When a client asks me to review an MVR evaporator quotation, the first thing I check is not the price. It’s whether the document actually describes a system or just lists equipment. A proper quotation should tell you the flow rate, the evaporation capacity, the compressor type, the heat exchanger area, the materials of construction, the electrical load, the control philosophy, and what is excluded. If any of those are missing, you are not comparing bids — you are comparing guesses. In this article I’ll walk through what a complete MVR evaporator quotation should contain, based on years of designing and commissioning these systems for industrial wastewater applications.
What an MVR Evaporator Actually Does
Mechanical vapor recompression, or MVR, is a thermal separation process. You feed wastewater into a heat exchanger, boil off the water, and compress the resulting vapor so it can be reused as the heating medium. The compressor does the work that a steam boiler would otherwise do, which is why MVR systems typically run on electricity rather than steam. For sites without a cheap steam supply, that is a major advantage.
The core idea is simple: instead of throwing away the latent heat in the vapor, you raise its pressure and temperature slightly and put it back to work. A well-designed mechanical vapor compression MVC evaporator can recover the majority of the energy that would otherwise leave through the condenser. That is why operating costs for MVR are usually dominated by the compressor motor, not by fuel.
But the simplicity of the concept hides the complexity of the design. Feed chemistry, scaling tendency, boiling point elevation, turndown requirements, and fouling behavior all shape the final equipment selection. A quotation that ignores those factors is a price tag, not an engineering proposal.
The Sections a Complete Quotation Should Contain
Over the years I’ve seen quotations that fit on one page and quotations that run to sixty. The long ones are not always better, but the short ones are almost always incomplete. Here is the structure I expect to see when a serious vendor responds to an inquiry.
1. Process Design Basis
This is the foundation. Without it, nothing else can be evaluated. The design basis should state:
- Feed flow rate (m³/h or m³/day), with minimum and maximum values
- Feed composition — TDS, TSS, COD, oil and grease, pH, chlorides, sulfates, hardness, and any volatile organics
- Feed temperature range
- Target concentrate concentration (percent solids or specific gravity)
- Required distillate quality — this drives whether you need a polishing step after the evaporator
- Site conditions: ambient temperature range, altitude, available utilities, seismic and wind loads
If the quotation does not state these, ask for them in writing. A vendor who cannot articulate the design basis will not be able to defend the equipment selection later.
2. Evaporation and Heat Balance
The quotation should show the evaporation rate, the boiling point elevation at the design concentration, and the resulting compressor duty. For a given feed, the compressor power is roughly proportional to the evaporation rate divided by the specific energy consumption of the compressor. Typical MVR systems operate in the range of 15 to 40 kWh per tonne of water evaporated, depending on boiling point elevation, compressor efficiency, and the number of effects in the system.
Those numbers are indicative. Actual consumption depends heavily on the chemistry. A brine with high boiling point elevation — say, a concentrated sodium chloride or sodium sulfate stream — will require more compressor work than a dilute stream. A quotation that promises a single specific energy figure without qualification is either naive or optimistic.
3. Compressor Specification
The compressor is the heart of the system and typically the single most expensive item. The quotation should specify:
- Type — centrifugal, roots, or screw, depending on flow and compression ratio
- Motor power (kW), voltage, phase, frequency
- Material of construction for the impeller and casing
- Seal type and seal flush arrangement
- Turndown capability and how it is achieved (variable frequency drive, inlet guide vanes, bypass)
- Noise level and whether an acoustic enclosure is included
I have seen projects where the compressor was undersized because the vendor used a nominal boiling point elevation instead of the actual value at the design concentration. The system ran, but it never reached nameplate capacity. That is an expensive mistake to correct after installation.
4. Heat Exchanger Design
MVR systems rely on a forced-circulation or falling-film heat exchanger to transfer heat from the compressed vapor to the circulating liquid. The quotation should state the heat transfer area, the tube material, the tube diameter and wall thickness, and the circulation pump duty. It should also state the expected fouling factor and how the design accounts for it.
For wastewater with high scaling potential, the choice between forced circulation and falling film matters. Forced circulation handles higher solids and is more forgiving of crystallization, but it uses more pumping energy. Falling film is more efficient but less tolerant of suspended solids. A good quotation will justify the selection based on the feed chemistry, not just offer whatever is on the shelf. More detail on this trade-off is available in this discussion of MVC evaporator heat exchangers.
