Operation Supervision of Municipal Wastewater Treatment Plants: Operational Requirements, Central Control Rules and Seven Classes of Performance Evaluation under HJ 2038-2014

1. What the standard does: turning operation into a checkable list

HJ 2038-2014, Technical specifications for operation supervision and management of municipal wastewater treatment plants, was approved on 2014-06-10 and took effect on 2014-09-01 as a first issuance, and is expressly a guidance standard. It applies to the operation, management, supervision and inspection of municipal wastewater treatment plants. Clause 4.1 requires that, in addition to this standard, operation shall comply with the relevant provisions of CJJ 60, the technical specification for operation, maintenance and safety of municipal wastewater treatment plants. It was drafted by the Tianjin Academy of Environmental Sciences through the Water Pollution Control Committee of the China Environmental Protection Industry Association, together with Tianjin Capital Environmental Protection Group and the Guangzhou Datanisha wastewater treatment plant.

Unlike process specifications, the value of this standard lies in breaking daily operation down into items that can be checked one by one: personnel and laboratory, signage, operating parameters for each unit, the discharge outfall, records, the central control system and annual performance evaluation. The sections below follow that thread.

2. General requirements: four management items and two classes of signage

Clause 4.2 sets four management baselines. Under 4.2.1, all operation and management personnel shall possess the required operating skills and their number shall meet the needs of the plant. Under 4.2.2, a dedicated laboratory shall be provided with the capability for pollutant testing and whole-process monitoring, whole-process testing shall be carried out as required, a laboratory analysis quality control standard shall be established, and measuring equipment shall be calibrated and verified periodically. Under 4.2.3, complete fire, explosion and emergency facilities, equipment and technical measures shall be in place, an environmental emergency response plan prepared, and environmental laws and regulations strictly observed. Under 4.2.4, the operation and management system shall be strengthened in the light of actual conditions, an operation and management manual compiled, and rules established for post responsibilities, operating procedures, routine inspection, work safety, equipment maintenance, personnel assessment and training, information records and archive management.

The signage requirements in clause 4.3 convert directly into a site checklist. Under 4.3.1, conspicuous identification shall be provided for the inlet, outlet or discharge outfall, water pollutant sampling points, structures for wastewater, sludge and odour treatment, all operating equipment, all categories of pipes and cables, and the main process nodes. Under 4.3.2, warning signs shall be placed where there is potential for falling, drowning, asphyxiation, poisoning, electric shock, fire, entanglement injury or infection.

3. The inlet end: metering, sampling and abnormal conditions

Chapter 5.1 covers the issues most often raised during inspection. Clause 5.1.1 requires that the lift pumps be operated according to the design or the actual influent flow, and that they not be shut down nor the number of operating units reduced without authorisation, so that all wastewater is collected and treated and the plant runs at full load. A metering device for the influent flow shall be provided for real-time measurement, with daily, monthly and annual totals compiled in accordance with CJJ 60. The metering device shall be maintained and calibrated periodically by a qualified quality inspection body. Clause 5.1.2 requires that continuous sampling and on-line monitoring devices be installed at the inlet in accordance with HJ/T 372 and HJ/T 355, and that the influent quality be tested against the indicators and frequencies specified in GB 18918. Clause 5.1.3 requires that where the influent flow or quality becomes abnormal and threatens stable compliance, effective control measures shall be taken and operating parameters adjusted promptly so as to prevent an operational incident.

4. Biological reactors: control items for activated sludge and biofilm processes

Clause 5.2.1 gives three general requirements: regulate the influent flow to each tank according to the arrangement of the tank trains and the operating mode, achieve uniform distribution, and maintain uniform aeration, plug-flow and mixing; adjust and control the influent flow, air-to-water ratio, dissolved oxygen (DO) and oxidation-reduction potential (ORP) in the reaction zone according to effluent quality requirements and the operating conditions of the process; ensure that key equipment such as submersible mixers, submersible flow propellers, blowers and diffusers or aerators, return sludge pumps, surplus sludge pumps, scrapers and suction sludge collectors, membrane separation units and high-pressure pumps remain in normal operation; and keep all tank surfaces free of scum, walls free of deposits and walkways free of foam and scum overflow.

Clause 5.2.2 addresses activated sludge reactors: dissolved oxygen shall be controlled effectively; operating parameters including sludge loading, settled sludge ratio, mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS), and sludge return ratio shall be controlled as the process design requires and adjusted according to flow and load, operating conditions and environmental factors; and parameter control for each activated sludge variant shall comply with the corresponding engineering specifications HJ 576, HJ 577 and HJ 578.

