Wastewater treatment is the process of purifying wastewater to meet certain water discharge standards or meet the water quality requirements for reuse. Wastewater treatment is widely used in various fields such as construction, agriculture, transportation, energy, petrochemicals, environmental protection, urban landscape, healthcare, catering, etc., and is also increasingly entering the daily lives of ordinary people. Wastewater treatment engineering refers to a project that uses various methods to separate pollutants from wastewater or convert them into harmless substances, thereby purifying the wastewater.

The processes for treating sewage include anaerobic filters, jet aeration, contact oxidation, oxidation ponds, and subsurface flow constructed wetlands.

Anaerobic filtration process

This process does not require electricity and is suitable for areas with difficult power supply.

The predicted processing capacity is about 50-70% for COD and BOD removal, 50-80% for SS removal, and 20-50% for ammonia nitrogen removal.

SBR process, also known as Sequential Batch Reactor Activated Sludge Process, is an activated sludge wastewater treatment technology that operates in an intermittent aeration manner. Unlike traditional sewage treatment processes, SBR technology adopts a time division operation mode instead of spatial division operation mode, non stable biochemical reactions instead of steady-state biochemical reactions, and static ideal sedimentation instead of traditional dynamic sedimentation. Its main feature is orderly and intermittent operation in operation. The core of SBR technology is the SBR reaction tank, which integrates functions such as homogenization, primary sedimentation, biodegradation, and secondary sedimentation into one tank, without a sludge reflux system. The SBR process has significant characteristics such as simple process, flexible and variable operation modes, the ability to form multiple process routes, spatial mixing, ideal flow pushing in time, shock resistance, high purification efficiency, good effluent quality, and prevention of sludge expansion. And enhancing biological adsorption is its more important advantage. Therefore, it has received attention in the field of wastewater biological treatment technology, and has undergone significant development and widespread application. There are successful examples of SBR treatment of leachate from garbage.

SBR process

Contact oxidation process, also known as "submerged biological filter", "contact aeration method", "fixed activated sludge method", is a sewage treatment technology that was pioneered in the early 1970s. Its technical essence is to fill the biological reaction tank with fillers, and the already oxygenated sewage submerges all the fillers and flows through them at a certain flow rate. Covering the packing with biofilm, sewage comes into extensive contact with the biofilm. Under the metabolism of microorganisms on the biofilm, organic pollutants in the sewage are removed and purified.

Contact oxidation process

The biological contact oxidation method combines the characteristics of activated sludge method and biofilm method. The concentration of biological solids in the tank (5-10g/l) is higher than that of activated sludge method and biofilter, and has a higher volumetric load (up to 2.0-3.0kgBOD5/m3. d). In addition, the contact oxidation process does not require sludge reflux, has no sludge expansion problem, and is simpler to operate and manage than activated sludge method. It has strong adaptability to fluctuations in water quantity and quality. It is a typical aerobic treatment method with the advantages of high aeration rate, high treatment degree, and automated control.

Oxidation pond process

The subsurface flow constructed wetland system is an animal and plant ecosystem formed by filling a certain amount of filling material (such as soil, gravel, etc.) in a depression with a certain aspect ratio and bottom slope to form a filling bed, and planting aquatic plants (such as reeds, etc.) with good treatment performance, high survival rate, strong water resistance, long growth cycle, beauty, and economic value on the surface of the bed.

Subsurface flow constructed wetland

Since 1990, the apparent consumption of sewage treatment worldwide has grown at an average annual rate of 6%. In the decade of the 1990s, the average annual growth rate of apparent consumption of sewage treatment in China reached 17.73%, which is 2.9 times the world's average annual growth rate. Entering the 21st century, China's sewage treatment industry is growing rapidly. From 2000 to 2004, the consumption of sewage treatment in China increased from 1.88 million tons to 4.47 million tons, a 2.3-fold increase, with an average annual growth rate of over 27%. In 2001, the apparent consumption of sewage treatment in China reached 2.25 million tons, surpassing the United States to become a major consumer of sewage treatment. At the same time, the import of sewage treatment has also significantly increased. In 1998, China imported 1 million tons of sewage treatment, thus becoming the ZLarge sewage treatment importing countries. Compared to 1998, the average annual growth rate of sewage treatment imports reached 27.14% in 2004. It is expected that in 2005, the apparent consumption of sewage treatment in China will reach 5 million tons, and imports will remain at around 3 million tons.

With the rapid development of the sewage treatment market, China's sewage treatment production has also ended its long-term stagnation and achieved high-speed growth. The sewage treatment production in China increased from 460000 tons in 2000 to 2.36 million tons in 2004, with an average annual growth rate of 82.6%. The proportion of domestic market demand also increased from 24.47% in 2000 to 52.80% in 2004. During the same period, the world's sewage treatment production only grew at a rate of about 6%.