人们一直担心过滤设备在为低微米（2至5微米）范围内的颗粒材料提供坚固屏障方面的有效性。过滤器成熟期已被确定为颗粒物质进入饮用水供应的关键问题。这种物质可能包括絮状物、细菌和微生物，如贾第虫和隐孢子虫。在中试规模上，使用不同的启动策略在减少过滤器成熟期通过的颗粒数量方面的效果已在之前报告过。观察到高达65%的减少。这项试点工作评估了两种策略，即慢启动和延迟启动。西北水务（NWW）目前已在其多家水处理厂（包括快速重力和压力过滤器）全面评估了这两种策略。 研究发现，这两种策略都显著降低了进入饮用水供应的颗粒物质总量。这可以在不产生重大成本的情况下实现。采用优化的过滤器启动程序可视为良好的操作实践。

There has been concern about the effectiveness of filtration plants in providing a robust barrier to particulate material in the low micron size range (2 to 5um). The filter ripening period has been identified as a key issue with respect to the passage of particulate material into drinking water supplies. This material may include floc, bacteria, and microorganisms such as Giardia and Cryptosporidium. The effects at pilot scale of the use of differing start up strategies in reducing the magnitude of numbers of particles passed during the filter ripening period have been reported previously. Reductions of up to 65% were observed. That pilot work evaluated two strategies namely slow start and delayed start. North West Water (NWW) has now evaluated both of these strategies at full scale on a number of its water treatment plants including rapid gravity and pressure filters. It was found that both strategies provided significant reductions in the total amount of particulate material passed into drinking water supply. This can be achieved without incurring significant cost. Adoption of an optimised filter start up procedure can be regarded as good operational practice.