sewage treatment plant directly undertakes the function of purifying sewage. it is the first battlefield to achieve the goal of water environment treatment, and also the main profit realization link of sewage operation company. however, with the improvement of effluent quality standards of sewage treatment plants and the intensification of environmental protection supervision, the operation of some sewage treatment plants has exposed problems. reports about the quality of effluent exceeding the standard are common in various media.
in the current situation of extensive publicity of social responsibility, high-pressure supervision and punishment, and the state attaches great importance to environmental protection payment, these situations still occur. apart from the technical reasons that can not be solved for individual projects, the inadequate operation and management of sewage plants is one of the important reasons.
the scale, water quality, process and equipment of sewage treatment plants are different, but the objectives, contents and measures of operation and management are basically the same.
the management objectives are to ensure the compliance of sewage treatment plants, that is, the effluent quality meets the standards, and on this basis to achieve the economic benefits of enterprises;
the content of management is water quality and cost management of corresponding objectives, safety and equipment management to ensure the realization of objectives, and brand creation to further extend.
management measures are the key to achieve quality assurance and efficiency in sewage plant operation. however, some of the workers in the sewage plant have low salaries, lack of managers and technicians, and low requirements for effluent indicators before. the operation and management of these wastewater plants are extremely extensive. there is basically no concept and mode of water quality and cost process monitoring. now, after the effluent quality is raised to level a, online monitoring of total nitrogen and total phosphorus has been added. there are no effective control measures to ensure that the effluent meets the standards blindly, increase the cost, or lead to the reduction of the effluent meets the standards. therefore, it is necessary to summarize the key management measures on the basis of practical experience for peer exchange and reference.
1. reasonable application of automatic control system to improve response speed and reduce the impact of human misoperation
automatic control system is an essential part of modern sewage treatment plant, its application function and role should include four parts: 1) real-time display of the status of key equipment and accurate data of key parameters; 2) energy saving and consumption reduction and equipment rotation; 3) timely response to changes in water quality and quantity to ensure that the effluent reaches the standard; 4) data statistics, printing and transmission.
in order to achieve the above functions, besides setting reasonable on-line instruments and data acquisition, the most important control content of the automatic control system is accurate aeration and accurate dosing. accurate aeration can save a lot of electricity for sewage treatment plants, and ensure that the quality of effluent reaches the standard. in the era of primary b effluent, many wastewater treatment plants do not care about the control of aeration. after the standard of primary a, especially the increase of total nitrogen on-line monitoring equipment, the total nitrogen in effluent of these wastewater treatment plants becomes a problem. at the same time, it is found that the ammonia nitrogen in effluent is very low, most of the time is less than 1.0 mg/l. excessive aeration is an important reason besides the scheduling reasons of the process itself.
for example, a sewage treatment plant that started to monitor the total nitrogen of effluent has found that the total nitrogen of effluent has increased for a period of time. after analyzing the reasons, it is found that due to the renovation of urban pipe network, the amount of water inflow at night has been greatly reduced. the automatic control system of the sewage plant does not link the data of water volume change, dissolved oxygen at the aerobic end of oxidation ditch with the frequency conversion of the blower, and still relies on manual adjustment of aeration at night. the fluctuation of inter-flow did not attract the attention of the attendants, which resulted in the large aeration air volume, the increase of dissolved oxygen in the effluent of oxidation ditch and internal reflux mixture, and affected the denitrification effect in anoxic section. facts have proved that a system can not be precisely controlled by manual work. no matter how the staff training is carried out, effective system measures must be deployed to reduce the impact of human errors.
because the feedback control of effluent quality is delayed for a long time, it is difficult to realize the precise automatic control of the dosage of phosphorus removal and denitrification agents. generally, the dosage of phosphorus removal agents in sewage plants is excessive, because it only affects the pharmaceutical cost of sewage plants, and the denitrification carbon source may require a more precise dosage according to its dosage location.
for the dosage control, on the one hand, the dosage should at least follow the change of the processing water quantity in the dosing link, on the other hand, it should reflect the man-machine interaction of the automatic control system. the key water quality indexes in the control process can be input through a certain frequency of manual testing. based on this water quality index, the change of the corresponding dosage can be determined by referring to the data of better historical experience.
for example, the total phosphorus data of the effluent of secondary clarifier should be detected to understand the efficiency of biochemical phosphorus removal and determine the dosage of chemical phosphorus removal. because the effect of biochemical system has certain impact resistance, the data can control the dosage more accurately in a certain period of time. the third key function of dosing control is to automatically adjust dosage of medicines in time according to the feedback of effluent indicators, but it still needs to set the benchmark data of corresponding indicators and the adjusting range manually. therefore, the effective application of the automatic control system must maintain enough man-machine interaction, and the dosage determined by the automatic control system should be managed by operators.
