International standards favor using a direct feed from the RO machine to the distribution loop within the Dialyses ward. From our experience as a vendor of water systems used for dialysis, the following advantages and disadvantages are considered. This document is not intended to fully describe the correct plant design and requirements for Direct or Indirect installations.
Direct Feed
Advantages
- Patient safety as there is less opportunity for bacteria to propagate and establish
- Less plant equipment affecting cost of ownership and capital expenditure
- Smaller footprint
- Reduced plant maintenance
Disadvantages. - Runs continuously even with minimal patient load. High water costs
- Water wastage
- Water intensive
- Plant equipment is Capital intensive to meet production volumes
- No buffer capacity in event of plant failure
- Dialyses service continuity affected by breakdowns
- Hi staff and recovery costs in the event of a breakdown
- High cost of redundancy measures to mitigate breakdown costs
- Higher consumable costs
- Higher plant wear
- Shorter plant life span
- Shorter RO membrane lifespan
- Higher electrical costs
- Higher cost of ownership
- Ecologically unfriendly
- Shorter distribution loop
Indirect Feed
Disadvantages
- There is a higher risk to Patient safety as there is more opportunity for bacteria to propagate and establish in the
plant requiring more intensive plant maintenance and possible service interruption - More plant equipment affecting cost of ownership and capital expenditure
- Larger footprint
- Higher plant maintenance
Advantages. - Runs only on demand and is unaffected by patient volume
- About 50% less water wastage
- Less Water intensive. Requires lower raw water feed
- Plant equipment is smaller due to reduced production volume requirements. The plant will replenish
during low patient loads. - Buffer capacity in the event of plant failure allows time for service intervention
- Dialyses service continuity unaffected by breakdowns
- Additional Staff and recovery costs are unlikely in the event of a breakdown
- Lower cost of redundancy measures to mitigate breakdown costs
- Reduced consumable costs ie Softener salt
- Lower plant wear as the plant only runs on demand
- Longer plant life span
- Longer RO membrane lifespan
- Lower electrical costs
- Lower cost of ownership
- Lower water costs
- Ecologically best practice
- Longer and variable elevation of the Distribution loop is possible
Whilst the direct feed model is suggested it is not ideal in our water-stressed environment. The indirect feed model requires a slightly larger footprint and more equipment however these costs are outweighed by the long-term cost savings and ecological best practice.
The possibility of bacterial propagation within the plant systems may be easily remedied by running the storage system continuously via ultraviolet sanitizer lamps. This practice will have a long-term effect in reducing bio-film development and bacterial colony manifestation further reducing capital expenditure.
Marlin Labs has developed an injection system for feeding Ozone gas through the Distribution loop during disinfection services. This practice will break down biofilm and help to reduce bacterial load within the plant.
It is the recommendation of Marlin Labs that In-Direct feed RO systems are preferable for the numerous reasons aforementioned. Patient risk is properly managed by the correct installation and design of plant equipment with frequent system monitoring and testing.
