Laserfiche WebLink
i <br /> :► I <br /> The following effluent characteristics are typical averages achieved by single-pass residential sand <br /> filters using"washed"ASTM C-33 concrete aggregate with less than 2 percent fines passing the 100 <br /> sieve: <br /> cBOD5: 5 mg/L <br /> TSS: 5 mg/L <br /> NO3-n: 30 mg/L f <br /> Single-pass sand filters have typically been used in onsite applications for single-family homes or small <br /> commercial/office facilities. <br /> Single-pass filters have been most successful when the influent has received primary septic tank <br /> treatment and screening with effluent filters to sufficiently ensure that the effluent characteristics applied <br /> to the sand filter do not exceed the typical criteria shown in Table 1: <br /> Table 1: Typical Primary Treated and Screened Residential Wastewater Strenaths <br /> Average Weekly Peak Rarely Exceed <br /> m2/L mg/L mz/L <br /> BODS 130 200 300 <br /> TSS 40 60 150 <br /> TKN—n 65 75 150 <br /> G&O 20 25 25 <br /> With higher influent strengths, maintenance may increase, although with a diligent service and <br /> monitoring program,performance is not expected to suffer. Typical single-pass sand filter design <br /> criteria are: <br /> T e of Design Filter Effective Uniformity <br /> YP g ty Dose <br /> Operation Loading Rate Depth Size Coefficient Limit <br /> gadlf? inches D0, mm C., gal/orifice/dose <br /> Single pass 1.25 24 =L 0.30 ± 3 to 4 0.25 <br /> Recirculating (multiple-pass) filters also treat septic tank effluent to advanced wastewater treatment <br /> levels or better. Below, in Figure 2, a typical recirculating filter is shown, <br /> g r.E <br /> Figure 2:Recirculating sand Ater(RSF) <br /> i <br /> NTP-FLT-TRB-1 <br /> Rev.1,1.11/02 <br /> Page 2 of 12 <br />