Literature Review
In the decentralized sanitation projects that are characterized by low-cost, much focus is put on the construction of toilet. This is very common in the developed countries. Such projects end to ignore the issue of grey water completely. It is important to note that comprehensive and sustainable management systems for sanitation with dry toilet are not achievable if the problem of grey water is not properly sorted out( Burian and Pomeroy 2010).
The consequences of doing that include negative impacts to the public health and the environment at large. The activities of the proper management of greywater include a collection of the grey water treatment and possible reuse if not disposal. Prevention of possible human contact with this water potentially limits or reduces the transfer of pathogens. Proper treatment of the grey water impacts the adjacent water bodies positively since it reduces the infiltration of nutrients that possibly facilitates the process of eutrophication.
Greywater extracts its definition from the cloudy appearance that it possesses. Also, this color is attributed to its characteristics of being found in between the fresh portable whitewater that is known to be white incur and also sewage water that is characterized with black color. The grey water is that wastes water from the showers, washbasins, kitchen, sinks and also washing machines. The issue of the management of the grey water has obtained several definitions. This is because wastewater excluding toilet wastes water is gaining use in most of the developed countries.
In these countries, the improper use of the wastewater is considered to be one of the many causes of the environmental pollution and also killer diseases. In the modern set up, there has been recognized that proper use of the grey water can actually lead to the creation of very potential water sources. This mission can only be achieved in the cases where very high technology is supported by legal frameworks.
The kitchen water is not normally recommended for applications as grey water., however, do not include wastewater from the urinals, toilets or bidets. This is basically called black water. The grey water can be collected from all these sources and then used for other activities such as flushing of the toilets and garden watering that do not require drinking quality of water (Boyjo,Pareek and 2013). . There is the scarcity of scientific knowledge in regard to characteristics of grey water and also perfect systems of treatment that will allow for proper disposal and reuse of the grey water. The main purpose of this project is to highlight some of the existing treatment methods, classes of grey water and also uses of the grey water especially in the sector of agriculture for irrigation.
The post treatment of waste water is also known as the secondary water treatement.These operations normally follow after the primary water treatment has been done. They seek to improve the quality of the water to meet specific requirements for particular uses. The activities are broadly grouped into two steps.
The major reason of this particular technique is simply to facilitate the removal of smaller particles and fibers to protect the possible infiltration of the pipes after major treatment. These particles may clog the pipes when they are not properly checked. The system transfers the water as soon as possible to the systems that assist in the removal of both macro and microorganisms. The stretch filters are meant to retain those large particles and fibers and also permits the large particles to move to the next level of treatment.
Methodology and Discussions
The filter system is best suited for public facilities in which the primary source of the waste is handwashing.The water is known to lack food particles. If this kind of filter is used to filter the water particles that have food particles that will accumulate and become anaerobic and effluent malodorous. This kind of treatment results in grey bucket grey water and also grey water from diversion devices.
In the cases where a significant quantity of food wastewater finds its way into the system from the places such as dishwashers and kitchen sink, this particular option is strongly recommended. The installation of this system involves operations that are almost similar to those of the traditional methods . The treated effluent, however, does not pollute the environment is of better quality as opposed to the ancient one (Fortier 2010).
Figure1 post treatment of water extracted from (Fortier 2010).
The set upon consist of three stage septic tank that is meant to separate the grease from the effluent. The separated sludge can then be removed frequently .This can be done after every fourth year as opposed to what used to be bi-yearly in the past. The outgoing effluent is considered anaerobic. The final stage is leading to the purified water that is almost near the portable quality. This option is considered one of the most defective and also simple to maintain processes. This kind of treatment results in the generation of grey water into the GTS
|
CLASS |
Quality objectives of water |
Process of treatment |
Agricultural uses |
Industrial uses |
|
A |
Accepted PH of 6-9;Protozoa reduction of 6-log,10 Ecoli of quantity 100mL |
Pathogen reduction through tertiary treatement.Also enough log reduction that give required parameters of bacterial level |
Drinking water for livestocks.Fodder supply to dairy cattle Road construction Raw food crops for human beings that are exposed directly to recycled water e.g. tomatoes. |
Road construction Residential uses e.g. for washing machines Industrial system that is open. Public access that is unrestricted like golf courses. |
|
B |
100Ecoli/100mL PH range of 6-9 20mg/LBOD 30mg/L of suspended particles of solid matter. |
Pathogen reduction through secondary treatment |
Drinking water a part from the pigs, grazing fodder for the dairy cattle, grazing and fodder supply for goats, sheep and cattle Processed food for human or those chosen crops that are not exposed to recycled water directly |
Used in the closed system of industries Construction of roads Public areas that are restricted like facilities of sports |
|
C |
PH range of 6-9 30mg/L of suspended solids 1000Ecoli/100mL |
Pathogen reduction through secondary treatment |
Cooked human food Fodder supply and grazing of goats, horses etc. |
Construction of roads Closed systems of industries |
|
D |
10000Ecoli/1oomL PH of 6-9 30mg/L |
Secondary treatment |
Nonfood crops like woodlots and flowers |
N/A |
This kind of grey water is considered easily accessible. It can be siphoned and distributed using buckets before it is allowed to go down the drain. Such activities may include collecting of the water used in the washing of the machine or from the sink. In most of the cases, there is no approval required to use this class of grey water. This water can be used for irrigation of the gardens, toilet flashings and also washing of the parts of the machine (Keely et al 2015).
