What wastewater streams does a Rajshahi data center need to treat?
A data center in Rajshahi needs an application-specific treatment train for each wastewater source, not one plant for every discharge. Cooling-blowdown reuse and fabrication wastewater have materially different contaminants and endpoints: the former is mainly inorganic and oxidant-bearing, while fabrication ultrapure-water blowdown may contain organics, fluoride, copper and TMAH. Bangladesh’s S.R.O. 229/Law/2023 inland surface-water screening limits include TDS ≤2,100 mg/L, pH 6–9 and residual chlorine ≤1 mg/L, according to the HydropureWater 2026 Bangladesh guide. Rajshahi discharge routes, receiving-water conditions, tariffs and permit terms must still be verified before equipment selection; a Dhaka treatment train cannot be relabelled as a Rajshahi design.
Begin with a source-by-source Rajshahi data center water balance. It should reconcile makeup water, cooling-tower evaporation, blowdown, domestic sewage, equipment washdown, drainage, firewater testing and any fabrication, semiconductor or industrial process wastewater. Confirm whether cooling is evaporative, hybrid or primarily air-cooled, and record the number of towers, design cycles of concentration, basin volume and emergency-dump practices. The data-center cooling-blowdown treatment guide provides a useful technical framework, but its plant assumptions must be replaced with Rajshahi measurements.
The International Journal of Advanced Research article Fitting G-Family Probability Distribution at the Rainfall Data of Rajshahi District, Bangladesh identifies Rajshahi District rainfall data as a relevant local dataset. It does not establish site flood levels. Request site-specific rainfall, drainage and flood records because the HydropureWater 2026 guide notes that monsoon conditions can materially increase hydraulic loading at open-yard facilities.
| Stream | Required accounting | Treatment decision |
|---|---|---|
| Cooling-tower blowdown | Makeup, evaporation, blowdown, cycles, dump events | Potential filtration, softening, RO and cooling-tower makeup reuse |
| Fabrication or industrial wastewater | Separate flow and contaminant mass load | Application-specific biological, membrane, ion-exchange and possibly ZLD train |
| Domestic sewage | Fixture flow, occupancy, peak discharge | Separate sanitary treatment route |
| Washdown, drainage and firewater testing | Event frequency, composition and discharge path | Segregation, pretreatment and controlled disposal |
Characterize the wastewater before selecting treatment equipment
Raw cooling-blowdown data must determine the treatment design because hardness, silica, oxidant and conductivity control membrane and pretreatment selection. The HydropureWater 2026 Bangladesh guide reports raw data-hall cooling blowdown at TDS 500–2,500 mg/L, silica 10–80 mg/L as SiO₂, conductivity 1,000–4,000 µS/cm, residual oxidizer 0.1–1.0 mg/L as ClO₂ or Cl₂, hardness 200–800 mg/L as CaCO₃ and pH 7.5–9.0. These are source-screening ranges, not guaranteed Rajshahi design values.
Fabrication wastewater requires a different sampling program. The same HydropureWater guide reports potential COD of 200–1,500 mg/L, fluoride 50–800 mg/L, copper 0.5–10 mg/L, ammonia-nitrogen 20–200 mg/L, TMAH 5–50 mg/L and TSS 50–300 mg/L. If the project includes an electronics or semiconductor operation, these parameters become mandatory inputs to equalization, precipitation, biological treatment, membrane and concentrate-management decisions.
At minimum, require flow and laboratory measurements for pH, conductivity, TDS or an equivalent parameter, hardness, silica, TSS, residual oxidizer, chloride, sulfate and temperature. Add COD, BOD, fluoride, copper, chromium, ammonia-nitrogen and TMAH where the relevant process exists. Sampling locations should distinguish tower basin water, controlled blowdown, drain or sump discharge, and the proposed discharge point. Use an automatic chemical dosing system only after the chemical demand, residual chemistry and dosing control philosophy have been established.