5. Materials of Construction
This is where a lot of quotations quietly cut corners. The materials should be specified for every wetted component: heat exchanger tubes and shells, circulation piping, pumps, valves, the separator vessel, and the distillate collection system. Common choices include 316L stainless steel, duplex stainless steel, titanium, and various nickel alloys. The right choice depends on chloride content, pH, temperature, and the presence of oxidizing species.
If the quotation says “stainless steel” without a grade, ask. If it says “corrosion-resistant” without a material, ask harder. The difference between 304 and duplex 2205 in a chloride environment can be the difference between a ten-year life and a two-year failure.
6. Instrumentation and Controls
A modern MVR system should come with a PLC-based control system, a human-machine interface, and enough instrumentation to run the plant safely and efficiently. The quotation should list:
- Temperature, pressure, flow, level, conductivity, and pH instruments
- Compressor protection devices (vibration, temperature, current)
- Anti-scaling and anti-foaming dosing systems, if required
- Emergency shutdown logic and interlock schedule
- Remote monitoring capability, if offered
- Control panel enclosure rating and area classification
I have seen plants where the control system was an afterthought, and the operators ended up running the evaporator manually because the automation was unreliable. That is a false economy.
7. Ancillary Equipment and Scope Boundaries
A quotation should clearly state what is included and what is not. Typical inclusions are the evaporator skid, the compressor, the circulation pumps, the heat exchanger, the separator, the distillate pump, the concentrate pump, the control panel, and the interconnecting piping within the skid. Typical exclusions are civil works, foundations, feed pretreatment, concentrate disposal, distillate polishing, and site electrical supply to the control panel.
Ambiguity here is the leading cause of disputes during project execution. If the vendor assumes you will provide the feed tank, and you assume they will, you will find out at the worst possible moment.
Comparison Table: What to Look For in Each Quotation Section
| Section | Minimum Information Required | Red Flag If Missing |
|---|---|---|
| Design basis | Flow, composition, temperature, target concentration | No feed analysis referenced |
| Heat balance | Evaporation rate, boiling point elevation, compressor duty | Single energy figure with no qualification |
| Compressor | Type, motor power, materials, turndown, seal type | “Compressor included” with no specification |
| Heat exchanger | Area, tube material, fouling factor, circulation rate | Area not stated |
| Materials | Grade for every wetted component | “Stainless steel” without grade |
| Controls | PLC, HMI, instrument list, interlocks | No instrument list |
| Scope | Explicit inclusions and exclusions | Vague battery limits |
| Performance | Guaranteed distillate quality and capacity | No performance guarantee |
| Service | Commissioning, training, spare parts, warranty | No commissioning scope |
Performance Guarantees and How They Are Written
A quotation without a performance guarantee is a quotation without accountability. The guarantee should specify the distillate quality, the concentrate concentration, the evaporation capacity, and the specific energy consumption under defined conditions. It should also state the correction factors that apply if the actual feed differs from the design basis.
Be careful with guarantees that are too broad. A guarantee of “distillate TDS below 100 mg/L” means nothing if the feed TDS is not fixed. A guarantee of “capacity within 5 percent of design” means nothing if the feed temperature is allowed to vary by 20 degrees. The best quotations define the guarantee envelope precisely and explain how deviations will be handled.
I also look for a statement on how performance will be verified. Will there be a site acceptance test? Who provides the test instruments? What happens if the system falls short? These are the questions that separate a serious vendor from a hopeful one.
Energy Consumption: What to Expect and What Drives It
Energy is the largest operating cost in an MVR system, so the quotation should address it honestly. The dominant factor is the compressor power, which depends on the compression ratio and the mass flow of vapor. The compression ratio, in turn, depends on the boiling point elevation and the temperature difference needed across the heat exchanger.
For dilute feeds with low boiling point elevation, specific energy consumption in the range of 15 to 25 kWh per tonne of evaporated water is achievable. For concentrated brines with high boiling point elevation, the figure can rise to 35 or 40 kWh per tonne. These are typical design ranges, not guarantees. Actual performance depends on the specific chemistry, the ambient conditions, and how the system is operated.
Some quotations include a multi-effect arrangement to reduce energy consumption. A multi-effect evaporator uses the vapor from one effect to heat the next, which reduces the compressor duty but increases capital cost and complexity. The trade-off depends on the ratio of electricity to steam cost at the site, and on the required capacity. For very large flows, multi-effect MVR can be attractive. For smaller flows, a single-effect MVR is usually simpler and cheaper to own.
