Greywater Effluent Research Articles

Prospects of Source-Separation-Based Sanitation Concepts: A Model-Based Study

Separation of different domestic wastewater streams and targeted on-site treatment for resource recovery has been recognized as one of the most promising sanitation concepts to re-establish the balance in carbon, nutrient and water cycles. In this study a model was developed based on literature data to compare energy and water balance, nutrient recovery, chemical use, effluent quality and land area requirement in four different sanitation concepts: (1) centralized; (2) centralized with source-separation of urine; (3) source-separation of black water, kitchen refuse and grey water; and (4) source-separation of urine, feces, kitchen refuse and grey water. The highest primary energy consumption of 914 MJ/capita(cap)/year was attained within the centralized sanitation concept, and the lowest primary energy consumption of 437 MJ/cap/year was attained within source-separation of urine, feces, kitchen refuse and grey water. Grey water bio-flocculation and subsequent grey water sludge co-digestion decreased the primary energy consumption, but was not energetically favorable to couple with grey water effluent reuse. Source-separation of urine improved the energy balance, nutrient recovery and effluent quality, but required larger land area and higher chemical use in the centralized concept.

A monitoring of environmental effects from household greywater reuse for garden irrigation

The option of reusing greywater is proving to be increasingly attractive to address the water shortage issue in many arid and semiarid countries. Greywater represents a constant resource, since an approximately constant amount of greywater is generated from kitchen, laundries, bathroom in every household daily, independent of the weather. However, the use of greywater for irrigation in particular for household gardening may pose major hazards that have not been studied thoroughly. In this study, a 1-year monitoring was conducted in four selected households in Perth, Western Australia. The aim of the monitoring works is to investigate the variability in the greywater flow and quality, and to understand its impact in the surrounding environments. Case studies were selected based on different family structure including number, ages of the occupants, and greywater system they used. Samples of greywater effluent (showers, laundries, bathtub, and sinks), leachate, soil, and plants at each case study were collected between October 2008 and December 2009 which covered the high (spring/summer) and low (autumn/winter) production of greywater. Physical and chemical tests were based on the literature and expected components of laundry and bathroom greywater particularly on greywater components likely to have detrimental impacts on soils, plants, and other water bodies. Monitoring results showed the greywater quality values for BOD, TSS, and pH which sometimes fell outside the range as stipulated in the guidelines. The soil analyses results showed that salinity, SAR, and the organic content of the soil increased as a function of time and affected the plant growth. Nutrient leaching or losses from soil irrigated with greywater shows the movement of nutrients and the sole impact from greywater in uncontrolled plots in case studies is difficult to predicted due to the influence of land dynamics and activities. Investigative and research monitoring was used to understand greywater irrigation in households. Greywater quality is very site specific and difficult to predetermine or control except for the use of some recommended household products when using greywater. Investigative and research monitoring was indicated that greywater quality is very site specific and difficult to predetermine or control except for the use of some recommended household products when using greywater.

Disinfection of greywater effluent and regrowth potential of selected bacteria

Chlorination and UV irradiation of RBC (rotating biological contactor)-treated light GW (greywater) was investigated. The ability of chlorine and UV to inactivate indictor bacteria (FC - Faecal Coliforms, HPC - Heterotrophic Plate Count) and specific pathogens (P.a. - Pseudomonas aeruginosa sp., S.a. - Staphylococcus aureus sp.), was assessed and their regrowth potential was examined. The RBC removed 88.5-99.9% of all four bacteria groups. Nevertheless, the treated GW had to be disinfected. Most of the chlorine was consumed during the first 0.5 h, while later its decay rate decreased significantly, leaving enough residual after 6 h to prevent regrowth and to further inactivate bacteria in the stored GW effluent. Under exposure to low UV doses (≤69 mJ/cm(2)) FC was the most resistant bacteria group, followed by HPC, P.a. and S.a. Exposure to higher doses (≤439 mJs/cm(2)) completely inactivated FC, P.a. and S.a., while no further HPC inactivation was observed. FC, P.a. and S.a. did not exhibit regrowth after exposure to all the UV doses applied (up to 6 h storage). HPC did not exhibit regrowth after exposure to low UV doses (19-69 mJ/cm2), while it presented statistically significant regrowth in un-disinfected effluent and after exposure to higher UV doses (147-439 mJ/cm(2)).

Performance of UV disinfection and the microbial quality of greywater effluent along a reuse system for toilet flushing

This paper examines the microbial quality of treated RBC (Rotating Biological Contactor) and MBR (Membrane Bioreactor) light greywater along a continuous pilot-scale reuse system for toilet flushing, quantifies the efficiency of UV disinfection unit, and evaluates the regrowth potential of selected microorganisms along the system. The UV disinfection unit was found to be very efficient in reducing faecal coliforms and Staphylococcus aureus. On the other hand, its efficiency of inactivation of HPC (Heterotrophic Plate Count) and Pseudomonas aeruginosa was lower. Some regrowth occurred in the reuse system as a result of HPC regrowth which included opportunistic pathogens such as P. aeruginosa. Although the membrane (UF) of the MBR system removed all bacteria from the greywater, bacteria were observed in the reuse system due to “hopping phenomenon.” The microbial quality of the disinfected greywater was found to be equal or even better than the microbial quality of “clean” water in toilet bowls flushed with potable water (and used for excretion). Thus, the added health risk associated with reusing the UV-disinfected greywater for toilet flushing (regarding P. aeruginosa and S. aureus), was found to be insignificant. The UV disinfection unit totally removed (100%) the viral indicator (F-RNA phage, host: E. coli F amp +) injected to the treatment systems simulating transient viral contamination. To conclude, this work contributes to better design of UV disinfection reactors and provides an insight into the long-term behavior of selected microorganisms along on-site greywater reuse systems for toilet flushing.

