Water Treatment Consulting Firms
Consulting firms scoping feasibility, technology selection, process optimization, and strategy for water projects.
48 specialist providers · 8 countries
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Buyer's guide
The buyer's guide to water treatment consulting firms
Water Treatment Consulting: Process Design, Due Diligence, and Regulatory Submissions
Water treatment consulting provides independent technical advice, process design, regulatory support, and specialist expertise to water utilities, industrial operators, developers, and technology vendors. Key consulting service areas: process design and optioneering (selection and sizing of treatment technologies for new or upgraded water treatment works; treatability studies; pilot plant design and management; performance guarantee development); regulatory submissions (DWI Regulation 31 new treatment process applications; EA Environmental Permit applications; Habitats Regulations Assessment; Strategic Environmental Assessment; WRMP optioneering support); technical due diligence (asset assessment for mergers, acquisitions, and project finance transactions; water company investment decisions; PPP/concession bids; project lender's technical advisor (LTA) review); expert witness (technical evidence for planning appeals, OFWAT appeals, HMCTS technical disputes; legal support for water quality incidents and regulatory enforcement); water quality investigations (source water characterisation; treatment performance audit; DWI investigation response; incident response (Cryptosporidium breakthrough, discolouration, taste and odour events)); operations support (commissioning assistance; process optimisation; asset management consulting; O&M contract performance review). Major UK water treatment consulting firms: Cranfield University Water Science Institute (academic consulting and research); a water research consultancy (Swindon: privatised 1989; UK sector technical reference for water quality, sewerage, and sludge management; UKWIR research delivery partner); several large engineering practices provide water treatment consulting within their wider businesses; specialist boutiques also serve the market.
DWI Regulation 31 process approval: a new treatment process or treatment chemical used for drinking water production in England requires approval from the Drinking Water Inspectorate (DWI) under Regulation 31 of the Water Supply (Water Quality) Regulations 2016 (Reg 31 applications; equivalent Regulation 28 in Wales, Regulation 17 in Scotland, Regulation 15 in Northern Ireland). Regulation 31 applies to: new treatment processes (e.g. UV/AOP, nanofiltration, electrochlorination); new treatment chemicals (coagulants, pH adjustment chemicals, corrosion inhibitors, antiscalants); changes to approved processes or chemicals (new supplier, specification change, concentration range extension).
Application requirements: technical dossier including: toxicological data (acceptable daily intake (ADI) calculation for by-products; genotoxicity and carcinogenicity data; exposure assessment; margin of exposure (MOE) calculation); process performance data (pilot or full-scale data demonstrating treatment objectives met without creating unacceptable by-products); materials contact data (BS 6920 extraction test for treatment media or plant materials); quality assurance documentation (product specification, manufacturing standards, Certificate of Analysis). DWI Reg 31 process: submission to DWI Drinking Water Policy Team; DWI publishes notifications of Reg 31 approvals (Annual Report and DWI website); evaluation takes 3 to 18 months depending on application complexity; DWI may require additional data or impose conditions on approval. Consultants specialising in Reg 31 support: WRc Group, Cranfield Water Science Institute, DWI technical advisors (former DWI inspectors now consulting).
Lender's Technical Advisor (LTA) role in water projects: for project financed water infrastructure (desalination plants, WTW PPPs, privately financed reservoir schemes), the project finance banks appoint an independent Lender's Technical Advisor to review the technical aspects of the project on behalf of the lending banks. LTA scope: review of project documents (technical schedule to concession agreement; output specification; EPC contractor's technical proposal; O&M contractor's technical proposal; insurance requirements); technical feasibility assessment (process design, feedwater quality characterisation, product water quality guarantee, technology maturity (TRL 7 to 9 for project-financed schemes)); independent engineer functions during construction (construction monitoring visits; variation order assessment; milestone certification for drawdown of construction loans; FAT/SAT witnessing; completion certificate for financial close); operations monitoring (monthly performance reporting review; annual technical audit; management of off-spec water quality events). LTA firms: the large multidisciplinary engineering practices with project finance experience. LTA appointment: banks appoint the LTA directly (not the project company or sponsors) to ensure independence; LTA fees funded from project development costs; LTA has direct reporting obligation to banks; LTA engagement starts at financial close and continues through operations phase (typically 15 to 25 year O&M period with annual reviews).
