Suppliers asked to quote stone dust control and wastewater treatment as two separate packages will embed incompatible assumptions at the boundary between them—typically around sludge routing, wet-process drain points, and the question of whether slurry from a wet grinding station feeds the water system, clogs a dry dust collector, or neither. That mismatch rarely surfaces in the bid documents; it shows up during commissioning when the installed ductwork terminates above a drain that was never included in the wastewater scope, or when a sedimentation unit is sized for a solids load that excluded one shift’s wet cutting output. The decision that closes this gap is a combined RFQ that treats air and water duties as a single process description, not two procurement events. Preparing that document correctly requires knowing, in advance, which data points each module depends on and where a gap in one creates a hidden design error in the other.
List workstations materials and wet dry process split
The workstation inventory is the foundation every other data point depends on, and the most common mistake at this stage is treating it as a headcount rather than a process map. A list that identifies twelve grinding stations but does not distinguish which four use water cooling, which three generate visible dry dust plumes, and which five alternate between wet and dry depending on the material being cut gives a vendor almost nothing to work from except assumptions—and vendors who must assume will either pad the scope to cover uncertainty or narrow it to win the bid.
Material identity matters beyond just naming the stone type. A supplier quoting on granite cutting needs to know grain size, typical moisture content, and whether the operation produces fine airborne particulate, a wet slurry discharge, or both simultaneously. Those characteristics directly affect whether a dry cartridge collector is appropriate, whether a downdraft table needs an integrated drain, and what solids concentration the wastewater treatment system should be designed to handle. A workstation listed only as “stone processing, mixed materials” leaves both the air and water modules without a defensible sizing basis.
The wet/dry process split is also where the integration problem becomes visible early. A wet station that drains to an unlined floor channel rather than a collection sump means the wastewater flow calculation will be incomplete. A station classified as dry that occasionally receives water for dust suppression creates an intermittent slurry load that a dry collector cannot handle and a wastewater system sized for continuous flow may not accommodate during peaks. Resolving these ambiguities at the workstation inventory stage prevents them from becoming locked-in scope conflicts once equipment is specified.
| Data Point | What to Specify | Why It Matters |
|---|---|---|
| Workstation ID/Name | Unique identifier and location for each dust or wastewater source | Ensures all emission points are scoped in the RFQ |
| Material(s) Processed | Type of stone or mineral, grain size, moisture content | Affects dust generation behaviour and wastewater solids load |
| Process Type | Classify as wet, dry, or mixed; indicate if water is used for cutting, suppression, or washing | Determines whether dust extraction, wastewater treatment, or both are needed |
| Dust and Mist Generation | Note visible dust, mist, or slurry produced during operation | Helps vendor select appropriate capture and control methods |
Provide CFM pickup geometry and layout constraints
Airflow figures submitted without a stated basis are not a design input—they are a guess that a vendor will either accept without challenge or quietly revise to match what their standard equipment produces. Both outcomes create problems: the first produces a system sized for conditions that may never have been measured, the second produces a quotation that reflects the vendor’s preferred equipment rather than the actual duty. The RFQ should require that each CFM figure be accompanied by its basis: measured during commissioning of a similar installation, calculated using capture velocity and hood geometry, or estimated from manufacturer data for that process type.
Hood geometry is where airflow demand becomes site-specific and where layout constraints interact directly with capture efficiency. A hood positioned 600 mm above a grinding surface requires substantially more airflow to maintain the same capture velocity as one positioned at 200 mm, and that difference has cascading effects on fan size, duct diameter, and operating energy cost. If the RFQ describes the pickup only as “overhead extraction,” a vendor designing for a close-capture slot hood and a vendor designing for a canopy hood will produce quotations that are structurally incomparable even if they carry the same CFM figure.
Layout constraints are routinely underspecified because procurement teams treat them as an installation detail rather than a design variable. In practice, a ceiling height that prevents a central duct from clearing overhead cranes, or a column spacing that forces a 90-degree duct bend within two duct diameters of the fan inlet, can require field modifications that invalidate the original pressure drop calculations and shift the system operating point off the fan curve. Identifying these constraints before quotation—not during installation—is the point at which layout data transitions from a background note to a hard design input. ISO 10780 provides a recognized framework for verifying airflow in installed ductwork during acceptance testing, which is relevant when specifying how post-installation performance will be confirmed.