The Genesis Water Technologies article Why Cooling Tower Blowdown Is Your Hidden Opportunity establishes a monitoring baseline of makeup-water flow, blowdown volume, evaporation, conductivity, pH and suspended solids. It reports a 15–30% gap between theoretical and actual blowdown because of unmeasured losses and emergency dumps. Meters and a reconciled water balance are therefore prerequisites for equipment sizing, not optional refinements.
| Decision point | Information required | Why it controls the train |
|---|---|---|
| Cooling-tower makeup reuse | Hardness, silica, TDS, conductivity, oxidant, temperature | Sets softening, RO, blending and residual-biocide controls |
| Controlled surface-water discharge | BOD, COD, TSS, TDS, pH, total chromium, residual chlorine, flow, temperature | Sets the compliance envelope and monitoring package |
| Sewer or CETP discharge | Local acceptance limits, temperature, TDS, pretreatment and monitoring conditions | May require additional treatment not required for surface-water screening |
| Fabrication wastewater | COD, fluoride, copper, chromium, ammonia-nitrogen, TMAH and flow | May require MBR, two-pass RO, selective ion exchange or ZLD |
Choose a cooling-blowdown treatment train that fits the site
The data-hall treatment train should follow the measured contaminants and the intended reuse endpoint, with biological treatment omitted unless another stream requires it. The HydropureWater 2026 guide gives a 2026 sequence of optional DAF, multi-media filtration, softening and industrial RO. The proposed pretreatment targets are hardness below 50 mg/L as CaCO₃ and silica below 20 mg/L as SiO₂, followed by industrial RO at 70–75% recovery. DAF is conditional rather than automatic: it is relevant where floc, corrosion-inhibitor carryover or other floatable material requires removal.
For a floc-bearing stream, compare a DAF system for cooling-blowdown pretreatment against direct filtration based on pilot results and reject handling. Protect the RO with multi-media filtration for RO pretreatment, followed by an industrial cooling-water softener where hardness and silica control support that route. The final unit is an industrial RO system for blowdown reuse. The 2026 guide reports RO permeate below 50 mg/L TDS, concentrate at 25–30% of feed and 70–85% of total blowdown volume recycled to the cooling-tower basin.
Control the loop by conductivity rather than fixed-time blowdown. The HydropureWater guide specifies automatic blowdown at 4,000 µS/cm on the RO reject line and identifies final discharge targets of TDS below 2,100 mg/L, residual chlorine ≤1 mg/L and pH 6–9. The 2026 data-center wastewater treatment guide provides another reference point, but its site conditions cannot replace Rajshahi chemistry and cooling-system data.
High overall recovery needs a separate feasibility review. IDE Tech’s 2026 article Data Centers’ Water Reuse: Cooling Tower Blowdown states that conventional brackish-water RO is commonly limited to 75–80% recovery because scaling becomes unmanageable. It describes a chemistry-aware brine-desalter case at approximately 95% recovery with permeate silica of about 1 mg/L, but that case cannot be transferred directly to a smaller Rajshahi installation without scale-specific testing and solids-handling review.
| Train | Indicative sequence | Selection condition | Main decision |
|---|---|---|---|
| Basic polishing | Filtration → softening → RO | Cooling-blowdown chemistry is predominantly inorganic and within stated pretreatment limits | Does measured silica, hardness and fouling support stable recovery? |
| Enhanced pretreatment | Optional DAF → multi-media filtration → softening → RO | Floc, inhibitor carryover or suspended solids are present | Does DAF reduce membrane fouling enough to justify added sludge and O&M? |
| High-recovery alternative | RO plus controlled salt precipitation or another chemistry-aware step | Conventional RO scaling prevents the project recovery target | Can precipitate be managed safely and economically under Rajshahi conditions? |
| No-reuse baseline | Controlled discharge, subject to permit acceptance | Treatment or concentrate handling is not technically or economically feasible | What discharge route and monitoring record are accepted locally? |
Calculate the water and recovery economics before buying equipment
Cooling-tower cycles of concentration determine blowdown volume, but the improvement from increasing cycles is smaller than operators often assume. The Genesis Water Technologies article defines the blowdown ratio as 1/(CoC−1): at 4 cycles of concentration, blowdown is 25% of makeup-water volume; at 6 cycles, it is 20%. The reduction is five percentage points, not 50%. The same source warns that biological and scaling risks rise sharply above 5–6 cycles without advanced treatment. Model any increase together with corrosion, microbiological, scaling and blowdown-control changes.
