Centralised Decentralised transportation system M K PANDEYP Jenssen

Centralised –Decentralised transportation system M. K. PANDEY/P. Jenssen 2111 2005

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Centralised system = Collection system 70 - 90 % = Treatment 10 - 30 % (Otis 1996, Mork et al. 2000) Sewer lines = The cost of conventional gravity system is up to 4 times higher than the cost of treatment and disposal Wastewater treatment plant treatment www. umb. no

Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES House hold human waste and wastewater { Urine ＋ } Excreta Feaces ＋ Flush ＋ Anal cleansing Wastewater Black water ＋ Greywater Or Sewage www. umb. no

Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES House hold human waste and wastewater Important constituents • Organic matter • Neutrients- Nitrogen, Phosphorus, Potassium • Pathognes { Urine ＋ } Excreta Faeces ＋ Flush ＋ Anal cleansing Wastewater Black water ＋ Greywater Or Sewage www. umb. no

Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Wastewater transportation =Wastewater transported to treatment plant as quickly as possible =Self cleansing velocity should be maintained at low flow =Velocity should not be higher than the maximum allowable velocity – to prevent wear and tear of the pipes =Formation of Hydrogen sulphide, airlock should be prevented =Should not be close to W/S lines =Proper selection of type and shape of sewer www. umb. no

Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Conventional gravity sewer • Pollution due to combined sewer overflow • Large dia sewer • Interference to other infrastructure • Contamination of water distribution system • High chances of system failure WW Treatment Plant G. L Over flow structure www. umb. no Pumping system River

Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Types of conventional sewerage system Combined sewer • • Storm and sanitary sewage (wastewater) collected in one sewer Suitable at places where rainfall is evenly distributed throughout the year Overflow structure required to divert the flow more than the design flow Large dia sewer required Large volume of wastewater to be treated Plumbing work reduced in houses Separate sewer – Storm sewage and sanitary sewage conveyed in separate sewer Chances of clogging Prone to formation of H 2 S Partially separate system Rainwater from houses and yards discharged into sanitatry sewers www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Investment Cost = Collection system 70 - 90 % = Treatment 10 - 30 % (Otis 1996, Mork et al. 2000) Sewer lines = The cost of conventional gravity system is up to 4 times higher than the cost of treatment and disposal Wastewater treatment plant www. umb. no

Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Decentralized system Collection in a septic tank and transport the effluent wastewater to nearby treatment system • Soak pit • Constructed wetland • Infiltration system • Pond system • Sand filter Septic tank (S. T) Natural Treatment Compost or transport to faecal sludge treatment facilities. www. umb. no

Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Decentralized system Low flush or pour flush Collection and treatment of blackwater and Greywater separately • Soak pit • Constructed wetland • Infiltration system • Pond system • Sand filter Septic tank (S. T) Compost or Transport to faecal sludge treatment facilities Settling tank and greese tap Natural Treatment www. umb. no

Department of Plant and Environmental Sciences NORWEGIAN UNIVERSITY OF LIFE SCIENCES Decentralized system Low flush or pour flush Urine Faeces Collection and treatment of urine, faeces and greywater separately Settling tank and greese tap Natural Treatment www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Decentralized system- STEG =Septic tank effluent gravity (STEG) 50 mm to 200 mm 100 mm =Can be laid in variable grade - because no solid to settle =Uniform slope with no high points to prevent airlock =H 2 S formation =Air release valve in high points =Clean out ports at junction www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Decentralized system- STEP =Septic tank effluent pump (STEP) and pressure sewer with grinder pumps =Sewer are under pressure – pressure generated by high head turbine pump =Advantage in high groundwater and rocky soil and rolling terrain - can follow the terrain =If grinder pumps used- septic tank not required www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Decentralized system- Vaccum sewer =Vacuum applied to transport sewage www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Hydraulics of wastewater collection system =Velocity and headloss are two governing parameter =Hazen williams equation (1) =Where =V= Velocity of flow, m/s =C = Hazen –williams coefficient, 150 may be used PVC pipe =R = Hydraulic Radius, (wetted area/wetted perimeter), m = (e. g for pipe flowing full =D = inside dia of sewer, m =S = Slope of energy gradeline, m/m, =hf = head loss due to friction, m =L = Length of pipeline www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Hydraulics of wastewater collection system =Manning`s equation (2) =Where V= Velocity of flow, m/s n = Manning’s coefficient, 0, 013 to 0. 009 may be used for PVC pipe R = Hydraulic Radius, (flowing full) D = inside dia of sewer, m S = Slope of energy grade line, m/m, hf = head loss due to friction, m L = Length of pipeline Sewer line (gravity sewers) are designed as a open channel or flowing just full www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Hydraulics of wastewater collection system = The velocity should be less than 1. 5 m/s to avoid excessive frictional loss. = No minimum velocity required for STEG system – (but usually kept at 1 m/s) www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Information's required for design and layout of STEG collection system =Site characteristics –Topography of the area –Depth of soil –Depth of water table –Depth of freezing zone =Equivalent dwelling unit (EDU) –Residence with given number of residents e. g if 1 EDU is defined as residence with 4 person then 8 person residence is 2 EDU www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES Information's required for design and layout of collection system =Peak flow rates –collection system based on peak flow rates – 1. 3 to 1. 9 lit/min/EDU (USA) – 0. 8 to 1. 2 lit/min/EDU (Norway) www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES STEPS for the design of Sewer collection system =Prepare a longitudinal profile =Select a pipe size =Calculate the velocity using Hazen Williams equations =Calculate the pipe cross sectional area and determine the actual capacity =Check for the surcharged condition www. umb. no

NORWEGIAN UNIVERSITY OF LIFE SCIENCES THANK YOU www. umb. no