Clause 5.2.3 addresses biofilm reactors. Inflow rate and quality shall be controlled as the priority, so that hydraulic and organic loading are matched and biofilm activity and thickness are maintained. The dissolved oxygen concentration shall be controlled to the design value so as to achieve anaerobic, anoxic or aerobic conditions as required. Parameters to be controlled include hydraulic retention time, organic loading, hydraulic loading, rotational speed for rotating biological contactors, and backwash interval and backwash water volume for biological aerated filters. Detailed parameters shall follow HJ 2009, HJ 2010 and HJ 2014.

5. Advanced treatment: three pointers to other specifications

Chapter 5.3 takes a practical approach: rather than repeating parameters, it names the governing document.

• Coagulation reactors (clause 5.3.1): control velocity, water level and hydraulic retention time according to the process design and operating conditions; parameter control shall comply with HJ 2006.
• Filters (clause 5.3.2): the bed shall be backwashed on the basis of head loss or filtration time; parameter control shall comply with HJ 2008.
• Membrane separation units (clause 5.3.3): chemical or physical cleaning shall be carried out automatically and periodically as the process design requires so as to keep operation stable; parameter control shall comply with HJ 579.
• Clearwater tanks (clauses 5.3.4 and 5.3.5): upper and lower operating water levels shall be set together with automatic level control, plus disinfection equipment and a sampling point for water quality testing; the tank top shall be sealed, the specified residual chlorine concentration shall be maintained after disinfection, and water quality testing shall be carried out daily.

6. Sludge, odour, noise and equipment

Chapter 6 sets five requirements for sludge. Under clause 6.1.1, sludge treatment and disposal facilities shall be planned, constructed and commissioned together with the wastewater treatment facilities. Under clause 6.1.2, all sludge generated shall be collected and subjected to effective stabilisation, volume reduction and mass reduction. Under clause 6.1.4, the volume or mass of sludge leaving the plant shall be recorded, the total quantity dispatched shall be compiled, and the sludge transfer manifest system shall be strictly applied. Under clause 6.1.5, the moisture content, transport requirements and destination of sludge leaving the site shall comply with the notice on strengthening sludge pollution prevention and control at municipal wastewater treatment plants. Clause 6.2.3 provides a check: the total sludge generated on a quarterly basis shall be essentially consistent with the total sludge treated. Clause 6.2.4 notes that the theoretical sludge production may be estimated using the empirical formulae in Annex A.

Chapter 7 addresses odour in two parts. Under the general requirements (clause 7.1): odour control facilities shall meet the boundary environmental protection requirements set out in the environmental impact assessment approval for the plant and shall be constructed and commissioned together with the wastewater and sludge facilities; the gas discharged from the deodorisation unit shall be stable and compliant; and the boundary odour concentration shall comply with the maximum allowable concentration of waste gas pollutants at the boundary or protective-zone edge specified in GB 18918, or with local standards. Under the operating requirements (clause 7.2): the collection and conveyance system shall be patrolled and maintained as specified, covering fans, hoods and gas pipework; gas conveyance pipework shall be kept sealed and the line pressure drop recorded; and condensate in the collection and conveyance pipework shall be drained once per shift, with the flow reaching the design rate. For biotrickling and biofiltration, the odour gas flow and pollutant concentration shall be measured on schedule together with temperature, humidity, pressure and pH; suitable humidity shall be maintained; and where biofilm detachment or swelling, bed compaction, or channelling and short-circuiting in soil beds occur, the cause shall be identified and corrected and the event recorded for inspection. For chemical oxidation, the dosing rate shall be adjusted to the odour load; packing shall be cleaned or replaced according to the pressure drop across the packed tower; and pH, odour concentration, flow, temperature and pressure shall be controlled. For activated carbon adsorption, hydrogen sulphide, odour flow, concentration, temperature, humidity, pressure and pH shall be controlled; carbon shall be replaced promptly once flow and pressure fall outside the rated range and saturation is confirmed; and spent adsorbent shall be regenerated by desorption and disposed of harmlessly where discarded. For whole-process deodorisation, the condition and performance of the bio-media shall be observed periodically; the activated sludge dosing pump and sludge conveyance pipework shall be inspected periodically; the air supply system of the microbial incubator shall be patrolled periodically; and the sludge dosing rate shall be adjusted according to influent flow and quality and odour intensity.

Chapters 8 and 9 are short but pointed. Clause 8.1 requires that noise and vibration control facilities be constructed and commissioned together with the wastewater and sludge facilities; clause 8.4 requires periodic measurement and recording of boundary noise in compliance with GB 12348; clause 9.1 requires complete equipment ledgers and files, with the ledger established at the point of equipment handover; and clause 9.4 requires adequate spare parts and consumables for all equipment.

