Status: Delivered · Region: East China · Ref. D-043
What We Delivered
Client: a food-processing company in East China (slaughtering plus a cooked-food production line); its name is withheld under our client-confidentiality policy. Daily wastewater flow is approximately 500 m³. The treatment system has been put into operation.
For the company's wastewater treatment plant, we completed the process design, supply of the main equipment and on-site commissioning. The delivered process is DAF + A/O + MBR + UV disinfection (the full process route is given under "Process Design" below); effluent is controlled to the design effluent targets set out below.
Delivery Record
The table lists what each delivery stage covered on this project and the record it produced.
| Stage | What it covered on this project | Record produced |
|---|---|---|
| 1. Design basis confirmation | Confirmed a daily wastewater flow of approximately 500 m³, with wastewater from slaughter-hall wash-down, offal washing, scalding, and floor wash-down in the production area; confirmed the influent quality (main parameters in the water-quality table below) and the design effluent targets. | Design basis sheet, influent quality data |
| 2. Process & mechanical design | Fixed the process route "oil separation + dissolved air flotation + A/O + MBR + UV disinfection" and the design parameters of each unit (equalisation tank 200 m³, saturator pressure 0.4 MPa, A/O HRT 24 h, MBR MLSS 8,000 mg/L, etc.). | Process flow diagram, P&ID, general-arrangement (GA) drawings, equipment list |
| 3. Manufacturing & quality control | Material inspection and in-process inspection of the main equipment, including the dissolved air flotation unit, the MBR system and the UV disinfection unit. | Material certificates, in-process inspection records |
| 4. Factory acceptance test (FAT) | Main equipment inspected and test-run against the design parameters before leaving the factory. | FAT record |
| 5. Packing & dispatch | Equipment packed according to the equipment list and dispatched to site. | Packing list, dispatch list |
| 6. Installation | On-site equipment installation, per contract scope. | Installation record |
| 7. Commissioning | Seeded the biological system with activated sludge and started up the A/O and MBR stages; issues handled during commissioning are described under "Commissioning Notes" below. | Commissioning log |
| 8. Performance verification (against the design basis) | 72-hour continuous-run test against the design influent and effluent parameters. | Performance test record |
| 9. Training, handover & after-sales | Handed over operating requirements to the operators, including DAF chemical-dosing control, A/O operation, MBR membrane cleaning and TMP monitoring, UV disinfection unit maintenance, and disposal of surplus sludge by a contracted third party. | O&M manual, training record, handover documents |
Delivery records for this project are on file and can be reviewed by qualified buyers under a confidentiality agreement.
Designed For
- Mixed slaughtering and cooked-food wastewater — with a large amount of coarse debris such as hair and bone fragments.
- High oil and grease — animal and vegetable oils 200–500 mg/L.
- High COD — 2,500–3,500 mg/L (mean 3,000 mg/L).
- High ammonia nitrogen — 80–150 mg/L, requiring nitrification–denitrification for nitrogen removal.
- High colour from blood pigments — visibly dark red, with a strong offensive odour.
Influent Quality and Design Effluent Targets
| Parameter | Influent concentration (design basis) | Design effluent target |
|---|---|---|
| COD | 2,500–3,500 mg/L (mean 3,000) | ≤ 100 mg/L |
| BOD₅ | 1,200–1,800 mg/L | ≤ 30 mg/L |
| SS | 800–1,500 mg/L | ≤ 70 mg/L |
| Animal and vegetable oils | 200–500 mg/L | ≤ 10 mg/L |
| Ammonia nitrogen | 80–150 mg/L | ≤ 15 mg/L |
| pH | 6.5–7.5 | 6–9 |
| Colour (blood pigments) | High (visibly dark red) | ≤ 30 (dilution factor) |
Process Design
To handle the high oil and grease, high COD and high ammonia nitrogen of this wastewater, our engineering team designed a combined process route: bar screen → equalisation tank → oil separation tank → dissolved air flotation (DAF, with PAC/PAM dosing) → A/O biological tank → membrane bioreactor (MBR) → UV disinfection → discharge.
Function of each treatment unit (design values)
- Bar screen (5 mm bar spacing) — removes large debris such as hair and bone fragments.
- Equalisation tank (200 m³) — equalises flow and quality, with pH held within 6.5–8.
- Oil separation tank — removes floating oil to reduce the load on the flotation stage.
- Dissolved air flotation (DAF) unit — saturator pressure 0.4 MPa, PAC dose 150 mg/L, PAM dose 3 mg/L; designed to remove approximately 70% of COD and 95% of oil and grease.
- A/O biological tank (anoxic + aerobic) — HRT 24 h; removes remaining organics and ammonia nitrogen, with nitrogen removal by nitrification–denitrification.
- Membrane bioreactor (MBR) — PVDF membrane, 0.04 µm pore size, MLSS 8,000 mg/L; membrane separation retains suspended solids and activated sludge.
- UV disinfection unit — 254 nm ultraviolet, for control of coliform bacteria in the effluent.
Commissioning Notes
Early in commissioning, the MBR transmembrane pressure (TMP) ran high. After inspection, our engineers confirmed that the cause was an insufficient seed dose of activated sludge, and the biofilm had not yet become stably established. Adding more seed sludge and adjusting the aeration rate resolved the problem, and the system then moved on to the 72-hour continuous-run test.
For Similar Projects
- Slaughterhouse and meat-processing wastewater is high in oil, grease and suspended solids. Ahead of the biological stage, place screening, oil separation and dissolved air flotation (with PAC/PAM dosing) in that order, so that most of the oil, grease and suspended solids are removed before the flow enters the A/O and MBR stages.
- Under the principle that the integrated discharge standard and industry discharge standards are not applied concurrently (GB 8978, Integrated Wastewater Discharge Standard), slaughterhouse and meat-processing wastewater is subject to its industry discharge standard. That standard has been updated to GB 13457-2025 (Discharge standard of water pollutants for slaughterhouse and meat processing industry), in force from 1 January 2026, which sets separate limits for direct and indirect discharge. For a new project, set the effluent targets against the current version together with local requirements for discharge to the municipal sewer.
- When starting up an MBR system, make sure the seed dose of activated sludge is sufficient, and monitor transmembrane pressure (TMP) continuously throughout commissioning.
- Where surplus sludge is to be disposed of by a contracted third party, secure the disposal route at the design stage.
Frequently Asked Questions
Why does slaughterhouse wastewater go through flotation before biological treatment?
On this project the design-basis influent contains 200–500 mg/L of animal and vegetable oils and 800–1,500 mg/L of SS; oil, grease and suspended solids add to the burden on the biological stage and the membrane modules. The design therefore removes floating oil in an oil separation tank first, then uses dissolved air flotation (with PAC/PAM dosing) to remove approximately 70% of COD and 95% of oil and grease (design values), reducing the load on the A/O and MBR stages.
Why use A/O + MBR for food-processing wastewater?
On this project the design-basis influent ammonia nitrogen is 80–150 mg/L and the design effluent target is ammonia nitrogen ≤ 15 mg/L. The A/O stage removes nitrogen through nitrification–denitrification; the MBR uses a PVDF membrane with a 0.04 µm pore size, runs at MLSS 8,000 mg/L and retains suspended solids and activated sludge by membrane separation.
What should you do if MBR transmembrane pressure runs high early in commissioning?
First check whether the seed dose of activated sludge is sufficient and whether the biofilm has become stably established. On this project, the high TMP early in commissioning was caused by an insufficient seed dose and was resolved by adding more seed sludge and adjusting the aeration rate (see "Commissioning Notes" above).
