the shoreline and water body, the pollution control effect of the water body is strengthened.
Scope of application: Mainly used for ecological restoration of hardened river banks (lake banks), which is a long-term measure for urban water pollution control.
Restrictive factors: the amount of engineering is large, and the disposal cost of ecological shoreline plants is high.

3.3.3 Artificial oxygenation
Mainly use water drop, fountain, jet, and other various forms of aeration to effectively increase the dissolved oxygen level of the water body.
Scope of application: it is mainly applicable to the water quality maintenance of urban water body after treatment, with water body reoxygenation function.
Limiting factors: severe black and odorous water body is not applicable, it needs continuous operation and maintenance, and consumes electric energy.

3.4 Other treatment measures

Other treatment technologies include active water circulation, clean water replenishment, on-site treatment, bypass treatment and other technologies.
After years of hard work, "JIUWU TIANHONG", a subsidiary of JIUWU HI-TECH, has developed a biological lake purifier and obtained related patents. The biological lake purifier adopts the contact oxidation biofilm process in the sewage treatment technology. It applies the high-efficiency biofilm sewage treatment technology to the treatment of river pollution, integrating aeration and reoxygenation, hydrolysis acidification, anaerobic treatment, and aerobic treatment. A river pollution treatment technology that integrates various biochemical treatment processes. The typical process flow is as follows:

After placing the matrix of the biological lake purifier combination in the contaminated area of the river, a reoxygen generator is installed on the river bank.
During operation, the compressed air generated by the reoxygen generator enters the special reoxygenation device through the transportation pipeline, releasing a large amount of fine air bubbles quickly provide dissolved oxygen in the black and odorous water body in the contaminated section of the river. The aerobic bacteria growing on the biological filler use dissolved oxygen to oxidize and metabolize the organic pollutants in the river water, and decompose the organic pollutants into water and carbon dioxide and other harmless substances. The ammonia nitrogen in the water is first oxidized to carbon dioxide by nitrifying bacteria, and then oxidized to nitrate, which is reduced to ammonia in the hypoxic area and overflows the river water.Carbon dioxide and water from the oxidation of ammonia and other organic matter return to nature, thereby completing the purification of polluted rivers. Moreover, this technology has the ability to continuously accept polluted water and purify up to the standard, which fundamentally solves the problem of black odor rebound.

Process advantages:

• Control system with uniform distribution of reoxygenation gas volume in different regions
• Layout plan of sewage treatment process with matrix A / O
• No need to intercept and dredge the river course for certain treatment
• The ability to degrade black and smelly river water with high concentration of COD and BOD, and has the ability to keep the river water up to the standard continuously
• The ability to clear the sediment of the silted river by itself