Managing turbidity to prevent infection


It is universally accepted that turbidity is a good indicator of overall water treatment plant performance. This is further evident in the Australian Drinking Water Guidelines: Draft Framework on Microbial Health Based Targets (HBT), where default recommended LRVs (Log Reduction Values) for Bacteria, Virus and Cryptosporidium are attributed to water treatment processes based on the plant’s performance, in terms of turbidity. Maintaining overall plant performance in terms of turbidity will be of increasing importance to ensure that the minimal acceptable risk of microbial infection – one μDALY, which is approximately equal to 1 case per year of mild diarrhoea (lasting 3 days) for every 1000 people, isn’t exceeded.

For example, a conventional water treatment plant will have 3.5 LRV for Cryptosporidium, provided the individual filter turbidity is less than 0.2 NTU for 95% of the month, and not greater than 0.5 NTU for more than 15 consecutive minutes. Operating a water treatment plant consistently below 0.2 NTU may be difficult during times of flooding rains, process upsets or component failure.

How do you ensure the consistent performance of a water treatment plant during challenging times? Reducing the flow rate, optimising coagulant dosing, investing in additional disinfection (e.g. UV) or additional filtration are some of the options available. However, the ideal solution will be one that offers turbidity reduction, additional disinfection (i.e. LRV for Cryptosporidium), small foot print, high efficiency (recovery), longevity, and a low operating cost.

Amiad is proud to offer the Automatic Microfiber (AMF) filter that has been certified by NSF for 2.15-log Cryptosporidium reduction, when fitted with a 2-micron cartridge. This certification validates what we’ve known for the last 20-years (on more than 70 municipal installations), that the AMF microfiber filter is the most compact, efficient and cost effective self-cleaning cartridge filter for Cryptosporidium reduction.

Following the Great Alpine Bushfires of 2006-07, East Gippsland Water experienced a significant change in their catchment and one of their water treatment plants were finding it difficult to deal with the increased turbidity and Total Suspended Solids (TSS). Amiad was commissioned to supply 2 x AMF-370K (7-micron) in response to this emergency that was threatening the quality of the drinking water supplied to a portion of their customers.

The filters were first installed at Wy Yung (Bairnsdale, VIC) where they achieved reduction in Turbidity, Iron, Manganese, DOC, TOC and Coliforms.

Parameter Amiad Filter Inlet Amiad Filter Outlet
Turbidity, NTU 1.0 0.7
Iron, as Fe 0.11 <0.02
Manganese,  as Mn 0.007 0.001
Dissolved Organic Carbon (DOC) 3 2
Total Organic Carbon (TOC) 3 2
Coliforms 75 54


The filters were later moved to the current site at Orbost, demonstrating how compact (37m² of filtration area in on 10m² foot print) and flexible the microfiber filters are to fit into various treatments plant at various stages of the treatment process. Amiad has been servicing these filters for the last 10 years, which has given us a valuable insight into the exceptional low life cycle cost of the AMF filter.

Please contact Amiad at or 1300 426 423.





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