IMPORTANCE OF THE WATER TREATMENT (REVERSE OSMOSIS) PLANT IN DIALYSIS SET UP

Importance of the Water Treatment (Reverse Osmosis) plant in dialysis set up

Watch: PRE-TREATMENT ELEMENTS
Watch: RO TREATMENT & POST-TREATMENT ELEMENTS
Watch: WATER CONTAMINANTS & POTENTIAL CLINICAL SYMPTOMS
Introduction:

An average person drinks 14L of water per week. Water arriving at faucets is acceptable for drinking but not acceptable for HD. It contains various contaminants such as chlorides, chloramines, fluorides, etc. Healthy kidneys are capable of extracting and excreating those contaminants. However, the same water may not be suitable for dialysis purposes since more than 90% of dialysate used in the machine is water. A dialysis patient will be exposed to 300L of water per week. Hence, if the water used for dialysis is not ultrapure it leads to potential clinical symptoms and complications.

Possible water contaminants Symptom

Watch here: Water contaminants & potential clinical symptoms

Water contaminants are a result of the source of the water. Main sources of water are

a) Surface water

b) Ground Water

Surface water will have a higher number of organic material, industrial waste, waste from flora & fauna, fertilizers, pesticides, etc.

Groundwater will be higher in Inorganic material & minerals.

If water for dialysis is not treated appropriately all these contaminants are going to get exposed to the patient's bloodstream causing severe complications. Hence, it needs to be made ultrapure before exposing it to the patient.

AAMI is an institute to lay standards for monitoring the purity of the water used for the dialysis center. Once a water treatment system is installed and shown to be operating properly, the staff of the dialysis facility must ensure that performance is maintained. The medical director of a facility has the ultimate responsibility for ensuring that the patients are treated with water that, at a minimum, meets the contaminant standards set forth by Association for the Advancement of Medical Instrumentation (AAMI) or any other applicable standards organization.

AAMI chemical standards for dialysis water

AAMI standards for dialysis water

To maintain these standards water needs to be treated by using an appropriate water treatment system that can remove all types of suspended, organic, inorganic material, electrolytes &  all other water contaminants from water.

Components of Water treatment system: The design of any water treatment system is dependent on
1) The quality of feedwater
2) Local requirements of the purity standards 

To be safe for the general public, drinking water is treated to help prevent disease.

1) First, an aluminum compound called alum may be used as a flocculent to remove solid particles from the water and make them settle in the bottom.
2) Then, the clearer water on top is passed through filters to clean it.
3) Chlorine is added to kill microbes. Since chlorine gas evaporates, a more stable compound called chloramines (chlorine plus ammonia) may be used instead.
4) Fluoride is used in many places to prevent tooth decay.
5) Some cities change the water pH(acid/base indicator)
Parts of a water treatment system:

Components of water treatment plant are divided into 3

1) Pre-treatment
2)Treatment
3) Post-treatment
Pre-Treatment components

Watch the clip on Pre treatment elements of the R O system

A) Backflow preventing device: 

The purpose of this is to prevent water flow from the water treatment equipment being pulled back through the main supply piping. The backflow prevention device also prevents the backflow of chemicals into the inflow water during the process of chemical disinfection of the water treatment system thus eliminating the risk of chemical exposure to the main water source

B) Temperature Blending Valve:

The feeding water treatment system operates at 77-80oF i.e 25 to 26 Celcius. This range allows for the optimal performance of the reverse osmosis membrane. If the water is too cold, the volume of RO water produced will decrease. If the water is too hot, you can harm the RO membrane, and if is too high, the dialysis machines would be in a high-temperature alarm state. RO product water decreases by 1.5% or by 3% per degree centigrade. The Temperature blending valve is a device that can be set to mix hot and cold water to achieve a specific water temperature.

What to Monitor? The performance of this device should be monitored daily by monitoring the temperature. A defective blending valve will not necessarily endanger your patient’s life as a Dialysis Machine has a bypass mechanism for overheated dialysate. 

C) Booster Pump:

Water filtration is a pressure-driven process. The booster pump is used to compensate for the pressure loss in the backflow prevention device and blending valve by providing a constant supply of water flow and pressure required by RO. The pump is followed by a pressure gauge and a flow switch to ensure the working of it within set points. What to monitor: water pressure 

What to look for: pump turning on and off at the appropriate pressure.