The bucketing of such water is considered low risk since the activity involves the use of the low volume of water that has been spread to different locations. The contamination of soil.is expected to be as minimal as possible and also the runoff experienced is very minimal. It is commonly known as kitchen waste water or grey water. It constitutes 15% of the total grey water.
It is also called laundry grey water. It constitutes 30% of the total grey water. This device is known to divert or directs grey water from a known waste pipe that may originate from the shower or laundry to the garden and used for sub-surface irrigation. This water cannot be used to support any other activity. There is no special treatment for this water apart from filtering of the larger particles that could potentially clog the pipes over time. In addition, there are no provisions for the storage systems for such wastewater. This device has a system of valve that diverts this grey water to a sewer in case the system is closed either permanently or temporarily.
Post-Treatment of Greywater
Most of the pumped systems come with different sizes that are basically designed for single fixture use.They are mounted on a wall at a position that is slightly raised with 50mm inlet and the entire underground fitted with pipes of 100mm diameter (Ravinia et al 2017).
It is also known as bathroom grey water in some cases. This is another step up in the complexity from a system of diversion. Apart from just filtering the bits that are considered lumpy, the system improves the quality of grey water that originates from the showers, baths, and even laundry. This water is treated to a level that it can be used for irrigation purposes or in the toilet. The disinfected grey water from the GTS is then pumped into a second tank for storage purposes. This water can be drained from the storage tank and then used for flushing toilets. This water constitutes 50% of the grey water. This clearly shows that the number of people bathing is very many.
Grey water can be used even in the untreated state, or it can undergo the process of treatment of varying degrees depending on the intended purpose. The treatment processes are meant to reduce the level of disease-causing organisms. The recycled water is used for the industrial purposes that include public parks, landscapes and also golf course irrigation. Other non-potable applications include the industrial processes and oil refineries ,cooling of power plants etc.
Figure1 cooling plants using recycled grey water from (Ravinia et al 2017).
The industrial processes like water mills and carpet dyes, concrete mixing, toilet flushing all utilize greywater that has been recycled (Sing et al 2016). The level of odor in the treated water must be as low as possible. This water should be generally fit for the other intended purpose or use. The water should be clear with much-reduced torpidity ( Jang et al 2014).
Figure 2 irrigation using recycled grey water extracted from (World Health Organization 2015).
In the arid and semi-arid places, the gray water that has been recycled is used to support agricultural activities through irrigation. In most of the large water treatment plants, the requirements and the composition of treated water is strongly regulated by the country authorities. These standards however must conform to the health standards that have been set aside by the health sectors before they are used for agricultural purposes.
Drinking water is treated under very stringent conditions. Although researchers have pointed out the present of micro plastics in the bottled water, their consequences have remained to be very minimal.
Treated grey water that has been recycled is used in other activities like washing, bathing among others.
Conclusion
The management of the grey water should not only be viewed as a pre-condition for healthy and clean living conditions but also as a potential means of getting wastewater reused. The treated water in the decentralized places is used for different operations in the whole world. In the recent years, there has been the emergence of the use of the treated greywater for agricultural purposes. This practice is common, especially in the semiarid places (World Health Organization 2015).
The practice can be attributed to the fact that there has been a scarcity of water in these places for irrigation, the high cost of the artificial fertilizer, so the grey water is seen to possess some traces of manure, the high cost of the treatment of water among other factors
References
Boyjoo, Y., Pareek, V.K. and Ang, M., 2013. A review of greywater characteristics and treatment processes. Water Science and Technology, 67(7), pp.1403-1424.
Burian, S.J. and Pomeroy, C.A., 2010. Urban impacts on the water cycle and potential green infrastructure implications. Urban ecosystem ecology, (urban ecosystem), pp.277-296.
Fortier, P.A., 2010. Detecting and estimating rectification of gap junction conductance based on simulations of dual-cell recordings from a pair and a network of coupled cells. Journal of theoretical biology, 265(2), pp.104-114.
Jang, H.M., Cho, H.U., Park, S.K., Ha, J.H. and Park, J.M., 2014. Influence of thermophilic aerobic digestion as a sludge pre-treatment and solids retention time of mesophilic anaerobic digestion on the methane production, sludge digestion and microbial communities in a sequential digestion process. Water Research, 48, pp.1-14.
Keely, S.P., Brinkman, N.E., Zimmerman, B.D., Wendell, D., Ekeren, K.M., De Long, S.K., Sharvelle, S. and Garland, J.L., 2015. Characterization of the relative importance of human?and infrastructure?associated bacteria in grey water: a case study. Journal of applied microbiology, 119(1), pp.289-301.
Ravinia, R., Girotto, F., Peng, W., Cossu, R., Pivato, A., Raga, R. and Lavagnolo, M.C., 2017. Effect of aerobic pre-treatment on hydrogen and methane production in a two-stage anaerobic digestion process using food waste with different compositions. Waste management, 59, pp.194-199.
Sing, D.K., Fortney, J.J., Nikolov, N., Wakeford, H.R., Kataria, T., Evans, T.M., Aigrain, S., Ballester, G.E., Burrows, A.S., Deming, D. and Désert, J.M., 2016. A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion. Nature, 529(7584), p.59.
World Health Organization, 2015. Sanitation Safety Planning: Manual for Safe Use and Disposal of Wastewater Greywater and Excreta. World Health Organization.
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