Ultrapure water plays a vital role in all Power Generation Plants.  A WTP may shut down for several reasons causing Power Providers to face losses in the millions for every hour of downtime.  While many plants operate 24/7 without interruption, there is a high chance a temporary WTP will be required at some point in time.

There are several factors in a WTP operation that determine the availability and reliability of the purified water. A temporary system may be required for several reasons such as: pump failure, PLC failure, boiler tube failure, electrical issues, weather events, supply chain disruptions, planned maintenance, increased capacity requirements, and or equipment retrofits.  Being prepared for all possibilities, expected or unexpected while developing a proper contingency plan prior to an emergency may avoid lost production and extra costs.

Determine What’s Essential and Available

Equipment always seems to fail at the most inconvenient time such as on a Friday night shift or Holiday Weekend.  When this occurs, typically several employees begin the scramble of trying to find the proper equipment for the job to place on-site as soon as possible.

The first question, to ask is “What is the ideal capacity required to avoid disruption at baseload for 24 hours?”  Regardless of the flow requirements,      that should be the flow used in the selection of a temporary WTP.  The Power Plant ultrapure water requirement is typically in GPM or m3/hr and this should be determined as part of the contingency plan well ahead of time.

Water treatment rental equipment varies widely among suppliers, and below you will find the most common packages.  This equipment can be trailer mounted, containerized, and or skid-mounted, and all designed for rapid deployment and installation.

  1. Booster Pumps
  2. Multimedia Filtration (MMF)
  3. Cartridge Filtration (CF)
  4. Microfiltration or Ultrafiltration (MF/UF)
  5. Single Pass Reverse Osmosis (RO)
  6. Double Pass Reverse Osmosis (RO)
  7. Electro-Deionization (EDI)
  8. Deionization Pods (DI)
  9. DI Trailers

A range of sizes and configurations are available with some common sizes listed below.  Normally, Power Generators have systems from 100 to 500 gpm and most of the equipment on the market is in this capacity.

You never want to be in a situation where you can’t get the right amount of pressure and flow to a mobile system.

Starting with Booster Pumps, providers often have them sized according to their mobile equipment.  Pump skids will provide the correct pressure and flow to feed most trailer-mounted systems if the plant pressure and flow requirements are outside of recommended operating ranges.  This helps avoid having to add additional equipment such as Pressure Regulation Valves (PRVs) and ensures proper feed pressure which accounts for the natural pressure drop that takes place as the CF system fouls.

Larger MMF, MF, and UF systems are commonly available from 500 – 700 gpm with MMF typically coming skid-mounted while MF and UF are Trailer Mounted.  Smaller systems may be mounted inside of a combination MMF or MF or UF plus RO Trailer but tend to come with operational challenges when they enter backwash, therefore, shutting the RO down on low feed water pressure.

Reverse Osmosis Trailers typically range from 100 – 500 gpm which includes single pass and double configuration options.  Redundancy, ease of operations, and maintenance should also play a part in the selection process of a temporary WTP.  For example, if the provider must change a pump inside a container how fast can it be executed or how easy is it to change RO Membranes.  A high-capacity system isn’t always the best as it can be very difficult to operate or provide routine maintenance in the field as the need arises.

Most RO rental systems will consist of the following:  common inlet/outlet connection box, cartridge filter skid, chemical feed systems, booster pumps, and required instrumentation.  Additional features that improve reliability and operations include High-Capacity Cartridge Filters, Submersible Pumps, VFDs, Auto-Reject Control, Pressure, Flow Transmitters, Sample Points, Remote Ops and Communications, and Permeate Flush Capability.

DI Pods and Trailers are straightforward, and this equipment can handle a wide spectrum of feed waters. They also allow for a broad variety of configurations ranging from a few pods to trailer-mounted systems with multiple Pods.

These systems tend to include minimal online instrumentation such as flow and conductivity. The plant should be certain that an appropriate silica analyzer with alarm or shutdown capability is tied into the outlet stream to ensure the Demin Storage Tank doesn’t get contaminated.  If using conductivity to swap out Pods or Trailers, the tank may be contaminated as silica breakthrough most often occurs far before sodium breakthrough.