Pre-treatment components:

1) Chemical Feed system:

Feedwater should have a pH in the 5.0-8.5 range before further treatment. If the water has a higher pH(more basic) then acids (e.g., hydrochloric acid or sulfuric acid) may be added to bring the pH down into the acceptable range. The chemical addition component must have a reservoir to hold the chemical, a metering pump to deliver the correct amount of chemical, and a mixing chamber to distribute the added chemical effectively into the feedwater line. To assure that the acid is fed at an appropriate rate pH must be monitored from the acid feed pump. This monitoring should be done with a pH meter or pH strip. The expected range of pH should be between 7-8.

2) Multimedia depth filter/ Sand filter: 

Large particles of size > 10 microns are removed by a multimedia depth filter. It contains multiple layers of various sized rocks that trap the large particles as the water filtered downward. Multimedia depth filter provides rapid and efficient removal of relatively large suspended or floating particles. This is very important, as particulate matter can plug up the carbon and water softener and prevent them from working properly. Its function is monitored by measuring the pre and post filter pressure > 10PSI.

3) Carbon Tanks: 

Carbon tanks remove chlorine & chloramines from the water which is normally added by the Municipal Corporation/ city council. This is the most important component in the water system. Chlorine and chloramine can readily pass through an RO membrane so it is necessary to remove it before it reaches the membrane. In the long run, it damages the membrane also it causes hemolysis in case it comes in contact with the patient's bloodstream.

Carbon filtration work on the principle of adsorption. The carbon filter is filled with activated carbon media. The size of the filter depends on the amount of chlorine and chloramines contained in the raw water. In areas with high chlorine/chloramines (eg.Sydney after the drinking water incident in 1998), it is recommended to use two carbon filters in series. The second filter is used as a backup only in case chlorine breaks through the first stage. To ensure the complete removal of chlorine/ chloramines, it is recommended to size the carbon filter to ensure a minimum contact time of 10 minutes (Each of the tanks will have an EBCT of 5 minutes). During the contact time, chlorine/chloramines are absorbed by the activated carbon. The media should be replaced on an annual base or as required.

What to monitor?

Chlorine and chloramines level after the water tank before each patient shift (Maintain chlorine level < 0.5 ppm) The working of a carbon filter is monitored by measuring the pre and post filter pressure > 10PSI. Backwash timer is set to activate when the facility is not working

5) Water softener & Brine tank:

Water softeners are used primarily to remove calcium & magnesium from the water which is responsible for making water hard. These ions will deposit on the surface of the softener bed causing scaling & disabling its capacity further to remove these ions. Most but not all, dialysis water systems have softeners to extend the life of the RO membrane. Water softeners need to be regenerated to enable its smooth working which is possible by passing sodium chloride (NaCl) through a softener bed. Hence a softener will be accompanied by a brine tank to hold sodium chloride. The frequency of regeneration depends upon the hardness of the water. The softener works on an Ion-exchange basis. Deposited calcium & magnesium gets exchanged with sodium from the brine tank releasing calcium chloride and magnesium chloride to drain.

Ca++ and Mg++) + NaCl--------Cacl2 + Mgcl2. It is good to have a regeneration timer to work when the unit is not in operation.

What to monitor?

Post softener hardness, amount of salt in the brine tank, pressure drop, timer settings.

What to look for? Brine tank

Hardness exceeding 1 Grain per Gallon (GPG) or 17.2 parts per million (PPM).

6) Prefilters:

Prefilters are particulate filters positioned immediately before the RO pump and membrane. It acts as a final barrier against particles or debris that can damage the RO pump & membrane. The primary function of pre-filter is to trap carbon particles released by a carbon tank. Prefiltersrange in pore size from 3-5 microns.

