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508 P. Kajitvichyanukul et al.
Table 11.3
Pilot-scale biological filters, a Cincinnati, OH (120)
Filter c Preozonated Backwash Filter media Biomass (nmol Percentage removals
Disinfectant lipid PO4/g dry
media)
DOC a THMFP HAAFP
1 Yes Chlorine 20" Anthracite/10"
Sand
28 12 8 26
2 Yes Chloramine 20" Anthracite/10"
Sand
120 19 17 33
3 Yes None 20" Anthracite/10"
Sand
130 23 23 39
4 Yes None 20" GAC b /10" Sand 288 42 53 62
5 Yes None 30" Sand 96 23 21 39
7 No None 20" Anthracite/10"
Sand
66 8 20 27
8 No Chlorine 20" Anthracite/10"
Sand
16 0 24 23
a Average filter influent DOC = 2.8 mg/L.
b Filtrasorb 400.
c Loading rate for all filters = 2 gal/min/ft 2 (5 m/h).
the water was ozonated prior to filtration (Filters 1–5), while the remainder went directly to
filtration (Filters 7 and 8). The average transferred ozone dose was 5.6 mg/L. None of the
filters were PC. Filters 1 and 8 were backwashed with chlorinated water (1.6 mg/L), Filter 2
was backwashed with chloraminated water (2.1 mg/L), and the remaining filters received
no disinfectant in the backwash. Once the plant reached steady-state operation, biomass
development, and removals of DOC, THMFP, and HAAFP across the filters were measured.
Formation potentials were measured under uniform formation conditions (UFC). These
consisted of chlorinating to yield 1 mg/L free chlorine residual after 24 h of holding time at
pH 8. Preozonation impacted biomass development and DBPFP removal. Preozonated filters
typically developed higher biomass levels and removed larger fractions of DOC. However,
the impact on THMFP and HAAFP removals were mixed. The preozonated NC inert media
filters (Filters 3 and 5) developed higher levels of biomass and removed more PM, as
measured by DOC and HAAFP, than their nonozonated counterpart Filter 7. However, all
three filters removed roughly equivalent amounts of THMFP. The preozonated, chlorinated,
inert media Filter 1 developed more biomass and removed more DOC than did the nonozonated,
chlorinated, inert media filter (Filter 8). However, both filters removed equivalent
fractions of HAAFP, and Filter 8 removed a larger fraction of THMFP. The presence or
absence of BWC impacted biomass development, DOC, THMFP, and HAAFP removals in
preozonated filters. NC, preozonated Filters 3 and 5 developed more biomass and removed
more DOC, THMFP, and HAAFP than did BWC, preozonated Filter 1. BWC had less of
an impact on nonozonated filters. Nonozonated, NC Filter 7 developed more biomass and