Department of Civil Engineering
ENCE 411: Seminar in Civil Engineering
SEPARATE COLLECTION AND TREATMENT OF DOMESTIC WASTEWATER
Prepared by: Aya salah hamayel ,1160111 Supervised by: Farhat Majadbeh
Date of submission:12-10-2019
Approximately 844 million humans are lacking the access to water, and about 300,000 children die from diseases related to unclean water and weak sanitation ,this leads to the reason of why waste water should be treated and more importantly and specifically why domestic waste water should be separated and this article will discuss this matter.
Domestic wastewater is water that comes from human actions in the household , composed of two important parts : one is the grey water which comes from sinks such as kitchen sinks ; washing dishes .washing machines , bathtubs and showers ,and this water is contaminated ,however it does not contain sewage ,but may contain chemicals, and it represents 50-70% of the domestic waste water. And the second one is the black water which comes from toilets and it has pathogens , feces , urine , and flush water , it contains sewage and its also contaminated and requires sophisticated processing and treatment to be used again , however its rich in organic materials because its associated with food processing
From the definition above, grey water looks like something reusable compared to black water and in fact Grey water may be used to water gardens if its either treated simply or if its not stored for more than 24 hours ; leaving grey water for a few days untreated makes it behave like a total sewage .
So the question to be asked in wastewater treatment whether separating grey water streams from black water streams is vital and should be taken into consideration?
To answer this question , the importance of separating and treating wastewater shall be discussed , as said before domestic wastewater plays an important role in our lives , insuring that the sewage is probably treated is very vital , ,and the most important reason is, in order to insure that the water is safe , free of contaminates that include disease-causing living creatures such as bacteria , viruses , chemicals and pathogens that can harm the health of humans , animals, and plants. In other words, retaining peoples health and saving our planet of pollutants, because, it has been shown that water pollution may result in many natural phenomena that cause damage, including global warming and the damage of ozone layer, moreover it can affect the biodiversity and limit it ; treating wastewater helps some living creatures though creating the perfect environment for it, so that these creatures could live in the treated water such as worms , spiders and reptiles and more .
Other important uses of waste water is agriculture use ,in irrigation of crops ;grey water may be used in watering gardens specially if there is a separation system that connects directly to gardens or other plants ,or on a higher scale watering harvests ,it is safe to use ,also beneficial as a source of nutrients and is also considered as a valuable fertilizer ,and of course after treating black water it shall act as a fertilizer too for the plants .
Additionally, Separating domestic wastewater and using grey water or treated grey water in concrete and mortar mixes showed ,according to ASTM/ the American Society for Testing and Materials that there is no major impact on the compressive strength , using them caused a rise in the setting time and a reduction in the slump test rate ,while the compressive strength of both the concrete and the mortar of the 7 days curing showed an increase using treated grey water while it showed a slightly negative effect using the raw grey water therefore, separating the domestic waste water gives the opportunity to this advantage which helps and leads into saving major amounts of drinkable water.
In general treating wastewater can be a source of providing drinking water after many treatments or easily when separating grey from black water , grey water is treated more easily to produce drinking water which helps in saving water in general and also saving water by reusing grey water in flushing water. Another treated grey water use or treated waste water in general is in central cooling , many industrial establishments are able to use wastewater in the central refrigeration units for example the Emirates , and in the future ,demand is expected to increase in this aspect.
This article will discuss three major topics ,separation and treatment process(mechanical method) ,urine separation system , and thirdly a case study on Norway(biological method) and lastly Palestine perspective on separation (primary treatment) .
How domestic wastewater is treated separately:
There are lots of method that are used to treat the separated wastewater varying from low cost treatment methods to high expensive secondary treatments producing high standard sterilized grey water (mechanical systems) and this method works as following :
Figure SEQ Figure * ARABIC 1: A mechanical system that treats wastewater ,CITATION GRE15 l 1033 (jenssen p. , 2015) Firstly, the wastewater system for example in the building should be initially designed to completely separate the grey water ducts from the black water ducts A drainage station is installed between the two systems to convert gray water to black water (not the other way round), for use when gray water is over-needed or when the water treatment system is being repaired, after that the grey water is collected in a tank to isolate the impurities from the water like oil, or soap, or others , after that it gets rid of these impurities by opening a trap in the lower part of the tank to be thrown into the black water framework.
Secondly ,The grey water gets carried by pumps from the collection tank to get to the filters, and water passes through sorts of filters, the first contains sand to remove remaining rigid impurities, and the second one contains active carbon (to get rid of any organic material if there is) . These filters are automatically cleaned to remove the plankton (Backwash Process) , after that some grey water treatment chemicals such as hypochlorite are also injected to sterilize water and kill pathogens , other chemicals are also added to neutralize the water (acidic )and to get rid of any unwanted smell. Water is also passed through an ultraviolet (UV) device to get rid of any residue of pathogens and bacteria, then water goes through the final microfilter to ensure there are no hair stuck or planktons.
Thirdly ,after the last stage, grey water becomes useable . The water from the former stage is collected in the production tank, after that it is carried to the upper tank using a lift pump, to be used again by distributing it to all the siphon boxes and bidets in the toilets, or to be used for irrigating gardens, washing cars or floors. And Regarding the black water, it is given some time to settle down and a primary habitation of bacteria works for an entire day , biting down the thick chunks ,then the settling black water is followed up to a secondary treatment tank that is divided to three isolated and separate chambers which are Aeration chamber, Sludge settling chamber and finally the Irrigation chamber. The water produced from black water treatment should never be utilized as drinking water or on irrigation of crops since they could contain hurtful microorganisms. It may be utilized for watering yards or non-food gardens.
