desalination plant I was asked this question recently and a person expected practical succinct guidelines from me on the spot. As a recourse I sent him a link to my post "How to prepare SWRO desalination plant bid" with a promise to return back.

Googling this question does not give any results, neither visiting the sites of major engineering services providers and consultants. Obviously, it is an experience nobody is willing to share. Even worse, lately the last two contractors removed from their websites the client's questionnaires.

Unlike internet transactions you make selecting nice pictures of things you trust you get, buying desalination plant is pivoted around the request for quotation having the power of contract. Its core is a set of technical and commercial requirements and conditions (R&C) covering design, manufacturing, and operation of the plant. To meet R&C, customization is needed - some parts are added or removed from the standardized plant scope.

To get what you really need, R&C shall be defined and thoroughly checked before any contact with the contractors to avoid biases in R&C (for instance, excluding other contractors from bidding). So nip in the bud your desire to press "Contact Us" button and follow the wisdom of 57 percent of the buyers who make purchase decisions before ever talking to supplier. Before this nearly all buyers (97%) make online research.

In compiling R&C I suggest two universal principles to follow. The first relates to your strategy in R&C execution verification.

Never ask the contractor for what you cannot verify or do not plant to verify.

For example, asking for the pump efficiency over 85% without providing means to measure it looks really unprofessional. Or asking for extended warranty for the pump sealing and coupling (over 18000 hours) without providing "window" for the contractor to the data acquisition system is a sure way not to get it.

I prefer the contractor defaults to what I cannot verify.

Hannah Arendt is quoted as saying "Prepare for the worst, expect the best, and take what comes". The second principle details the first part of this quote.

Always start with the worst end in mind - you sue your contractor in the court for not meeting your R&C.

How can you convince the independent expert selected by the court that your R&C are reasonable? I would not exaggerate by saying that nearly all projects came close to this point or really ended in court. It is a lose - lose situation for both parties.

The primary reason is that the contractor emphatically promises you what he/she optimistically anticipates to get from the OEM in the future after the project award - ideal back-to-back guarantees. It never works this way.

The R&C structure and scope are well defined and discussed below.

Feed water source

Feed water is what you are going to desalinate. To select optimal process, standard water analysis suffices taken at different times and locations. Special attentions shall be given to Total Suspended Solids (TSS) and turbidity during stormy seasons.

The manufacturer treats your water source analysis data as an envelope for guaranteed operability; any conditions beyond this envelope are considered off-design.

On the other hand, boggling the contractor down with hundreds of measurement points to extend guaranteed performance range and to transfer risks entirely to the contractor will not help - identical and insignificant entries shall be removed first.

For example, the RO membranes will exhibit the same performance for all pairs of temperature and salinity given in Table 1.

Table 1
TDS, ppm33300360003830040000

What the contractor rightfully expects is representative - not necessarily real - data covering the following cases.

  1. Minimum temperature & maximum salinity,
  2. Maximum temperature & minimum salinity
  3. Maximum membrane fouling & maximum product output
  4. Minimum membrane fouling & minimum product output

Now we have a third parameter - the membrane fouling affecting the plant performance envelope much stronger than possible variations in water salinity and temperature pairs. It's the weakest point in your defense against the contractor if such a need arises. Why? Because fouling mechanism is often site-specific. Recent example is the Ashdod desalination plant (Israel) court case.

Feed water before membranes

As pretreatment is the heart of RO desalination, it is perfectly normal to request from the contractor the guarantees on the pretreatment quality represented as "average value" and "peak value" groups for such categories as SDI, turbidity, TSS, TOC, COD, Aluminum, Iron, oil and grease.
For this guarantee to work, the peak values shall be paired with the relevant feed water data. In most cases clients are not aware of this link.

Product water output and quality

The product quality is characterized by TDS, NTU, pH, calcium, carbonate alkalinity, Br, LSI, CCPP, and total chlorine ranges within each grade - technical, potable, low Br, or process water. They are all met by contractors, and reliably monitored on site.

The real problem is the following set of closely interrelated technical terms that are expected to be set by the client in R&C.

  1. Plant total capacity
  2. Plant reliability
  3. Turn-down ratio
  4. Operation mode
  5. Daily storage capacity

Have you ever watched "Lost in translation" movie? These terms should somehow relate to the translation source - actual water consumption forecasts - annual, diurnal, hourly. In all cases known to me they don't as the client is not experienced enough to do this translation. It means that chances are high that all these categories are not set correctly. It's a big breach in your defense.

What would you say in court if your plant would fall short in delivering water by the same reasons Carlsbad desalination plant (USA) did. This plant was shut for 15 days owing to an algal bloom along the coast, and it was out of action in February for 10 days for water tank repairs. The owner of the plant - Poseidon has paid a penalty of $3.5 million to compensate for the shortfall. None of the above 5 categories are to blame as they are not set by the contractor! The lesson learnt is that feed water source availability should be taken into account as well.