Frequently asked questions
When do water projects need a consulting engineer or independent expert?
Water projects typically require consulting engineers or independent experts in the following circumstances: (1) Technical design: any new or significantly upgraded water treatment works (new membrane system, new biological treatment, UV disinfection installation) requires process design by a qualified engineer (CEng MCIWEM, CEng MICE, or CEng MIChemE); design should be peer-reviewed by an independent checker (BS EN ISO 9001 quality management requirement for most water company procurement frameworks; CDM 2015 requires Principal Designer to coordinate design review). (2) Regulatory submissions: DWI Regulation 31 (new process or chemical for drinking water) requires a technical dossier that is typically prepared or reviewed by a consulting firm with toxicological and process expertise; EA Environmental Permit applications for new or modified discharges require supporting technical evidence from a qualified environmental engineer. (3) Project finance: lender's technical advisor (LTA) appointed by project finance banks for any debt-financed water infrastructure exceeding approximately GBP 20 to 50 million; LTA provides independent assessment of technical feasibility, contractor risk, and performance guarantees. (4) Legal disputes and expert witness: water quality incidents resulting in regulatory enforcement (DWI enforcement undertaking, EA civil sanction or prosecution) may require technical expert evidence; Planning appeal (PINS, Planning Inspectorate) for water supply or wastewater infrastructure requires technical witnesses; OFWAT price review disputes (fast-track or redetermination) may require technical experts. (5) Due diligence: acquisition of a water company, water utility, or water infrastructure asset requires technical due diligence (asset condition, regulatory compliance, capex forecast, water quality risk) by an independent engineering firm; scope covers existing facilities, treatment works condition, asset management plans, and regulatory risk.
What is a process design basis document for a water treatment works?
A process design basis (PDB) document establishes all the technical parameters, assumptions, and design criteria that govern the design of a water treatment works before detailed engineering begins. A well-prepared PDB prevents misalignment between client expectations and final design, reduces design changes during execution, and provides a reference for project management. Typical PDB contents for a drinking water treatment works: (1) Site and regulatory context: site location; applicable regulations (WS(WQ)R 2016; Environmental Permit; planning conditions); design standards applicable (BS EN, ISO, CIBSE, WRAS); DWI Regulation 31 status; (2) Source water quality: raw water quality design envelope (minimum, average, and maximum for all relevant parameters: turbidity, colour, TOC, pH, alkalinity, hardness, temperature, manganese, iron, ammonia, nitrate, Cryptosporidium, pesticides, PFAS; based on minimum 2 years of monitoring data); seasonal variation profiles; worst-case design event (e.g. 1-in-100-year high turbidity storm event: 5,000 NTU turbidity; post-storm elevated THM precursor); (3) Design flows: maximum day demand (MDD); peak hour demand (PHD); average daily demand (ADD); minimum night demand; fire flow allowance; treatment works minimum flow (for process stability); backwash/CIP reject flow allowance; net output (= gross abstraction minus recycle and waste); (4) Product water quality: all Prescribed Concentration Values (PCVs) under WS(WQ)R 2016 at point of compliance (outlet of works before service reservoir entry); process guarantee: works outlet turbidity target less than 0.1 NTU (100 percent), less than 1.0 NTU (99 percent); THM less than 50 ug/L (works outlet); Cryptosporidium reduction target: 4-log; (5) Process outline: treatment train; key unit process selection and sizing criteria (coagulant dose range, filter loading rate, UV target dose, chlorine dose and residual target, pH range); (6) Utilities: electricity supply (kVA demand); chemical delivery and storage (NaOCl, ferric sulphate, lime/CO2, antiscalant); water for drinking water contact (process water specification); drainage (process drains, storm drains, chemical containment bunding); (7) Performance criteria: effluent quality guarantee; throughput availability (98 percent availability, 4 hours planned maintenance per week); energy consumption target (kWh/m3).
How does water treatment consulting differ from engineering design?
