Status: Delivered · Region: West Africa · Ref. D-038
What We Delivered
We delivered a packaged, containerised MBR plant for a 60-bed hospital dialysis centre in West Africa. The plant was sized for 30 m³/day of hospital wastewater discharged over an 8-hour operating window — a 3.75 m³/h peak against a 1.25 m³/h daily average — and designed to the client's effluent guarantee of BOD₅ ≤ 40 mg/L, COD ≤ 100 mg/L, TSS ≤ 50 mg/L, TN ≤ 30 mg/L and TP ≤ 10 mg/L (design values). The client is a hospital dialysis centre; its identity, the site and the contract terms are withheld under our client-confidentiality policy.
The delivered process train covered fine screening, a 24 m³ equalisation tank with dechlorination ahead of the biology, anoxic and aerobic stages, an MBR membrane tank (approximately 70 m² of membrane at 18 LMH) and chlorine dioxide disinfection. The packaged format was chosen because the hospital compound had limited space and the plant had to be commissioned without a long local construction programme.
| Parameter | Value |
|---|---|
| Facility type | Hospital dialysis centre |
| Region | West Africa |
| Beds | 60 |
| Design flow | 30 m³/day |
| Discharge window | 8 h/day |
| Peak flow | 3.75 m³/h |
| Effluent character | Hospital wastewater, domestic-equivalent strength |
| Delivery format | Packaged, containerised MBR unit |
Delivery Record
The project ran through nine delivery stages. The table lists what each stage covered on this project and the record it produced.
| Stage | What it covered on this project | Record produced |
|---|---|---|
| 1. Design basis confirmation | The client-supplied influent envelope (BOD₅ 150–300 mg/L, COD 300–600 mg/L, TN 20–60 mg/L, TP 5–15 mg/L, conductivity 1,000–3,500 µS/cm, residual chlorine 0–5 mg/L), the 30 m³/day flow over an 8-hour window, and the effluent guarantee were fixed as the contractual design basis, with every unit process sized at the upper bound of each range. | Design basis sheet |
| 2. Process & mechanical design | Equalisation volume (24 m³), dechlorination dosing (about 220 g/day NaHSO₃ on ORP control), anoxic and aerobic stages, membrane area (approximately 70 m² at 18 LMH), ClO₂ disinfection, and a containerised layout for the limited footprint. | Process calculation sheet, P&ID, general-arrangement (GA) drawings, equipment list |
| 3. Manufacturing & quality control | Fabrication and assembly of the packaged unit: fine screening, equalisation and ORP-controlled dechlorination dosing, biological and membrane sections, and the chlorine dioxide generator. | Material and quality-control inspection records |
| 4. Factory acceptance test (FAT) | Pre-dispatch function check of the packaged unit's mechanical equipment, dosing equipment and ORP control. | FAT record |
| 5. Packing & dispatch | The containerised unit and associated equipment packed and dispatched for shipment to site. | Packing list and dispatch documents |
| 6. Installation (per contract scope) | Placement and hook-up of the containerised unit on the hospital compound, without a long local construction programme. | Installation record |
| 7. Commissioning | Start-up of the biological process and setting of equalisation level control, ORP-based dechlorination dosing, membrane operating flux and ClO₂ dosing. | Commissioning log |
| 8. Performance verification | Effluent BOD₅, COD, TSS, TN and TP checked against the guaranteed design values in the design basis. | Performance test record against the design values |
| 9. Training & handover / after-sales | Handover to the hospital maintenance team: routine operation, membrane care, dechlorination and ClO₂ dosing, and periodic sludge haul-off. After-sales support per contract scope. | O&M manual, training record, handover record |
Delivery records for this project are on file and can be reviewed by qualified buyers under a confidentiality agreement.
Designed For
- Residual chlorine from dialysis and ward disinfection — up to 5 mg/L reaching the drain.
- High-conductivity influent — up to 3,500 µS/cm.
- Temperature effects on nitrification — ambient temperature sets the nitrification rate and therefore aerobic tank sizing.
