Basic Knowledge of Sewage Treatment
1. What is self-purification of water?
Self-purification of water: The polluted river reduces or transforms the concentration of pollutants through physical, chemical and biological processes, and the water recovers to its original state, or decreases from exceeding the water quality standard to equal the water quality standard.
2. What are the basic methods of sewage treatment?
The basic method of sewage treatment: is to use a variety of means and technology, the sewage pollution substances separation and removal, recycling, or into harmless substances, so that the sewage is purified. Generally divided into water supply treatment and sewage treatment.
3. What are the current sewage treatment technologies?
Modern sewage treatment technology, according to the principle of action can be divided into physical treatment, chemical treatment, biological treatment.
4. Five measurement indicators of water
Biochemical oxygen demand (BOD) : The amount of oxygen required to degrade organic matter under aerobic conditions due to the action of microorganisms. It is a comprehensive index indicating that sewage is polluted by organic matter.
Theoretical oxygen demand (thOD) : The theoretical oxygen demand of an organic substance in water. Usually refers to the theoretical value of oxygen demand for the complete oxidation of carbon and H in organic matter to carbon dioxide and water (that is, oxygen demand calculated according to the complete oxidation equation).
Total oxygen demand (TOD) : refers to the amount of oxygen in water that can be oxidized, mainly the amount of oxygen required when organic materials are turned into stable oxides during combustion. The result is expressed in mg/L of O2.
Chemical oxygen demand (COD): is a chemical measure of the amount of reducing substance in a water sample that needs to be oxidized. The oxygen equivalent of a substance (usually organic matter) that can be oxidized by a strong oxidant in wastewater, wastewater treatment plant effluent, and contaminated water.
Total organic carbon (TOC) : refers to the total amount of carbon contained in dissolved and suspended organic matter in the water body.
5.what is the use of biochemical treatment?
It is generally believed that only the wastewater with BOD/COD value greater than 0.3 is suitable for biochemical treatment.
6. What are the sanitary standards for drinking water?
Physical indicators of hygienic standards for drinking water: color, turbidity, odor and taste.
7. What is water eutrophication?
Water eutrophication is a natural phenomenon which occurs in fresh water and is caused by the excessive content of nitrogen, phosphorus and potassium in water.
The main reason for the formation of water eutrophication is that nitrogen, phosphorus, potassium and other elements are discharged into the surface water with a slow flow rate and a long renewal period, which makes algae and other aquatic organisms grow and reproduce in large numbers, so that the production rate of organic matter far exceeds the consumption rate, the accumulation of organic matter in the water and the process of destroying the aquatic ecological balance.\
8. What is dissolved oxygen?
Oxygen dissolved in water is called dissolved oxygen. Dissolved oxygen is the oxygen on which organisms and aerobic microorganisms live in water bodies. Different microorganisms have different requirements for dissolved oxygen.
9. What are the basic methods of modern sewage treatment?
Modern sewage treatment technology, according to the principle of action can be divided into physical treatment, chemical treatment, biological treatment.
10. What is the stability of colloid?
Colloidal stability: refers to the colloidal particles in water for a long time to maintain the dispersion of suspension characteristics.
11. What is electric bit?
Galvanic potential: The zeta potential on the colloidal sliding surface.
12,.hydrophobic colloid how to form large particles?
For hydrophobic colloid, the peaks of repulsion energy must be reduced or eliminated by decreasing or eliminating the ζ potential of the colloids in order to form large particles through Brownian motion collisions.
13. what is the role of adsorption bridge?
Adsorption bridging refers to the adsorption and bridging of macromolecule and colloidal material.
14. What does the grille do?
Grille function: to intercept thicker suspended matter or floating impurities.
15. What are the main factors affecting the coagulation effect?
The main factors affecting coagulation effect are water temperature, pH value and alkalinity of water, concentration of suspended matter in water and hydraulic conditions.
16. How many types of precipitation? What are they?
There are four types of precipitation. They are:
Free precipitation: particles present a discrete state in the precipitation process, their shape, size and mass do not change, the subsidence speed is not disturbed, and each completes the precipitation process independently.
Turbulent precipitation: The size, mass and settling velocity of particles increase with the increase of depth during the precipitation process.
Crowded precipitation: particles have a large concentration in water and interfere with each other in the process of sinking, forming an obvious interface between clear water and muddy water, and gradually moving downward.
Compression precipitation: the concentration of particles in water is very high. In the process of precipitation, particles contact with each other and are mostly supported by compressors, and the gap of the lower particles is squeezed out.
17. According to the direction of water flow in the pool, which kinds of sedimentation tank can be divided into?
According to the different direction of water flow in the tank, the sedimentation tank can be divided into flat flow, oblique flow, radial flow and vertical flow.
18. What is the law of the impurity distribution in the filter material layer?
Impurity distribution law in the filter material layer: At the beginning of filtration, the filter material is relatively clean, the pores are large, the water shear force is small, the adhesion effect is strong, at this time, the water particles are first intercepted by the surface filter material, with the extension of filtration time, the impurities in the filter layer, the porosity gradually decreases, especially the surface fine filter material, the water shear force increases, the shedding effect is enhanced, Finally, the particles that are adhered to first fall off and move to the lower layer and are intercepted by the lower filter material.
The result is that: under a certain filter head, the filtration rate will decrease sharply, or at a certain filter speed, the loss of the head reaches the limit value, or because of the uneven force on the filter surface, the mud film cracks, a large number of water flows out of the cracks, resulting in the impurity particles in the water through the filter layer and the effluent quality deteriorates.
19. What are the ways to improve filtration efficiency?
The way to improve filtration efficiency: in order to change this situation to improve the filter layer containing pollution capacity, there is a "reverse particle size" filtration, that is, the direction of the flow, the filter size from large to small, due to the upward flow and two-way flow filter structure is complex, inconvenient washing and other reasons.
20. homogeneous filter media composed of what?
Homogeneous filter material composition: homogeneous filter material refers to the whole filter layer depth direction of any cross section, filter material composition and average particle size is uniform, rather than referring to the filter material particle size is exactly the same.
21. What is negative head phenomenon? What are some ways to avoid it?
Negative head phenomenon: During filtration, when the filter layer traps a large amount of impurities, so that the head loss at a depth below the sand surface exceeds the water depth at that depth.
The way to avoid negative water head is to increase the water depth on the sand surface, or the filter water position is equal to or higher than the filter surface. This is why siphon filters and valveless filters do not have negative water heads.
22. How many ways are there to supply ordinary fast filter backwashing water?
There are two ways to supply backwash water to ordinary fast filter: flushing pump and water tower.
23. What is fold point chlorination?
When the organic matter in water is mainly ammonia and nitride, its actual chlorine demand meets, the amount of chlorine increases, the amount of residual chlorine increases, but the latter growth slowly, after a period of time, the amount of chlorine increases, the amount of residual chlorine decreases, and then the amount of chlorine increases, the amount of residual chlorine rises again, after this break point free residual chlorine appears, continue to add chlorine disinfection effect is the best, that is, the break point add chlorine.
24. activated sludge method which several systems?
Activated sludge process is composed of aeration tank, sedimentation tank, sludge reflux, residual sludge removal system.
25. What is the sludge settlement ratio?
Sludge settling ratio (SV%) : refers to the volume ratio (%) of the settled sludge to the mixed liquid in the aeration tank, which is settled for 30min in a 1000ml measuring cylinder.
