Microsoft PowerPoint - L12_Flowrate & loading

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2 Wastewater management infrastructure Consumer wastewater collection system (sewer pipeline + pumping stations if needed) wastewater treatment facility outfall to river or ocean Sewer system Combined sewer: collects sanitary sewage and stormwater runoff in a single pipe system Separate sewer: collects sanitary sewage and stormwater runoff separately 2

Combined vs. separate sewer system http://www.

org Wastewater and stormwater treatment systems

3 Combined vs. separate sewer system Wastewater and stormwater treatment systems Wastewater treatment facility Combined sewer overflow treatment facility Stormwater treatment systems 3

4 1) Domestic wastewater: Wastewater discharged from residences and from commercial, institutional, and similar facilities. 2) Industrial wastewater: Wastewater in which industrial wastes predominate. 3) Infiltration/inflow (I/I): Water that enters the collection system through indirect and direct means. Infiltration is extraneous water that enters the collection system through leaking joints, cracks, and breaks, or porous walls. Inflow is stormwater that enters the collection system from inappropriate connections. 4) Stormwater: Runoff resulting from rainfall and snowmelt. Sanitary sewer of separate system: 1) + 2) + 3) Combined sewer: all of above 4

the late morning Second peak in the early evening * note

5 Daily variations For relatively small collection systems: Minimum flow during the early morning hours First peak in the late morning Second peak in the early evening * note the lag time for wastewater to reach the treatment plant 5

6 Seasonal variations Different seasonal patterns for different locations due to weather patterns (temp. and precipitation), specific activities (e.g., college campuses, ski resorts), etc. Generally high flowrate in the summer and low flow rate in the winter in Korea Peaking factor: comparing the peak flowrates to average values,,, 6

7 Max. day of the year Average day of the year Wastewater flowrate PF day = Q max hour /Q avg hour Wastewater flowrate PF day = Q max hour /Q avg hour PF season = Q avg hour,max day /Q avg hour,avg day 0 AM 6AM 12 PM 6 PM 0 AM Hour of the day 0 AM 6AM 12 PM 6 PM 0 AM Hour of the day 7

8 Constituents discharged by individuals Per capita mass constituent discharges: used as background data to design wastewater treatment systems [Per capita waste discharges in the U.S.] unit: g/capita/d Constituent Range Typical without ground up kitchen waste Typical with ground up kitchen waste BOD COD TSS NH 3 as N Organic N as N Total P as P Potassium, K Oil and grease

9 [Per capita waste discharges for various countries] unit: g/capita/d Country BOD TSS TKN Total P Brazil Denmark Egypt Germany Greece ND ND India ND ND ND Italy Japan ND Palestine Sweden Turkey Uganda United States Korea* *2011 Seoul, selected value for sewer system masterplan 9

10 Q: Estimate the BOD, TSS, and ammonia nitrogen concentrations for the Gaza Strip assuming the wastewater flowrate of 60 L/capita d. Use following average per capita discharge for the constituents: BOD = 50 g/capita/d TSS = 62 g/capita/d NH 3 N = 4 g/capita/d 10

11 [Typical unit loading factors and expected wastewater constituent concentrations from individual residences in the U.S.] Constituent Typical value, g/capita/d Concentration, mg/l Volume, L/capita/d BOD COD TSS NH 3 as N Organic N as N TKN as N Total P as P Potassium Oil and grease

12 Determination of constituent mass loading rates and concentrations for wastewater treatment facilities: Mass loading rates (e.g., in kg constituent/d) Use per capita mass discharge and predicted population to obtain mass loading by residential sources Add mass loadings by commercial, institutional, and industrial sources Wastewater flow rates (e.g., in m 3 /d) Use per capita wastewater discharge and predicted population to obtain wastewater flow discharge by residential sources Add flow discharge by commercial, institutional, and industrial sources Add infiltration/inflow and stormwater (stormwater for combined sewer only) Constituent concentrations (e.g., in mg/l) = (Mass loading rate) / (Wastewater flow rate) Consider daily/seasonal variations of mass loading & conc. 12

13 Daily variations in constituent concentrations Seasonal variations For domestic sources, the concentration may not change significantly (but mass loading & flowrate may change significantly (e.g., for resorts)) Infiltration/Inflow may result in seasonal variations of constituent concentration High I/I in rainy seasons lower concentrations of BOD, TSS, etc. High seasonal concentration variations for combined sewers Lower concentrations of BOD, TSS, etc. during storm events 13

14 Objective: dampen flowrate variations to i) overcome the operational problems caused by flowrate variations ii) improve the performance of the downstream processes iii) reduce the size and cost of downstream treatment facilities 14

15 Method of application: in line or off line In line: can achieve dampening of constituent concentration in addition to the dampening of flowrate Off line: pumping requirements are minimized [In line] [Off line] 15

