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Joe, sorry that this reply has been a while in coming. I haven't found anyone who has hands on experience of the Aquasentry filter but this review of the product information has been carried out by Chris, a water treatment specialist:

I reviewed the product information available on the internet and provide the following comments.

Rainwater is generally low in contaminants and most water quality risks can be managed through proper design, operation and maintenance of the rainwater harvesting and storage system (with the exception of heavy industrial and urban air pollution). There are lots of guides for rainwater systems covering design, first flush diverters, materials, maintenance, preventing contamination (such as animals getting into the storage tanks), etc. I don’t have a specific one for an emergency setting but the Australia government summarises it for the Australian context here… https://www.health.gov.au/internet/main/publishing.nsf/Content/ohp-enhealth-raintank-cnt.htm Mellisa also suggested this site… https://wedc-knowledge.lboro.ac.uk/search.html?q=rainwater&l=10&s=score&o=desc

For a typical household rainwater harvesting system, you are usually concerned with faecal contamination (health issue) from birds and animals droppings/carcases along with organic material (aesthetic issue) from leaves, etc. You are also at the mercy of rainfall variability to provide a reliable supply. As noted above, good design and regular cleaning can help to reduce contamination and ensure that you have sufficient storage to maintain a reliable supply.

In theory, an ultrafiltration membrane (as per the AquaSentry) can provide an effective additional barrier to most types of human infective pathogens in faecal matter. The exceptions are some viruses (which are very small) and can pass through UF membranes. Therefore keeping human and domestic animal faecal matter out of the rainwater system is an important barrier in a rainwater supply system even if an effective UF system is in use.

From review of the AquaSentry specification, the following may impact on its applicability to a remote or emergency setting generally: • It appears to be a relatively robust small UF system that is designed to last for years without replacement if operated and maintained correctly. • It is sensitive to feed water turbidity and may require upstream filtration (although probably unlikely for a clean roof top catchment). • It requires care with the hydraulic design to operate successfully (water stored 3-4 meters above the unit to provide the pressure to drive the water through the unit) • It requires regular manual cleaning – with frequency depending on the level of turbidity/organic material in the feed water. The specification suggests at least daily manual back wash (a few minutes), weekly chlorine clean and monthly citric acid clean. These procedures seem relatively simple if the chemicals are available. • The cleaning processes also use water so this should be taken into account in any assessment of water resource. • There are some rules for protecting the membranes… such as don’t let them dry out, keep them out of direct sunlight, etc. (refer the manufacturer’s manual) Also, if rainfall is only reliable enough to use for part of a year, then the membranes would need to be stored appropriately when the system is not being used so they don’t dry out. • A key risk with a field based membrane unit is that we cannot check the membrane integrity (in the same way as we do in Australia). It is therefore important to do regular testing for numbers of faecal coliforms in the filtrate water. If you lose your membrane integrity, then you get no pathogen reduction and it can be hard to assess this in the field from visual inspection of the unit. Adding a chlorination step after the membranes would provide an additional barrier and a chlorine residual to reduce the risk of recontamination. • I don’t have any experience with this unit so can’t comment on the actual maintenance in the field or robustness of the equipment (ie frequency of breakages, ease of repairs, availability of spare parts, cost of spare parts). Membranes can be expensive so I would want to understand the up front and replacement costs and frequency over the proposed product life (particularly as you will be locked into the one supplier).

That said, assuming the AquaSentry is installed, operated and maintained as per the manufacturers recommendations, it would likely provide an effective additional barrier for most pathogen contamination in a rainwater supply (noting the issue with some viruses above.)

So, is this a suitable product for a rainwater application? The question is really in two parts. 1. Is UF required for this rainwater application? 2. Assuming that UF is required, is AquaSentry an appropriate UF product for this application?

In considering the first question, it is worth noting that rainwater can be drunk in Australia without treatment to remove pathogens if the rainwater collection and storage system is designed, operated and maintained appropriately. Generally a risk based approach is recommended to determine if additional treatment is required. I know about this specific application but there are rainwater applications where UF is not required. Other treatment options (say chlorination and UV dosing) could also be considered depending on the risk profile of the source water.

In considering the second question, the product specification, design capacity (10,000L/d), maintenance requirements and case studies suggest that this product is targeted to a water treatment plant that supplies a (smallish) community, not a household rainwater application. A household rainwater supply is unlikely to collect anywhere near 10,000L/d. The hydraulic design with a tank elevated 3-4 m above the unit does not sound particularly practical for a household type rainwater system. Furthermore, the ongoing operation and maintenance does not lend itself to a household type application nor easy community roll out on a large scale in an emergency context. The AquaSentry appears more applicable to a community supply or say a community hospital or similar where it can be properly installed and operated.

Hopefully this is helpful. These are general points for a typical rainwater system without knowing the specifics of the question.

Best Wishes

Chris