Waterless System with Urine separation:
Urine-Diverting Dry Toilet (UDDT), enables Urine and Feces to be independently gathered , in other words it isolates the urine from the feces ,the feces gets dried out as well as using the urine for valuable use.
Lack of hydration Vaults are utilized for the Collection and Treatment of Feces . firstly when putting away the Feces in vaults, they should be dry as possible, to motivate the hydration or even the hygienization ,and care ought to be considered to guarantee that no amount of water is presented. As for the Anal cleansing water it must not be placed into the dehydration feces Vaults, instead it should be redirected to a Soaking Pit, aslo its very vital that there should be a stable supply of ash or lime or soil or sawdust in order to cover the Feces. Which assists in absorbing humidity , limit scents, blocks the Feces from potential vectors (flies) and also If either of the ash or the lime are utilized, the pH will rise which helps in killing pathogenic creatures . on the other hand ,Urine Storage Tank are utilized, Urine can be redirected straightforwardly to the ground through an Irrigation because its nearly sterile with a law risk ratio ,thanks to its nutrient-rich content ;it acts as a good fertilizer. The Treated feces should be stored for at least six months if the ash or the lime are utilized and after that it could be used as fertilizier for the soil .
Figure SEQ Figure * ARABIC 2 : A urine diverting toilet , CITATION Bea19 l 1033 (Stauffer, 2019) Figure SEQ Figure * ARABIC 3: illustration on how diverting toilets work, (Elizabeth Tilley, 2008)
There are some consideration for the system ;the system can be utilized in any place , yet is particularly fitting for rocky zones where digging soaks pits is somewhat hard or if there is a sort of high groundwater table or , water rare-districts ,in addition , hot and dry atmosphere areas helps in quicker drying of the feces . It should be added that human power is required for the transport of the dry feces because the material that is expelled is safe ,Offers a high hygiene level, lowers the water pollution ,kill smells ,it doesnt catch flies ,No water gone to waste ,Produces excellent fertilizer ,and it has low construction cost
Norway case study (Biological systems treatment):
Norway constructed a system that separates waste water and treats it ,in two stations kaja and Torvetua, and for both grey water and black water , the main objectives were saving water ,saving huge amounts of energy that are usually consumed on the traditional treatments of wastewater .furthermore recycle nutrients ; Wastewater consists of organic matter ,and the three main vital nutrients for plant creation are nitrogen, phosphorus and potassium. Hypothetically, the nutrients in domestic wastewater and organic material that comes from the household waste are about adequate to make enough food for all of the world population, and also to have a positive impact on the environment and the health of the living creatures. for the grey water system ,the system is called bio and wetland filter , a constructed wetland system is a system that uses biological process to treat water but needs big areas , it consists of three layers , the first one is an impermeable layer such as clay which prevents the infiltration of the waste down, secondly a gravel layer defined as the zone that gives nutrients and backing for the root zone usually (reed) and some systems are built with a grass cover , reed has a positive effect on the Nitrogen removal because, and the last layer is an above-surface vegetation zone .The general concept consists of pre-treatment of the wastewater in a septic tank, pumping to a vertical down-flow single pass aerobic bio filter followed by a subsurface horizontal-flow porous media filter CITATION Pau06 l 1033 (Telkamp, 2006)
Figure SEQ Figure * ARABIC 4: advanced grey water treatment illustration , CITATION jam15 l 1033 (constucted wetlands, 2015)The bio filter ,as shown in figure 5, in the constructed bio wetland filter is a method of controlling contamination by using living materials such as bacteria or algae that phase out pollutants and biologically decomposes it. It contains of non-corroding matter like plastic or fiberglass, ceramic or rock which has huge amounts of bacteria cells its also wrapped with a dome which helps in spraying the grey water across the bio filter surface. On the other hand the black water is separated and treated using systems such as the urine diverting toilets.
Figure SEQ Figure * ARABIC 5: grey water treatment in Norway , CITATION Pau06 l 1033 (Telkamp, 2006)In my opinion ,the fate of separating wastewater depends on the awareness of people although wastewater plays a huge role in our lives but not all people know the importance of separating it and the huge positive impact it has ,and most importantly how it may affect our lives especially at the moment where the environmental situation is going downhill . Regarding the separation of wastewater in Palestine , it may be hard ,particularly that we dont have control over water resources but on a smaller range the idea may work , it can be used in schools especially the diverting toilets or in universities and that alone would help in reducing the water consumption in general , with only a bit of easy instructions ,furthermore the separation of both grey and black water could be applied on newly built cities or even newly build building or houses ,for example a project (a house) in Ein sena palestine that is currently being built is separating the water that comes from sinks from the bathroom water with a little non-chemical treatment (primary treatment),as shown in figure 6 and figure 7 ,the resultant water will be piped to irrigate the garden, this idea was also done in beit reema-palestine and it works effectively .
Figure SEQ Figure * ARABIC 6: primary grey water treatment, CITATION pet04 l 1033 (jenssen, 2004)
Figure SEQ Figure * ARABIC 7: primary treatment in Ein senia palestine
To sum up ,in order to develop into a maintainable healthy society we need to recycle nutrients, reduce the overall water consumption, and limit the energy needed on waste treatments and all of this may be accomplished through the separation of wastewater even if it was on a small range .
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