I have been recommended an Aquasentry water filter for use on a rain water harvesting system. It is manufactured by Aqua Solutions in Australia. Does anyone have experience of these filters and are they fit for purpose?

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/mai... Mellisa also suggested this site… https://wedc-knowledge.lboro.ac.uk/se...

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 ... (more)