Ponchatoula Residents
Procedures To Follow If You Have Brown Water
Effective 12:55 p.m. September 14, 2016
The City of Ponchatoula Boil Water Advisory has been lifted. All test results returned negative for contamination.
Louisiana Department of Health & Hospitals Report
DHH Test Results 9.14.2016Thornton, Musso & Bellemin, Inc.
P.O. Box 181
Zachary, LA 70791
Ph. (225) 654-4955
Fax (225) 654-9533
To: Chuck Spangler
Mayor Robert Zabbia
Cc: David Oppdenhoff
Ernie Drake
Re: City of Ponchatoula Potable Water Discoloration
On Monday, March 21rd, 2016 I received a request to investigate the cause of recent discolored water occurrences in the potable water of the City of Ponchatoula distribution system. On March 23rd TMB personnel responded to this request.
We obtained samples from each of the two active well heads, their corresponding points of entry into the system (POE), each of the designated total coliform sample sites (TCR) and the two monthly additional chlorine residual sites (ACR). These are all designated sites by DHH and can be found on the City Monitoring Plan.
The parameters that we measured and their significance are listed below.
1. Ph. This is a measure of the acidity of the water. 7.2 is considered neutral while measurements below this level indicated acidic conditions and those above it are designated as basic. This is a secondary standard. EPA guidelines are that potable water should be above 6.0 and below 9.0
2. Conductance. This is a measure of the indication of dissolved solids in water. Distilled or pure water would have a conductivity of zero and as solids were dissolved this measure would increase. The majority of ground water in this area has some level of solids.
3. Total Dissolved Solids. This is a companion measurement to Conductivity. Along with conductivity it is read with a probe. This measure has implications in industrial applications. In potable water it is used more as a fingerprint of a water source. When water is allowed to evaporate the solids are deposited. This is typically referred to as water spots.
4. Free Chlorine. Chlorine that is available for disinfection in water. DHH now requires a minimum of 0.50 parts per million of free chlorine at all points in the system. The maximum level for chlorine in water is four parts per million.
5. Total chlorine. This is a measure of the free chlorine and any chlorine that has reacted with ammonia to form chloramines.
6. Iron (Fe). Iron is a natural mineral that is found in some ground water. It is a secondary standard with a suggested limit of 0.30 parts per million. It is a secondary standard and presents no health risks according to EPA. When oxidized by chlorine it can give water a reddish appearance. Its’ main effects are esthetic.
7. Manganese. Like iron it is a naturally occurring element in some ground water. It is listed as a secondary standard with no health risks. It has a suggested limit of 0.05 parts per million. Both iron and manganese are found components of many vitamin supplements sold over the counter.
8. Phosphorous. Phosphorous is found in most drinking water obtained from ground sources. It does not have an EPA limit. Phosphorous has many beneficial characteristics and is often added to enhance corrosion control in distribution piping and to sequester iron and manganese.
9. Hardness. This is a measure of calcium and magnesium in water. Hard water is considered to be in the range of 50 parts per million and above. Below that water is considered to be soft. Very hard water can deposit scale on surfaces.
10. Alkalinity. Another fingerprint of a water source. When this characteristic is considered alongside Ph, conductivity and TDS a consistent pattern should emerge. Typically, these results will move up and down together.
11. ATP. This is a non- compliance test that we use. It is a measure of the total biological activity in sample of water. This test is a measure of adenosine tri phosphate in a sample. This molecule is the energy carrier for all cells. By extracting and measuring this molecule the amount of biological activity can be inferred. All water systems are measured monthly for total coliform activity by Louisiana DHH. While this gives an indication of coliform activity, it does not measure all activity. By using ATP we can see if there is a potential for other organisms that can cause problems such as corrosion. Any result under 1 pg/ml is considered excellent control. A level of 10 pg/ml and above is a range at which we would recommend remediation.
Attached you will find a table which lists all sites sampled and the results obtained.
Discussion of Findings
Biological Activity
Results of monthly coli form bacteria samples submitted to Louisiana DHH and analyzed at their lab were reviewed back to December of 2014. In this time period, and including the current month, there were no positive coli form results.