If your site has access to low-cost steam, a thermal multi-effect system without MVR may be more economical. If electricity is cheap and steam is not available, MVR is usually the better choice. The quotation should make this comparison transparent, not assume the answer.
Pretreatment: The Part Most Quotations Underestimate
MVR evaporators are robust, but they are not indestructible. The feed has to be conditioned before it enters the evaporator, or the heat exchanger will foul, the compressor will erode, and the system will underperform. Pretreatment requirements depend on the feed chemistry, but common steps include:
- Oil and grease removal, typically by dissolved air flotation or coalescing separation
- Suspended solids removal by filtration or clarification
- Hardness removal by softening or chemical precipitation
- pH adjustment to keep the feed within the material’s corrosion envelope
- Deaeration if dissolved oxygen is a concern
A quotation that does not mention pretreatment is either assuming you will handle it or hoping you won’t notice. Either way, you should ask. If pretreatment is required, it should be scoped, priced, and included in the overall project budget. If it is not required, the quotation should say why.
For leachate and complex industrial streams, pretreatment often includes membrane concentration before the evaporator. A DTRO membrane system can reduce the volume that has to be evaporated, which lowers both capital and operating cost. The quotation should show whether this option was considered and why it was or was not selected.
Operating Cost: What the Quotation Should Show
A good quotation will include an operating cost estimate, even if it is approximate. The estimate should break down:
- Electricity for the compressor, circulation pumps, and auxiliary equipment
- Chemicals for antiscalant, antifoam, and cleaning
- Labor for routine operation and maintenance
- Replacement parts and consumables
- Concentrate and distillate disposal costs, if applicable
These figures should be presented as a range, with the assumptions stated. If the vendor gives a single number without assumptions, treat it as a marketing figure, not an engineering estimate.
I also ask for a sensitivity analysis. How does the operating cost change if the feed TDS is 20 percent higher than expected? If electricity prices rise by 30 percent? If the plant runs at 70 percent capacity instead of 100 percent? A vendor who can answer those questions has actually modeled the system. A vendor who cannot is guessing.
Maintenance and Service: The Long-Term View
The quotation should describe the maintenance requirements and the service offering. Key items include:
- Recommended cleaning frequency and cleaning procedure
- Spare parts list with lead times
- Warranty period and what it covers
- Commissioning scope and duration
- Operator training
- Remote support and response time
I have seen projects where the warranty was one year on parts only, and the first major compressor overhaul was needed at eighteen months. The owner paid for it. If the quotation had specified a longer warranty or a service agreement, the outcome would have been different.
Ask about the expected life of the compressor, the heat exchanger tubes, and the pumps. Ask what the typical maintenance cost is as a percentage of capital cost per year. A reasonable range for a well-designed MVR system is two to four percent of capital cost per year, but that depends on the feed chemistry and how hard the system is pushed.
Common Mistakes I See in Quotations
After reviewing hundreds of quotations, the same problems come up again and again:
- No feed analysis referenced. The vendor quotes a system without knowing what it will treat. This is the single biggest cause of underperformance.
- Optimistic energy figures. The specific energy consumption is quoted at the low end of the range without stating the assumptions.
- Underspecified materials. “Stainless steel” instead of a grade, or a grade that is not suitable for the chloride level.
- Missing pretreatment. The evaporator is quoted as a standalone unit, but the feed requires conditioning.
- Vague scope boundaries. Nobody knows who supplies the feed tank, the electrical supply, or the concentrate handling.
- No performance guarantee. The vendor promises results verbally but not in writing.
- Unrealistic delivery schedule. The schedule assumes everything goes right, which it rarely does.
If you see two or more of these in a quotation, slow down. Ask questions. Ask for a revised quotation that addresses the gaps. A vendor who is serious will respond. A vendor who is not will disappear, which is also useful information.
How to Compare Quotations Fairly
Comparing quotations is not about finding the lowest number. It is about finding the lowest total cost of ownership for a system that actually works. To do that, normalize the quotations against a common specification. Ask each vendor to quote the same scope, the same materials, the same performance guarantee, and the same service package. Then compare.
The comparison should include:
- Capital cost, broken down by major equipment item
- Operating cost over a five-year or ten-year horizon
- Maintenance cost and expected major overhauls
- Performance guarantee and the consequences of missing it
- Delivery schedule and commissioning plan
- Service and spare parts availability
I have seen a quotation that was 20 percent cheaper than the next bid turn out to be 40 percent more expensive over five years, because the compressor was undersized, the heat exchanger fouled faster, and the service response was slow. The lowest bid is not always the best value.
