Waste water treatment

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Waste water treatment

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  • It is an aeration tank or basin containing a suspension of the wastewater and microorganisms
    The contents of the aeration tank are mixed vigorously by aeration devices which also supply oxygen to the biological suspension.
    Aeration devices commonly used include submerged diffusers that release compressed air and mechanical surface aerators that introduce air by agitating the liquid surface.
    Hydraulic retention time in the aeration tanks usually ranges from 3 to 8 hours but can be higher with high BOD5 wastewaters
    Following the aeration step, the microorganisms are separated from the liquid by sedimentation
    A portion of the biological sludge is recycled to the aeration basin and the remainder is removed from the process
  • A trickling filter or biofilter consists of a basin or tower filled with support media such as stones, plastic shapes, or wooden slats.
    Wastewater is applied over the media
    Microorganisms become attached to the media and form a biological layer or fixed film, to which organic matter diffuses and metabolized.
    Oxygen is normally supplied to the film by the natural flow of air either up or down through the media
    The thickness of the biofilm increases as new organisms grow, and periodically, portions of the film removed off the media
  • Rotating biological contactors (RBCs) are fixed-film reactors similar to bio-filters in that organisms are attached to support media.
    In the case of the RBC, the support media are slowly rotating discs that are partially submerged in flowing wastewater in the reactor
    Oxygen is supplied to the attached biofilm from the air when the film is out of the water and from the liquid when submerged
    oxygen is transferred to the wastewater by surface turbulence created by the discs' rotation.
  • Waste water treatment

    1. 1. Wastewater Treatment Al-Azhar University-Gaza Master Program of Water and Environmental Science
    2. 2. Outline Definitions: Characteristics of wastewaters: The global extent Economic benefits and risks of Wastewater treatment Economic Benefits Economic risks Social and health benefits and risks Environmental benefits and risks Conventional wastewater treatment processes: Preliminary treatment Primary treatment Secondary treatment Tertiary and/or advanced treatment Disinfection
    3. 3. Outline Waste water treatment in the Gaza Strip Wastewater Treatment Plants in the Gaza Strip Beit Lahiya Treatment Plant Sheikh Ajleen Treatment Plant Rafah Treatment Plant Khanyounis Temporary Treatment Plant Nitrate pollution of ground water in Gaza Strip aquifer References
    4. 4. Definition: Waste water: Sewage water is known as the quantities of water used by the human population, whether for domestic or industrial purposes. It contains both dissolved and solid contaminants. It is generally collected in sewers that all together compose the sewage system.
    5. 5. Definition: Wastewater: Urban wastewater is usually a combination of one or more of the following which makes it polluted water: Domestic effluent consisting of blackwater (excreta, urine and faecal sludge, i.e. toilet wastewater) and greywater (kitchen and bathing wastewater) Water from commercial establishments and institutions, including hospitals Industrial effluent where present Storm-water and other urban run-off.