16 Benefits Biological treatment is enhanced because shock loadings are eliminated or minimized, inhibiting substances can be diluted, and ph can be stabilized The effluent quality and thickening performance of secondary sedimentation tanks is improved through improved consistency in solids loading Effluent filtration surface area requirements are reduced, filter performance is improved, and more uniform filter backwash cycles are possible by lower hydraulic loading In chemical treatment, dampening of mass loading improves chemical feed control and process reliability 16

17 Drawbacks Relatively large land areas are needed Equalization facilities may have to be covered for odor control Additional operation and maintenance is required Capital cost is increased 17

18 Volume requirements for the equalization basin Cumulative inflow volume Average daily flowrate Inflow mass diagram Required equalization volume In practice, the equalization basin volume will be larger than the theoretical value for several reasons Draw Fill Midnight Noon Midnight Time of day 18

19 하수도시설기준 (2011 개정 ) 하수도계획의절차 19

20 계획목표년도 (design lifetime) 의설정 고려사항 구조물과기계설비의내구년수 확장공사의난이도 도시의산업발전과인구증가율에대한전망 경제적요인 : 예산, 건설비, 화폐가치의변동, 하수도수입의연차별예상등 하수관로등비교적증설이어려운시설의경우장기간을, 하수처리장기계설비등비교적변경이용이한시설의경우단기간을설정 우리나라의경우, 하수도계획의목표년도는 20년을원칙으로함 계획구역 (drainage area) 의결정 원칙적으로관할행정구역전체를대상으로함 행정구역에지나치게구애됨없이분수령등자연조건과장래도시계획등을고려할필요 20

21 계획인구수 (design population) 의추정 연평균증가수에의한방법, 연평균증가율에의한방법, 지수함수곡선식에의한방법, Logistic 곡선식에의한방법등다양한수학적모델중가장잘부합하는방법선정 [ 예 ] 연평균증가율에의한방법 ( 등비급수법 ) 1 : 현재로부터 년후의추정인구수 : 현재인구수 : 설계기간 (year) : 연평균인구증가율 / / 1 : 현재로부터 년전의인구수 21

22 계획하수량 (design flowrate) 계획 1 일최대오수량 (design maximum daily sewage flowrate) 하수처리시설용량결정의기준값 계획 일최대오수량 인 일최대오수량 계획인구수 공장폐수량 지하수량 1 인 1 일최대오수량 : 상수도계획상의 1 인 1 일최대급수량을기준으로함 공장폐수량 : 대규모공장및사업장에대하여개별적으로장래폐수량추정 지하수량 (I/I): 1 인 1 일최대오수량의 10~20% 로가정하거나, 관거연장 / 배수면적등을고려한추정치를사용 22

23 계획1일평균오수량 (design average daily sewage flowrate) 펌프장운용및하수처리에사용되는첨가제비용등의계산에필요 하수처리장유입수질의예측에필요 계획1일최대오수량의 70~80% 로산정 (1/ 0.7~0.8) 계획시간최대오수량 (design maximum hourly sewage flowrate) 하수관거및펌프장용량결정의기본값 계획 1 일최대오수량의시간당값의 1.3~1.8 배로산정 ( 1.3~1.8) 대규모하수도의경우오수량의시간적변동이평균화되므로낮은배수 (1.3) 를, 중소규모하수도의경우높은배수 (1.8 또는경우에따라그이상 ) 를적용 23

24 계획우수량 (design stormwater flowrate) 합리식 : 계획우수량 (m 3 /s) : 유출계수 : 유달시간내의평균강우강도 (mm/hr) : 배수면적 (ha) 고려사항 배수지역의강우자료및확률년수 ( 하수관거의경우 10~30년빈도 ) 배수지역의유출계수, ( 강우량대비유출량 ) 예 : 도심지역 0.70~0.95, 교외지역 0.25~0.40 유달시간 ( 유입시간 + 유하시간 ) 배수면적 24

25 계획하수량 (design flowrate) 의결정 분류식하수도의오수관거 (sanitary sewer): 계획시간최대오수량 분류식하수도의우수관거 (storm drain): 계획우수량 합류식관거 (combined sewer): 계획시간최대오수량 + 계획우수량 25

26 계획오염부하량및계획유입수질 계획오염부하량 (design pollutant mass loading) = 생활오수 + 영업오수 + 공장폐수 + 관광오수오염부하량 생활오수오염부하량의산정 : 1인당오염부하량원단위참고 우리나라생활오수의오염부하량원단위 (2011, 서울시 ; g/capita d) BOD SS T N T P 기타항목은기존실측값 / 문헌값 / 세부항목별원단위등을활용하여계산 계획유입수질 (design influent pollutant concentration) = ( 계획오염부하량 ) / ( 계획1일평균오수량 ) 26

27 Supplementary reading: 하수도시설기준, 2011, 한국상하수도협회, p Or guideline for sewer systems in your own country 27

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