Water Treatment PFD, P&ID and RFQ Checklist for EPC Buyers

BFD vs PFD vs P&ID vs RFQ: What Is the Difference?

These documents serve different purposes. An RFQ is a procurement package; the other three are diagrams that may form part of that package.

The required detail depends on the project stage and procurement strategy. A PFD does not replace a P&ID. A P&ID does not replace piping layouts, isometric drawings, electrical drawings, control narratives or fabrication drawings. None of these documents alone is a complete construction package.

BFDs are typically used in concept design; PFDs support process development and basic engineering. P&IDs develop through basic and detailed engineering, with instrumentation detail appropriate to their status. RFQs support procurement and technical bid evaluation, using drawings as supporting documents rather than substitutes for the procurement requirements.

Organize the Documentation by Design Maturity

Use the following sequence as a working framework:

Project Requirements → Design Basis → BFD → PFD → Equipment Data Sheets → P&ID → RFQ Package → Supplier Clarifications → Technical Bid Evaluation

This is a recommended working logic, not a requirement to finalize every P&ID before issuing an RFQ. Basic design, equipment enquiries and P&ID development may proceed in parallel. Identify the revision, design maturity and responsible party for each document.

Start with a Confirmed Design Basis

The Design Basis records the conditions against which the process and equipment are selected. State the source, date, units and approval status of each input. Separate confirmed requirements from preliminary assumptions and information still to be provided.

The owner provides the original project conditions; the EPC contractor verifies them and establishes the design basis under the agreed responsibility structure. Mark every item Confirmed, To Be Confirmed, or Not Applicable.

Do not infer applicable regulations, certifications or discharge limits from the country name alone. Record unconfirmed requirements as requiring verification.

Design Basis checklist

• ☐ Identify the project, country, installation site, owner and responsible design authority.
• ☐ Describe the water or wastewater source, production process and intended treated-water use or discharge destination.
• ☐ Provide average, peak and minimum flow conditions where relevant, operating hours, batch discharge patterns and seasonal variation.
• ☐ Attach representative analysis reports with sampling dates, sampling locations and operating conditions.
• ☐ Identify relevant parameters, such as pH, COD, BOD₅, TSS, oil and grease, temperature, salinity and application-specific contaminants. Do not assume one list is sufficient for every source.
• ☐ Define outlet requirements, applicable project standards and the point at which compliance will be assessed.
• ☐ Describe existing treatment equipment, available capacity and any known operating constraints.
• ☐ Confirm available power, water, air and other utilities, including their supply boundaries.
• ☐ Record space, access, ambient conditions, drainage arrangements and site restrictions.
• ☐ Define operating philosophy, redundancy requirements, automation scope and maintenance access needs.
• ☐ Assign responsibility for missing data, assumptions, process selection and design approval.

For integrated water treatment enquiries, see how to prepare a raw-water report. Laboratory data should be interpreted together with source variability and the intended duty.

Stage 1: Prepare the BFD and Define the System Boundary

A BFD should explain the treatment functions without implying that detailed equipment selection has already been completed.

An illustrative sequence is:

Feed → Pretreatment → Main Treatment → Polishing → Treated Water

This is a conceptual example, not a recommended process for every project. Some systems need a different sequence or fewer stages.

BFD checklist

• ☐ Show the main treatment blocks and flow direction.
• ☐ Identify the feed, treated-water outlet and package boundaries.
• ☐ Show significant residual streams, such as sludge, concentrate or spent cleaning solution, where applicable.
• ☐ Identify connections to existing plant and equipment supplied by others.
• ☐ State the purpose of each treatment block.
• ☐ Mark optional, future or unresolved treatment stages clearly.
• ☐ Confirm that the proposed functions address the Design Basis before developing equipment details.
• ☐ Include the document number, issue date and revision status.

For industrial wastewater treatment packages, define each treatment function and the equipment supplied by others before selecting the process. A membrane-system BFD might show Raw Water / Wastewater → Pretreatment → Membrane Filtration → Treated Water. Concentrate, backwash water or cleaning waste streams depend on the selected membrane technology and arrangement. For ceramic membranes, identify whether the design uses flat-sheet, tubular or another configuration and state the filtration objective. Do not transfer specifications from UF, PVDF-based or RO systems to the selected ceramic membrane system without validation.

