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' a s 714 CHAPTER 11: Intermittent and Recirculating Packed-Bed Filters Early Development and History of Use The first attempt to treat wastewater with sand and gravel filters can be traced back to Ealing and Chorley, England, in the late 1860s (Frankland, 1870). it should be" noted that in the 1860s, the germ theory had not yet been developed and,the role of microorganisms in bringing about the conversion of organic matter was unknown. Following the early experiments at Ealing and Chorley, Sir Edward Frankland, a member of the Royal Commission, conducted experiments in 6-ft (1.8-m) glass cylinders filled with various types of granular media including: (1) a coarse porous gravel from the much cited Beddington (sewage)irrigation meadows near Croydon, (2) sand from the red sandstone near Hambrook, (3) soil from Barking (sewage) ir- rigation farm, (4) a light yellowish-brown loamy marl from Dursley, and (5) peaty soil from Leland(Dunbar, 1908).The columns were dosed, at rates varying from.3.5 to 13 gal/yd3,every morning and evening with wastewater from the city of London. The results of the experiments were very satisfactory and the Royal Commission came to the conclusion that "with the best of the filters (No. 1) 44,000 gallons of sewage could be thoroughly purified on one acre, if drains were laid at a depth of 6 feet." It should be noted that in the filtration experiments conducted by Frankland and later,at Lawrence,Massachusetts, as described below, the formation of a surface mat was a common operational feature of the filters. The degree of mat formation and surface clogging depended on the degree of pretreatment the wastewater had received. Interestingly, the loading rate established in these early experiments is es- sentially the same as the rate used currently for the design of these filters where a high level of treatment is required. It is also interesting to note that these early ex- periments form the first basis for the modern practice of the biological treatment of wastewater and of land treatment. Frankland's experiments might have been forgotten were it not for the Mas- sachusetts State Board of Health, which became interested in the subject, and in the 1870s constructed the Experiment Station at Lawrence,Massachusetts,with the express purpose of conducting experiments into the treatment of wastewater using sand and gravel filters along the lines suggested by Frankland.By the late 1870s the concept of ISF was put into practice in Massachusetts. The first community to con- struct an ISF system was Lenox,Massachusetts,in 1876(Mand and Peeples, 1991). Between 1891 and 1937 the Massachusetts State Board of Health monitored the per- formance of over 26 community ISF systems. Data on a selected number of these 26 systems are presented in Table 11-1. Despite the excellent performance of these sand filters, increasing population and the resultant increased land requirements led most of the communities to change to trickling filters or activated sludge.In 1920,the U.S.Public Health Service published a report describing the treatment of wastewater from single homes and small communities (Frank and Rhynus, 1920). Intermittent sand filters were featured prominently (see Fig. 11-8), along with extensive data on their performance. The use of sand filters waned until the 1940s,when pilot-scale studies were con- ducted at the University of Florida.These experimental ISF systems were more shal- low and the sand size was coarser than was used in the Massachusetts systems.The sand sizes ranged from 0.26 to 0.46 mm,and the bed depths were 18 to 30 in(0.46 to