Summary of Performance

Table 5.2 and Table 5.3 summarize the performance of intermittent sand filters treating lagoon effluents during the 1970s and 1980s. Table 5.2 is a summary of studies reported in the literature and EPA documents, and Table 5.3 is a summary of results from field investigations at three full-scale systems consisting of lagoons followed by intermittent sand filters. These are the most extensive studies conducted in the United States and show that it is possible to produce an effluent with TSS and BOD5 less than 15 mg/L from anaerobic, facultative, and aerated lagoons followed by intermittent sand filters with effective sizes less than or equal to 0.3 mm.

Rich and Wahlberg (1990) evaluated the performance of five facultative lagoon-intermittent sand filter systems located in South Carolina and Georgia. A summary of the design characteristics and performance of these systems is shown in Table 5.4. The systems provided superior performance when compared with ten aerated lagoon systems. Six of the systems consisted of one aerated cell followed by a polishing pond; three were designed as dual-power, multicellular systems, and one was a single-cell, dual-power system. Based on the data reported by Niku et al. (1981), the performance of the facultative lagoon-intermittent sand filter systems compared most favorably with activated sludge plants. A performance comparison of the activated sludge and aerated lagoon systems is provided in Table 5.5.

Truax and Shindala (1994) reported the results of an extensive evaluation of facultative lagoon-intermittent sand filter systems using four grades of sand with effective sizes of 0.18 to 0.70 mm and uniformity coefficients ranging from 1.4 to 7.0. As shown in Table 5.6, performance was directly related to the effective size of the sand and hydraulic loading rate. With sands of effective size 0.37 mm or less and hydraulic loading rates of 4.9 gal/ft2-d (0.2 m3/m2-d), effluents with biological oxygen demand (BOD5) and total suspended solids (TSS) of less than 15 mg/L were obtained. Total Kjeldahl nitrogen (TKN) concentrations were reduced from 11.6 to 4.3 mg/L at the 4.9-gal/ft2-d (0.2-m3/m2-d) loading rate. The experiments were conducted in a mild climate, and it is unlikely that similar nitrogen removal will occur during cold months of more severe climates.

Melcer et al. (1995) reported the performance of a full-scale aerated lagoon-intermittent system located in New Hamburg, Ontario, Canada, that had been in operation since 1980. Results for 1990 and from January to August of 1991 are presented in Table 5.7. Surface loading rates for both periods were 79.6 gal/ft2-d (3.24 m3/m2-d) with influent BOD5, TSS, and TKN concentrations of 12,

16, and 19 mg/L, respectively. Filter effluent quality was exceptional, with BOD5, TSS, and TKN concentrations less than 2 mg/L.

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