Stage 2: Develop the PFD and Process Data

The PFD develops the concept into a process arrangement. Its supporting stream information should allow reviewers to understand the principal duties and the basis for equipment selection.

PFD checklist

• ☐ Identify the main equipment and use consistent equipment tags.
• ☐ Show principal process streams and flow direction, with a stream table where appropriate.
• ☐ State relevant flow rates and key operating conditions, distinguishing normal conditions from design limits.
• ☐ Identify recycle, bypass, overflow and discharge streams where applicable.
• ☐ Show chemical dosing and significant auxiliary process steps.
• ☐ Provide the applicable water or material balance and identify the operating case to which it applies.
• ☐ Account for treatment losses and intermittent operations when defining net treated-water delivery.
• ☐ Identify the basis for major equipment duties and unresolved selection assumptions.
• ☐ Check consistency with the Design Basis and equipment data sheets.
• ☐ Record main equipment quantities as well as equipment names and tags.
• ☐ Identify key inlet and outlet water-quality conditions, relevant pressures and temperatures.
• ☐ State chemical types and principal dosing locations, and show required cleaning flows.
• ☐ Identify key process control conditions and normal, maximum and relevant special operating cases.
• ☐ Include the drawing number, revision and review status.

For a flotation stage, use the DAF system RFQ checklist to define wastewater data, chemical-conditioning assumptions and sludge outlets. For integrated water treatment and supply systems, identify treatment, storage and downstream pumping as separate duties.

Before seeking a fixed price, check that the PFD explains why the major equipment is needed, how the equipment works together and which conditions support preliminary selection. If these points remain unclear, bidders may price different technical scopes.

Do not compare systems solely by their stated feed capacity. Confirm whether quoted capacity means feed flow, gross production or net water available at the agreed delivery point.

Stage 3: Prepare Equipment Data Sheets and the P&ID

Equipment data sheets translate process duties into procurement requirements. The P&ID then defines the connections and control relationships needed for the agreed engineering stage.

Equipment data sheet checklist

• ☐ Match each data sheet to its equipment tag, service and drawing references.
• ☐ State the required duty and applicable operating and design conditions.
• ☐ Define material requirements and the basis for corrosion or chemical compatibility review.
• ☐ Identify connections, utility requirements and instrumentation interfaces.
• ☐ Define required accessories, standby arrangements and maintenance provisions.
• ☐ Separate purchaser requirements from information to be completed by the supplier.
• ☐ List inspection, testing and document requirements applicable to that item.

P&ID checklist

• ☐ Use the project drawing legend, tagging convention and agreed symbols.
• ☐ Identify equipment, piping connections and package tie-in points consistently.
• ☐ Show line numbers, sizes and applicable piping specification references at the required design maturity.
• ☐ Identify valves and their functions; specify tags and actuation details where required.
• ☐ Show instruments, measurement locations, signal relationships and control loops.
• ☐ Define or reference required alarms, interlocks, protective functions and operating sequences.
• ☐ Show applicable isolation, drains, vents, sampling points and maintenance connections.
• ☐ Identify chemical dosing, flushing, backwash and cleaning connections where relevant.
• ☐ Reference related control narratives, cause-and-effect documents and equipment details rather than treating the drawing as a substitute for them.
• ☐ Mark battery limits and state who supplies each connecting item.
• ☐ Resolve discrepancies between the P&ID, PFD, equipment list and data sheets.

P&ID review register

Use the following register to check the required detail at the agreed design stage. An item may be marked not applicable where supported by the project design.

For variable-frequency constant-pressure water supply equipment, define pump duty, pressure measurement, changeover and protection interfaces. Identify the collection and transfer interfaces for any sludge dewatering package separately.

A drawing marked for enquiry may contain open items. Record those items and their effect on the quotation; do not silently treat an enquiry drawing as approved for construction.

Stage 4: Assemble the Water Treatment RFQ Package

The RFQ should tell every bidder which requirements are fixed, which selections they must propose and which exclusions they must declare.

