Microbial and Physicochemical Qualities of Septic Tank Wastewater: An Evaluation.

The physicochemical and microbial qualities of septic tank effluent samples from households within the study area were evaluated. Three replicate samples from Locations A, B, and C representing Agbor, Benin City, and Sapele regions of Delta and Edo States, Nigeria were collected from both the inlet tank (raw sewage) and the outlet chamber (semi-treated sewage) for physicochemical and microbiological analyses using standard methods. Results of the physicochemical analyses showed that pH values ranged from 6.5 – 7.7 across locations and in both the raw and semi-treated samples. Electrical conductivity (EC), Total suspended solid (TSS) and BOD was significantly higher (p>0.05) in the raw sewage (RS) than in the semi-treated (SS), while DO was higher (p>0.05) in the SS in all three locations sampled. Microbial analysis shows that total heterotrophic bacteria (THB) was highest in the RS in two locations. Microbial isolates from wastewater samples included Staphylococcus aureus, Proteus mirabilis, Escherichia coli, Pseudomonas aeruginosa, and Aspergillus niger. DO was low at an average of 3.20 and 3.73 mg/L in both chambers of the septic tank. Average BOD5 of 59.4 and 42.8 mg/L and COD average of 206.8 and 153.2 mg/L were reported for the RS and SS chambers. 0.3 was the value of the ratio of BOD5/COD for the RS and SS in the study. This infers that biodegradation was slow and inefficient in the septic tank system, and that modification of the design is recommended to increase retention time in the RS chamber

Treatment of seawater salinity sewage with intermittent sand bioreactors

In water stressed areas, flush toilets using fresh water are unsustainable. This paper explores the ability of intermittent sand bioreactors (ISBs) to treat seawater salinity septic tank effluent for on-site wastewater treatment in coastal regions. Two ISB designs, sand only and layered sand and gravel, are compared for treatment efficacy. Six columns of each design were constructed in the laboratory and dosed four times per day, for a total hydraulic loading rate of 4 cm/day, with artificial seawater salinity septic tank effluent over 21 months. Average TOC and ammonia removal for both designs averaged >90% and >96%, respectively. No statistically significant difference existed in the percent removal or effluent concentrations between the two designs. Half of the columns of each design produced effluent with >4 mg/L ammonia at least once during the study, resulting in discontinuation of wastewater application for seven weeks. This resting approach resulted in effective treatment for up to 9 months (limited by the end of the study). The results indicate that both ISB designs can treat artificial seawater salinity septic tank effluent, but that an additional 1/3 capacity is needed to maintain a consistent hydraulic loading rate while accounting for resting ISBs when treatment efficacy declines.

Characterisation of Organic Matter and Its Transformation Processes in On-Site Wastewater Effluent Percolating through Soil Using Fluorescence Spectroscopic Methods and Parallel Factor Analysis (PARAFAC)

This research has used fluorescence spectroscopy and parallel factor analysis (PARAFAC) in order to characterize dissolved organic matter in septic tank effluent, as it passes through the biomat/biozone, infiltrating into the unsaturated zone beneath domestic wastewater treatment systems (DWWTSs). Septic tank effluent and soil moisture samples from the percolation areas of two DWWTSs have been analyzed using fluorescence excitation–emission spectroscopy. Using PARAFAC analysis, a six-component model was obtained whereby individual model components could be assigned to humified organic matter, fluorescent whitening compounds (FWCs), and protein-like compounds. This has shown that fluorescent dissolved organic matter (FDOM) in domestic wastewater was dominated by protein-like compounds and FWCs and that, with treatment in the percolation area, protein-like compounds and FWCs are removed and contributions from terrestrially derived (soil) organic decomposition compounds increase, leading to a higher degree of humification and aromaticity. The results also suggest that the biomat is the most important element determining FDOM removal and consequently affecting DOM composition. Furthermore, no significant difference was found in the FDOM composition of samples from the percolation area irrespective of whether they received primary or secondary effluent. Overall, the tested fluorometric methods were shown to provide information about structural and functional properties of organic matter which can be useful for further studies concerning bacterial and/or virus transport from DWWTSs.