Watch : RO treatment & post treatment elements

7) Reverse Osmosis Membranes: RO membrane is one of the most important components in the water treatment system. RO overcomes natural osmosis by forcing feed water under pressure thru a semi-permeable membrane leaving contaminants behind. Osmosis is the process wherein fluid gets shifted from low concentration to the high and it is a natural process but during reverse osmosis process, water/fluid shifts from the high concentration to the low concentration due to a pressure applied. RO membrane is an important part of the RO system. It filters out every tiny particle right from Metals to bacterias, endotoxins & viruses. The most commonly used membranes are thin-film composite made of polyamide. These membranes are spirally wound around a collecting tube with fine pores to collect ultrapure water. RO water rejects 99% of charged ionic particles also organic and inorganic substances.

Scale can build up and clog the membrane hence routine cleaning is recommended as per the manufacturer's instructions to remove scale build-up.

Monitoring: Feed water temperature, pre & post membrane pressure drop should be monitored on a daily basis. 

8) Deionization:

Deionization removes anions & cations from water but it does not remove non-charged particles like microbes. Most often it is used as a back up for broken R O plant. It does not provide protection from bacterial contamination hence can be dangerous if exhausted. It can be used as a main purification system or can be used after the RO system to further purify or polish the product water. It can be used as a back system in case of RO of distribution system malfunction but need to have an appropriate chlorine tank followed by pyrogen filters as it can’t take care of bacteria instead it could become a main source of bacterias. It needs regeneration. For regeneration of cations, hydrochloric acid and for anions sodium hydroxide can be used. 

Monitoring:

—Chemical & Microbiological Analysis.

—Change in pressure > 10PSI

—Resistivity 1MEGAOHM

9) Distribution System:

Stages of distribution system: RO distribution loop can be direct or indirect depending upon whether water from the dialysis room is circulated back to the storage tank.

There are four stages of a distribution system.

A.Storage tanks

B.UV irradiator

C.Submicron and ultrafiltration

D.Piping system

A) Storage tank:

According to AAMI and FDA, storage tanks should be made of inert materials that do not contaminate the purified water. The bottom should be conically shaped for complete emptying. The size of the tank should be in proportion to meet the facilities' peak demands, no larger. Unused portions of the product water are re-circulated back into the storage tank. The RO unit will stop and start filling the tank by receiving signals from the high and low-level switches on the storage tank. 

B) Ultraviolet light:

Ultraviolet light is used to kill bacterias from the water. It is an effective way of killing bacterias but it has to be maintained properly because improperly maintained UV lights can become a source of endotoxins hence it is necessary to have ultrafilters/ submicron filters in place downstream of them to catch dead bacteria and prevent endotoxins from getting into the bloodstream.

Maintainance & monitoring :

Regular maintenance of the UV device includes:

— Continuous monitoring of radiant energy output (30 milliwatts sec/cm2).
— An audible and visual alarm.
— Replacing the lamp at least annually.

— routine cleaning of the quartz sleeve.

There are 2 problems with UV

—It is possible for some species of bacteria to become resistant to UV irradiation.

—UV does not destroy endotoxin, and it may even increase the level as a result of the destruction of the bacteria cell wall where endotoxin harbor.

—Therefore, other filtrations are required after this stage.

C) Submicron & Ultrafiltrators:

Both of these are membrane filters. A submicron filter can reduce levels of bacterias and ultrafilters can remove both bacterias and endotoxins. Submicron and ultrafilters, even though they remove microbes, are targets for bacterial infestation. Therefore, it is required to routinely be disinfected or replaced. The pressure differentials should be monitored continuously and documented at least daily

Monitoring:

Submicron and ultrafilters, even though they remove microbes, are targets for bacterial infestation. Therefore, it is required to routinely be disinfected or replaced.

The pressure differentials should be monitored continuously and documented at least daily. 

D) Piping System: An expensive water treatment system can be ruined by a bad piping system hence it should not be allotted to any household plumber.

Problems with the distribution loop:

* An expensive water treatment system can be ruined by a bad piping system

* Piping must not leach. It is recommended to use lead-free PVC, UPVC, CPVC OR Pex pipes.

* The dimension of a pipe used should enable an appropriate flow rate which increases water pressure causing no growth in the piping system.

* There should be no dead spaces & corners to avoid bacterial growth.

IMPORTANCE OF THE WATER TREATMENT PLANT(REVERSE OSMOSIS) PLANT IN DIALYSIS SET UP