Domestic sewage is the wastewater discharged from residents' daily lives, mainly from residential and public buildings such as residences, government offices, schools, hospitals, shops, public places, and industrial enterprise bathrooms.

The pollutants contained in domestic sewage are mainly organic matter (such as proteins, carbohydrates, fats, urea, ammonia nitrogen, etc.) and a large number of pathogenic microorganisms (such as parasite eggs and intestinal infectious viruses, etc.).

The organic matter present in domestic sewage is extremely unstable and prone to decay, producing a foul odor. Bacteria and pathogens multiply in large quantities using organic matter in domestic sewage as a nutrient, which can lead to the spread and prevalence of infectious diseases.

1、 The hazards of sewage

1. Pathogen contamination

Mainly from urban domestic sewage, hospital sewage, garbage, and surface runoff. The characteristics of pathogenic microorganisms are: ① large quantity; ② Widely distributed; ③ Long survival time; ④ Fast reproduction speed; ⑤ Easy to develop resistance and difficult to eliminate; ⑥ After traditional secondary biochemical wastewater treatment and chlorination disinfection, certain pathogenic microorganisms and viruses can still survive in large numbers; This type of pollutant actually enters the human body through multiple pathways and survives in the body, causing human diseases.

2. Aerobic organic pollution

The common characteristic of organic matter is that these substances directly enter the water body and are decomposed into simple inorganic substances such as carbon dioxide and water through the biochemical action of microorganisms. During the decomposition process, dissolved oxygen in the water is consumed, and pollutants decompose and deteriorate water quality under anaerobic conditions. These organic substances are often referred to as aerobic organic matter. The more aerobic organic matter in the water, the more oxygen is consumed, and the worse the water quality, indicating that the water pollution is more severe.

3. Eutrophication pollution

It is a water pollution phenomenon caused by excessive content of plant nutrients such as nitrogen and phosphorus. Eutrophication of aquatic ecosystems can occur through two pathways of chemical pollutants: one is through an increase in the amount of inorganic nutrients that normally limit plants; Another way is through the increase of organic matter as decomposers.

4. Stinky odor

Odor is a common pollution hazard that also occurs in polluted water bodies. There are over 4000 types of foul odors that humans can smell, with dozens of more harmful ones. The harm of foul odor is manifested as: ① obstructing normal respiratory function and reducing digestive function; Mental restlessness, reduced work efficiency, decreased judgment and memory; Long term work and living in a foul odor environment can cause olfactory dysfunction, damage the excitation and regulatory functions of the central nervous system and cerebral cortex; ② Some aquatic products are contaminated with a foul odor and cannot be consumed or sold; ③ Odorous water bodies cannot be used for swimming, fish farming, or drinking, which destroys the use and value of water; ④ It can also produce toxic hazards such as hydrogen sulfide and formaldehyde.

5. Acid, alkali, and salt pollution

Acid and alkali pollution cause changes in the pH of water bodies, disrupt their buffering effect, eliminate or inhibit the growth of microorganisms, hinder water self purification, and can also corrode bridges, ships, and fishing equipment. Acid and alkali often enter the same water body at the same time, and after neutralization, certain salts can be produced. From the perspective of pH value, acid and alkali pollution self purifies due to neutralization, but various salts are produced, which become new pollutants in the water body. Because the increase of inorganic salts can increase the osmotic pressure of water, it has adverse effects on the growth of freshwater organisms and plants. In saline alkali areas, salt in surface water and groundwater will further harm soil quality.

6. Groundwater hardness increases

The hazards of high hardness water, especially permanent high hardness water, are manifested in various aspects: unpleasant to drink; Can cause digestive disorders, diarrhea, and miscarriage in pregnant and livestock; Inconvenience to people's daily lives; High energy consumption; Affects the lifespan of water kettles and boilers; Boiler water scaling can easily cause explosions; Softening and purification treatment are required, and the loss of acid, alkali, and salt into the environment can cause an increase in groundwater hardness, forming a vicious cycle.

7. Toxic substance pollution

Toxic substance pollution is a particularly important category in water pollution, with a wide variety of types, but the common feature is the toxic harm to biological organisms.

2、 Domestic sewage treatment process

1. Aerated biological filter

Introduction to sewage treatment process: Aerated biological filter is a device that sets up fillers in the biological filter treatment equipment, and uses artificial oxygen supply to promote the growth of a large number of microorganisms on the fillers. This sewage treatment process device consists of a filter bed, gas distribution device, water distribution device, drainage device, etc. The aeration device adopts a matching dedicated aeration head, and the small and medium-sized bubbles generated are repeatedly cut by the packing material to achieve a near micro controlled aeration effect. Due to the high sludge concentration in the reaction tank and compact treatment facilities, it can greatly save floor space and reduce reaction time.

2. SBR phosphorus removal process

Introduction to sewage treatment process: The main reason for eutrophication of water bodies is the discharge of large amounts of ammonia nitrogen and phosphorus by humans, with phosphorus being the most important factor in eutrophication of water bodies. Throughout the domestic sewage treatment process, phosphorus removal technology has always been a difficult problem for the operation of sewage treatment plants. The traditional physical and chemical phosphorus removal technology requires a large amount of chemicals and has the disadvantages of high operating costs and large sludge production; The pre anaerobic biological phosphorus removal process has the advantage of low operating costs, but due to its complete dependence on microbial phosphorus uptake and release, it is difficult to meet the requirements of the national sewage treatment process. When considering the reuse of reclaimed water, it is even more difficult to meet the requirements.

3. A/O biological filter

Introduction to sewage treatment process: Due to the scattered distribution of residential areas in small towns in China, there are more and less sewage sources, and the scale of urban sewage plants is often less than 10000 tons per day. The sewage treatment processes commonly used by domestic large and medium-sized urban sewage treatment plants include traditional activated sludge method A2/O、SBR、 If these technologies are used to construct small town sewage treatment plants, such as oxidation ditches, it will result in high operating costs and inability to operate normally. It is necessary to adopt processes that are low in investment, low in operating costs, stable and reliable in technology, and relatively simple in operation and management, tailored to the characteristics of small towns.

This article is compiled by domestic sewage treatment equipment and does not represent the views of this website.