Technical RFQ checklist

• ☐ Include the Design Basis and an indexed list of enquiry documents with revision numbers.
• ☐ Attach the available BFD, PFD, P&ID, equipment list and relevant data sheets.
• ☐ State the maturity and intended use of each drawing.
• ☐ Define equipment supply, package piping, valves, instruments, control panels and software scope.
• ☐ Separate supplier scope from civil works, installation, field piping, cabling and site utilities supplied by others.
• ☐ Define package inlet and outlet interfaces and responsibility for final tie-in engineering.
• ☐ Specify required supplier drawings, calculations, manuals and document formats.
• ☐ Define inspection, factory checks, site tests and acceptance responsibilities.
• ☐ State the operating conditions, measurement methods and acceptance points for any requested performance commitment.
• ☐ Define commissioning, training, spares and after-sales scope to be quoted.
• ☐ Request an explicit schedule of assumptions, exclusions and technical deviations.
• ☐ Require the supplier to identify outstanding information that affects selection or price.

Commercial and logistics checklist

• ☐ Identify the delivery destination and the requested trade term, named place and applicable Incoterms edition.
• ☐ Request itemized equipment, optional items, services and transport charges as applicable.
• ☐ Request quotation currency, validity, payment proposal and delivery schedule.
• ☐ Clarify packing, shipment dimensions, weights, unloading and storage responsibilities.
• ☐ Define the required proposal return date and clarification contact.
• ☐ Distinguish requested commercial terms from terms subsequently agreed in a contract.

The RFQ should also distinguish documents supplied by the purchaser for bidding from documents the successful supplier must develop after award. Final P&IDs need not exist before every enquiry, but responsibilities and unresolved scope must be explicit.

For packaged systems, review treatment and pumping supply boundaries before comparing a complete plant offer with a limited equipment package.

Documents the EPC Buyer Should Issue

Battery limits define supply or engineering responsibility boundaries between the package and other systems. Physical piping tie-ins are part of those interfaces, but a P&ID alone does not define every contractual responsibility.

Documents to Request from Suppliers

Some submissions may be preliminary at bid stage and developed after award. Agree the required document depth, acceptance conditions, delivery terms and performance responsibilities for the specific project.

Ceramic Membrane Systems: Additional Documentation Checks

Ceramic membrane plates, assembled modules and complete filtration systems are different supply packages. Clarify the procurement level before requesting a price.

Ceramic membrane checklist

• ☐ State whether the enquiry covers plates, modules, replacement elements or a complete system.
• ☐ Identify the application, filtration objective and membrane form: flat-sheet, tubular or another structure.
• ☐ Provide feed analysis, source variability, existing pretreatment and the treatment objective.
• ☐ Confirm feed temperature, particulate characteristics, design flow and operating hours.
• ☐ Request confirmation of the actual membrane material, pore size and membrane area for the proposed selection.
• ☐ Request the proposed membrane configuration and the evidence or testing basis for its selection.
• ☐ Distinguish gross filtration capacity from net production after applicable cleaning, backwashing and downtime.
• ☐ Ask the supplier to state proposed design assumptions and operating limits rather than inserting generic flux, recovery or removal figures.
• ☐ Identify the proposed filtration arrangement and its feed, permeate, reject or sludge connections, as applicable.
• ☐ Define relevant instrumentation and the basis for monitoring pressure, differential pressure or transmembrane pressure for the selected arrangement.
• ☐ Clarify whether backwash, air cleaning, chemical cleaning or other cleaning provisions apply, and identify their equipment and utility scope.
• ☐ Request compatibility limits for the complete assembly, including seals, housings, valves and piping, as well as the membrane material.
• ☐ Define cleaning waste and residual discharge interfaces and responsibility for their treatment or disposal.
• ☐ For replacements, verify dimensions, connections, mounting, sealing and compatibility with the existing equipment.
• ☐ Request supplier confirmation of test requirements, maintenance documents and spare-parts scope.

Material descriptions alone do not establish suitability for a particular liquid, cleaning chemical or operating condition. Do not assume that a ceramic membrane assembly can replace another membrane technology without a system review.