When to Consider Alternatives to MVR
MVR is not always the right answer. If the feed is dilute and the discharge limits are not tight, conventional biological treatment or membrane separation may be cheaper. If the site has cheap steam, a thermal multi-effect system may be more economical. If the flow is very small, a simple single-effect evaporator may be sufficient.
The quotation should acknowledge these alternatives and explain why MVR was selected. If it does not, ask. A vendor who cannot explain the trade-offs is not in a position to advise you.
For zero liquid discharge projects, MVR is often the final concentration step, but it is rarely the only step. A typical ZLD train includes pretreatment, membrane concentration, and evaporation or crystallization. The quotation should show how the MVR system fits into the overall train, not just quote a standalone unit. More on this is covered in this overview of zero liquid discharge ZLD systems.
Frequently Asked Questions
What is the most important thing to check in an MVR evaporator quotation?
The design basis. If the quotation does not clearly state the feed flow, composition, temperature, and target concentration, the rest of the document is built on sand. Everything else — compressor size, heat exchanger area, materials, energy consumption — depends on the design basis being correct and complete.
How much does an MVR evaporator cost?
Capital cost depends on capacity, materials, compressor type, and scope. For a small system treating a few cubic meters per day, the cost may be in the low hundreds of thousands of dollars. For a large system treating hundreds of cubic meters per day, the cost can run into the millions. Operating cost is dominated by electricity, typically in the range of 15 to 40 kWh per tonne of water evaporated. These are indicative ranges, and actual figures depend on the specific project.
How often does an MVR evaporator need cleaning?
Cleaning frequency depends on the feed chemistry and how close the system runs to saturation. For a clean feed with low scaling potential, cleaning may be needed every few months. For a scaling feed, it may be needed weekly or even more often. The quotation should state the expected cleaning frequency and the cleaning method, and it should include a chemical cleaning system if needed.
Can an MVR evaporator handle high TDS wastewater?
Yes, within limits. MVR systems are commonly used for brines and concentrates with TDS in the range of tens of thousands of milligrams per liter. The limiting factors are scaling, corrosion, and boiling point elevation. As TDS rises, the boiling point elevation increases, which raises the compressor duty and the energy consumption. The materials also have to be selected for the chloride and sulfate levels. A well-designed system can handle high TDS, but the design has to account for it.
What happens if the feed composition changes after the system is installed?
The system will still run, but performance may degrade. If the feed becomes more concentrated, the compressor may not be able to maintain capacity, and the distillate quality may suffer. If the feed becomes more corrosive, the materials may fail sooner. The best protection is a design basis that includes a realistic range of feed conditions, and a performance guarantee that defines how deviations will be handled. If the feed changes significantly, the vendor should be consulted before the system is pushed beyond its design envelope.
Do I need pretreatment before an MVR evaporator?
Usually, yes. Oil and grease, suspended solids, and hardness all cause problems in the heat exchanger and the compressor. The specific pretreatment depends on the feed, but common steps include oil removal, filtration, softening, and pH adjustment. The quotation should state whether pretreatment is included or excluded, and if it is excluded, it should explain what is required.
How long does it take to commission an MVR system?
Commissioning typically takes one to three weeks for a small system, and longer for a large or complex one. The schedule depends on the completeness of the installation, the availability of feed and utilities, and the experience of the commissioning team. The quotation should include a commissioning plan and a schedule, and it should state who is responsible for what.
What spare parts should I keep on hand?
At minimum, keep a set of gaskets, seals, and instrument spares. For the compressor, keep the recommended spare parts as specified by the manufacturer, which may include bearings, seals, and vibration sensors. For the heat exchanger, keep spare tubes if the design allows tube replacement. The quotation should include a recommended spare parts list with prices and lead times.
Final Thoughts
An MVR evaporator quotation is a technical document, not a sales brochure. It should tell you what the system will do, how it will do it, what it will cost to build and operate, and what happens if something goes wrong. If it does not answer those questions, it is not ready to be compared against other bids.
My advice is to read every quotation with the same skepticism you would apply to a design review. Ask for the missing information. Ask for the assumptions behind the performance figures. Ask what happens if the feed is not what was expected. The vendors who answer clearly are the ones worth working with. The ones who dodge are telling you something important.
If you are evaluating MVR options for a specific wastewater stream and want a second opinion on the technical scope, feel free to reach out to our engineering team. We are happy to review your design basis and help you ask the right questions, whether or not you end up working with us.