This Power Point presentation explains: 1. the forms of chlorine found in municipal water supplies; 2. how to monitor them; 3. and, methods of treating them in hemodialysis water treatment systems. 1
Water as supplied from municipal water companies can contain chlorine as a gas, liquid (dissolved), and solid (suspended). When chlorine issues arise, it is critical to identify the form(s) (type) of chlorine present in order to treat the problem. Hemodialysis water treatment systems must be designed to be able to remove every form of chlorine present in the influent water. 2
Chlorine in Municipal water supply. Free chlorine exists as gas in water. Combined chlorine (mono-chloramine from city and naturally-occurring multichloramines and other chlorine compounds) exist as dissolved solids in the water. Chlorinated solids (organics) exist as suspended solids 3
Free chlorine Reacts with carbon on contact 4
Combined chlorine These are dissolved chlorine compounds. There are two broad categories of dissolved chlorine. mono-chloramines. multi-chloramines (and other chlorine compounds) 5
Combined chlorine Mono-chloramines The city makes mono-chloramine by adding ammonia to free chlorine. This is to reduce the amount of THM (Trihalomethane) in the water that is classified as carcinogenic. Mono-chloramines are removed by adsorption to the carbon in the carbon filters. This is a time-determinant process. That is why AAMI recommends a minimum empty bed contact time (EBCT) of 10 minutes to ensure that the process of removing the mono-chloramines is complete. 6
Combined chlorine Multi-chloramines Other chlorine compounds such as multichloramines can occur naturally in the water distribution system by the reaction of free chlorine and other compounds. These compounds are not readily adsorbed by the carbon filters. Fresh granulated activated carbon (GAC) can remove these compounds but usually for a very short period of time (very limited capacity). 7
Chlorinated solids (organics) These are solids that react with free chlorine. They are not actually dissolved in the water but transported by the water. These typically are colloidal in form. 8
Chlorine Monitoring When chlorine is detected after the carbon filters, chlorine monitoring equipment can be used to identify the type of chlorine that has been detected. 9
Chlorine Monitoring Equipment 1. DPD Kit with color wheel 2. DPD with Pocket colorimeter 3. Test strips 10
Chlorine Monitoring Equipment DPD Pocket Colorimeter DPD Color Wheel Test Strips 11
Monitoring Equipment Chlorine Type DPD Color wheel DPD Pocket colorimeter Test Strips (RPC type) Free Reacts Reacts Reacts Combined Reacts Reacts Reacts Chlorinated solids Reacts Reacts No reaction 12
Troubleshooting Chlorine 1. Use DPD method and record combined and free chlorine. 2. Use RPC test strip to detect total chlorine. 13
If test strip shows negative chlorine, the detected chlorine is in the form of suspended solids (false positives). Around 90% of these solids can be filtered out with an in-line chlorine sample port filter kit using 0.1um filter pads. 14
If test strip shows positive, the chlorine is either free or dissolved in the water. The DPD-based equipment will define whether the chlorine is free or dissolved. 15
Defining the type of chlorine will determine the corrective action required. 16
If chlorine is detected after both the worker and polisher carbon filters, test the RO product water for chlorine. 17
1. If chlorine is detected, shut down the water treatment system immediately and advise medical director as patients are at risk. The problem is free chlorine. The RO membranes will only remove 40% to 60% of free chlorine from the water. 18
2. If no chlorine is detected, the product water needs to be periodically tested (every 30 minutes?) to ensure that no chlorine is detected. The detected chlorine is dissolved and/or suspended. Either way, the RO membranes will filter out the chlorine compounds. The risk is that there could be a leak in the membranes which would pass untreated water. For this reason, it is critical to periodically test the product water. 19
Again identifying the form of chlorine will define the required treatment. 20
Free Chlorine Issue -- Four Possible Paths for chlorine to pass through carbon filter 1. Through the valve (seals) 2. Between the head and riser 3. Between the distributor & riser 4. Through the by-pass valve 21
Carbon Filter Service Mode 22
Carbon Filter Break Thorough Due To Distributor Problem 23
Solutions for Detected Free Chlorine Verify all possible flow paths. Common causes are: Head seals that are out-of-place, damaged, or improperly placed. Distributors what have become disconnected from the riser tube Scratches on the riser tube under the o-ring. 24
