A variety of sewage treatment principles and technical summary!

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What is wastewater treatment capacity or total BOD5 removal and treatment quality?‍

Sewage treatment capacity or total BOD5 removal: the total sewage flow (in m3/d) entering the sewage treatment plant every day can be used as an indicator of the treatment capacity of the sewage plant. The total amount of BOD5 removed per day can also be used as an indicator of the treatment capacity of the sewage plant. The total amount of BOD5 removed is equal to the product of the treatment flow rate and the difference of BOD5 in and out of the water, in kg/d or t/d.

◆ Treatment quality: The secondary sewage treatment plant uses the factory BOD5 and SS values as the treatment quality indicators. According to the new sewage treatment plant effluent discharge standards, two sewage treatment plant effluent BOD5, SS are less than 30mg/L. The quality of the treatment can also be measured by the removal rate. The removal rate is the influent concentration minus the effluent concentration divided by the influent concentration. Ammonia nitrogen, TP effluent value or removal rate are also applied to treatment quality indicators.

What is pH and its significance?‍

◆ pH indicates the acid-base degree of sewage. It is the logarithmic value of the reciprocal of the hydrogen ion concentration in water. Its range is 0~14, and the pH value is equal to 7, the water is neutral, less than 7 is acidic, the smaller the value, the stronger the acidity, and the more alkaline it is greater than 7. The greater the value, the stronger the alkalinity. The pH value of sewage has a certain influence on pipelines, pumps, gate valves and sewage treatment structures. The pH value of sewage treatment plants dominated by domestic sewage is usually 7.2~7.8. Too high or too low pH can indicate the entry of industrial wastewater. A value that is too low will corrode the pipeline, pump body and may cause harm. For example, the sulfide in sewage will produce H2S gas under acidic conditions. High concentrations make the operation work headache, runny nose, suffocation and even death. To this end, it is found that the pH reduction must be strengthened monitoring, looking for sources of pollution, and taking countermeasures. At the same time, the allowable pH range of biochemical treatment is 6~10, too high or too low can affect or destroy the biological treatment.

What is Total Solids (TS)?‍

◆ refers to the total amount of solids left by the water sample evaporating to dryness in a water bath at 100 ℃. It is the sum of dissolved solids and non-dissolved solids in sewage. It reflects the total concentration of solids in the effluent. The effect of the sewage treatment structure on the removal of total solids can be reflected by the analysis of the solids in and out of the water.

What is Suspended Solids (SS)?

◆ refers to the amount of solid substances in the sewage that can be intercepted by the filter. A portion of the suspended solids may precipitate under certain conditions. The determination of suspended solids is usually carried out by asbestos filter. The main equipment is Gulfstek crucible. When the test equipment conditions are not available, filter paper can also be used as a filter to obtain the amount of suspended solids from the subtraction of total solids and dissolved solids. When determining suspended solids, large differences are often produced due to different filters.

This indicator is one of the most basic data of sewage. The determination of suspended solids in the influent and factory water can be used to reflect the reduction of suspended solids after the sewage is treated by the primary sedimentation tank and the secondary sedimentation tank, which is the main basis for reflecting the sedimentation efficiency of the construction.

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