When using raw water as makeup for a DI system, resin exhaustion, and hence breakthrough can take place within hours especially if the system is not monitored closely.  In most cases, it makes sense to pair a DI system with a RO system upstream even when the installation can require additional power and plumbing.  This is especially true with supply chain challenges.

Piping, hoses, secondary containment, generators, storage tanks, and other items are typically furnished by the customer but can also be provided by the water treatment rental company for the most part.

Operating Requirements

Inlet water pressure, available power sources, permeate discharge, reject discharge, and footprint are additional factors that the supplier will need to know ahead of time to size equipment accordingly.  Care should be taken when connecting multiple pieces of equipment as it may be challenging to balance operating conditions.

Storage Tanks

Frac Tanks can be easily brought in as temporary storage and help balance operating swings.  20,000-gallon tanks are the most common and can be tied together for optimal storage needs.  They should be lined to minimize iron corrosion and a best practice is to steam clean them prior to placing in service.

Pressure

Inlet water pressure required typically runs 40 – 80 PSI for most rental equipment.  If the system doesn’t have adequate inlet pressure the equipment will frequently trip on low pressure, especially as any upstream filters foul.  Most pumps will need a minimum of 15 PSI to operate without cavitation.  If plant feed pressure is above 80 PSI a PRV is most likely required; a Cla-Val™ will work in most applications.

For RO systems, care must be taken for the permeate discharge pressure and should not exceed 20 PSI.  Exceptions can be made, but if operating above 20 PSI on the permeate some connections may not be designed to handle much above 30 PSI.  Remember that the permeate side of an RO Membrane is technically at atmospheric pressure, in other words, 0 PSIG, and pressure seen on the permeate line is a function of the backpressure coming from any downstream pipes and tanks.

The RO reject should be plumbed to a sump or open drain to reduce the operating back pressure on the unit.

Power

Rental Equipment in North America is sized for 480V/3ø/60HZ and it is critical to note the power requirements to ensure you have adequate supply whether the power is plant provided or from a temporary generator.  Very rarely is equipment rated Class 1 Div 2 rated so it will need to be placed in the appropriate area or have the area temporarily reclassified. Rarely will this be seen in standalone Power Plants except for cogeneration units located in the petrochemical industry.

Ancillary Equipment & Other Services

Proper pretreatment is vital to the success of water purification.  If your pretreatment equipment such as clarifiers, MMF, UF, etc is down or has frequent upsets, additional equipment should be included in the temporary WTP to provide complete treatment of the source water.  Most companies maintain a wide variety of ancillary equipment to support their rental fleet.

Support services may be provided if requested by the customer.  This might include engineering services, logistical support, Process Flow Diagrams (PFDs), P&IDs, O&M manuals, installation and startup support, operator training, or full-time operators.

Installation Location

The location of the temporary WTP should be easily accessible to all required utility connections, both power, and water. The location should also be able to support the weight of the equipment.  Placing equipment directly on any unstable ground is a recipe for disaster and should be carefully examined prior to placement.  At the sign of any rain, the equipment will sink. Hard pipe such as HDPE poly pipe will be stressed and could damage connected equipment.

We always recommend the first connection to any temporary equipment be a flexible hose to provide for any expansion or contraction that takes place.  Secondary containments may be required by the facility and an area of 12’ x 60’ should be required if this is the case.  If a suitable foundation cannot be located, cranes and special rigging can be used to place the equipment in an ideal location.

Electrical terminations and tie-ins will need to be performed by plant electricians or approved contractors.  Most rental companies will not have a certified electrician on staff, and this is usually handled by the plant.

Mobilization & Logistics

While most equipment is in a “green-tag” state and ready-to-go, some equipment may require additional prep and is not always ready for immediate shipment.  MMFs require media loading ahead of shipment, RO systems require membrane loading, and DI Trailers require DI Pod loading, which all take some time. Material loading may have to be done in the field, especially for MMF systems where the combined weight of media and equipment may exceed 40,000 lbs.  Loads above this weight will most likely require an oversized load permit.

