40 GPM Reverse Osmosis System Design

Current System Layout:

The customer current system layout was a duplex softener followed by a Portable DI Exchange Tank. With the current demand for purified water this design was not the best nor most cost-effective option. The increased demand would result in additional salt usage along with significant DI Exchange tank costs.

Design: What Will The RO Water Quality Be?

Prior to design and layout Complete Water Solutions was able to secure a water sample. This sample was sent to a 3rd party lab which helped identify the incoming water quality. Some of the items we tested for were

  • Alkalinity “P” as CaC03
  • Alkalinity “M” as CaCO3
  • Fluoride
  • Nitrate NO3
  • TOC
  • NTU
  • Potassium
  • Sodium Na
  • Chloride CL
  • Phosphate Ortho
  • Conductivity @ 25c
  • Aluminum AL
  • Barium
  • Hardness Total CaCO3
  • Copper Total
  • Iron Total
  • Sulfur Total
  • Silica Total

Based off of the water analysis received we were able to perform a projection analysis. The projection analysis will help us provide a permeate water quality estimate. (Good RO Water). This analysis also helped in identifying the best design, membranes and options available for the application.

This particular analysis spotted iron as a significant factor in potential fouling and that reducing it would be beneficial to the RO membrane performance along with recovery. The higher the recovery the less wastewater the RO will produce. Increasing the recovery too much can result in fouling. It’s a good practice to consult with your water treatment equipment provider to discuss ways to reduce waste water.

This water source is chlorinated, and if not treated can cause irreversible damage. A carbon filter was selected as the main solution to remove the chlorine prior to the RO System.

Another benefit of having the water analyzed is to help in selecting the best antiscalant. Antiscalant is used to control scale forming on the surface of the RO membrane. If left untreated it can foul the membranes or cause irreversible damage. Not all antiscalants are the same, some products will work better for certain contaminants.  Getting your water tested can help minimize water quality and equipment problems.

 

Scope:

Based on current and future demands, we were able to determine that a 35-40 Gallons Per Minute Reverse Osmosis System would be the most beneficial. The new water system design eliminated the need for a water softener and portable DI Exchange Tanks.

The machine used in this project was a LT8-9. This was the new design by Suez that replaced the E8-57K Machine. This machine was selected for a few reasons:

  • The first reason for selecting the LT8-9 was the options. The customer future plans required the ability to produce more RO water. The LT8-9 allowed us to install a larger pump and motor on the unit, thus eliminating the future cost of adding a larger pump and motor. It was already taken care of in this original purchase. The only thing to do in the future will be the addition of RO housings and membranes (with a little pvc piping). This will save costs and longer down times during the upgrade.
  • The 2nd reason was the ability to select cold water membranes. (Learn More About Different Membranes- Click Here). Most membranes are rated at 77 Degrees F for output production. Cold water membranes will allow you to operate at 55 Degree F and provide the same output. This reduces costs of pre-heating the water prior to the RO System.
  • The 3rd reason is the pump and motor. Tonkaflo pumps have been around along time and are very robust. Learn More About Tonkaflo Pumps

 

The RO System was able to be up and operational in (2) two 12 hour days of installation. This included the soaking time required for the carbon filter media. The system specifications:

  • System Inlet Filtration: Bag filtration installed prior to the carbon filter to help trap particulate greater than 1 micron. The bag filter housing was stainless steel with a high efficiency 1 micron bag filter.
  • Carbon Filter: The carbon filter selected was a Fleck 3150 valve with the new NXT2 Digital Controller. The carbon filter is equipped with a regeneration lock out switch to turn of the RO system during backwash. This will save the membranes from experiencing contact with chlorinated water.
  • Antiscalant: The antiscalant selected is a NSF 61 drinking water approved product. The product was selected based on the ability to run the RO at a higher recovery rate which will reduce the wastewater. The antiscalant chemical pump selected was a Grundfos DDA pump which has a 3000:1 turn down ration. This allows for neat feeding of the chemical product. No diluting or mixing.
  • RO System: The RO System is a Suez Model LT8-9. The unit is a 8” Membrane unit with 9 membrane elements. The system was equipped with a Horner PLC and HMI. Additional features included: Permeate Conductivity Probe, Water Temp Sensor, Inlet Pressure Safety Switch, Flow Meters, Inter-stage Pressure Gauges.

 

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