DHH now requires a minimum of 0.50 parts per million (ng/lt) residual be maintained at all sites in the system. We tested all entry points, TCR sites and ACR sites and found this residual was maintained at all locations. 0.69 was the lowest residual we found. This indicates the minimum required residual is being maintained plus an additional buffer. The maximum limit allowed by EPA is 4.0 ppm. Water treated to this level would have unpleasant chlorine taste and odor.
Additionally, TMB personnel performed an ATP analysis on each sample. This procedure detects all biological activity and would indicate the presence of organisms other than coliform. As described above, a finding of 10 pg/ml would lead to concern. Over all, the profile of the system was very good. We did not even get a reading of five pg/ml, which would lead us to further monitor a site. Additionally, this test would reveal the potential for microbial induced corrosion within the system. We found no indication of this.
Biologically, there were no indications of outside contamination.
Ph., TDS, Hardness and Alkalinity
All results of these parameters were normal for ground water found in this area. The water is alkaline. It is very soft. The Ph is on the higher end of recommended ranges. In checking these parameters at all locations it is possible to detect water from an unknown source that could be connected to the distribution system. A significant variation in any of these parameters could indicate a cross connection. The fact that all these parameters, along with chlorine residuals, were consistent would tend to rule out this possibility.
Iron and Manganese
Iron and manganese are naturally occurring elements that may be found in ground water. Both can be very common in our area and both are found in many wells. We tested two of the three wells that serve Ponchatoula. The third well is off line currently due to a rehabilitation project on the elevated tank attached to it. Once this well comes back on line and a flowing sample can be obtained, we will check it.
Results from the well designated as the Tower well indicated non detectable levels of both iron and manganese.
While the well designated as the Vets well or Hwy 51 well showed no detectable level of iron, we did obtain a result of 0.072 ppm of manganese. I cross checked this with the latest test results from DHH and this was confirmed. When left untreated, this level of manganese can cause brown to black discoloration in water. Generally this color develops when the manganese is oxidized. This occurs when chlorine is added for disinfection. In the past two years, DHH has increased the required minimum residuals from a trace of measurable total chlorine to 0.50 ppm minimum. This has increased the potential for this problem. In testing the point of entry of this well into the system we found no measurable manganese. In all probability, the manganese is oxidizing and precipitating out of the water in the elevated tank. There is probably a buildup of manganese along the walls of the tank. Periodically, this water is disturbed and the manganese is carried out into the system causing discoloration. At some point, if we can obtain a sample of discolored water, we can confirm this. As previously discussed, higher required chlorine residuals have aggravated this problem. This water is also low in natural phosphate which acts as a sequestering agent that helps to inhibit oxidation of metals.
Recommendations
Moving forward I would recommend the following actions.
1. Adding a sequestering agent to the water produced at the Hwy 51 well. This will supplement the natural ammonia and help keep the manganese in solution. This is a common practice in the United States. I suggest using TMB-460. This is a polyphosphate based product. It is NSF approved for drinking water at a dosage rate of up to 25 parts per million. Typically it is fed at a rate of under 10 parts per million. There will be no noticeable change to the water.
2. Ponchatoula should enhance its’ current flushing program. A uni-directional should be designed. Additional flushing will help to keep a buildup of oxidized metals minimized in the distribution system.
3. Corrosion test racks be installed at each well and at a site central to the system. Analysis of steel coupons in these racks will give an indication of any long term corrosion potential to the metal components of the distribution system. Coupons will be analyzed at 30 and 60 day intervals. If a need for further corrosion control is indicated, this will be indicated.
4. When the current tower project is completed, consideration should be given to taking the tower located at the new Wal Mart off line and cleaned. It is not possible to take both towers off line at the same time. This cleaning should help remove any accumulated manganese that has oxidized and precipitated out.
Periodic discoloration events are seldom totally eliminated from a distribution system. Their occurrence and the scope of their severity can be limited through the above actions. I am available to answer any questions or provide further testing.
Bill Travis
btravis@tmbwater.com
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