旧金山水署（SFWD）进行了规模的病原体播种调查与它的HeTCH HeTeCH源水。本研究的一个目的是评估隐孢子虫卵囊通过直接过滤、使用无烟煤单介质过滤器和高达14 gpm/ft2的过滤速率的去除效率。处理包括臭氧或氯气预氧化，然后进行混凝、絮凝和过滤。结果表明，当过滤速率为6gpm/ft2时，隐孢子虫的去除率相当。结果还表明，在过滤器成熟期间，去除效率超过2-log，保持在2到3之间- 大部分过滤器运行期间的原木去除，然后在颗粒突破期间显著下降。总的来说，颗粒去除效率往往略低于隐孢子虫去除效率。此外，当过滤水浊度小于0.1 NTU时，隐孢子虫去除率通常超过2-log。

The San Francisco Water Department (SFWD) conducted a pilot-scale pathogen seeding investigation with its Hetch Hetchy source water. One purpose of the investigation was to evaluate the removal efficiency of Cryptosporidium oocysts through direct filtration, using anthracite mono-media filters and filtration rates up to 14 gpm/ft2. Treatment consisted of preoxidation with either ozone or chlorine, followed by coagulation and flocculation and filtration. Results indicated that Cryptosporidium removal was equivalent at filtration rates of 6 gpm/ft2. Results also showed that removal efficiency exceeded 2-log during filter ripening, remained between 2 and 3-log removal for most of the filter run, and then declined significantly during particulate breakthrough. In general, particle removal efficiency tended to slightly underestimate Cryptosporidium removal efficiency. Also, when filtered water turbidity was less than 0.1 NTU, Cryptosporidium removal typically exceeded 2-log.