Evaluation of Septic Tank and Subsurface Wetland for

More documents

Recommendations

Info

(Crites et al., 1998). Design must balance the need for large surface area to create slow overflow rates that promote ideal particle settling, sufficient depth to store settled solids and chambers to prevent resuspension of settle solids or an effluent filter. Septic tanks in Jamaica are usually constructed of a concrete slab floor with concrete block walls, and the inside is rendered watertight with neat cement. The R2RW septic systems were designed according to the two-chamber septic tank principle, but construction costs were reduced by using two separate cylindrical plastic tanks (see Figure 2.2). These tanks were very similar to the water storage tanks seen on rooftops in Jamaica, but the wall thickness was doubled and piping connections were customized. The tank sizing was based on the desire to have a 3 day HRT with an expected water use of 10 USgal/person per day (USgal/p-d). Inlet First Chamber Tank Second Chamber Tank Outlet Figure 2-2 Ridge To Reef Watershed Project two-chamber septic tank made from plastic tanks. 9
Subsurface Flow Constructed Wetlands A constructed wetland is a simulated natural environment for the filtration and biological treatment of wastewater. Horizontal subsurface flow (SSF) wetlands are shallow beds filled with rocks and are usually planted with aquatic vegetation (see Figure 2-3). They are designed to keep the liquid level 3 to 4 inches below the surface of the rock media to prevent public exposure to the wastewater and mosquito breeding. Figure 2-3 Side view of a horizontal subsurface flow wetland showing vegetation. (Illustration by Cooper, 1993. Republished with permission.) SSF wetlands are a widely accepted technology for reducing wastewater BOD, TSS and coliform (Crites et al., 1998; USEPA, 2000; Reed et al., 2001). Several mathematical models are available for calculating the wetland surface area or volume necessary to achieve the required BOD and nitrogen removal. TSS treatment follows closely with BOD removal so that designing for BOD parameters will provide sufficient treatment to meet similar TSS treatment standards (Reed et al., 2001). According to one authority, a wetland designed with 6-10 day HRT, BOD mass load below 100 lb/ac-d (89 kg/ha-d) and influent nitrogen below 25 mg/l should meet effluent standards of 20 mg/l BOD, 20 mg/l TSS and 10 mg/l N (Crites et al., 1998). Removal efficiencies based on inflow and outflow concentrations through horizontal SSF wetlands in Europe and North America 10
Page 1 and 2: Evaluation of Septic Tank and Subsu
Page 3 and 4: Abstract Locally designed wastewate
Page 5 and 6: Acknowledgments Major funding was p
Page 7 and 8: Chapter 6 - Costs ……………
Page 9 and 10: Table 5-6 Parameters Influencing Bi
Page 11 and 12: The predominant geological formatio
Page 13 and 14: plants discharging a volume of 20m
Page 15 and 16: lack access to acceptable excreta d
Page 17: Critical design parameters for sept
Page 21 and 22: inging larger rock from a distant q
Page 23 and 24: Chapter 3 - Site Descriptions Figur
Page 25 and 26: Wetland inlet sample point Flush to
Page 27 and 28: Figure 3-4 Pisgah wetland beds befo
Page 29 and 30: times over a two-week period, grew
Page 31 and 32: Figure 3-7 Retrieve youth in front
Page 33 and 34: Chapter 4 - Methodology Field Data
Page 35 and 36: out (see Figure 4-2). Locating the
Page 37 and 38: Figure 4-3 Media porosity measureme
Page 39 and 40: Laboratory Water Quality Analysis A
Page 41 and 42: NEPA laboratory also does not test
Page 43 and 44: Since evapotranspiration decreases
Page 45 and 46: The water level in the middle of th
Page 47 and 48: BOD was determined to be 53% at Pis
Page 49 and 50: solids than a sample point that pul
Page 51 and 52: Table 5-4 Ammonia (NH3-N) for Pisga
Page 53 and 54: Table 5-5 Nitrate (NO3-N) for Pisga
Page 55 and 56: o Alkalinity Nitrification and deni
Page 57 and 58: system were measured to be 3.3 mg/l
Page 59 and 60: coliform by 88%. The Retrieve septi
Page 61 and 62: Chapter 6 - Cost of Pisgah and Retr
Page 63 and 64: The septic tanks will have to be pu
Page 65 and 66: Jamaica may refer to the hydraulic
Page 67 and 68: Chapter 8 - References APHA (Americ
Page 69 and 70:
Pennant, Joseph, (2005), Assistant
Page 71 and 72:
Chapter 9 - Appendices Appendix 1 -
Page 73 and 74:
7-Dec- 2004 SET FIVE Sample BOD TSS
Page 75 and 76:
Appendix 3 - Determination of 90% C
Page 77 and 78:
Appendix 4 - Conductance of Water C
Page 79 and 80:
Appendix 6 - Total Dissolved Nitrog
Page 81 and 82:
Appendix 8 - Evapotranspiration Det
show all

Evaluation of Septic Tank and Subsurface Wetland for

Create successful ePaper yourself

Delete template?

Save as template?