Septic Tank Impacts on Ground Water Quality and Nearshore Sediment Nutrient Flux

Abstract

Field studies were conducted at three coastal plain sites to characterize inorganic nutrient and fecal coliform bacteria ground water quality and intertidal sediment nutrient fluxes under the influence of residential septic tank effluent. Mean drainfield DIP (dissolved inorganic phosphorus) and DIN (dissolved inorganic nitrogen) concentrations varied between 294 to 336 and 4494 to 5391 μmol/L, respectively, with mean fecal coliform bacteria densities ranging from 105.04 to 106.29 MPN (most probable number) /100 mL. DIP and fecal coliform bacteria exhibited a high degree of attenuation with shoreline concentrations at or near background levels. In contrast, septic tank nitrogen loadings to shallow ground water were significant and resulted in mean shoreline DIN concentrations ∼50 to 100 times greater than adjacent surface water concentrations. Mean site sediment DIP and DIN flux to surface waters varied from 1.1 to 1.6 and 52 to 135 μmol/m2/hr, respectively. Whereas DIP sediment fluxes were similar to reported values for sites adjacent to forested and agricultural lands, DIN fluxes were elevated compared to forested lands and near the lower end of the range reported for agricultural lands within the southern Chesapeake Bay region. Maximum measured sediment DIN flux was 1514 μmol/m2/hr. Estimated waste water nitrogen loading to shallow ground water (5.7 to 10.7 kg/household/yr) was significant and with 0.5 to 1 acre lot sizes, comparable to water table nitrogen loadings from dominant row‐crop land use in the mid‐Atlantic Coastal Plain. Given the trends in population growth in the Chesapeake Bay watershed and other coastal regions, nitrogen loads from septic tanks to these systems should also be expected to increase.

Assessment of the River Water Pollution Levels in Kuantan, Malaysia, Using Ion-Exclusion Chromatographic Data, Water Quality Indices, and Land Usage Patterns

“…In Kuantan, there are 228 sewerage treatment plants, many of which were built in the early 1970s, of which individual septic tanks (ISTs) serve 51%, the centralized sewer system serves 47%, and individual primitive systems serve the remaining 2% of sewage/household wastewater. 27 However, ISTs are not highly efficient in removing nutrients and organic compounds (COD) with removal capacities of 5-18% 28 and 50-78%, 29 respectively. As a result, high concentrations of TIN and COD were presumed to be obtained in the Galing River samples, owing to deficiencies in the water treatment capacity for sewage/ household wastewater from the Galing River basin area.…”

Wastewater Nitrogen Contributions to Coastal Plain Watersheds, NC, USA

“…Previous research (Ferrell and Grimes 2014;Humphrey et al 2013;Wang et al 2013) conducted in a variety of settings has revealed that nutrient concentrations can be elevated in water resources partially because of contributions from septic systems. Septic systems installed in sandy soils can generate nitrogen-enriched plumes that extend greater than 15 m (Harman et al 1996;Humphrey et al 2013;O'Driscoll et al 2014;Reay 2004;Robertson et al 1991). Owing to high density of active septic systems installed in sandy soils with shallow water tables (NCDENR 2005), the Coastal Plain of North Carolina is an ideal location to study the effects of septic systems on watershed nitrogen inputs.…”

Determination of Water Quality Degradation Due to Industrial and Household Wastewater in the Galing River in Kuantan, Malaysia Using Ion Chromatograph and Water Quality Data

“…In Kuantan, there are 228 sewerage treatment plants, many of which were built in the early 1970s, of which individual septic tanks (ISTs) treat 51%, centralized sewer systems treat 47%, and individual primitive systems treat the remaining 2% of sewage/household wastewater [28]. However, ISTs are not highly efficient in removing nutrients and organic compounds with removal capacities of 5%-18% [29] and 50%-78%, [30] respectively. Therefore, higher COD/TP correlation could be due to wastewater containing incomplete or untreated raw sewage water.…”