For facilities calculating extraction requirements from first principles before preparing the RFQ, the CFM sizing guide for cartridge dust collectors provides a worked methodology.
| Data Point | What to Specify | Why It Matters |
|---|---|---|
| Capture Point Identifier | Label each hood, pickup, or enclosure, linked to the workstation ID | Correlates airflow demand with specific dust sources |
| Required Airflow (CFM) | Target or estimated flow rate per pickup, with basis (measured, calculated, or assumed) | Drives fan sizing, duct design, and energy cost estimates |
| Pickup Geometry | Type (hood, slot, canopy), dimensions, distance to dust source | Affects capture efficiency and required CFM |
| Layout Constraints | Available space, duct routing limitations, nearby obstructions | Prevents rework, ensures installability, and avoids hidden field modifications |
Provide wastewater flow solids pH and sludge route
Wastewater treatment equipment for stone processing is typically sized around three variables—flow rate, suspended solids concentration, and pH—and an error in any one of them propagates through the entire treatment train. A sedimentation unit sized for average flow without accounting for peak discharge from a wet-cutting shift will overflow during high-production periods. A chemical dosing system configured for a neutral pH stream will underperform if the actual feed is mildly alkaline from concrete-type aggregate processing. These are not edge cases; they are the standard failure pattern when flow and quality data are transferred from a process estimate rather than measured or sampled at source.
The solids load specification deserves particular attention because it determines not just the sedimentation equipment but everything downstream of it. Particle size distribution affects settling rate and the feasibility of gravity separation alone. High-density mineral fines from granite or marble cutting settle differently than softer silicate slurries, and a supplier who receives only a TSS concentration without particle size data will make assumptions about settling velocity that may require a significantly different tank volume or residence time than the quotation reflects. ISO 5667-10 provides a reference framework for wastewater sampling methodology that can be used when preparing grab samples or composite samples to characterize the stream before the RFQ is issued.
Sludge route is the variable most frequently omitted from RFQs and the one with the largest footprint consequence. Whether sludge will be dewatered on-site by a filter press, directed to an on-site lagoon, or transferred off-site as a wet cake determines whether the quotation needs to include dewatering equipment, the spatial envelope that equipment requires, and the access provisions for sludge removal vehicles or containers. A vendor who has not been told the sludge route will assume one, and that assumption shapes the integrated system footprint in ways that may not be correctable after civil works are complete. For a structured view of how treatment stages connect in heavy-solids applications, the wastewater treatment sequencing guide sets out the grit removal, dosing, settling, and pressing logic that drives equipment selection.
| Data Point | What to Specify | Why It Matters |
|---|---|---|
| Wastewater Flow Rate | Average and peak flow, batch or continuous discharge pattern | Drives treatment equipment sizing and equalisation needs |
| Solids Load | Total suspended solids (TSS) concentration and particle size distribution | Determines separation and dewatering technology selection |
| pH Range | Minimum and maximum pH of wastewater streams | Influences material selection and chemical dosing strategy |
| Sludge Handling Route | Where sludge is directed (dewatering, lagoon, off-site disposal) and available space | Shapes the integrated solution footprint and disposal cost outlook |
Define utilities installation and maintenance access
Utility specifications are where projects that look complete on paper stall at commissioning. A compressed air connection undersized for a pulse-jet cleaning cycle, a power supply rated for the dust collector motor but not for the chemical dosing pump and control panel on the same circuit, or a floor drain sized for process water but not for the additional flow during a system flush—each of these creates a delay that does not appear in the equipment specification but shows up as a modification cost after the equipment arrives on site.
The RFQ should specify available voltage, phase, and breaker capacity at the point of connection for each equipment cluster, not at the main distribution panel. It should also identify whether compressed air is available at adequate pressure and flow for pulse-jet filter cleaning, or whether a dedicated compressor is part of the scope. Water supply and drain connection points should be dimensioned and located on a drawing, not described in text, because a verbal description of “nearby drain” has resolved nothing when a vendor’s equipment requires a 150 mm gravity drain and the nearest floor drain is 75 mm.
Maintenance access is a planning criterion that reduces lifecycle operating cost and, in some jurisdictions, intersects with local equipment safety requirements. A cartridge dust collector positioned with less than 600 mm clearance on the filter access side will require filter change-outs to be performed in a posture that increases task time, consumable spillage risk, and the likelihood that the maintenance interval is extended beyond what the system’s pressure drop performance requires. For wet treatment equipment—particularly sedimentation tanks and dosing systems—access for cleaning, pump maintenance, and chemical container exchange should be identified in the RFQ so vendors can confirm that their standard equipment configurations fit the available envelope or propose a modified layout before the order is placed.