Physical separation followed by targeted treatment can reduce makeup demand. Genesis Water Technologies reports 15–25% lower makeup demand after facilities adopt blowdown treatment and reuse, but this is an outcome range rather than a guaranteed Rajshahi saving. The project calculation should start with measured stream flow and the selected treatment recovery, then subtract evaporation, unusable concentrate and other losses.
The HydropureWater 2026 guide provides a screening benchmark for a 200 m³/day train: BDT 6–12 crore CAPEX and BDT 25–55/m³ OPEX. Its stated OPEX components are energy at BDT 8–18/m³, chemicals at BDT 6–15/m³, sludge handling at BDT 3–7/m³, labour at BDT 4–9/m³ and membrane replacement reserve at BDT 2–5/m³. These are Dhaka-published 2026 benchmarks, not a Rajshahi quotation.
For comparison, the guide reports that 60% recovery on a 200 m³/day plant operating throughout the year saves approximately 73,000 m³/year, equivalent to BDT 44–88 lakh/year against its cited municipal tariff, with a 2.5–4-year simple payback. Replace every local assumption with verified Rajshahi values. The broader circular-water-economy procurement guide explains why lifecycle cost, not headline water savings alone, should support the investment decision.
| Calculation input | Verified Rajshahi input required | Use in the decision |
|---|---|---|
| Makeup-water cost | Applicable BDT/m³ tariff | Annual value of recovered water |
| Disposal route | Sewer, CETP or surface-water charge | Baseline disposal cost and avoided cost |
| Electricity | Power tariff and calculated kWh/m³ | RO and pumping OPEX |
| Chemicals and waste | Supplier pricing, consumption and disposal route | Consumables and residual-handling cost |
| Recovery | Measured flow, permeate yield and expected availability | Annual water and discharge volume |
Verify Bangladesh compliance and the Rajshahi discharge route
The permitted discharge route must be established before the treatment train or environmental budget is frozen. The HydropureWater 2026 guide uses S.R.O. 229/Law/2023 inland surface-water limits as its initial screening envelope: BOD ≤50 mg/L, COD ≤200 mg/L, TSS ≤150 mg/L, TDS ≤2,100 mg/L, pH 6–9, total chromium ≤2 mg/L and residual chlorine ≤1 mg/L. These are screening values; the current permit and receiving-water conditions applicable to the Rajshahi site remain the controlling requirements.
The same guide states that environmental-clearance renewal requires two years of compliant 24-hour composite-sampling records. Design margin should therefore sit above the limits, and the monitoring system should support the required sampling record from commissioning. The Bangladesh industrial ETP and DAF selection guide explains how discharge-route assumptions affect pretreatment and compliance costs, but it does not establish a Rajshahi permit.
Determine whether the discharge enters an inland surface water, municipal sewer, CETP or another controlled route. Each option can impose different temperature, TDS, pretreatment and monitoring requirements. A sewer or CETP acceptance test should not be replaced by an assumption that industrial users are admitted; obtain the current acceptance criteria, capacity position and agreement conditions directly.
Verify the Rajshahi environmental clearance, receiving-water conditions, sewer capacity, industrial-user agreement and current Department of Environment requirements with the relevant authorities. The supplied sources do not establish a Rajshahi-specific permit, tariff or receiving-water allowance. The regional data-center wastewater guide can support checklist development, but it cannot supply local approvals.
At minimum, the control and monitoring specification should cover conductivity, pH, residual chlorine, flow and temperature, plus every site-approved parameter. Include alarms, data logging, automatic blowdown and composite-sampling arrangements. The selected control set must follow the verified route rather than the initial inland-surface-water screening envelope.
Build a modular procurement package for the Rajshahi project
A comparable RFQ requires separate performance packages for cooling blowdown and fabrication or industrial wastewater. Blending the streams into one unspecified ETP obscures the contaminant load, treatment endpoint, sludge quantity and concentrate route, and it prevents bidders from pricing like-for-like equipment. The package should also distinguish process equipment from civil works, utilities, instrumentation, commissioning and local O&M support.
