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Preliminary Study on Process Control of Wastewater Treatment Plant Process

Release time:2021-05-27 10:43:11  Views: 472
Description:The sewage treatment process of the sewage treatment plant is a process-oriented production system. Water, gas, and mud ...

The sewage treatment process of the sewage treatment plant is a process-oriented production system. Water, gas, and mud each have their own different processes, from water inlet to water outlet, from blower to biological tank aeration, from residual sludge pump to mud cake The smooth operation of these processes ensures the stability of the overall process of the sewage plant, and can make the final effluent water quality stable and up to standard. More and more wastewater treatment plant process managers have realized that it is not feasible to control the results of wastewater treatment, and that the result control must be realized lagging behind. The original control based on changes in the effluent index can no longer satisfy the environmental protection system’s impact on the wastewater treatment plant. The supervision of the process, moving the control point forward and entering the sewage treatment process, is a way to improve the effect of process control.


Process control has become the direction to improve the management and control capabilities of sewage plants in the future. This requires operators to reverse the idea of judging the process by focusing only on changes in effluent water quality, and requires process personnel to move their focus forward and enter the water, gas, and mud processes of the sewage plant. In the process, discover and predict process changes from process changes, and take corresponding process adjustment measures to prevent process changes from affecting the effluent water quality.


The process control commonly used in sewage plants is mainly concentrated on the data in the middle of the three processes of water, gas and mud. These data are changing all the time. The operating personnel need to understand and master the process parameters of the three processes, and find out in time Abnormal, generally speaking, the main parameters of the sewage treatment plant involved in the sewage treatment process are:


Process name

Process parameter name

effect






Sewage treatment process

Inlet water flow: Q

Detect the data of daily processed water volume,Determine whether the processing capacity of the system meets the demand

PH: PH

Detect the pH value of sewage to determine whether there is an abnormality in the pH of the sewage.

Dissolved oxygen: DO

Detect the changes of dissolved oxygen at each stage of the biological pool, and judge whether the dissolved oxygen meets the environmental requirements of each stage.

Sludge concentration: MLSS

Detect the sludge concentration in the biological pond to determine whether the biomass is sufficient.

Volatile sludge concentration:MLVSS

Detect the level of biomass in the activated sludge in the biological pond to determine whether the biomass is sufficient.

Redox potential:ORP

According to the electric potential, the progress of the biological reaction of denitrification and phosphorus removal can be judged.

Nitrate:NO3-N

Detect the effect of nitrification and nitrification in the nitrification section to determine the degree of biological denitrification reaction.

Return sludge volume:Qh

Detect the sludge return flow rate and judge whether the sludge return ratio of the biological tank meets the requirements of activated sludge treatment

Internal return sludge volume:Qnh

Detect the internal reflux of the nitrification solution, determine the reflux ratio in the biological tank, and the degree of denitrification reaction.

Biological phase and quantity:

The number and status of microorganisms in activated sludge, to determine the changes in the types of microorganisms


Sludge treatment process

Moisture content:%

Detect changes in moisture content before and after sludge dewatering

Sludge concentration:MLSS

Detect the sludge concentration before sludge dewatering

Sludge flow:Qn

Detect the daily output of desliming

Mud cake transportation volume:Qgn

Detect the daily export quantity of mud cakes

PAM dosage:qy

Detect the daily usage of PAM medicament and calculate the proportion of medicine consumption.


Gas supply process

Gas flow: Qq

Detect the air output of the blower, determine the soda-water ratio, and evaluate whether the oxygen demand of the activated sludge in the biological pond is sufficient.

Gas pressure: P

Detect the air outlet pressure of the blower, determine whether the operation of the fan meets the aeration needs of the biological pond, and judge the blockage of the aeration device of the biological pond.


The parameters listed in the table are the data that needs to be understood in the process control of the process of the sewage treatment plant. These data are the operating data of each process line. These data also reflect the state of the water vapor sludge in each process. And change. Process control is to change the original process judgment based on the biological treatment results of activated sludge to the process judgment of changes in the activated sludge biological treatment environment. This requires the analysis of the detection parameters of the living environment of the activated sludge, and the wastewater treatment plant Process analysis is also based on the detection of the living environment of microorganisms.


After the process parameters are determined, these parameters need to be collected, tested, and counted on a daily basis. The wastewater treatment plant traditionally uses manual tests, but manual tests are restricted by the equipment personnel. The frequency of all process item parameter tests is low and the cycle is long. Sampling also has a certain degree of contingency, and there is a certain lag and misleading in the prediction of the process. If the sewage plant tests these parameters stably for a long time, this lag and contingency can be partially eliminated, but it cannot fully meet the needs of process control. . With the wider application of sewage treatment instruments, these process parameters can be detected by online instruments. Dissolved oxygen, sludge concentration, flow and other parameters can be quickly and conveniently detected, so that the changes in process parameters can be reflected in real time , To provide massive data support for the process management of the sewage plant, but the sewage environment of the sewage plant is harsh, and a large number of microorganisms growing in the biological pond will breed biofilm on the surface of the instrument probe placed in it, which affects the accuracy of the probe. In daily use, it is necessary to strictly implement the maintenance procedures of the instrument probe, and perform regular maintenance and manual comparison and verification. The adoption of a large number of online instruments, on the one hand, makes up for the shortcomings of manual testing, on the other hand, it also puts forward new requirements for the adjustment of the work focus of the sewage treatment plant, which requires the sewage treatment plant to effectively manage the automatic control instruments and play its due control and management role. , Improve the accuracy and real-time of process management.


These process parameters reflect the changes in the living environment of microorganisms at all times. These data generally have two changes. One is the impact of abnormal water ingress, and some environmental factors change the data in the first time; Species are changes that gradually accumulate over time. Some short-term changes, such as the sudden increase in water volume caused by the ingress of rain in the rainstorm season, the rapid change of pH caused by abnormal pollutants in the inflow, and the rapid decline of dissolved oxygen in the biological pond caused by high concentration of inflow, are easy for operators to perceive in the first time It is possible to conduct investigations based on abnormally changing process parameters in a timely manner, determine the reasons for the changes in process parameters, and take corresponding measures to adjust. The long-term cumulative process parameter changes are often overlooked, such as temperature changes, the gradual increase in sludge concentration caused by delayed sludge discharge, etc. These changes are a cumulative process, which requires operators to draw a change curve to observe the changes. According to the operating experience, the warning line shall be set. When the warning line is reached, the corresponding process control measures shall be taken to ensure that the environmental state of the system is in a stable operating condition, and the effluent water quality is stable and up to standard.


The process control of the sewage treatment plant is the supervision and management of the sewage treatment process, and it is the front-end quality management approach to ensure that the effluent quality is stable and up to the standard. The process backwards from the results is a clear lagging management. In terms of quality assurance, the sewage plant should reverse the results as soon as possible. Process management, improve the management level of the wastewater treatment plant through pre-management, and ensure the stable and up-to-standard effluent water quality.