Water treatment consulting and engineering design both contribute to the delivery of water infrastructure but serve different primary functions: Engineering design produces deliverables (drawings, specifications, calculations) that will be built and certified; the engineer holds legal responsibility for the design (professional indemnity insurance; CDM Principal Designer duties; PE stamp in some jurisdictions); the engineer is typically engaged under a design services contract (NEC4 Professional Services Contract or ACE (Association for Consultancy and Engineering) terms); delivered through RIBA/ICE Plan of Work stages (Feasibility through to Detailed Design and Construction Support). Water treatment consulting provides technical advisory services (strategy, assessment, review) rather than certifiable design deliverables; the consultant's output is advice, reports, and recommendations; the consultant may not hold CDM Principal Designer duties; advisory engagement is typically less formal than design (consulting framework agreement or time-and-materials agreement); examples of consulting (not design) outputs: options report recommending preferred treatment process; due diligence report on acquired water assets; expert opinion on DWI investigation; pilot study assessment report; review of third-party design (peer review or value engineering). Overlap: in practice, most engineering firms provide both consulting and design services; the distinction matters for: procurement (consulting contracts procured under OJEU/FTS services threshold; design-construct contracts procured under works threshold); liability (design liability vs advisory liability; D&B contracts transfer design liability to contractor; consulting advice liability is usually limited by contract); DWI: for Reg 31 applications, DWI distinguishes between process design evidence (must be from qualified water treatment engineer) and toxicological evidence (must be from qualified toxicologist).
What is a technical due diligence for a water infrastructure asset?
A technical due diligence (TDD) for a water infrastructure asset (water treatment works, pumping station network, service reservoir, desalination plant, or water company) is an independent technical assessment commissioned by a prospective buyer, investor, or lender to understand the current condition, performance, compliance status, and future capital requirements of the assets. TDD scope: (1) Asset condition assessment: review of asset register (age, design life, condition grade per asset); recent inspection reports (CCTV for sewers; pressure testing for mains; vibration surveys for pumps; structural inspection for tanks and reservoirs); maintenance records (planned preventive maintenance compliance; reactive callout frequency and trends; corrosion protection surveys for steel tanks and pipelines; concrete carbonation and chloride penetration for RC structures); (2) Regulatory compliance: current DWI compliance status (check of recent Drinking Water Quality Monitoring data; DWI correspondence; any enforcement notices or undertakings; Regulation 28/31 approvals); EA Environmental Permit compliance (effluent quality monitoring data; any pollution incidents; permit conditions met vs breached; WINEP investment obligations); abstraction licence status; planning conditions compliance; (3) Operational performance: treatment process performance vs consent and design; energy consumption (kWh/m3 vs benchmark); chemical dosing efficiency; leakage performance (for distribution networks); availability (planned and unplanned downtime); (4) Capital expenditure forecast: forecast capital replacement and maintenance expenditure over 5, 10, and 25 years; risk-adjusted capex using condition assessment data; comparison with current owner's AMP/capex plan; identification of hidden or unfunded capital requirements; (5) Deliverable: TDD report with: executive summary; risk register (technical, regulatory, and financial risks); recommended adjustments to purchase price or investment structure based on identified risks and capex requirements; specific areas for vendor warranty protection. TDD is typically completed in 4 to 12 weeks; key risk areas in water TDD: legacy contamination (PFAS in source water requiring new treatment investment); ageing lead pipework (regulatory replacement obligation); WINEP investment obligations (P removal, CSO reduction); pension liability (defined benefit pension schemes in privatised water companies).
Illustrative scenario · Water treatment process consultancy and regulatory submissions
A composite drawn from typical projects in this category, not a single client engagement. Figures are indicative.
- Challenge
- A private equity-backed independent water services company in the East of England operating under a long-term bulk supply agreement with a regulated water company needed to demonstrate to the DWI and to the regulated company's technical team that its proposed nanofiltration (NF) treatment upgrade for a 12 Ml/day chalk groundwater works would reliably remove PFAS to below the DWI 100 ng/L standard and manganese to below 50 ug/L, while also managing the NF concentrate (25 percent of feed) under the existing EA Environmental Permit.