Ask suppliers to state assumptions behind each module
A quotation that does not disclose its assumptions is not a quotation—it is a price for an unspecified system. The practical risk is that two quotations for the same RFQ can appear comparable in headline price while being based on inlet solids loads that differ by a factor of three, or on airflow requirements calculated from different hood geometries, or on sludge handling assumptions that include or exclude the press depending on what the vendor considered part of their standard scope. Comparing those quotations without surfacing the assumptions produces a purchasing decision that selects the most optimistic estimate rather than the most accurate one.
The RFQ should explicitly require each supplier to state the inlet conditions they have assumed for each module, the utility connections they have included and excluded, the site preparation they expect the client to complete before installation, and any performance condition that depends on an input variable the client has not yet confirmed. This is not a request for additional paperwork; it is the mechanism that makes quotation comparison meaningful. A vendor who has assumed a peak wastewater flow of 5 m³/hour should state that, so a reviewer can immediately identify that the actual peak is 12 m³/hour and the quotation requires reissue rather than a purchase order.
The secondary benefit of requiring disclosed assumptions is that it identifies which vendors have actually read the RFQ and which have submitted a standard offering with the client’s name on the header. Suppliers who engage with the process split, the layout constraints, and the sludge route data will produce assumption lists that are specific to the project. Suppliers who have not engaged will produce generic exclusion clauses or leave assumption fields blank. That distinction is a reliable signal of whether a vendor’s commissioning performance will match their bid.
Specify dust and water acceptance checks together
Acceptance criteria defined separately for dust control and wastewater treatment create a specific failure mode: each system passes its individual performance test, but the combined system does not meet the actual operating condition because the wet/dry boundary was never tested as an integrated load. A wet grinding station that produces both a mist plume and a slurry discharge needs both the extraction system and the wastewater inlet to be verified simultaneously under the same process load—not sequentially under idealized single-system conditions.
The RFQ should require that acceptance criteria for both modules be stated in the same document section, with an explicit statement of whether testing will be conducted separately or under combined operating conditions. For dust-side verification, particulate concentration at the emission point and airflow within the design envelope are the primary checks; ISO 10780 provides a recognized measurement framework for installed duct systems. For the wastewater side, TSS concentration and flow rate in treated discharge are the primary checks, with sampling methodology aligned to the project protocol—ISO 5667-10 is a recognized reference for structured wastewater sampling during performance runs. Visual checks for visible dust escape, overflow, foaming, and sludge accumulation confirm operational behavior that instrument readings alone may not capture.
The residual handling confirmation—where does the collected dust go, and where does the dewatered sludge go—is an acceptance check that is almost always omitted from the performance test protocol but has downstream compliance and operational consequences. A system that meets all particulate and TSS criteria but discharges filter cake into an unmarked skip with no weigh-scale record has passed the instrumented test and created an unresolved operational gap. Including residual handling verification in the acceptance framework closes that gap before the system enters routine operation.
| Acceptance Aspect | Dust Control Check | Wastewater Control Check | Verification Method |
|---|---|---|---|
| Concentration Limit | Particulate concentration at emission point (e.g., opacity or mg/m³) | TSS or contaminant concentration in treated water discharge | Stack testing and grab sampling per agreed protocol |
| Visual / Operational Check | No visible dust escape from capture zones | No overflow, foaming, or sludge accumulation beyond limits | Walk-through inspection and shift logs |
| System Capacity | Airflow and pressure drop within design envelope | Flow rate and solids loading within design envelope | Measurement during performance test run |
| Residual Handling | Dust disposal or recycling pathway confirmed | Sludge dryness and disposal route confirmed | Observation and weigh-scale records |
Compare quotations by scope and test basis
Scope comparison is only meaningful when the RFQ has required suppliers to disclose their assumptions. Without that, a lower-priced quotation may have excluded ductwork, sludge piping, or controls that the higher-priced quotation included, and the comparison produces a ranking based on what each vendor chose to omit rather than on the merit of their technical approach or commercial terms. The first comparison step is not price—it is a line-by-line check of what each quotation includes and what it explicitly excludes, mapped against the RFQ scope boundary.
Test basis alignment is the check that determines whether acceptance is enforceable. A quotation that commits to “meeting specified performance” without naming the test method, the test conditions, and who is responsible for conducting and witnessing the test has not committed to anything that can be verified. Before comparing prices or technical specifications, confirm that each quotation states the measurement method for dust concentration, the sampling protocol for wastewater quality, the duration and operating conditions of the performance run, and whether the vendor or the client bears the cost of retesting if the first run fails. Ambiguity on any of these points is a commercial risk that typically surfaces as a dispute, not a technical dialogue.