    6. 6. Treated wastewater: Is wastewater that has been processed through a wastewater treatment plant up to certain standards in order to reduce its pollution or health hazard; if this is not fulfilled; the wastewater is considered at best as partially treated. Reclaimed wastewater: or recycled water is treated wastewater that can officially be used under controlled conditions for beneficial purposes such as irrigation
    7. 7. Characteristics of wastewaters: Municipal wastewater is mainly comprised of water (99.9%) together with relatively small concentrations of suspended and dissolved organic (carbohydrates, lignin, fats, soaps, synthetic detergents, proteins…) and inorganic solids Wastewater = clean water supply + solids
    8. 8. Table1:Majour constituents of typical domestic wastewater Constituent Total solids Dissolved solids (TDS)1 Suspended solids Nitrogen (as N) Phosphorus (as P) Chloride1 Alkalinity (as CaCO3) Grease BOD52 Strong 1200 850 350 85 20 100 200 150 300 Concentration, mg/l Medium 700 500 200 40 10 50 100 100 200 Weak 350 250 100 20 6 30 50 50 100 In arid and semi-arid countries, water use is often fairly low and sewage tends to be very strong
    9. 9. Table 2: Average composition of wastewater in Amman, Jordan Constituent Dissolved solids (TDS) Suspended solids Nitrogen (as N) Phosphorus (as P) Alkalinity (as CaCO3) Sulphate (as SO4) BOD5 COD1 TOC1 Concentration mg/l 1170 900 150 25 850 90 770 1830 220
    10. 10. Table 3: Chemical composition of wastewater in Alexandria and Giza , Egypt Constituent EC pH SAR Na2+ Ca2+ Mg K+ ClSO42CO3 HCO3NH4+ NO3 P Mn Cu Alexandria Unit Concentration dS/m 3.10 7.80 9.30 me/l 24.60 me/I 1.50 me/I 3.20 me/I 1.80 me/I 62.00 me/I 35.00 me/I 1.10 me/I 6.60 mg/l 2.50 mg/l 10.10 mg/l 8.50 mg/l 0.20 mg/l 1.10 Unit dS/m mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l Giza Concentration 1.7 7.1 2.8 205 128 96 35 320 138 0.7 0.4
    11. 11. Table 4: Possible levels of pathogens in wastewater Type of pathogen Viruses: Bacteria: Enteroviruses Pathogenic E. coli Salmonella spp. Shigella spp. Vibrio cholerae Protozoa: Helminths: Entamoeba histolytica Ascaris Lumbricoides Hookworms4 Schistosoma mansoni Taenia saginata Trichuris trichiura Possible concentration per litre in municipal wastewater1 5000 ? 7000 7000 `1000 4500 600 32 1 10 120
    12. 12. The global extent Earth contains an estimated 1351 million cubic km of water, Only 0.003 % of this is classified as fresh water. The common needs for water fall into the following categories: Drinking water Agriculture Personal hygiene and public sanitation Domestic uses (food preparation, cleaning, outdoor uses)
    13. 13. The common needs for water  Commerce and services  Industry  Recreation and tourism  Environmental and ecological maintenance, conservation and protection
    14. 14. Table 5: Threshold values used to characterize water stress within a region Characteristic Threshold Water stress <1 700 Chronic water scarcity <1 000 Situation Water Scarcity Index, m3/ capita /yr The region begins to experience water stress and the economy or human health may be harmed The region experiences frequent water supply problems, both short and long-term Absolute water <500 stress The region completes its water supply by desalting seawater, overexploiting aquifers or performing unplanned water reuse Minimum survival level Water supply for domestic and commercial uses is compromised, since the total availability is not enough to fulfil demand for all uses (municipal, agricultural and industrial) <100
    15. 15. Economic benefits and risks of Wastewater treatment Economic Benefits: Serve as a more dependable water source. Enhance urban, rural and coastal landscapes, thereby increasing employment and local economy through tourism Be substituted for freshwater or potable water to meet specific needs and purposes (such as irrigation, toilet flushing, cooling...) Reduction or elimination of fertilizer application. In many applications, treated wastewater reuse is less costly than using freshwater, pumping deep groundwater, importing water, building dams or seawater desalination
    16. 16. Economic risks  The     economic impact of public health epidemics or environmental pollution High distribution and storage costs due to the distance between supply and demand location Weak economic justification when water prices do not cover the true cost. The local market demand for treated wastewater is not clearly defined and agreed Negative branding of treated wastewater reuse by the general public.