What if your plant will be powered by the solar energy with the availability well below 95 percent?
What if you plan to engage your plant in peak shaving - the reduction of the amount of electricity drawn from a power utility during utility designated peak time periods? In this mode of operation the plant doesn't produce water during noon peak hours when the electricity tariffs are the highest. To do this you need at least 20% extra capacity.


The client is encouraged to explicitly specify the standards DIN or ANSI for mechanical equipment, IEC or NEMA for electrical, NPT or BSP threading for instrumentation, British or metric units. Generally it is enough to mention seismic design category and area classification to engage the eligible standards for design. Maximum noise levels shall be set as well.

Power supply

It is described by a power supply voltage and frequency, instrument voltage, PLC voltage and control air pressure (if used). You need to decide whether to use soft starting for motors or not. But the trickiest question is Uninterrupted Power Supply (UPS) source. It is used to gracefully shut down the plant and maintain it in a "hot" standby mode in case of general power outage.

Basis of design

Basis of design is a set of guiding practices and magic numbers enforcing the plant design robustness. (Otherwise you may get flimsy design with much shorter life expectancy.)

In the absence of engineering experience, the client resorts to a faulty old practice of asking the contractor (!) to fill the basis of design forms mirroring the equipment specifications. This practice contributes to nothing and a big waste of time by the following reason.

True basis of design is generic and does not depend upon the plant size.

The first part of the basis of design shall set such figures as maximum trains number, design fouling of RO membranes, maximum recovery, motor service factors, pump performance tolerances, type of pumps, piping overload capacities and vibration criteria, the membrane manifold design criteria, the equipment pieces service life, energy recovery method and chemicals storage capacities. It should contain fluid-materials compatibility matrix for all mechanical equipment types, piping material - velocity matrices, membrane software projection tolerances, and the extreme cases matrix for membrane software runs.

The second part is a collection of clauses describing how to design for robustness. This part is entirely missing in the requests for quotation for small-capacity plants (below 20 - 30 MLD). You may get some idea from these R&C.


If the feed water intake and brine outfall are included in the plant scope, extra information is needed. It is summarized in the landscape drawing, bathymetric and sea-bed map, and the brine dispersion map.

The landscape drawing shows the plant plot, intake pumping station, water intake and brine outfall points and the points for water sampling and soil sampling. The landscape ground levels shall be shown as well.

The bathymetric map show the water depths inside the triangle between the onshore intake station, the water intake and the brine outfall. These data are accompanied with the sub-sea-bed map showing the soil composition (sedimentation, submerged and buried rocks, etc.).

Brine dispersion map shows the areas of mixing and dilution. They should not overlap the areas of the water intake.


The plant main systems and subsystems scope shall be explicitly described. For example, ultrafiltration unit cannot go without backwash subsystem. The same applies for Cleaning-In-Place (CIP) subsystem. Chemical storage systems are often forgotten items (which allow much longer runs between replenishment). Do your final product water need pH correction or stabilization? Chemical reagents availability, sources location, quality and pricing shall be taken into account in optimizing the pretreatment and posttreatment configurations.


Instrumentation is what makes your plant remotely controllable and visible. Instrumentation is needed to automate the plant operation and to implement trend analysis and predictive maintenance. These are criteria used to select minimum instrumentation scope. It is a simple task not requiring deep understanding of controlled processes.


Submittals are the documents and drawings submitted with the plant proposal or with the purchase order. As I have mentioned above small - capacity plants are all standardized. So submittals availability and quality are the best indicators of the contractor experience and readiness to supply the plant. Submittals are a confirmation that the contractor understands your R&C correctly.

One of the most important documents is the spare items and parts list as it is an expensive part of the plant scope. This pack cost may reach 10% of that of the plant. The recommended list of submittals you may find here.


I'll skip such simple things as the scope of supply and work and the requested delivery time. The latter is defined by the first, its most popular form being "turn-key" scope. In this case you shall ask for all-inclusive cost covering packing & forwarding, freight, taxes and duties, installation, commissioning and handing-over.

Do you remember the second principle - always start with the worst end in mind?
If it would happen, you would use two documents - Warranty (W) and Purchasing Terms & Conditions (T&C) - to mitigate (not to entirely shield from) the consequences of the contractor failure to meet your R&C.

Good written W and T&C are a message to the contractor that you are a tough smart client and your intentions are serious. The funny thing is that every second request for quotation or tender does not have them or have them too general to miss the target! The reason for this negligence is simple - both documents shall identify and address the major risks sources at different stages of the project life cycle. The risk categories and details of the project execution are unknown to the procurement personnel responsible for tailoring W and T&C to a specific project.

How to create the T&C proxy from scratch without any previous experience? Without waiting for my next post covering this topic?

Start from searching web sites of contractors for the aggressively anti-client T&C and mirror it to the buyer side. It may work in some cases. For example, if the contractor labels seals, gaskets, elastomers, membranes, filters, couplings as "disposable component" without any warranty, set the warranty period for each named part and so on. If the contractor tries to sell you the OEM as-is original warranty, immediately replace it for the equipment type "back-to-back" warranty. Special attention is to the warranty termination conditions. Remove them all.

Download the R&C sample

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