Most companies use a combination of in-house logistics along with third-party logistics for the delivery of equipment.  On short notice, hot-shot freight can be arranged but tends to be more difficult at the end of the week as many company drivers are short on hours.  Nights, holidays, and weekends can prove to be challenging for equipment shipping and will most often create additional delays.

Contingency Planning and Installation

WTP rental companies provide rental equipment but don’t usually include installation.  While rental companies have qualified service technicians, they don’t typically have plumbers or electricians on staff for mobile water treatment equipment installs.  While not always possible, a site walk-down is tremendously helpful as a part of a contingency planning visit before the use of any temporary WTP. Some installations are as simple as a few pieces of 3” hose and others require several pieces of equipment and thousands of feet of pipe.

Such a visit will help predetermine the following:

  • What is the PFD of the temporary WTP?
  • Where shall the equipment be staged?
  • Where will the installation location be at the plant?
  • Where will the tie-ins be made?
  • Are proper flows and pressures going to be provided?
  • What type of hose or pipe will be used?
  • How much hose or pipe is required?
  • How much power is required and where will the tie-in be?
  • How long does the power cable need to be?
  • What is the correct electrical cable size based on the distance and Full Load Amps?
  • Where are the chemical feed systems going to be placed?
  • Who handles the chemical logistics?
  • What are the operating requirements?
  • Who is going to handle the routine operations?

We highly recommend using a local contractor to install your WTP as there are many qualified providers of these in-plant-services.  Process flow diagrams (PFDs) and P&IDs can be provided as part of the package and should aid greatly in the installation process.

Supplier Selection

Five things to consider when choosing a supplier of WTP:

  • Total Cost of the Project or Ownership
  • Response Time
  • Equipment Quality & Reliability
  • Supplier Capabilities
  • Flexibility

Rental companies’ estimates can have several charges that make up the total cost of the project.  Be sure to carefully read the estimate and or contract to understand all fees.  The critical WTP equipment makes up only a percentage of an estimate while other items such as labor, consumables, generators, installation cost, water processing fees, and other ancillary equipment add significant costs to the project.  Most companies offer two types of contracts, a de-bundled or flat rate.  De-bundled contracts are great to make sure you’re only paying for what is required for the job and flat-rate contracts are great to make sure costs don’t exceed a certain amount.  Ask for detailed and or firm estimates prior to contract execution.

Response times are one of the most important factors in selecting a WTP supplier.  If it takes three weeks to get an estimate, how long do you think it will take to deliver the equipment?  Work with a supplier who is responsive and understands the importance of operating a critical plant.

Equipment quality and reliability are also major factors that shouldn’t be overlooked.  Take time to pre-inspect the equipment at the supplier’s yard if convenient.  If not, you may opt for recent pictures, video calls, or ask the supplier to bring the equipment to your plant for a demonstration.  A plant demo is a great way to familiarize yourself with any equipment and field service support ahead of time and typically only involves minimal freight charges.  If the equipment looks good, it probably runs good.

Supplier capabilities are always important.  It is always a good idea to understand the rental company’s total capabilities to best treat the water.  In the event of additional issues, does the provider have the ability to solve additional problems?  Is the supplier familiar and comfortable with your type of plant?  Are they familiar with industrial safety procedures?  It’s that old saying that competence breeds confidence; it never hurts to have a confident supplier.

Finally, flexibility should not be overlooked.  A 20-page long MSA is great, but a great contract doesn’t always solve problems in the field. The people in the field matter and can make a big difference when dealing with additional issues or challenges.  Does the field service support have the ability to solve problems quickly without major internal red tape?  Is the supplier flexible when issues come up? How they solve those issues should play a major role in supplier selection.

Conclusion

Having a solid understanding of the market and your plant needs will go a long way to a smooth installation of a temporary WTP whether planned or unplanned.  This preparation time will allow you to be up and running within hours upon equipment arrival versus days in some cases.  When planning for WTP equipment an old military saying should keep you out of trouble; “Two is one and one is none.”  Download Basin Water Resource’s Contingency Plan Worksheet to prepare for your next temporary WTP whether scheduled or unscheduled.