    17. 17. Social and health benefits and risks Social and health benefits Helping to achieve Millennium Development Goals (MDG) through increasing water availability and poverty reduction Contributes to food security, better nutrition and sustains agricultural employment for many households Increased quality of life, well being and health through attractive irrigated landscapes in parks and sports facilities in rich and poor communities
    18. 18. Social and health risks  Threat to public health, especially if illegal and unhealthy wastewater reuse practice expands due to water scarcity.  Social tensions in case of non-acceptance:
    19. 19. Environmental benefits  Treated wastewater reuse allows for the conservation and      rational allocation of freshwater resources, particularly in areas under water stress. Reduces the amount of discharges and therefore the level of nutrients or other pollutants entering waterways Provides a mitigation solution to climate change through the reduction in green house gas by using less energy for wastewater management rather than importing water, pumping deep groundwater, seawater desalination or exporting wastewater Reduces the need for chemical fertilizers Sludge can be used as soil conditioners Treated wastewater can be used to recharge aquifers.
    20. 20. Environmental risks  Hazardous or toxic waste and salts from industry can reduce the quality of the wastewater and risk public health  Reused treated wastewater may constitute an additional pressure onto the aquatic environment
    21. 21. Conventional wastewater treatment processes  Conventional wastewater treatment consists of a combination of physical, chemical, and biological processes and operations to remove solids, organic matter and, sometimes, nutrients from wastewater  General terms used to describe different degrees of wastewater treatment are, preliminary, primary, secondary, and tertiary and/or advanced wastewater treatment
    22. 22. Preliminary treatment Preliminary treatment: screening and grit removal to remove coarse solid and other large materials often found in raw wastewater. It includes coarse screening and grit removal.
    23. 23. Primary treatment: Primary treatment: sedimentation – simple settlement of solid material in a primary settling tank. Solid particles settle at the bottom, and oils and greases rise to the top. This material is removed as sludge, for separate treatment. Approximately 25-50% of the incoming BOD5, 50-70% of the total suspended solids (SS), and 65% of the oil and grease are removed during primary treatment Some organic nitrogen, organic phosphorus, and heavy metals associated with solids are also removed during primary sedimentation but colloidal and dissolved constituents are not removed.
    24. 24. Table 6: Quality for raw wastewater and primary effluent at selected treatment plants in California Quality parameters (mg/l, except as otherwise indicated) City of Davis Raw Primary wastewater effluent San Diego Raw Primary wastewater effluent Los Angeles County Joint Plant Raw Primary effluent wastewater BOD5 112 73 184 134 - 204 Total organic carbon 63.8 40.6 64.8 52.3 - - Suspended solids Total nitrogen NH3-N NO-N Org-N Total phosphorus 185 43.4 35.6 0 7.8 - 72 34.7 26.2 0 8.5 7.5 200 21.0 - 109 20.0 10.2 - 219 39.5 14.9 11.2 Ortho-P - 7.5 11.2 pH (unit) Cations: Ca Mg Na K Anions: SO4 7.7 - 7.3 7.3 - - - - - - 78.8 25.6 357 19 359 19 Cl Electrical conductivity, dS/m - - 160 270 - 120 397 2.52 2.34 2.19 Total dissolved solids - - Soluble sodium percentage, % - Sodium adsorption ratio - - - - 8.85 6.8 Boron (B) Alkalinity (CaCO3) - - - - 1.68 322 1.5 332 Hardness (CaCO3) - 829 821 - - - 1404 1406 70.3 265
    25. 25. Secondary treatment  Wastewater from primary treatment flows into an aeration tank, to which micro-organisms are added to consume the remaining organic matter.  Following aeration, the mixture is clarified. The residue is removed as sludge, for separate treatment and disposal.  Several aerobic biological processes are used for secondary treatment differing primarily in the manner in which oxygen is supplied to the microorganisms and in the rate at which organisms metabolize the organic matter.  High-rate biological treatment processes, in combination with primary sedimentation, typically remove 85 % of the BOD5 and SS originally present in the raw wastewater and some of the heavy metals.