For cooling blowdown, request option prices for DAF, multi-media filtration, softening, RO, concentrate management, permeate reuse, residual-oxidizer control, automatic blowdown and monitoring. State whether DAF is mandatory or conditional on influent characterization. The RO and UF membrane elements and treatment valves, filter media and parts should be specified by duty, material compatibility and performance requirements rather than by product family alone.
For fabrication wastewater, request a conditional alternative covering equalization, DAF, MBR, two-pass RO, selective ion exchange and ZLD wherever measured contaminant loads justify them. Do not include these units as unconditional scope unless representative samples support them. Likewise, do not require the cooling-blowdown train to carry a mixed-stream discharge when the recovered permeate has a defined internal reuse endpoint.
Every bidder should state design flow, operating redundancy, recovery target, permeate quality, concentrate destination, chemical consumption, power demand, membrane-replacement assumptions, commissioning deliverables and local service capability. Require the proposal to demonstrate that the design handles Rajshahi ambient temperature, rainfall variability, source-water variability and the actual permitted discharge route.
| RFQ package | Required technical response | Acceptance basis |
|---|---|---|
| Cooling-blowdown train | Flow, recovery, pretreatment, RO, reuse and concentrate details | Measured Rajshahi chemistry and verified cooling-water endpoint |
| Fabrication-wastewater alternative | Contaminant removal, stage-by-stage conditions and ZLD trigger | Representative wastewater data and applicable permit |
| Controls and monitoring | Conductivity blowdown, alarms, logging and sampling interface | Site-approved monitoring and record requirements |
| Lifecycle commitment | Energy, chemicals, membranes, sludge, labour and service | Documented assumptions and measurable guarantees |
Frequently Asked Questions
What will wastewater and cooling-blowdown treatment cost for a Rajshahi data center?
The HydropureWater 2026 guide gives 2026 CAPEX screening ranges of BDT 1.5–3.5 crore at 50 m³/day, BDT 6–12 crore at 200 m³/day, BDT 18–28 crore at 500 m³/day and BDT 30–45 crore at 1,000 m³/day. These are not Rajshahi quotations. Request a price against the measured stream flow, selected process scope, reuse endpoint, concentrate route, civil works, utilities, redundancy and commissioning deliverables.
How should a supplier be selected for a Rajshahi data-center treatment package?
Require bidders to demonstrate the proposed process using representative Rajshahi wastewater data, pilot or equivalent performance evidence, a recovery guarantee, permeate specification, concentrate plan, control philosophy, commissioning method and local service capability. For high-recovery claims, require evidence under the actual scaling chemistry rather than relying only on nominal recovery. Local capability should include named service personnel, response arrangements and spare-parts planning.
How should the treatment plant be sized?
Size from measured flow, the reconciled water balance and operating redundancy—not a generic data-center flow assumption. Confirm cooling-system design cycles, basin inventory, emergency dumps and evaporation before defining the blowdown treatment flow. Then add the permitted discharge and reuse constraints. For fabrication wastewater, size from representative peak flow and contaminant mass load, with equalization and pretreatment based on the actual treatment objectives.
What compliance risks should be resolved before procurement?
Early verification is essential because the HydropureWater 2026 guide identifies S.R.O. 229/Law/2023 screening limits and states that renewal requires two years of compliant 24-hour composite-sampling records. Obtain the current Rajshahi permit and confirm the receiving water, sewer or CETP route before setting final treatment targets. If the route has stricter temperature, TDS or pretreatment conditions, those requirements—not the initial screening envelope—must control the design.
Can raw cooling blowdown be reused directly?
Direct reuse is possible only when the raw stream chemistry matches the receiving process and its scaling, microbiological and oxidant risks are controlled. A filtration, softening and RO train produces higher-quality permeate intended for cooling-tower makeup reuse; it is not the same as returning untreated blowdown to the basin. For any reuse endpoint, verify hardness, silica, conductivity, residual oxidizer, temperature and the cooling system’s own water chemistry limits.
