Septic Tank Wastewater Research Articles

In vitro examination of the application of saline concentrate to septic tank wastewater

Salinity of water sources is a worldwide problem. Desalinization technologies improve the water quality but produce a highly saline residual waste. One proposed method of disposal is transfer into septic systems. We investigated the microbiological response of septic wastewater to saline backwash. Salinity concentration within the range of residual saline waters in the region was included. Diversity of bacteria and fungi was determined using 454-pyrosequencing. Treatments shared a very similar distribution and richness of bacterial and fungal diversity. Fungal diversity was represented mostly by Dothideomycetes members; Pezizomycetes were inhibited with treatment. Operational taxonomic units from Gammaproteobacteria were common throughout treatments and wastewater control, but increased with treatment. Bacterial populations underwent selection with salinity treatment, likely a statistically significant effect (p = 0.06). The study shows that microbial populations in wastewater are an important aspect to consider when introducing brackish waste into waste stream even in these short-term field conditions.

Chemical and isotopic composition of nitrogen and boron in septic tank wastewater samples

Most of earth’s population depends on onsite sewage systems to dispose of their wastewater to the environment. Samples used to estimate contaminant transport in the environment have typically been collected from nitrogen loads external to the septic tank. Here we characterize the isotopes of boron, nitrate–nitrogen and nitrate–oxygen in partially clarified liquid collected directly from within septic tanks located in Florida. Among other parameters, total Kjeldahl nitrogen (TKN) and total boron were also evaluated. Nitrate–nitrogen isotopes from three samples ranged from +1.25 to +10.00‰, and boron isotopes from five samples ranged from +8.8 to +31.3‰. Nitrate–oxygen isotopes ranged from −3.23 to +19.96‰ and were indicative of an anoxic environment. On average, residential septic tanks were found to contain 96 µg L−1 total boron and 63 mg L−1 TKN. Utilizing isotopes of boron, among other parameters, our findings show that the partially clarified liquid in septic tanks contains a distinguishable δ11B signature.

Evaluation of full-scale vertical peat biofilters for treatment of septic tank effluents

The performances of single-pass vertically loaded fibrous peat biofilters treating septic tank wastewater from a single household (pe 6) and a small rural housing estate (pe ~100) are compared. Both systems achieved >90% BOD removal and consistently low suspended solids <11 mg L−1. Pathogen removal was generally >95% but inconsistent. Nitrification was linked to temperature with removal rates seasonal (50–98%) with no denitrification; this resulted in final effluents with either high NH4 or NO3 concentrations, both unsuitable for discharge to surface or ground waters. Phosphorus removal was generally poor. The filters responded poorly to sudden increases in hydraulic loading, causing a reduction in BOD removal in particular. Subsequent soil treatment of effluents after filtration caused a small decrease in both physicochemical and microbial quality. Single-pass vertical peat filters cannot meet the more stringent EU nutrient and microbial standards required for on-site treatment without tertiary treatment to ensure full compliance.

Fe(III) reduction-mediated phosphate removal as vivianite (Fe3(PO4)2⋅8H2O) in septic system wastewater

Phosphate is a water contaminant from fertilizers, soaps, and detergents that enters municipal and onsite wastewater from households, businesses, and other commercial operations. Phosphate is a limiting nutrient for algae, and is one of the molecules that promotes eutrophication of water bodies. Phosphate is especially problematic in onsite wastewater because there are few removal mechanisms under normal operating conditions; a system must be amended specifically with compounds to bond to or adsorb phosphate in the septic tank or within the leach field. Vivianite (Fe3(PO4)2⋅8H2O) is a stable mineral formed from ferrous iron and phosphate, often as the result of Fe(III) reducing microbial activity. What was unknown was the concentration of phosphate that could be removed by this process, and whether it was relevant to mixed microbial systems like septic tank wastewater. Data presented here demonstrate that significant concentrations of phosphate (12–14mM) were removed as vivianite in growing cultures of Geobacter metallireducens strain GS-15. Vivianite precipitates were identified on the cell surfaces and within multi cell clusters using TEM–EDX; the mineral phases were directly characterized using XRD. Phosphate was also removed in dilute and raw (undiluted) septic wastewater amended with different forms of Fe(III) including solid phase and soluble Fe(III). Vivianite precipitates were recovered and identified using XRD, along with siderite (ferrous carbonate), which was expected given that the systems were likely bicarbonate buffered. These data demonstrate that ferric iron amendments in septic wastewater increase phosphate removal as the mineral vivianite, and this may be a good strategy for phosphate attenuation in the septic tank portion of onsite wastewater systems.