    26. 26. Activated Sludge
    27. 27. Trickling Filters
    28. 28. Rotating Biological Contactors
    29. 29. Table7: Quality of secondary effluent at selected wastewater treatment plant in California Quality parameter (mg/I except as otherwise indicated) Plant location Trickling filters Activated sludge Chino Basin MWD (No. 1) Chino Basin MWD (No. 2) Santa Rosa Laguna Montecito Sanitary District BOD5 21 8 - 11 COD - - 27 - 18 25 0.7 - 26 11 19 - 10 8 1.7 12.5 3.4 - 13 1.4 5 7.6 43 12 83 17 55 18 102 20 41 18 94 11 82 33 - 293 85 81 476 2.9 0.7 156 192 143 90 591 3.1 0.6 200 165 66 121 484 3.9 0.6 175 192 245 1.39 940 3.7 0.7 226 Suspended solids Total nitrogen NH3-N NO3-N Org-N Total phosphorus Ortho-P pH (unit) Cations: Ca Mg Na K Anions: HCO3 SO4 Cl Electrical conductivity dS/m Total dissolved solids Sodium adsorption ratio Boron (B) Alkalinity (CaCO3) Total Hardness (CaCO3)
    30. 30. Tertiary and/or advanced treatment  It is employed when specific wastewater constituents which cannot be removed by secondary treatment must be removed  Individual treatment processes are necessary to remove nitrogen, phosphorus, additional suspended solids, refractory organics, heavy metals and dissolved solids  Advanced treatment processes are sometimes combined with primary or secondary treatment
    31. 31. Disinfection  Involves using of chlorine solution injection, ozone and     ultra violet (UV) Chlorine solution is the most common disinfectant used in wastewater treatment The bactericidal effects of chlorine depends on pH, contact time, organic content, and effluent temperature. Dosages of 5-15 mg/l are common, with contact time of 30 minutes To meet advanced wastewater treatment requirements, a chlorine contact time of as long as 120 minutes is sometimes required for specific irrigation uses of reclaimed wastewater
    32. 32. Waste water treatment in Gaza Strip Table 8: waste water networks coverage in Gaza strip governorates Governorate Covering % North % 80 Gaza % 90 Middle Area % 70 Khanyouness % 40 Rafah % 70 The overall ratio wastewater coverage % 70.7
    33. 33. Middle area  There is currently no wastewater treatment plant in this Governorate.  Most raw sewage is collected in a concrete pipe through Salah Aldeen Road and slopes to Wadi Gaza, and then flows to the sea.  The flow rate of untreated sewage into the sea is about 10,000 m3/day.
    34. 34. Wastewater Treatment Plants in the Gaza Strip  The quantity of wastewater produced in Gaza strip is more than 30 million cubic meter per year. The BOD5 level is about 600 mg/l, which means that the wastewater in Gaza Strip is strong, and that due to the low portion of fresh water for citizens (70-90 liters per capita / day).  In the Gaza Strip, there are three main treatment plants and one temporary plant for collecting and treating wastewater  The current treatment plants still do not meet the standards of treating wastewater in Gaza
    35. 35. Beit Lahiya wastewater treatment plant  Beit Lahiya treatment plant was established in 1974 by the Israeli Civil Administration in the town of Beit Lahiya in the northern area of the Gaza Strip  The aim behind the plant establishment was to re-use the treated wastewater for agricultural purposes but this aim was not achieved  Current inflows to the plant are greater than 17,000 m3/day, beyond plant capacity  The partially treated wastewater is pumped to the northern and eastern infiltration lagoons in the same governorate.