- Approach
- A water treatment consultant was engaged to lead the DWI Regulation 31 application, the EA Environmental Permit variation, and the process design basis for the NF system. A 3-month pilot study (NF membrane, 4 x 4-inch modules, 15 percent recovery) was conducted first to characterise actual PFAS rejection (PFOS 99.1 percent, PFHxS 98.3 percent, PFBA 82 percent) and manganese rejection (98.9 percent); the data informed the Reg 31 dossier. The EA permit variation was negotiated to allow concentrate discharge to sewer at up to 5 m3/h with a PFAS sum limit of 2,000 ng/L (below the sewage treatment works inlet capacity for PFAS), supported by a groundwater impact assessment showing no WFD deterioration risk.
- Outcome
- DWI Regulation 31 approval obtained in 8 months. EA Environmental Permit variation granted in 5 months (concurrent with Reg 31 process). Full-scale NF system (3 x 24-module racks at 85 percent recovery with inter-stage dosing) commissioned 4 months after approvals. PFAS sum at NF permeate consistently below 8 ng/L (98 percent removal), well within the 100 ng/L standard. Manganese below 5 ug/L. The consultant's regulatory strategy of running Reg 31 and EA permit variation in parallel, rather than sequentially, saved 4 to 6 months versus the default sequential approach.
Questions to ask shortlisted providers
5
- 01
Does your firm hold Professional Indemnity insurance of at least GBP 5 million per claim for water treatment process design and DWI Regulation 31 submissions, and do you have named staff with specific experience of DWI approval submissions in England?
DWI Regulation 31 submissions require a level of toxicological and process engineering expertise that not all engineering consultancies possess; insufficient professional indemnity cover (the minimum expected by most water companies in consultant appointments is GBP 5 million) creates a financial risk to the client if a negligent submission causes project delay or a compliance failure after commissioning.
- 02
For the proposed treatability study or pilot programme, what source water quality parameters will be characterised and over what sampling period, and will the pilot be sized to generate representative flux and recovery data for the full-scale design?
A pilot study sized for 1 percent of the full-scale flow at 75 percent recovery will generate design data with an uncertainty of plus or minus 15 to 25 percent on membrane element count and antiscalant dose; scaling from pilot data requires the membrane manufacturer's validated design software calibrated against the pilot dataset, not just the manufacturer's generic design tool with default inputs.
- 03
How does the firm structure its fees for regulatory submission projects (DWI Reg 31, EA permit variation), and are the costs of additional data requests or DWI queries included in the fixed fee or treated as additional time-and-materials charges?
DWI Regulation 31 submissions frequently generate additional data requests that require supplementary toxicological analysis (GBP 5,000 to 30,000 per additional data set) and revision of the dossier; a fixed-fee contract that excludes DWI query responses can result in significant cost overrun and adversarial client-consultant relationships; a clear scope and change mechanism is essential for regulatory submission engagements.
- 04
In your lender's technical advisor (LTA) assignments, how does your firm manage the conflict of interest if you have previously provided design services to the same project company or its sponsors?
An LTA appointed by project finance banks has a direct reporting obligation to the banks, not to the project company; a firm that has provided design or development services to the same project cannot act as LTA without disclosing and managing the conflict; most banks' appointment processes include a formal conflict of interest screening and may exclude firms with prior engagements on the same project.
- 05
What is your firm's track record on delivering expert witness evidence in Ofwat regulatory appeals or planning inquiries for water infrastructure, and can you provide references from cases in the last 5 years?
Expert witness work in technical disputes (Ofwat AMP redeterminations, PINS planning appeals for reservoirs or STW upgrades) requires a specific skill set (ability to produce court-standard reports, defend opinions under cross-examination, and comply with Part 35 CPR requirements for experts) that is distinct from standard consulting; not all engineering firms have staff with this experience, and appointing an unqualified expert witness risks the client's case being damaged by poor expert report quality.