Applied Hydrothermal Carbonization

The technology of hydrothermal carbonization (HTC) is a thermal chemical conversion process of organic waste into products in a reactor at low and medium temperatures and pressures, with catalysts, using residual raw materials of diversified origin, such as domestic, industrial, or agricultural. The products from the process have several energies (renewable sources) and environmental applications, such as carbon sink, soil conditioners and nanostructured materials. Implications inherent to the process, such as the type of residual biomass, the carbon phases produced (products), and adaptation of the small-scale system, have been researched in the activities. Experiences show that a laboratory-scale system transforms wet biomass from industrial waste, such as septic tank sludge, into products with application potential. The septic tank effluent originating from the great region of Goiânia was treated through hydrothermal carbonization, generating products in nanometer scale to which value could be added (potential result), in case of application at an industrial scale. A tecnologia de carbonização hidrotermal (HTC) trata de processo de conversão termoquímica de substâncias residuárias orgânicas em produtos em reator em baixas e médias temperaturas e pressões, com catalisadores, utilizando matérias-primas residuais de origem diversificada, tais como doméstica, indústria ou agrícola. Os produtos do processo apresentam diversas aplicações energéticas (fontes renováveis) e ambientais, tais como sumidouro de carbono, condicionadores de solo e materiais nanoestruturados. Implicações inerentes ao processo, tais como o tipo de biomassa residuária, as fases de carbono produzidas (produtos) e adaptação do sistema de pequena escala, têm sido pesquisadas nas atividades. Experiências mostram que sistema em escala laboratorial transforma biomassa úmida de resíduos industriais, como lodo de fossas sépticas, em produtos com potencial de aplicação. O efluente de fossa séptica originário da grande região de Goiânia foi tratado através da carbonização hidrotermal, gerando produtos na escala nanométrica, aos quais poderiam ser agregados valor (resultado potencial), em caso de aplicação na escala industrial.

Mesocosm– and Field–Scale Evaluation of Lignocellulose– Amended Soil Treatment Areas for Removal of Nitrogen from Wastewater

Non–proprietary N–removal onsite wastewater treatment systems are less costly than proprietary systems, increasing the likelihood of adoption to lower N inputs to receiving waters. We assessed the capacity of non–proprietary lignocellulose–amended soil treatment areas (LCSTAs)—a 45–cm–deep layer of sand above a 45–cm–deep layer of sand and sawdust—to lower the concentration of total N (TN) in septic tank effluent (STE) at mesocosm and field scales. The mesocosm received wastewater for two years and had a median effluent TN concentration of 3.1 mg/L and TN removal of 60–100%, meeting regulatory standards of 19 mg/L or 50% removal. Removal varied inversely with temperature, and was lower below 10oC. Removal was higher in the mesocosm than in five field sites monitored for 12–42 months. Median effluent TN concentration and removal met the standard in three continuously–occupied homes but not for two seasonally–occupied homes. Sites differed in temporal pattern of TN removal, and in four of five sites TN removal was greater—and effluent TN concentration lower—in the LCSTA than in a control STA containing only sand. The performance of non–proprietary LCSTAs was comparable to that for proprietary systems, suggesting that these may be a viable, more affordable alternative for lowering N inputs to receiving waters.

Woven-Fiber Microfiltration (WFMF) and Ultraviolet Light Emitting Diodes (UV LEDs) for Treating Wastewater and Septic Tank Effluent

Decentralized wastewater treatment systems enable wastewater to be treated at the source for cleaner discharge into the environment, protecting public health while allowing for reuse for agricultural and other purposes. This study, conducted in Thailand, investigated a decentralized wastewater treatment system incorporating a physical and photochemical process. Domestic wastewater from a university campus and conventional septic tank effluent from a small community were filtered through a woven-fiber microfiltration (WFMF) membrane as pretreatment for ultraviolet (UV) disinfection. In domestic wastewater, WFMF reduced TSS (by 79.8%), turbidity (76.5%), COD (38.5%), and NO3 (41.4%), meeting Thailand irrigation standards for every parameter except BOD. In septic tank effluent, it did not meet Thailand irrigation standards, but reduced TSS (by 77.9%), COD (37.6%), and TKN (13.5%). Bacteria (total coliform and Escherichia coli) and viruses (MS2 bacteriophage) passing through the membrane were disinfected by flow-through UV reactors containing either a low-pressure mercury lamp or light-emitting diodes (LEDs) emitting an average peak wavelength of 276 nm. Despite challenging and variable water quality conditions (2% < UVT < 88%), disinfection was predictable across water types and flow rates for both UV sources using combined variable modeling, which enabled us to estimate log inactivation of other microorganisms. Following UV disinfection, wastewater quality met the WHO standards for unrestricted irrigation.