2. reasonable dispatch to give full play to the effect of nitrogen and phosphorus removal by the process itself
in general, the automatic control system can only regulate the operation of sewage treatment plants in a limited way under a set operation mode. reasonable adjustment of process operation mode is a more important measure. for municipal sewage treatment plants, due to the installation of septic tanks and imperfect distribution of rain and sewage pipelines, the concentration of bod in influent water is generally low, while the total nitrogen may be higher, and the ratio of carbon to nitrogen can hardly reach 3:1. according to the requirement of material denitrification, the main purpose of process operation scheduling is to rationally adjust the distribution of anoxic and aerobic space in biochemical pond, make full use of carbon source of influent, and achieve the target of total nitrogen of effluent as far as possible without additional carbon source. according to practical operation experience, total nitrogen of effluent can not be controlled more than 15mg/l under the condition of low bod:tn, but if it is to be controlled stably below 10mg/l, generally. additional carbon sources are still needed.
a municipal wastewater treatment plant with improved oxidation ditch is the main process in operation. the quality of water in and out of the wastewater during the initial period of bidding is as follows:
after adjusting the operation mode of the oxidation ditch and controlling the aeration and dissolved oxygen index, the water quality data of the highest value of total nitrogen in the effluent are as follows:
the adjustment measures of oxidation ditch are as follows: (1) increasing the volume of anoxic section, closing several aeration modules at the front end of the aerobic tank and the outlet area of the oxidation ditch, so as to increase the volume of anoxic section, further prolong the reaction time of anoxic denitrification, and reduce the dissolved oxygen content of mixed reflux liquid. (2) controlling do value of oxidation ditch effluent (denitrification and reflux mixture) and controlling do value of oxidation ditch effluent is not higher than 1.0 when ammonia nitrogen of oxidation ditch effluent is not higher than 3.5 mg/l. the adjustment is as follows: the shadowed area is the aeration area.
3. optimize production and operation records, pay attention to analysis and improvement
the well-managed wastewater treatment plants should include daily production reports, daily laboratory water quality reports, on-duty inspection records, shift records, equipment maintenance records, sludge transfer orders records, etc. the function of these documents is not only to record the operation of sewage treatment plants for managers and supervisors to understand, inspect and supervise, but also to guide the corresponding operators how to carry out their work, to find out the causes when they find problems (such as increased power consumption or drug consumption), and to provide the basis for managers'active analysis, evaluation and improvement and optimization.
after the automatic control system can accurately record the operation status of the equipment, the manually filled production records can be simplified appropriately. for example, a daily production report should be considered to cover other contents besides the sludge transfer list, simplify the work content of the document, and be more conducive to the focus of management. the daily production report includes daily water inflow and effluent volume, outflow sludge volume, average daily water inflow and effluent index and maximum value. key records of dosage of various medicines, daily water consumption, electricity consumption, equipment maintenance, process adjustment, etc.
the dosage of reagents should also be recorded and analyzed in more detail. as mentioned in the application of the automatic control system in point 1 above, the dosage in the table should not simply be filled into the water quality of the influent based on the data, but should be the key water quality index for recording and controlling the process.
analysis and evaluation table of drug dosage
4. pay attention to the situation of the surrounding water environment and take the initiative to communicate with the outside world.
although the operation of the sewage treatment plant is only the work inside the wall of the plant area, all the relevant parties (residents, drainers and government supervisors) who are affected by the operation of the sewage treatment plant and the effluent after treatment are outside the plant. therefore, the operation and management of the sewage treatment plant should pay close attention to the situation of the surrounding water environment at all times. understanding and forecasting the possible changes of water quantity and water quality, understanding the changes of water quality and the orientation of water use of effluent receiving bodies, and conducting periodic satisfaction surveys to the surrounding residents and government departments, actively assisting government departments to carry out regional water environmental quality improvement planning, reclaimed water reuse planning and exchange of experience in construction and operation of sewage plants, etc., can make more active control and improvement. the operation quality of the sewage treatment plant should be improved, and the brand of the company and the operation efficiency of the sewage treatment plant should be improved.
conditional sewage plants should carry out the construction and certification of the quality management system of iso 9001. through timely monitoring and evaluation of the external environment, managers should take the lead in rational operation planning, improve the corresponding personnel, hardware and software support, carry out adequate internal and external communication, operate under controlled conditions, timely and adequate record, evaluation and improvement of the entire operation process. to realize the safety, quality assurance and efficiency of sewage plant operation.
source: polaris water treatment network
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