7. Central control: one requirement that cannot be bypassed

Chapter 10 is the technical handle for supervision. Clause 10.1.4 is the hardest of all: central control system records shall not be modifiable, monitoring of established key data shall not be removable, and the system shall not provide functions for modifying system data or selectively removing monitoring targets. This determines both the selection and the acceptance criteria of the central control system. In addition, clause 10.1.1 requires a fully functional central control platform and large screen display to record comprehensively and reflect in real time the operating status of the plant; clause 10.1.2 requires the system to provide data display, processing, recording and analysis together with automatic generation of dynamic trend curves, in accordance with Annex B; clause 10.1.3 requires the monitoring scale to match the design and the field data record to match the host computer record; clause 10.1.5 requires complete records, archived for inspection, with data retained for at least one year; and clause 10.1.6 requires data transmission to comply with HJ/T 212.

On recorded content, clause 10.2.2 requires the central control system to record in real time the influent and effluent flow, including cumulative flow, and the influent and effluent quality, covering key indicators such as COD and ammonia nitrogen, and to generate dynamic trend curves automatically; total nitrogen, total phosphorus and suspended solids may be recorded as selective indicators; and a reclaimed water flow meter shall be installed with flow data recorded and transmitted, with monitoring and recording of characteristic indicators such as colour and turbidity, and additional selective indicators where the reuse water has a defined purpose. Clause 10.2.3 requires recording of key equipment operating data: lift pumps, covering sump level, operating current, operating frequency and running time; aeration equipment, covering blower air volume and total current for blower aeration or total operating current for mechanical aeration, plus running time, speed or opening degree; and sludge dewatering equipment, covering running time, operating current and dosing rate. Clause 10.2.4 requires real-time recording and display of: dissolved oxygen in each biological tank; oxidation-reduction potential and activated sludge concentration for activated sludge processes; operating liquid level in each tank of SBR processes; and for BAF processes, the running time of the backwash blower and backwash pump, backwash air volume and water volume, clogging rate, and the head loss through the biofilter.

8. Information records and seven classes of performance evaluation

Chapter 11 divides the records into four categories. The facility construction record (clause 11.2) includes, but is not limited to: the project design approval or verification document, the environmental impact assessment approval document and the completion environmental acceptance report for the construction period; the design documents, covering treatment capacity, treatment process, commissioning date, the service area of the plant, catchment area, population served and the industrial enterprises within it; and information on sewer network construction, changes in collected wastewater volume, emission reduction accounting and environmental statistics. The facility operation record (clause 11.3) includes, but is not limited to: daily records of influent and effluent flow and quality and of the quantity of sludge generated, transferred and its destination; the operating status and maintenance and repair of major equipment such as aerators; and monthly records of power consumption, chemical consumption and dry sludge disposed. Separate records cover pollution reduction (clause 11.4) and facility upgrading (clause 11.5). Clause 11.6.2 lists the operating evidence: supervision monitoring reports, on-site inspection reports, and notices of rectification and penalties issued by the competent ecology and environment authority; plus electricity payment records, chemical purchase records and sludge disposal and transport records.

Clause 11.6.3 sets requirements for the operating report: the operating organisation shall periodically summarise operation and pollutant reduction, compile an annual facility operation report from the records, and transmit it promptly using information systems for data interconnection and wireless upload. The content includes, but is not limited to: influent flow and quality; treated volume and discharge compliance; sludge generation, treatment and disposal; reduction of key pollutants; and problems with the facilities and their operation together with corrective plans. Where sudden accidents, facility failures, excessive influent flow causing overload, or serious deterioration of influent quality directly affect compliance, the plant shall report promptly to the competent environmental protection authority as required.

The seven classes of performance evaluation in chapter 12 form a complete framework for annual self-assessment: 12.2.1 treatment process performance; 12.2.2 sludge treatment performance; 12.2.3 odour and noise control performance; 12.2.4 equipment maintenance and energy performance; 12.2.5 central control system and outfall management; 12.2.6 execution of the plant monitoring regime; and 12.2.7 the plant operation and management system. Clause 12.1.2 specifies that the evaluation covers, but is not limited to, the treatment capacity of the facilities, their operating performance in terms of effluent compliance and reduction of key pollutants, the process performance for removal of characteristic pollutants covering water pollutants, sludge and odour, and the current levels of energy and material consumption together with the economic performance relevant to reducing treatment cost. Clause 12.1.3 requires the operating organisation to carry out an annual assessment, with objectives covering the reduction of key pollutants and any operating problems together with their corrective plans.

Two closing caveats. The standard does not reproduce the numerical bands for dissolved oxygen, mixed liquor concentration or sludge return ratio; per clause 5.2.2 c those shall be taken from the dedicated engineering specifications HJ 576, HJ 577 and HJ 578. Second, the detailed display indicators for the central control system appear in Annex B, which is informative, whereas the prohibition on modifying records or removing monitoring sits in the normative text of clause 10.1.4. The two carry different weight and must be distinguished when preparing tender documents. This article is based on the issued draft; the formally published standard text prevails.