Chapter 3 Decision Support Model (IUWS-DSM) - Tubdok

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Chapter 2 · New Conception 21 Three most popular disinfection methods are enumerated in Table 6 with short specification. Other treatment methods and trains have the function of disinfection too, such as potassium permanganate, air stripping, activated carbon and membrane processes, etc. (Hazen and Sawyer 1992), which are not involved, as selecting disinfection methods is not the main task of planning IUWS in the early project phase, and also because other methods are not often used or considered as disinfection options. Table 6: Summation of common disinfection methods no. methods specification 1 chlorination 2 ozone inactivation of pathogens and bacteria of concern for human health, control of biological growth in distribution system -advantages: applicable to large facilities, low energy intensive; can maintain a residual level in distribution system -disadvantages: not effective for Giardia and Crypto; formation of DBP; pH dependent oxidation of organic and inorganic matter and disinfection -advantages: kills Giardia and Crypto; Applicable for large facilities; used as oxidant -disadvantages: needs skilful operation; possibility of producing DBP 3 UV light for disinfections of small facilities -advantages: no produce halogenated organics or inorganic by-products -disadvantages: not effective for Giardia and Crypto; not lasted effects; not convenient for large facilities Adapted from Río González (2007) Abbreviation: DBP – disinfection by-products Solids/sludge treatment is quite complicated, especially the sludge from WWTP. Due to the same reason, only the general treatments methods are involved and simplified into several steps (Table 7). The treatment processes of solids/sludge from waterworks and WWTP are listed parallel, so that a comparison can be easily made. Concerning blackwater, so far the often considered treatment process in cities is the anaerobic digestion. Figure 10 is a schema of typical blackwater treatment process. In order to guarantee the treatment efficiency, the toilet flushing water entering the digesters has to be as little as possible. Therefore, the vacuum sewerage is compulsory. As one type of the collection systems, the vacuum toilets are discussed in the next section. Meanwhile, the kitchen refuse can be added into digesters in order to enhance the process and simultaneously generate more biogas, which also means that more energy is recovered. As a relative new concept, the blackwater systems have not been practised in large scales in cities, although some pilot projects are taking place in Europe and Asia (Wendland 2008). In urban area, blackwater system can be quite expensive due to the complexity of the process control, the strict reaction conditions and very importantly, the safety reasons.
22 New Conception and Decision Support Model for IUWS Table 7: Classification of solids/sludge treatment steps treatment step seq. unit process included conditioning 1 -physical -chemical thickening 2 -natural -gravity per. [%] seq. unit process included from waterworks from WWTP per. [%] [1] (as the third step) -- 8 ~ 25 1 -settling, gravity, flotation -centrifuge, gravity belt, rotary drum stabilisation (not involved) -- 2 -lime, anaerobic digestion -aerobic digestion conditioning (as the first step) -- 3 -chemical -others dewatering 3 -centrifuge -mechanic filter (Heat) drying thermal reduction 4 -natural -thermal 35 ~ 60 >35 ~ 60 4 -centrifuge, filter press -drying beds, reed bed 5 -(in)direct dryer, -composting, long-term storage, pasteurisation (not involved) -- 6 -incinerator -- Summarised based on AWWA & ASCE (1998), Metcalf & Eddy (2003), and Río González (2007) Abbreviations: seq. – sequence; per. – percent dry solids [1] it improves the ability of thickening or dewatering. [2] it has the function of mass reduction (i.e. with digestion). Flow Schema of Typical Blackwater Treatment Blackwater Anaerobic/ biogas reactor Methane reactor Micropore filter Energy (back to grid) UV radiation /Ozone Clean pathogen-free water Figure 10: Flow schema of typical blackwater treatment (redrawn based on IAP 1 ) 1 Indoor Agriculture Products (accessed 08.2008), http://www.verticalfarm.com/plans-2k3.htm CO2 3 ~ 6 [2] [1] 60 ~ 90 >60 ~ 90
Page 2 and 3: New Conception and Decision Support
Page 4 and 5: Acknowledgements By this chance, I
Page 6 and 7: Contents Indices I TABLES .........
Page 8 and 9: Indices III 3.6 Realisation Method
Page 10 and 11: Indices V Table 32: Sheet of averag
Page 12 and 13: Indices VII Figure 31: Cost estimat
Page 14 and 15: Definitions term definition & expla
Page 16: Abstract Indices XI Traditionally,
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Page 28 and 29: Composition of Modern Urban Water S
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Page 36 and 37: Classifcation of Urban Water Treatm
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WUU WUC type area [ha] popul. [capi
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Chapter 3 Decision Support Model (IUWS-DSM) - Tubdok

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