    36. 36. Sheikh Ajleen Treatment Plant  The plant was established in 1979 with an infiltration basin next      to it In 1986 the (UNDP) established another two infiltration basin to develop the plant. In1996 the Municipality of Gaza and UNRWA developed it in order to recharge 12,000 cubic meters per day. In 1998 the plant was rehabilitated and its capacity was enlarged to recharge 35,000 cubic meters per day. In 2009 the water pumped to the plant increased to 60,000 cubic meters per day and this exceeds the plant capacity After the year 2005 many people seized the plant infiltration basins and turned them into agricultural lands, thus the semitreated WW was pumped to the sea
    37. 37. Rafah Treatment Plant  Rafah treatment plant was established in 1989 near in Tel Al     Sultan in the western of Rafah It consists of a lagoon with four aerators The capacity of the treatment plant is 4,000 cubic meters only per day. the current flow is up to 8,500 m3/day The treatment of the plant is inadequate (effluent characteristics are BOD 300ppm, COD 550ppm, and TSS 250ppm) virtually untreated sewage is being discharged to the sea
    38. 38. Khanyounis Temporary Treatment Plant  In late 2007, CMWU gradually established wastewater lagoons     in Almawassi area where the last one was established in early 2009 Those lagoons were established to pump the water from Hai ElAmal lagoons Hai El-Amal lagoons were established in year 2003 to collect and infiltrate storm water of khanyounis, but due to the frequent closure and the Israeli harassments during the establishment of project the project was suspended deteriorated infrastructure changed the lagoons into an outlet for the wastewater pumped from the whole district The current flow rate is about 5,000 m3/day
    39. 39. Nitrate pollution of ground water in the Gaza Strip aquifer  The groundwater aquifer of Gaza is extremely susceptible to surface-derived contamination because of the high permeability of sands and gravels that compose the soil profile of Gaza.  Almost 90% of the groundwater wells of the Gaza Strip sampled between 2001 and 2007 showed NO3 – concentrations two to eight times higher than the WHO standards.  NO3 − in the groundwater of the Gaza Strip occurred as a result of NO3 − leaching from irrigation, wastewater septic tanks, sewage sludge, animal manure and synthetic fertilizers.
    40. 40. Nitrate pollution of ground water  Recent observations revealed a high positive correlation between the concentrations of NO3 − (N80 mg/l) in groundwater of the Gaza Strip and the occurrence of methemoglobinemia in babies younger than six months of age  Among 640 babies tested in Gaza, 50% showed signs of methemoglobinemia in their blood samples.
    41. 41. References 1. 2. 3. 4. 5. Abdel Fattah N. Abd Rabou .2011. Environmental Impacts Associated with the Beit Lahia Wastewater Treatment Plant, North Gaza Strip, Palestine: Middle-East Journal of Scientific Research 7 (5): 746-757, 2011. ISSN 1990-9233 B. H. Shomar, G. Muller, and A. Yahya, “Potential use of treated wastewater and sludge in the agricultural sector of the Gaza Strip”, Clean Techn Environ Policy, Vol. 6, 2004. Baalousha H (2008) Analysis of nitrate occurrence and distribution in groundwater in the Gaza Strip using major ion chemistry. Global NEST J 10:337–349 Basem Shomara, Karsten Osenbrückb and Alfred Yahyaa. (2008). Elevated nitrate levels in the groundwater of the Gaza Strip: Distribution and sources. SCIENCE OF THE TOTAL ENVIRONMENT 398 164–174. CMWU, 2010,Annual Report on Water Status in the Gaza Strip,
    42. 42. References 6. 7. 8. FAO (1992) Wastewater treatment and use in agriculture - FAO irrigation and drainage paper 47. FAO, Rome. Fareed Ashour1, Bashar Ashour2, Marek Komarzynski3, Yasser Nassar4, Mary Kudla5, Najla Shawa6 and Graham Henderson6 , 2009, A brief outline of the sewage infrastructure and public health risks in the Gaza Strip for the World Health Organisation. The Economics of Wastewater Use in Agriculture. In: FAO Water Reports, 35/ FAO, James Winpenny, et,al. (2010). Rome, Italy, Electronic Publishing Policy and Support Branch Communication Division. (ISBN: 978-92-5106578-5, ISSN: 1020-1203).
    43. 43.  mrbakr1991@gmail.com

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