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Secondary treatment
Published in Rumana Riffat, Taqsim Husnain, Fundamentals of Wastewater Treatment and Engineering, 2022
A septic system consists of a septic tank and a drainfield for absorption of the effluent. The septic tank can consist of one or two compartments. The underground tank is usually made of concrete, although fiberglass and polyethylene tanks are also used. The tank must be watertight to avoid leaking out and seepage into the groundwater. It works as a primary sedimentation tank with a long detention time. Both settling and anaerobic treatment reduce the solids and organic matter and moderately treat the wastewater. Digestion of organic matter and separation of fats, oil, and grease (FOG) takes place in the tank. The effluent is discharged into the drainfield through perforated pipes and chambers, or pumped to help trickle through sand, soil, or constructed wetlands to remove the pathogens, nutrients, and other contaminants. The discharge of waste effluent in the soil may cause groundwater pollution; thus, some systems use evaporation or disinfection before discharge. A typical septic tank system with two compartments is illustrated in Figure 8.20.
Sewage Disposal Systems
Published in Herman Koren, Best Practices for Environmental Health, 2017
Problems with the septic system can be determined by: the slow flushing of toilets; surface flow of wastewater; very green grass over the absorption field indicating upward flow instead of downward flow where the soil may be clogged; nitrates and bacteria found in well water; increase in aquatic weeds or algae in ponds or other bodies of water adjacent to the home; and bad odors around the house. The extreme occurs when the sewage backs up into showers, sinks, floor drains, and/or toilets, which then overflow.
Anaerobic Systems
Published in Subhash Verma, Varinder S. Kanwar, Siby John, Environmental Engineering, 2022
Subhash Verma, Varinder S. Kanwar, Siby John
Septic tanks are onsite systems and are more common in rural areas, isolated buildings and institutions, hotels, schools, hospitals and small residential areas. To prevent contamination, septic systems must be set away from the source of drinking water and should not be located in swamp areas or areas prone to flooding. In addition, the soil should be porous to absorb effluent from septic tanks. A typical section of a septic tank is shown in Figure 27.1.
Multi-site watershed model calibration for evaluating best management practice effectiveness in reducing fecal pollution
Published in Human and Ecological Risk Assessment: An International Journal, 2020
J. Sebastian Hernandez-Suarez, Sean A. Woznicki, A. Pouyan Nejadhashemi
The cost of implementation to meet the E. coli TMDL varies largely based on the source of pollution. If all implementation dollars go to fixing septic tanks, the cost varies from less than $4,000 (EBC2) to around $180,000 (EBC 5) and is a function of the number of septic systems in the subwatersheds draining to each sampling location. The most cost-effective scenarios (percent implementation area and percent reduction) that meet the E. coli TMDL targets are presented in Table 5 for each sampling location. Locations EBC6 and EBC9 already met the targets prior to implementation and excluded from Table 5. The subwatersheds upstream of each location in which addressing the E. coli load is required to meet the reduction target are presented in SI Figures A13–A19. It is unsurprising that the greatest cost is in subwatersheds that have the most septic systems and drain into the monitoring locations that experience the highest E. coli concentrations.
Synoptic snapshots: monitoring lake water quality over 4 decades in an urbanizing region
Published in Lake and Reservoir Management, 2023
C. Doucet, L. Johnston, A. Hiscock, T. Bermarija, M. Hammond, B. Holmes, T. Smith, B. Lalonde, D. Parent, C. Deacoff, R. Scott, J. Kurek, R. Jamieson
Five wastewater treatment facilities (WWTF) discharge into surface waters in the study area, with all but one utilizing tertiary treatment (Table S2). Three lakes directly receive WWTF effluent, namely, William, Fletcher, and Grand, while another 4 lakes are indirectly affected (i.e., are downstream of lakes/streams receiving WWTF effluent), namely, Kinsac, Soldier, Miller, and Thomas (Table S2). Residences located beyond the boundary of the municipal sewer system rely on septic systems to treat wastewater. At a minimum, 40,000 septic systems are located in HRM (Halifax Regional Council 2007), servicing ∼14% of the municipality’s population (Statistics Canada 2011, 2015).