Wastewater Treatment for Plants and Factories: how to size the capacity and pick the right system

A wrong choice of industrial treatment plant costs more than the unit itself. An undersized system chokes in the first quarter; an oversized one runs half-empty and drains the client on power and reagents. Below is what a proper calculation looks like and how to avoid the «ballpark» numbers half of the market still throws at buyers.

Every project starts not with «how many cubic metres per day?» but with the composition of the effluent. A garment shop mostly discharges surfactants and fine textile lint. A meat plant — fats, blood, protein sludge with BOD in the 3000-5000 mg/l range. A galvanic shop — heavy metals, acids, cyanides. Three factories at 50 m³/day each need three fundamentally different schemes: mechanical plus biology for garments, grease separation plus two-stage aerobic biology for meat, reagent neutralisation plus ion exchange for galvanics. Sizing by flow alone, without an effluent analysis, is the standard rookie error in the field.

Capacity is calculated against three numbers at once: average daily flow, peak hourly flow, and unevenness coefficient. For a single-product plant on a steady shift (assembly shop) the coefficient is 1.3-1.5. For plants with slug discharges (a laundry, or a meat plant at end of shift) — 2.5-3. That is why a station «designed for 100 m³/day» must actually handle 15-20 m³/hour peaks without losing treatment quality. Skip that headroom and slug discharges shoot straight through the bioreactor, giving practically untreated water at the outlet.

The scheme is picked by two criteria: incoming quality and discharge requirements. Discharge into a city sewer? Mechanical plus biological is enough — utilities will accept water up to BOD 300 mg/l. Discharge to soil or a water body? You need polishing on membranes or an MBR (membrane bioreactor) plus UV disinfection. Water back into the cycle? Reverse osmosis as a final stage. The cost gap is 3-5×, which is why «where do we discharge?» has to be answered before the contract is signed, not after.

The most common equipment mistakes. First — cutting corners on the equalisation tank. Without it slug flows crash the biology and the aerobic colony dies of overload. Second — Chinese compressors with no service in Uzbekistan: they run for a year, then you spend a month hunting for spare parts. Third — steel instead of fibreglass in the plant housing: Uzbek soil with a high water table and high mineralisation eats steel in 5-7 years. Fourth — cutting corners on automation: manual control in 2026 is a guaranteed downtime the first time the operator takes leave.

Uzbek market pricing reference. An industrial plant of 30-50 m³/day turnkey — 250 to 400 million UZS. 100-200 m³/day — 500 to 900 million. From 500 m³/day — bespoke, starting at 1.5 billion. Installation (excavation, piping, wiring with automation) is another 40-60% on top of the plant itself. Annual service — 3-5% of the plant cost.

Indicative project cost. The figures above are approximate and are provided only for general budgeting purposes. The final cost of a treatment plant depends on many factors, including wastewater analysis results, the required treatment level, throughput capacity, equipment configuration, and site-specific conditions. A precise commercial proposal with detailed pricing is issued only after we review the input data and complete the engineering calculation for the project.

What the client should get besides the hardware. A full project with calculations (not a «napkin sketch»), a plant passport with outlet parameters, an equipment warranty of at least 24 months, and a service contract with a 24-hour on-site response. If the supplier is missing any of these, they are not a supplier — they are a reseller, and it is safer to walk away.