- A 3:1 peak-to-average flow ratio — the full daily volume arrives within an 8-hour discharge window.
- A space-constrained hospital compound — operated by maintenance staff rather than wastewater specialists.
Influent Design Basis
The following influent envelope was supplied by the client as the contractual design basis. Ranges — not single values — are what a treatment plant must actually be sized against.
| Parameter | Design range | Sizing value used |
|---|---|---|
| BOD₅ | 150–300 mg/L | 300 mg/L |
| COD | 300–600 mg/L | 600 mg/L |
| TSS | 50–150 mg/L | 150 mg/L |
| Total nitrogen | 20–60 mg/L | 60 mg/L |
| Ammonia nitrogen (NH₄⁺) | 10–40 mg/L | 40 mg/L |
| Total phosphorus | 5–15 mg/L | 15 mg/L |
| Conductivity | 1,000–3,500 µS/cm | 3,500 µS/cm |
| Residual chlorine | 0–5 mg/L | 5 mg/L |
Source: client-supplied design basis. Every unit process below is sized against the upper bound, not the midpoint.
Effluent Guarantee (Design Values)
| Parameter | Guarantee (design value) | Required removal (worst-case influent) |
|---|---|---|
| BOD₅ | ≤ 40 mg/L | 87% |
| COD | ≤ 100 mg/L | 83% |
| TSS | ≤ 50 mg/L | 67% |
| Total nitrogen | ≤ 30 mg/L | 50% |
| Total phosphorus | ≤ 10 mg/L | 33% |
Source: client-specified treatment guarantee. Removal percentages are calculated against the upper bound of each influent range.
The Two Constraints That Drove the Design
1. A 3:1 peak-to-average ratio makes equalisation non-negotiable
The facility discharges its entire daily load in 8 hours, then goes quiet for 16. Sizing the biological stage for the 3.75 m³/h peak would mean paying for three times the aeration and membrane capacity actually needed — and then starving the biomass overnight.
The design instead buffers the flow. During the 8-hour discharge window, 30 m³ arrives while the plant treats 8 h × 1.25 m³/h = 10 m³. The equalisation tank must therefore hold the 20 m³ difference; with 20% freeboard the specified working volume is 24 m³. Downstream, every process runs at a steady 1.25 m³/h, 24 hours a day.
Source: HydropureWater design calculation from the client's stated flow profile.
2. Residual chlorine will kill the biology before it treats anything
This constraint is frequently missed on hospital projects. Wards and dialysis units disinfect aggressively, and up to 5 mg/L of free chlorine reaches the drain. Nitrifying bacteria — the organisms responsible for ammonia removal — are inhibited well below that level, so an untreated chlorine slug can stall nitrification for days.
The design places a dechlorination step in the equalisation tank, ahead of any biological process, dosing sodium bisulphite (NaHSO₃). On a stoichiometric basis of 1.46 mg NaHSO₃ per mg Cl₂, the worst-case load of 5 mg/L × 30 m³/day = 150 g Cl₂/day requires roughly 220 g/day of NaHSO₃, dosed on ORP feedback so consumption tracks actual chlorine rather than the worst case.
Source: HydropureWater design calculation, stoichiometric basis.
Process Train
Screening → equalisation with dechlorination → anoxic tank → aerobic tank → MBR membrane tank → ClO₂ disinfection → discharge. Sludge is aerobically digested and periodically hauled off site.
- Fine screening — removes gauze, plastics and dialysis consumables that would otherwise foul membranes.
- Equalisation + dechlorination (24 m³) — flattens the 3:1 peak and neutralises residual chlorine before it reaches the biology.
- Anoxic tank — denitrification driven by internal mixed-liquor recirculation. The influent BOD:TN ratio of roughly 5:1 provides sufficient carbon without a supplemental source, comfortably above the 4:1 minimum denitrification generally requires.
- Aerobic tank — carbon oxidation and nitrification of the 40 mg/L ammonia peak.
