The mass and water balance — tracking flow, solids and contaminant load through every unit so each is sized on what actually reaches it.
Process Design & P&IDs — in depth
The mass balance is the backbone of process design. We track water flow, suspended solids and contaminant load through every unit operation — accounting for recycles, sludge streams and removal efficiencies — so each item is sized on the real load it sees, and the effluent prediction is defensible.
What matters in practice
Forward flow, recycles and sludge streams.
TSS generation, capture and wasting.
BOD/COD and nutrient removal per stage.
Internal returns added to fresh load.
| Output | Use | Note |
|---|---|---|
| Stage flows | Hydraulic sizing | Inc. recycles |
| Stage loads | Process sizing | Per unit |
| Sludge mass | Dewatering | Daily DS |
| Effluent | Compliance | Predicted |
Continue across this series
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Read MoreA companion deep-dive in this series.
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Read MoreReynolds & Bauhm designs and delivers process design & p&ids solutions backed by process engineering and performance guarantees.
Fundamentals, design drivers and practical guidance
The mass and water balance — tracking flow, solids and contaminant load through every unit so each is sized on what actually reaches it.
The hydraulic profile sets the elevations so water flows through the works against friction and unit head losses with adequate freeboard, minimising intermediate pumping; the P&IDs then formalise instrumentation, control philosophy, interlocks and safety. Equipment selection weighs capital against operating cost, robustness, turndown and maintainability — choosing technology that suits the operator's site and skills, not just the lowest tender.
Reynolds & Bauhm develops plant designs from a rigorous mass balance through hydraulic profile, P&IDs and equipment selection, so the works is sized for its true duty, flows correctly, and is specified for whole-life cost and operability.
Process plant design turns an effluent characterisation and a discharge consent into a buildable, operable works, and it proceeds through recognisable deliverables: mass balance, hydraulic profile, P&ID development and equipment selection. Each builds on the last — the mass balance sizes the duties, the hydraulic profile makes them flow by gravity where possible, the P&IDs capture control and safety, and equipment selection commits the technology.
What our engineers assess on every scope of this type
| Parameter | Typical basis | Why it matters |
|---|---|---|
| Turndown | Range of duty | Handles diurnal/seasonal swing |
| Operability | Suited to operator | Keeps the plant runnable |
| Mass balance | Flows + loads tracked | Sizes every unit to real duty |
| Hydraulic profile | Elevations + losses | Flow by gravity where possible |
| P&IDs | Control + interlocks | Formalises operation and safety |
| Equipment | Whole-life basis | Balances capex and opex |
Common questions on treatment plant design
On whole-life cost, robustness, turndown and maintainability — matched to the operator's site and skills — not simply the lowest capital tender. The cheapest item often costs the most to run.
Real plants see diurnal and seasonal swings in flow and load. Designing for turndown, with appropriate redundancy, keeps treatment stable and efficient across the full operating range, not just at average duty.
Because it sizes everything — flows and loads through each unit, including solids and recycles. Mass & Water Balance and every downstream deliverable depend on a correct balance, so it is built and checked first.
It sets the elevations so water flows through the works against friction and unit head losses with adequate freeboard, minimising costly intermediate pumping and avoiding surcharge at peak flow.
Our expertise spans multiple industries with sector-specific water treatment solutions.
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Send your influent analysis and our engineers assess your process and recommend a tailored treatment solution — free, confidential and no obligation.
Select the regulatory standard for your country — it sets which parameters we need for a compliance-aware process assessment.
Required parameters for the chosen standard are flagged on the sample form. You can still submit a partial set and we will advise what else to test.
Your sample is stored against your company so we can track the project. Provide a company name or email as a minimum.