Stable aerobic granules in continuous-flow bioreactor with self-forming dynamic membrane

A novel continuous-flow bioreactor with aerobic granular sludge and self-forming dynamic membrane (CGSFDMBR) was developed for efficient wastewater treatment. Under continuous-flow operation, aerobic granular sludge was successfully cultivated and characterized with small particle size of about 0.1–1.0mm, low settling velocity of about 15–25m/h, loose structure and high water content of about 96–98%. To maintain the stability of aerobic granular sludge, strategies based on the differences of settling velocity and particle-size between granular and flocculent sludge were implemented. Moreover, in CGSFDMBR, membrane fouling was greatly relieved. Dynamic membrane was just cleaned once in more than 45days’ operation. CGSFDMBR presented good performance in treating septic tank wastewater, obtaining average COD, NH4+−N, TN and TP removal rates of 83.3%, 73.3%, 67.3% and 60%, respectively, which was more efficient than conventional bioreactors since that carbon, nitrogen and phosphorus were simultaneously removed in a single aerobic reactor.

Reeds as indicators of nutrient enrichment in a small temporarily open/ closed South African estuary

This study investigated the use of δ15N levels in Phragmites australis reeds as an indicator of nutrient input into the small temporarily open/closed East Kleinemonde Estuary, Eastern Cape, South Africa. Nutrient (NH4 and SRP) concentrations decreased from the bank towards the main estuary channel, suggesting that nutrients introduced into the estuary in groundwater and surface runoff were taken up by the fringe of reeds. The roots, rhizomes, stems and leaves of Phragmites at the site with the greatest Phragmites biomass and density had significantly higher δ15N (∼20‰) than the leaves at a site with no groundwater input, consistent with nutrient enrichment by septic tank wastewater and stormwater runoff. This study suggests that the δ15N level in reeds can be used to detect enrichment in small estuaries threatened by changing land use and deteriorating water quality.

Removal of nitrogen from wastewater for reusing to boiler feed-water by an anaerobic/aerobic/membrane bioreactor

Abstract The innovative process anaerobic/aerobic/membrane bioreactor (A/O/MBR) was developed to enhance pre-denitrification without the energy consumption of the recirculation pump for reusing wastewater to boiler feed-water. The performance of this bioreactor was investigated. Firstly, the septic tank wastewater with low ratio of COD/TN was disposed by a dynamic membrane bioreactor (DMBR). It was found that, although the high concentration of NO 2 − –N in the effluent implied the potential ability of DMBR to realize shortcut nitrification and denitrification, the effluent of single DMBR was difficult to reach the criteria of reusing to boiler feed-water. Then, the process A/O/DMBR in disposing the septic tank wastewater was studied. The results indicated that this process not only accomplished the removal of 91.5% COD, 90.3% NH 4 + –N and 60.2% TN, but also successfully realized pre-denitrification without additional recirculation pump. At last, based on the A/O/DMBR, a pilot plant A/O/MBR was built to dispose the municipal raw sewage. In the stable operation period, the average removal efficiencies for COD, NH 4 + –N, TP and turbidity reached 90%, 95%, 70% and 99%, respectively. During the tested HRT run of 9.0 h, the effluent of COD, NH 4 + –N, TP and turbidity was about 10 mg/L, 3 mg/L, below 1 mg/L and 1.2 NTU, respectively, which reached the criteria of the boiler feed-water in China.

