Contents
Research questions
Has this system been used before? Which have been the results?
Given that our value proposition is the reduction of drinking water consumption, are there any application cases that confirm this and quantify their results?
Is it possible to occupy the gray water system in urban areas?
Normally, water reduction is directed at rural areas with little access to water, but this phenomenon can also occur in urbanizations. Since our segment is urban areas, is it possible to apply it?
Greywater systems and their operation
Alomran, A., & Al-Wabel, M. (2012). Potential Reuse of Gray water form Mosques for Toilet Flushing and Garden Irrigation in Saudi Arabia. [1]
- Research question you answer
- Operation of a gray water system
- Article Summary
- Greywater is all used water discharged from a home including shower, bath, toilet, kitchen sink, dishwasher, washing machine, and laundry tub water, excluding toilet water .
- The system consisted of PVC sand filters, an activated carbon filter, ultraviolet unit, valves and regulators.
- Greywater systematically passes through four sand filters to remove suspended materials, then through an activated carbon filter to remove color and some organic and inorganic anions, and finally through an ultraviolet unit to kill and remove debris. pathogenic microbes and other impurities.
- Chemicals in the gray water system
- The concentrations of soluble elements in the gray water were relatively similar to or higher than those in tap water. However, when using the system, the concentrations of the ions studied became more or less the same as in tap water.
Sharifi, F., Nourouzi, MM & Tahmourespour, A. Effect of gray water reuse on toilet flush tank bacterial and scum formation. Sustain. Water Resour. Mgr. 6, 105 (2020). https://doi.org/10.1007/s40899-020-00461-0 [2]
- Research question you answer
- Generation of bacteria when using gray water
- Article Summary
- Greywater is defined as domestic wastewater with a non-toilet plumbing source, including sources from baths, showers, lavatories, washing machines, dishwashers, and kitchen sinks.
- Approximately 27% of indoor water consumption corresponds to toilet flushing. One of the ways to supply water is to use gray water as substitute water in the discharge tank.
- One of the most efficient and autonomous wastewater treatment systems is the septic tank. Its use is considered an economical way, due to its lower costs than centralized wastewater treatment.
- bacteria formation
- No bacterial growth was observed in the galvanized tank even without any sanitizing agent.
- If disinfection methods are used, it is possible to reuse the gray water from the discharge tank and the most appropriate option is to use a galvanized discharge tank to control bacteria growth and scum formation and also imposes a lower cost.
O'Connor, M.C. (2011). The toilet, re-imagined: four water-saving designs. ZDNet. [3]
- Research question you answer
- Design types of a toilet with a gray water system
- proposed designs
- 1. Sink integrated into the toilet: after going to the bathroom, the sink is used to wash hands. The used potable water from the sink is stored in the tank as gray water and then when the toilet is flushed, it uses the gray water instead of more clean water.
- 2. DIY: collects the water from the bathroom sink and leads it to the toilet water tank. The sink does not have to be located right next to the toilet for the system to work, as you can channel the water across the room to the toilet.
- 3. All in one: Integrate toilet bowl, sink, mirror and a vanity into one. There is a water storage tank just below the sink, where you can choose to store your currently used water or allow it to drain off. The tap water pressure can be moderated to four different levels.
Advantages and disadvantages
Al-Adhadh, Ahmed & Aziz, Hussein & Abbas, Basim. (2020). Reviewing the Advantages and Disadvantages of reusing the Greywater. 78-82. 10.9790/1684-1606037882. [4]
- Research question you answer
- Advantages and disadvantages of using a gray water system
- Advantages
- Using greywater can not only reduce household water bills and consumption, but also reduce stress on sewer and septic systems.
- In addition to the toilet, they can also be used in irrigation systems.
- Using greywater for landscape irrigation has many benefits in addition to reducing potable water consumption and stress on sewer and septic systems. Greywater often contains detergents that have nutrients such as nitrogen and phosphorous, which are beneficial for plant growth.
- Disadvantages
- Greywater is that it can have high levels of turbidity and microbial contamination such as bacteria, protozoa and viruses.
- Greywater may also be subject to microbial contamination from humans.