What drives cost in this category
4
- DWI Regulation 31 approval programme cost and specialist resource
- A DWI Reg 31 submission for a new treatment process (UV/AOP, NF, electrochlorination) typically requires: toxicological risk assessment by a qualified toxicologist (GBP 15,000 to 50,000); pilot or full-scale performance data collection and reporting (GBP 20,000 to 80,000); dossier preparation by a specialist water treatment consultant (GBP 10,000 to 30,000); total Reg 31 programme cost of GBP 50,000 to 200,000; projects that do not budget for Reg 31 at the outset frequently experience 6 to 18-month delays in the capital programme when the approval is required at commissioning stage.
- Lender's technical advisor (LTA) fee on project-financed water schemes
- LTA fees for project-financed water infrastructure (desalination plants, WTW PPPs, strategic reservoirs) are typically 0.3 to 0.8 percent of total project cost (CAPEX); for a GBP 100 million water project, LTA fees of GBP 300,000 to 800,000 cover the full project lifecycle (pre-financial close review, construction monitoring, completion certification, and annual operations audits); LTA costs are funded by the project company as part of development costs and are included in the project finance model.
- Complexity of multi-disciplinary regulatory submissions (DWI plus EA plus Planning)
- Projects requiring simultaneous DWI Reg 31, EA Environmental Permit variation, and Town and Country Planning application (TCPA 1990) require coordination of three regulatory agencies with different determination timescales (DWI 6 to 18 months, EA 4 to 12 months, LPA 8 to 26 weeks for standard; 12 to 24 months for EIA projects) and three sets of supporting technical documents; poor coordination results in the fast-determining authority completing before supporting evidence for the slower authority is available, stalling the programme; an experienced consulting project manager coordinating the three streams reduces risk of critical-path slippage.
- Treatability study and pilot plant cost versus reduced design uncertainty
- A 3-month treatability pilot study for a 10 Ml/day membrane treatment system costs GBP 50,000 to 150,000 (hire of pilot skid, analytical costs, consultant time); this reduces capital cost estimate uncertainty from plus or minus 50 percent (Class 4, without pilot data) to plus or minus 20 percent (Class 3, with pilot data); on a GBP 5 million full-scale capital project, the uncertainty reduction saves GBP 750,000 to 1,500,000 in contractor contingency at tender, giving a clear economic case for the pilot study investment.
Key regulations and standards
4
- Water Supply (Water Quality) Regulations 2016 Regulation 31 - DWI New Process Approval
- Regulation 31 of WS(WQ)R 2016 requires DWI approval before a new treatment process or treatment chemical is used for drinking water production in England; the application must include toxicological safety data, process performance evidence, and materials contact data; DWI determination takes 6 to 18 months; no new process may be used without a current Reg 31 approval; DWI publishes approved processes on its website and in Annual Reports.
- CDM 2015 (SI 2015/51) - Principal Designer Appointment and Design Phase Duties
- The Construction (Design and Management) Regulations 2015 require appointment of a Principal Designer for projects involving more than one contractor; the Principal Designer must plan, manage, monitor, and coordinate the pre-construction phase; water treatment consultants providing process design for construction projects must confirm whether they are acting as Principal Designer and, if so, must comply with all CDM 2015 PD duties including preparation and maintenance of the pre-construction health and safety information pack.
- NEC4 Professional Services Contract (PSC) - Consulting Engagement Terms
- NEC4 Professional Services Contract is the standard form for engaging water treatment consultants on UK water company projects; NEC4 PSC requires: agreed scope of services (Works Information); early warning notices for programme or scope changes; compensation event mechanism for scope changes (preventing uncontrolled scope creep); key dates for regulatory submission milestones; professional indemnity insurance requirement (typically GBP 5 million per claim minimum for DWI and EA regulatory submissions).
- Expert Witness - Civil Procedure Rules Part 35 and Practice Direction 35
- Water treatment consultants acting as expert witnesses in litigation, planning appeals, or Ofwat regulatory proceedings must comply with CPR Part 35 (Experts and Assessors); the expert's duty is to the court or tribunal, not to the instructing party; the expert report must include a statement of truth, the expert's qualifications, the facts and instructions relied on, the expert's opinion, and a declaration that the expert understands their duties; non-compliance with Part 35 can result in expert evidence being disregarded by the tribunal.
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