UV disinfection of RBC-treated light greywater effluent: Kinetics, survival and regrowth of selected microorganisms

The microbial quality of raw greywater was found to be much better than that of municipal wastewater, with 1.6×10 7 cfu ml −1 heterotrophic plate count (HPC), and 3.8×10 4, 9.9×10 3, 3.3×10 3 and 4.6×10 0 cfu 100 ml −1 faecal coliforms (FC), Staphylococcus aureus sp., Pseudomonas aeruginosa sp. and Clostridium perfringes sp., respectively. Further, three viral indicators monitored (somatic phage, host: Escherichia coli CN 13 and F-RNA phages, hosts: E. coli F + amp, E. coli K 12) were not present in raw greywater. The greywater was treated by an RBC followed by sedimentation. The treatment removed two orders of magnitude of all bacteria. UV disinfection kinetics, survival and regrowth of HPC, FC, P. aeruginosa sp. and S. aureus sp. were examined. At doses up to 69 mW s cm −2 FC were found to be the most resistant bacteria, followed by HPC, P. aeruginosa sp. and S. aureus sp. (inactivation rate coefficients: 0.0687, 0.113, 0.129 and 0.201 cm 2 mW −1 s −1, respectively). At higher doses (69–439 mW s cm −2) all but HPC (which exhibited a tailing curve) were completely eliminated. Microscopic examination showed that FC self-aggregate in the greywater effluent. This provides FC an advantage at low doses, since the concentration of suspended matter (that can provide shelter from UV radiation) in the effluent was very low. FC, P. aeruginosa sp. and S. aureus sp. did not exhibit regrowth up to 6 h after exposure to increasing UV doses (19–439 mW s cm −2). HPC regrowth was proven to be statistically significant in un-disinfected effluent and after irradiation with high UV doses (147 and 439 mW s cm −2). At these doses regrowth resulted from growth of UV-resistant bacteria due to decreased competition with other bacteria eliminated by the irradiation.

Physical, chemical and biological characteristics of stored greywater from unsewered suburban Dakar in Senegal

There is a lack of data on the characteristics of greywater (GW) from developing countries. Published data on GW quality in Senegal were not found in the literature. The lack of data has probably led to the public perception that GW is innocuous and, as such, to the careless handling of it. A physical, chemical and microbiological characterization of mixed household GW was undertaken at Apecsy, in unsewered north suburban Dakar, with the view of determining the extent of health hazards related to the hand carrying disposal of GW effluents. Samples were collected from a GW holding tank every 2 hours over a 24-h period and analysed for temperature, pH, electrical conductivity (EC), faecal coliforms (FC), E. coli, dissolved oxygen (DO), BOD5, COD, TOC, TS, SS, VTS, TN, NH4 – N, NO3 – N, TP and PO4 – P. Results were then compared with raw combined domestic wastewater (CDW) data from Dakar and reported data on GW and CDW from both industrial and developing countries. FC and E. coli densities were lower in GW than in CDW but remained significantly high in spite of the absence of urine and faeces. The organic matter was five times higher in GW and its chemical nature quite different from that of organic matter in CDW. GW was three times higher in solids than CDW but the chemical characteristics and size distributions of solids were found to be quite similar in two samples. GW was slightly lower in nitrogen and phosphorus than CDW. The high GW strength seems to be due to the much lower flow associated with the presence of large amounts of food particles and the storage of effluents. Results have shown that GW generated from unsewered suburban Dakar may be equally or more polluted than CDW and, as such, deserves much more attention from both public authorities and populations themselves.

Potential changes in soil properties following irrigation with surfactant-rich greywater

The use of insufficiently treated greywater (GW) for irrigation is becoming increasingly common, a practice mistakenly considered safe. Concentrations of surfactants found in greywater effluents range from 0.7 to 70 mg L −1 and on average are higher than concentrations in raw domestic wastewater. However, there is little information regarding the environmental impact of surfactants. Pollutants such as boron, salt, and faecal coliforms are also commonly found in greywater but are not the focus of this study. The capillary rise in sand that was pre-treated with a laundry detergent solution was lower than that in sand pre-treated with fresh water, and exhibited hydrophobic properties. As with the capillary rise, a flow pattern typical of hydrophobic soil was noted when the imbibition of fresh water into sands pre-treated with laundry detergent solution was tested. It is suggested that surfactant accumulation in the soil due to greywater irrigation can create water-repellent soils, thereby affecting their flow patterns and productivity.