- Greywater has been found to have high alkalinity (low acidity) due to soap and detergent residues, which can have adverse effects on plant growth.
Maimon, A., & Gross, A. (2018). Greywater: Limitations and perspective. Current Opinion in Environmental Science & Health, 2, 1–6. doi:10.1016/j.coesh.2017.11.005 [5]
- Research question you answer
- Advantages and disadvantages of using a gray water system
- Advantages
- The most prominent benefit to greywater users is where water availability is low and/or water rates are high.
- Since high water tariffs are not always the result of water scarcity, but also represent large investments in water management, the financial savings can also benefit users in water-abundant regions.
- It has been estimated that the urban reuse of greywater for toilet flushing alone can reduce a building's water consumption by 30%.
- Disadvantages
- Microbial risks associated with greywater include the presence of pathogens from fecal contamination, skin preparation, mucus, and food.
- Several environmental concerns have been raised regarding the reuse of greywater that are related to contamination of surface or groundwater and soil, as well as effects on plant growth.
Applications in the world
Ghisi, E., & Ferreira, DF (2007). Potential for potable water savings by using rainwater and greywater in a multi-storey residential building in southern Brazil. Building and Environment, 42(7), 2512–2522. doi:10.1016/j.buildenv.2006.07.019 [6]
- Research question you answer
- Effects of the implementation of a gray water system for the toilet
- Results
- The potential for drinking water savings through the use of gray water for toilet flushing was 28.7%, 29.7%, and 34.8%, respectively.
- The gray water tank does not need to store more gray water than the amount needed daily to flush the toilet. Therefore, the gray water tank was sized to store the smallest volume between the available gray water and the water needed to flush the toilet.
Ali, F., Lestari, D.L., & Putri, M.D. (2020). Eco-friendly toilet for sustainable wastewater management in tourism area. International Symposium of Earth, Energy, Environmental Science and Sustainable Development. [7]
- Research question you answer
- Effects of the implementation of a gray water system for the toilet
- Results
- The ecological toilet concept is maximizing the recycling cycle of water, rainwater and wastewater for subsequent reuse according to the needs of water use in the sanitation system.
- The total need for water for toilets is 4,825 liters per day. Therefore, the use of water can be saved up to 68%, compared to using a plumbing tool as usual use.
Use of the system in urbanizations
V. Lazarova, S. Hills, R. Birks; Using recycled water for non-potable, urban uses: a review with particular reference to toilet flushing. Water Supply 1 August 2003; 3(4): 69–77. doi: https://doi.org/10.2166/ws.2003.0047 [8]
- Research question you answer
- Greywater systems in urban areas
- Article Summary
- Interest in water reuse is growing steadily, not only in areas of recognized water scarcity, but also in countries that historically did not appear to have a water supply problem.
- Collected greywater represents approximately 50-70% of total water use within apartments, which appears to be more than the requirement for flushing toilets, even accounting for losses within the treatment process.
- One of the key factors with the use of recycled water is the perception of the users. Studies related to the schemes reported in this paper generally find a positive attitude towards the use of recycled water for flushing toilets.
Christova-Boal, D., Eden, RE, & McFarlane, S. (1996). An investigation into greywater reuse for urban residential properties. Desalination, 106(1-3), 391–397. doi:10.1016/s0011-9164(96)00134-8 [9]
- Research question you answer
- Greywater systems in urban areas
- Article Summary
- The estimated water conservation benefits for a typical household reusing greywater in Melbourne is 20% if it is reused in the toilet, 21% for irrigation and 31% for both.
- Greywater must be of adequate quality to prevent the accumulation of undesirable materials in the cistern or its operating components. The water inlet valve must be capable of being fully closed when the design capacity of the cistern has been reached.
- It is important that the water appears aesthetically acceptable, that it is treated with disinfectants, and that effective and easy-to-replace filters are used.
Ilemobade, AA, Olanrewaju, OO, & Griffioen, ML. (2013). Greywater reuse for toilet flushing at a university academic and residential building. Water SA, 39(3), 199-210. Retrieved August 01, 2021 [10]
- Research question you answer
- Implementation of a gray water system in university complexes
- Article Summary
- The lower the possibility of contact with greywater, the more acceptable the GWR will be to potential beneficiaries.