Membrane area or nominal flux alone does not establish actual treatment capacity. For complex industrial wastewater, request evidence of suitability and, where necessary, sample testing or pilot trials to confirm the design conditions. Data for another membrane material or a different application must not substitute for validation of the proposed ceramic membrane product.

See the available ceramic membrane supply scopes when defining whether you need individual components or a complete filtration package.

Compare Supplier Quotations on the Same Basis

A lower total price may reflect a smaller supply scope or different assumptions. Normalize the technical basis before drawing a commercial conclusion.

Use a technical clarification register to close material differences before final bid evaluation. Where operating cost matters, compare calculations using the same operating assumptions and confirmed unit costs.

Record each bidder's installation-material scope, commissioning services, spare parts, after-sales support, delivery schedule and exclusions. Use separate EXW and FOB entries where those terms are requested; do not compare the quoted totals without understanding the different delivery responsibilities and cost boundaries. Confirm how export formalities, inland transport and port-related costs are allocated in the actual offers. Agree the trade term and named delivery point for the specific project.

The technical deviation checklist provides a related framework for recording assumptions and exclusions.

Control Drawing Revisions and Supplier Clarifications

Document control prevents bidders and engineers from working from different requirements. A revised drawing should have a traceable purpose, review status and distribution record.

Revision management checklist

• ☐ Assign each document a unique number, title, revision, date and status.
• ☐ Identify the originator, reviewer and approving authority.
• ☐ Maintain a master document register and a record of issue to each recipient.
• ☐ Mark changes using the project's revision convention and record the reason for each change.
• ☐ Link supplier clarifications and accepted deviations to the affected requirements.
• ☐ Record which RFQ revisions and addenda each bidder used.
• ☐ Assess changes for effects on scope, price, schedule and acceptance criteria.
• ☐ Withdraw superseded documents from active use while retaining the audit trail.
• ☐ Reconcile final supplier documents with the agreed contract and engineering interfaces.
• ☐ Require verified as-built updates and handover documents at the agreed project stage.

Drawing status and revision number are separate controls. The latest revision is not automatically approved for procurement, fabrication or construction.

Use project-defined issue statuses, such as For Review, For Enquiry, For Approval, or For Construction. Record unresolved points in a remarks field. Update verified as-built records so that the final documents reflect the installed system.

Final Checklist Before Issuing the RFQ

• ☐ The Design Basis is confirmed and open items are identified.
• ☐ The process arrangement addresses the treatment objective.
• ☐ Applicable BFD, PFD and P&ID revisions and statuses are clear.
• ☐ The main equipment list is complete for the enquiry scope.
• ☐ Key equipment data sheets are available.
• ☐ Supply boundaries are explicit.
• ☐ Electrical and control interfaces are defined.
• ☐ Applicable standards and acceptance requirements are identified.
• ☐ All suppliers receive the same quotation format and enquiry revisions.
• ☐ Technical deviation submission requirements are clear.
• ☐ Document deliverables are defined.
• ☐ Commercial terms and quotation exclusions are explicit.

For a concept-stage project, identify the request as a budget enquiry, state that the design conditions are not frozen and use the resulting quotation for preliminary evaluation.

Common Documentation Mistakes to Avoid

• Treating a BFD, PFD, P&ID or RFQ as interchangeable documents.
• Issuing a capacity figure without feed data, outlet requirements or operating conditions.
• Using inconsistent equipment tags or superseded drawing revisions.
• Treating a P&ID tie-in as a complete definition of contractual supply responsibility.
• Applying another membrane product's parameters without application-specific validation.
• Comparing prices before aligning supply scope, acceptance requirements and delivery terms.
• Treating an enquiry drawing as approved for construction or leaving as-built changes unrecorded.

Prepare Your Water Treatment Equipment Enquiry

Share your available Design Basis, water-analysis reports, BFD or PFD, preliminary P&ID, equipment scope and project country for an initial written review. Identify missing information and the current revision of each drawing so the enquiry can be assessed on a consistent basis.

Include your intended treated-water use or discharge requirements, site utilities, supply boundaries and target schedule. Equipment configuration, pricing, delivery and acceptance terms are confirmed for the specific project.

Send your water treatment project requirements

Suggested email subject: Water Treatment RFQ – [Project / Company] – [Country]