Dissolved Chlorine issue This is true chlorine breakthrough and is one of the most difficult chlorine issues to solve. Since these usually are naturally-occurring chlorine compounds, they cannot be controlled. They may come and go depending on natural phenomena. 25
Solutions for Dissolved Chlorine issue The best solution is to use an oxygen scavenger to remove the dissolved chlorine. The most common method is to use sodium bisulfite injection. This definitively resolves the problem. 26
Chlorine in Suspended Solids Two common sources of suspended solids are organics in municipal-treated surface water and municipal periodic flushing of distribution lines using 100% free-chlorine. 27
Organics in the treated surface water These organics, usually in colloidal form, can vary from somewhat constant to extreme levels due to weather conditions and other natural occurrences. Frequently, these organics are also accompanied with natural-occurring multi-chloramines. 28
Solutions for Organics in the treated surface water There are two common methods of controlling organics in the influent water: organic scavengers and sodium bisulfite injection 29
Solutions for Organics in the treated surface water organics scavengers Organic scavengers use a specially prepared anion resin media. The organics are adsorbed onto the media. The media is placed into a bed filter in the typical softener configuration. The only differences between an organic scavenger and a softener is the media and the backwash flow is less for the organic scavenger. Both are regenerated by salt. The organic scavenger must be placed after the softener to prevent cationic fouling. 30
Solutions for Organics in the treated surface water sodium bisulfite If there is a high degree of variability in the organic content and/or composition, sodium bisulfite injection will most likely be the preferred solution. 31
100% Free Chlorine from City Periodically municipal water systems will convert from a mixture of free chlorine and mono-chloramine to 100% free chlorine. The reason is to purge the water distribution system of nitrication bacteria that thrive on the mono-chloramine that is added at the water treatment plant. 32
100% Free Chlorine from City Typically this is for a two week period. The first few days of this shock treatment results in a significant bloom of dead bacteria in the water line. Because of the usually high dosage of the free chlorine in the water, this organic material is highly chlorinated. 33
100% Free Chlorine from City Hemodialysis facilities that are not prepared for this change in city water will typically go into panic mode as they get positive chlorine readings past both the worker and polisher carbon filters in very short period of time. 34
Chlorine False Positives Chlorine false positives are caused by chlorinated solids that are transported by the water. The chlorine is not dissolved in the water. 35
Service Mode Flow Path 36
Backwash Mode Flow Path 37
Forward Rinse Mode Flow Path 38
Service Mode Flow Path 39
Solutions to false positive chlorine issues Go to Nelson Water Systems for Hemodialysis website www.nws.bz and refer to the Procedures For False Positive Reading file in the technical papers section. 40
Changes in Protocols during municipal distribution system flushing 1. Be proactive when advised by the city of the disinfection reformulation. Put two PE carbon tanks in parallel (or other sediment filtration devices) before the carbon filters. The PE carbon tanks can help if there is any temporary dissolved chlorine in the water; however, their principal use is to filter out the chlorinated dead bacteria body parts. 2. Use test strips for chlorine monitoring 3. Test RO permeate water for chlorine. 41
Changes in Protocols during municipal distribution system flushing 4. Do not backwash carbon filters during this event. Carbon filter Backwash flow rates (25 to 30 gpm) will overwhelm the capacity of the PE tanks (15 gpm) thus making them ineffective for capturing all of the dead bacteria body parts. 42
Sample Of Portable Carbon Filter Connection 43
Sample Of Portable Carbon Filter Connection 44
Changes in Protocols during municipal distribution system flushing Protect your bottom!!! 1. Put PE carbon tanks before carbon filters 2. Set carbon filter heads to not backwash during this period 45
In Summary Chlorine in influent water: free (gas), dissolved (mono-chloramine, multichloramine liquids), and suspended solids Monitoring equipment: DPD color wheel, DPD pocket colorimeter, test strips RO Product Water monitoring during chlorine event Solutions for chlorine issues: fix mechanical failures, sodium bisulfite injection, organic scavengers, temporary change of water treatment protocols. For technical support: Nelson Water Systems for Hemodialysis, technical department 46