Industry Trends

In modern society, along with the acceleration of urbanization, the production of sewage, a category of pollution source, is increasing. Urban sewage is the wastewater discharged into the municipal sewage system, which mainly includes three parts: domestic sewage, industrial sewage and rainwater. Among them, domestic sewage is a general term for all kinds of sewage produced in human's daily life, and as common municipal sewage, it is closely related to our life. Sewage will pollute our environment and produce water pollution, air pollution and soil pollution, so sewage cannot be directly discharged into the natural environment. So how should domestic sewage be collected and treated?

First district drainage system for each single-family residents to collect the sewage generated, the collected sewage into the municipal pipe network pipeline, a small part of the sewage into the water station distributed around the pipe network for treatment, the majority of the remaining sewage Z flow into the sewage treatment plant for centralized treatment.

Sewage treatment can be divided into primary, secondary and tertiary treatment. Primary treatment is the physical treatment part, mainly to remove solid pollutants in suspension (suspended SS, etc.), secondary treatment is the biological treatment part, mainly to remove organic pollutants in colloidal and dissolved state (COD, BOD, TN, TP, etc.). The tertiary treatment, i.e., the deep treatment part, further removes fine suspended matter and hard-to-degrade organic substances, etc. The following is a brief introduction to the general process flow of municipal wastewater treatment, using the Huashan plant of Everbright Water Jinan as an example.

Sewage into the physical treatment area (pretreatment area), mainly including coarse grating, lifting pump room, fine grating, aeration and sand sedimentation tank and fine grating. The main function of the coarse grating is to remove the larger organic debris in the sewage, such as branches, wood blocks, plastic bags, etc., to extend the service life of the equipment and ensure the normal operation of the subsequent treatment structures. The lifting pump lifts the sewage to a certain height to ensure that the sewage flows by gravity to the subsequent treatment units. The fine grate removes smaller debris, such as cigarette butts, paper scraps, etc.

The role of the aeration sedimentation tank is to remove organic pollutants attached to the grains of sand under the action of aeration, the grains of sand in the sewage rub against each other and withstand the aeration shear force, and have a pre-aeration effect. The removal of larger gravity grit can protect subsequent pipelines, valves and other facilities from wear and tear, and avoid the deposition of grit in subsequent structures. After the aeration and sedimentation tank, the wastewater flows through a fine grate with 1mm diameter holes to further intercept and remove fine debris from the wastewater to ensure the normal operation of the subsequent MBR membrane tank unit.

After the pretreatment unit is the biological treatment area - AAO bioreactor, mainly including pre-anoxic zone, anaerobic zone, anoxic zone, aerobic zone, which is the core unit of sewage biological treatment. A large number of microorganisms in the activated sludge use their own metabolism to adsorb and degrade pollutants in the water in order to purify the water.

One of the main functions of the bioreactor is nitrogen removal and phosphorus removal. The principle of denitrification reaction is: in the aerobic zone, nitrifying bacteria convert ammonia nitrogen and organic nitrogen in the sewage into nitrate nitrogen by nitrification; in the anoxic section, denitrifying bacteria convert nitrate nitrogen brought in by the internal reflux into nitrogen gas by denitrification and escape into the atmosphere to achieve denitrification. The principle of phosphorus removal reaction is as follows: in the anaerobic section, the phosphorus-polyphosphorus bacteria release phosphorus; entering the aerobic section, the phosphorus-polyphosphorus bacteria then absorb phosphorus in excess and discharge through the remaining sludge, thus achieving the purpose of phosphorus removal.

After the biological pond is the MBR membrane pond area, MBR membrane bioreactor is a new technology combining membrane technology with biochemical reaction in wastewater treatment, which is widely used in the range. MBR pond uses membrane to filter the mud-containing wastewater in the biochemical reaction pond to realize mud-water separation, integrating the functions of traditional secondary sedimentation pond and deep treatment system in one. On the one hand, the membrane retains the microorganisms in the reaction tank, which greatly increases the concentration of activated sludge in the tank and makes the degradation of pollutants more complete, on the other hand, due to the high filtration precision of the membrane, the produced water is guaranteed to be clear and transparent.

The water filtered by the MBR membrane pool then comes to the Z process of our whole process - UV disinfection canal. It is the use of ultraviolet light between 200-280nm wavelengths to destroy the DNA or RNA molecular structure of microbial cells, causing microbial growth cell death and (or) regenerative cell death, to achieve sterilization effect. The E. coli content in the disinfected effluent is much lower than the standard of 1,000 per L.

The treated effluent can be reused as medium water, including car washing water, landscape water, green irrigation, road spraying, industrial water, etc.