- Non-residential buildings are likely to be preferred over residential buildings to use the system.
- To ensure efficient operation of the systems, it is important that there is regular engagement with beneficiaries and maintenance and repair activities.
- To be economically feasible, initial and recurring costs must be significantly lower than those experienced in the study.
Final comments
Currently there is a positive trend towards the use of gray water to help preserve water. We all know the possibility of running out of this very soon; The need to create projects for its conservation has become an urgent and important issue, not only in low-income areas, but also in urban areas with a large consumption of drinking water.
This bibliographical review has allowed us to know that the reuse of gray water requires the implementation of a complex system, not only a good design, but also paying special attention to the chemical substances coming from the products we use, to the possible treatments with disinfectants and the selection of a good filter.
We found it interesting that gray water can also be used to irrigate plants; Many would believe that their chemicals would harm them, but this is not always the case. This additional use allows maximizing potable water savings in homes and communities, as well as reducing stress on sewer and septic systems. On the other hand, what we find worrying is the possibility of the creation of bacteria, which is why some articles mentioned the importance of using disinfectants. This allowed us to identify that for our business model it was essential to incorporate the maintenance service, to achieve the highest possible level of hygiene.
The information found leads us to consider that this project has several potential uses in the country, since day by day more people see their access to water compromised; many receive it for a few hours and sometimes it is not even drinkable. This is why a gray water reuse system could improve the living conditions of many Salvadoran homes.
Finally, this review allowed us to answer our question about whether the systems are applicable to urban areas (our market segment). We can conclude that this has great potential, since people are increasingly aware of the need to take care of water and the studies found reveal that savings between 20 and 30% can be achieved. This benefits to preserve the water resource and reduce the expense of the water rate. If this system is implemented in several homes in the urban area, the precious and scarce resource of drinking water would be safeguarded.
References
- ^ Alomran, A., & Al-Wabel, M. (2012). Potential Reuse of Gray water form Mosques for Toilet Flushing and Garden Irrigation in Saudi Arabia.
- ↑ Sharifi, F., Nourouzi, MM & Tahmourespour, A. Effect of gray water reuse on toilet flush tank bacterial and scum formation. Sustain. Water Resour. Mgr. 6, 105 (2020). https://doi.org/10.1007/s40899-020-00461-0
- ^ O'Connor, MC (2011). The toilet, re-imagined: four water-saving designs. ZDNet.
- ↑ Al-Adhadh, Ahmed & Aziz, Hussein & Abbas, Basim. (2020). Reviewing the Advantages and Disadvantages of reusing the Greywater. 78-82. 10.9790/1684-1606037882.
- ^ Maimon, A., & Gross, A. (2018). Greywater: Limitations and perspective. Current Opinion in Environmental Science & Health, 2, 1–6. doi:10.1016/j.coesh.2017.11.005
- ↑ Ghisi, E., & Ferreira, DF (2007). Potential for potable water savings by using rainwater and greywater in a multi-storey residential building in southern Brazil. Building and Environment, 42(7), 2512–2522. doi:10.1016/j.buildenv.2006.07.019
- ^ Ali, F., Lestari, D.L., & Putri, M.D. (2020). Eco-friendly toilet for sustainable wastewater management in tourism area. International Symposium of Earth, Energy, Environmental Science and Sustainable Development.
- ↑ V. Lazarova, S. Hills, R. Birks; Using recycled water for non-potable, urban uses: a review with particular reference to toilet flushing. Water Supply 1 August 2003; 3(4): 69–77. doi: https://doi.org/10.2166/ws.2003.0047
- ^ Christova-Boal, D., Eden, RE, & McFarlane, S. (1996). An investigation into greywater reuse for urban residential properties. Desalination, 106(1-3), 391–397. doi:10.1016/s0011-9164(96)00134-8
- ^ Ilemobade, AA, Olanrewaju, OO, & Griffioen, ML. (2013). Greywater reuse for toilet flushing at a university academic and residential building. Water SA, 39(3), 199-210. Retrieved August 01, 2021