LWW Standard Clean Water Systems in Areas with Hard Water

In selecting the best technology for a clean water system,
Living Waters for the World (LWW) uses water hardness (as CaCO3) and Total
Dissolved Solids (TDS) as its primary criteria.  If the water hardness is greater than 220 ppm and TDS is greater than 450 ppm, then a Reverse Osmosis and Softening (ROS) system is recommended.  The chart below from the Clean Water Handbook depicts the regions indicating which technology would best treat the
water.

Please note that the disinfection option for a Standard System with hard water as its source must be ozone.  UV equipment manufacturers do not recommend UV disinfection if the water hardness is greater than 120 ppm.

In some cases, the water analysis for a site indicates that ROS technology is needed, but the partners agree that they cannot justify a more expensive and complicated ROS system.  In these cases, partners may ask LWW what measures might be taken to mitigate the long term adverse effects of hard water on their clean water system.

So what measures might a LWW Team consider when installing a Standard Clean Water System where the source water has a hardness greater than 220 ppm? 

1.  Venturi – have a spare

Because the venturi is the most vulnerable component in the Standard Ozone System, LWW recommends having an extra venturi on site from start-up.

2.  Instrumentation – More pressure gauges and a water flow meter

Added instrumentation on the system is also recommended.  Having a
pressure gauge on each filter is suggested as well as having a water flow meter
installed before the venturi.

3.  Instrumentation – Air flow meter

A meter to measure the air flow through the ozonator is recommended.
This flow will be between 0 and 20 standard cubic feet per hour (SCFH).

4.  Protected/shaded raw water tank

The raw water tank should be shielded from overheating in the sun.

5.  Raw water feed from the tank – several inches above the bottom

The tank should be configured such that the water feed is not off the bottom of the tank.  There should be two take-off points on the tank, one several inches above the bottom for water feed and one at the bottom to remove accumulated sediments.

6.  5.0 micron Big Blue Filter without carbon

LWW recommends that the 5 micron Big Blue filter not be the carbon impregnated filter.  This filter will be the first to foul and will need to be replaced more frequently than 1x per year.  The outside or surface of the 5.0 micron filter should also be inspected for sediment buildup and cleaned as needed.  The 0.5 micron Big Blue filter should continue to be the carbon impregnated filter.

7.  Use more unions to increase component access

Because the system will have to be inspected for scale and cleaned out more often, the team recommends that all equipment and pipe runs in the churn be installed with unions to isolate it and make removal easier.

8.  Additional instruction and training

Extra instruction will be needed to emphasize the importance of data collection and recording.  Hardness in the raw water will have a negative impact on the performance of the system.  In order to identify these trends before it is too late, data will need to be recorded, trended, and analyzed.  Good communications between the partners will be important to ensure that data is not lost and that problems are identified and corrected in a timely manner.

Contributed by Ralph Young

The Weakest Link in the Standard Ozone System

Over the years and many hours of operation, LWW has found that the venturi injector is the weakest link in the Standard System with ozone disinfection.  The problem has been that when the system is down, water migrates from the venturi back through the tubing and contaminates the ozone lamp cartridges in the ozonator.  The root cause of the problem is a failure of the check valve inside the venturi and the plastic Kynar plastic check valve in the tubing connecting the venturi and ozonator.

The internal check in the venturi is shown in the picture below.  The failure mode is not certain, but the rubber disk probably gets stuck in the open position allowing water to flow back through the tubing.  Ths can be confirmed when water is observed leaking out the venturi air connection nipple.

Rubber disk check valve

In order for the failure to damage the ozonator lamp cartridge, the Kynar plastic check valve or the older gray PVC spring-loaded check valve must fail.  Several years ago, the PVC check valve was replaced with a more reliable low-pressure plastic check valve.

Kynar Plastic Check Valve on the left

LWW recommends that the air/ozone tubing be run to a point higher than the churn when connecting to the ozonator.  The plastic check valve should be at the highest point in the loop.

In the event your Operating Partner observes water leaking out the venturi and into the tubing, the following corrective action can be taken:

1.  Replace the venturi, if you have a spare.  LWW does not recommend taking the venturi apart to troubleshoot and replace the internal rubber disk check valve.

2.  If you do not have a spare venturi, you can modify the operating procedures to disconnect the air/ozone tubing at the venturi at the end of every batch.  Water can be drained from this leg of piping to relieve any internal pressure on the venturi.

3. LWW is investigating installing a valve in the tubing in order to isolate the venturi from the ozonator.  At the end of each batch, this valve should be closed.

If you have any suggestions or troubleshooting tips, please post them.

LWW Technology Blog Contributors

Here are some of the Lead Instructors for CWU-103 and potential contributors to the Technology Blog. From left to right they are: Wil Howie, Chris McRae, Jerry Goode, Ralph Young, Bubba Martin, Jerry Vaughan, and Randall Swan.

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Welcome to the Living Waters for the World Technology Blog. This blog is a forum for discussing ideas, issues, or opportunities related to the clean water systems LWW utilizes and how to ensure they produce the safest water possible for those who consume it. If you feel the information in this blog may be of value to others, please share it with them via a conversation, Facebook, Twitter or e-mail.