The warranty and support comparison is where scope gaps that survived the bid evaluation become visible. A warranty clause that covers equipment defects but excludes performance shortfalls that occur when inlet conditions differ from the stated assumptions transfers the commissioning risk to the client while appearing on paper to offer protection. Reviewing warranty terms against the disclosed assumptions—specifically whether actual inlet conditions are within the tolerance the warranty requires—is the final check before a purchase decision.
| Comparison Item | What to Check in Quotations | Risk if Left Unclear |
|---|---|---|
| Scope of Supply | Does the offer include all dust collectors, wastewater units, ductwork, piping, controls, and sludge handling? | Unscoped items become costly change orders later |
| Performance Test Basis | Are acceptance criteria, test methods, and responsibility for proving performance clearly stated? | Disputes over whether the system meets requirements |
| Assumptions and Exclusions | Are inlet conditions, utility connections, site preparation, and disposal clearly assigned? | Hidden scope gaps and unexpected cost overruns |
| Warranty and Support | What is covered, for how long, and what triggers warranty obligations? | Ambiguity about after-installation responsibilities |
The practical output of a well-prepared combined RFQ is not a better-looking document—it is a set of quotations that can actually be compared, and a set of suppliers who have been forced to engage with the real operating conditions before they price the work. The data gaps that matter most are rarely the obvious ones; they are the wet/dry boundary at each workstation, the peak flow conditions that differ from average, the sludge route that determines whether a filter press fits in the available footprint, and the maintenance clearances that determine whether the system can be serviced at the interval the filter media actually requires.
Before issuing the RFQ, confirm that the workstation inventory identifies every emission point and classifies each by process type, that airflow figures carry a stated basis and are linked to documented hood geometry, that wastewater data includes peak as well as average conditions, and that acceptance criteria for both modules reference agreed test methods rather than general performance language. Suppliers who receive that level of specification have no defensible basis for scope assumptions that diverge from the project reality—and that is exactly the condition under which quotation comparison becomes a genuine procurement decision rather than a negotiation over what was and was not included.
Frequently Asked Questions
Q: What if our facility generates only dry dust or only wastewater, not both?
A: You do not need a combined air-and-water RFQ if there is genuinely no interaction between the two streams. However, before making that call, verify that no station ever produces both airborne dust and slurry, that no dust-suppression water enters the air system, and that no wet-process overflow could reach a dry collector. If the streams are wholly independent, issue a single-scope RFQ using the same data disciplines described for the relevant side—omitting the integration checks but still specifying airflow basis, hood geometry, or wastewater peak flows and sludge route exactly as you would inside a combined document.
Q: After we issue the combined RFQ, what is the immediate next step to keep the procurement on track?
A: Prepare a structured comparison framework before quotations arrive. Build a matrix that captures whether each supplier stated inlet assumptions, identified included and excluded utility connections, committed to a named test method for both dust and water acceptance, and disclosed the sludge handling scope. If you wait until bids are on the table to define how you will compare them, uneven assumptions will hide behind headline prices and the evaluation will regress to a price-only ranking. Scheduling a site walk or clarification call immediately after bids open can also surface layout or access misunderstandings before a purchase order locks them in.
Q: Our peak wastewater flow is extremely high relative to the average—how do we communicate that without oversizing the whole system?
A: Do not send only a peak flow number. Instead, provide the peak flow rate, the duration and frequency of peak events, the average flow, and the minimum flow, so the supplier can assess whether an equalization or buffer tank ahead of the treatment unit is more cost-effective than scaling sedimentation and dosing equipment to handle a short-duration spike. The RFQ should ask each vendor to explicitly state how they accounted for the peak-to-average ratio and whether they included surge buffering in their scope, so you can compare proposals that handle the profile differently rather than hiding it behind a single worst-case number.
Q: Is it ever acceptable to separate dust and wastewater into two RFQs instead of one combined package?
A: It is rarely the better route, but it is workable only when the facility has a hard physical and operational separation between wet and dry processes—different building wings, dedicated drains, independent sludge handling, and no stations that could shift between wet and dry modes. If you do split the scopes, you must still define every interface assumption inside each RFQ: drainage connection points, slurry routing, and the responsibility boundary for the wet/dry crossover, otherwise the gap that a combined RFQ prevents will reappear as a missing scope item when the two systems meet during installation.
Q: Our shop is small—only a couple of dry grinding benches and one wet saw. Is the full RFQ data checklist really necessary?
A: The same physical principles apply at any scale, so the core data points—workstation emission type, airflow basis, wastewater solids concentration, sludge destination—remain essential to avoid sizing errors. For a very small operation you can compress the documentation into a short technical annex rather than a large RFQ package, but skipping the data altogether invites suppliers to assume a generic duty that may not match your real peaks or layout limits. Shortening the document is fine; omitting the process characterisation is not.
