WAL S.A. Independent Laboratory Study on the Effectiveness of the WAL SafeWater UTC cartridge when challenged with bacteria and virus
Summary The WAL SafeWater UTC antimicrobial cartridge is a versatile gravity fed water treatment cartridge designed to be used in conjunction downstream of pre-filtration media such as high performance ceramic candles, low performance ceramics, or carbon blocks. In such configurations the UTC is able to provide a ≥ 99.9% reduction (or ≥ 3-log reduction value) of waterborne pathogenic bacteria and virus over a volume capacity of 1500 liters. Test Procedure UTC cartridges are assembled into gravity canister devices with an upper and lower reservoir. The upper reservoir contains the pre-filtration element followed by the UTC. A usual use pattern is to fill the top reservoir at night, which can carry from 5 – 10 liters of water, and allow the water to filter into the bottom reservoir overnight for use in the morning. In the lab devices are filled Monday – Friday with a microbial load in the influent water of 1x103 cfu/mL of bacteria (typically E. coli) and 1x103 cfu/mL of virus (typically MS2 or a combined Polio virus and Rota virus) suspended in a test water formulation with an increased TDS and halogen demand as TOC as described in table 1. Periodically the devices are tested for microbial reduction with a minimum frequency of 0%, 25%, 50%, and 100% capacity of 1500L. The upper reservoirs are filled with microorganism dosed test water and after the water has filtered into the bottom reservoir a 100mL sample is collected into a sterile cup containing sodium thiosulfate to inactivate any residual halogen. Each sample is analyzed for bacteria and virus reduction and expressed as percent reduction and log reduction value (LRV).
Table 1: Test Water and Microorganisms Used Test Water
6.5 – 8.5
TOC (humic acid)
0.1 – 1
19 – 21
TDS (sea salts)
500 – 600
190 - 210
Results The UTC with a carbon block pre-filter configuration achieved a ≥ 99.9% reduction of E. coli and MS2 when tested against a combined E. coli and MS2 challenge at 1x103 cfu/mL over a volume of 1500L (chart 1) representing a ≥ 3-log reduction value (LRV). With this configuration the average flow rate was 50 mL/min with a range of 17 – 98 mL/min and the average residual bromine in produced water was 0.29 ppm with a range of 0.17 – 0.47. In a different configuration, the UTC with a ceramic candle as the pre-filter was tested for 5 continuous months with E. coli, MS2, and a periodic Polio-Rota virus combination. Under these conditions, the UTC was able to achieve a ≥ 99.9% reduction of bacteria and virus (a ≥ 3 LRV) as seen in chart 2.
Chart 1: Log reduction of an influent concentration of 1x103 cfu/mL E. coli and MS2 over a 1500L volume capacity with a UTC and carbon block pre-filter.
Chart 2: Log reduction of a minimum influent concentration of 1x103 cfu/mL E. coli, MS2, and Polio-Rota virus over a 23 week time period of continuous use with a UTC and ceramic candle pre-filter.
Page 2 Conclusion The WAL UTC was developed to provide a ≥ 99.9% reduction of pathogenic waterborne bacteria and virus (≥3 LRV) under increased TDS and halogen demand water conditions using a canister gravity device application with a suitable pre-filtration technology (ceramics or carbon blocks). Under these conditions, the UTC is able to provide a ≥ 99.9% reduction of bacteria and virus to 1500L volume capacity.