- MBR membrane tank — at a design flux of 18 LMH, the 1.25 m³/h continuous throughput needs approximately 70 m² of membrane area. The membrane barrier makes the TSS ≤ 50 mg/L guarantee structural rather than operational.
- ClO₂ disinfection — chlorine dioxide is specified over hypochlorite because it does not form the chlorinated by-products hospital effluent is already prone to.
Source: HydropureWater design calculation. Flux of 18 LMH is a conservative operating point for municipal-strength effluent.
Equipment Delivered
The plant was delivered as a packaged, containerised unit rather than a civil-works build — a decision driven by the site's limited footprint and the need to commission without a long local construction programme.
- Medical wastewater treatment unit — the process core for healthcare effluent.
- MBR integrated wastewater treatment system — membrane separation stage.
- Chlorine dioxide generator — final disinfection.
Why MBR Rather Than a Conventional Process
The effluent guarantee itself (BOD₅ ≤ 40 mg/L, TSS ≤ 50 mg/L) is a secondary-treatment standard that conventional activated sludge can meet on paper. MBR was selected for three reasons specific to this site:
- Footprint — operating at 8,000–10,000 mg/L MLSS instead of 3,000–4,000 mg/L, an MBR needs roughly half the biological tank volume, which matters on a constrained hospital compound.
- Shock tolerance — the membrane retains biomass regardless of sludge settleability, so a chlorine slug or a load spike cannot wash out the process the way a clarifier upset would.
- Operator load — no sludge-blanket management, no return-sludge tuning. Hospital maintenance teams are not wastewater operators.
The full trade-off between membrane and fixed-film processes is covered in our MBR vs MBBR comparison.
For Similar Projects
- Fix the influent envelope as ranges and size every unit process at the upper bound, not the midpoint.
- Where ward or dialysis disinfection reaches the drain, place dechlorination ahead of the biological stage and dose it on ORP feedback.
- Size equalisation from the discharge window: the volume that arrives during discharge hours, minus what the plant treats in those hours, plus freeboard.
- Re-check influent conductivity and ambient temperature for your own site before reusing this configuration; both affect nitrification and aerobic tank sizing.
- Where the plant will be run by hospital maintenance staff, weight operator load as heavily as capital cost when choosing the process.
- Budget and quote against your specific site: freight, installation and local civil works vary widely by destination.
Frequently Asked Questions
How much does a 30 m³/day hospital wastewater treatment plant cost?
Equipment cost for a containerised MBR plant at this scale is driven by membrane area, degree of automation and disinfection type, not by nameplate flow alone. Because freight, installation and local civil works vary widely by destination, we quote against a specific site rather than publishing a figure. Send us your flow profile and effluent standard and we will return a scoped quotation.
Why does residual chlorine matter so much in hospital wastewater?
Because it attacks the process that removes ammonia. Nitrifying bacteria are inhibited at chlorine concentrations far below the 5 mg/L that hospital drains can deliver, and nitrification recovers slowly once lost. Any hospital design that omits dechlorination ahead of the biological stage is carrying an unpriced risk.
Can an MBR handle a hospital that only discharges 8 hours a day?
Yes, provided equalisation is sized correctly. The membranes themselves should never see the raw peak — in this design a 24 m³ equalisation tank converts a 3.75 m³/h peak into a steady 1.25 m³/h feed. Without that buffer, the plant would need triple the membrane area and would still starve the biomass for 16 hours a day.
What footprint does a 30 m³/day MBR need?
At this scale the packaged plant is typically containerised, with the equalisation tank as the largest single component. Elevated MLSS roughly halves the biological volume compared with conventional activated sludge, which is generally the deciding factor on hospital sites where space is already committed.
Is this design specific to West Africa?
The process train is not, but two inputs are climate- and region-sensitive: influent conductivity (1,000–3,500 µS/cm here) and ambient temperature, which affects nitrification rate and therefore aerobic tank sizing. The same configuration transfers to comparable dialysis and small-hospital projects once those two inputs are re-checked.