Disinfection of septic tank and cesspool wastewater with peracetic acid.

Wastewaters of private household septic tanks and cesspools have been treated with peracetic acid (1-2 g L(-1)). Adding 1 g L(-1) peracetic acid to wastewaters was easy and has been found to be effective in destroying enteric indicator microorganisms. The careful mixing of peracetic acid and wastewater was found to be important. Winter periods with frozen soil, ice and snow did not constitute extra problems. The bad smell of these wastewaters almost totally disappeared during the treatment. When wastewaters treated with peracetic acid were emptied into animal slurry tanks, hygienization still continued in the mixture of animal slurry and the wastewaters. These wastewaters could thus be released into agricultural soil without risk of microbiological pollution to groundwaters.

Disinfection of Septic Tank and Cesspool Wastewater with Peracetic Acid

Disinfection of Septic Tank and Cesspool Wastewater with Peracetic Acid

Low-temperature kinetics of anaerobic-filter wastewater treatment

The effects of wastewater temperature on treatment efficiency in an anaerobic-filter process were examined based on laboratory data on anaerobic filters treating septic-tank effluent, dairy wastewater, slaughterhouse wastewater, potato-processing wastewater and whey wastewater. Three anaerobic filters were operated at 5, 10 and 20°C treating septic-tank effluent at different hydraulic retention times (HRTs), three anaerobic filters treating dairy wastewater were operated at 12.5, 21 and 30°C at different HRTs, an anaerobic filter treating slaughterhouse wastewater was operated at 23.6, 24.3, 25, 26.6, 26.7 and 27.1°C at different HRTs, an anaerobic filter treating potato-processing wastewater was operated at 2, 4, 10 and 20°C and an anaerobic filter treating whey wastewater was operated at 16, 20, 26 and 30°C at different HRTs. Data were analyzed for the effect of temperature using the Arrhenius equation and a relationship was developed between system temperature and first-order rate constant for each anaerobic filter system. The simple kinetic model did not fit the experimental data very well for two of the three wastewaters tested.

Soak-away Systems and Possible Groundwater Pollution Problems in Developing Countries

People in the developing countries do not have adequate sanitation and everyone defaecates somewhere. Those who do not have a toilet or latrine have to resort to indiscriminate defaecation either in the sea shore such as in the Lagos lagoon in Nigeria, or vacant plots and open drains as in Iddo area of Lagos and sides of rural footpaths. Water closets (W.C.s) are the most accepted sanitation system, but the cost of operating and maintaining them is high. As a result sewerage is not appropriate for the majority of people in developing countries whose greater population live in rural areas and small towns. The majority of people in urban areas use septic tanks and very often most of these septic tanks are not properly designed or sometimes located too close to sources of water supply, which then become contaminated. It is generally believed that systems like septic tanks, pit latrines and aqua privies are capable of totally eliminating these pathogens. There are many problems associated with the physical, chemical and biological processes that may result in groundwater pollution from septic tanks. Many experiments have shown that faecal organisms do not travel any significant distance radially as a result of concentration gradient. They are, however, carried with groundwater flow. The task is to prevent pathogens from getting into the aquifer. This paper attempts to highlight the ability of some enteric viruses to survive septic tank wastewater treatment.

The Performance of the Rotating Disc System under the Tropical Conditions in Taiwan

In this investigation, the discharge from a septic tank and community wastewater were treated in a pilot scale rotating disc system (RDS) to evaluate the performance of this system under the tropical conditions in Taiwan, with the intention of developing design criteria useful for this region. It was found that by varying the organic loading to the system, different degrees of treatment could be obtained. Results of this study indicated that with an organic loading of 8-10 g B0D/(m2, d), 90% removal of BOD as well as NH4-N removal could be achieved. Ambient temperature was found to have no significant effect on the treatment efficiency, and the optimum hydraulic detention time was within 3 hours. Biological sludge production amounted to 0.6-0.8 kg/kg BOD removed.