Final Exam (continue) Topics covered: (Water hydrology) through (Chlorination) Including: Hydrology (Ch 4, section 4-1) Water Pressure and relationship with height Open channel flow (Ch 4, sections 4-8) Manning’s equation Flow measurement in open channels (Ch 4, sections 4-10) Parshall flumes V-notch weirs Groundwater Hydrology (Ch 4, sections 4-14) Soil porosity and subsurface flow Darcy’s law Hydraulic conductivity Aquifers (unconfined, confined) Well hydraulics Calculation of well discharge Calculation of permeability (pumping tests) Types and sources of water pollution Water quality regulations Clean water act (Ch 5, section 5-4) NPDES (Ch 5, section 5-4) SPCC Safe Drinking water act (Ch 5, section 5-1) Primary standards Secondary standards MCLG, MCL SWTR Groundwater protection (Ch 5, section 5-7) Drinking water treatment Treatments for surface water and groundwater Treatment reactors Rapid mix reactors Plug flow reactors (Ch 7, section 7-2) Flocculation (Ch 7, section 7-8) Coagulation Paddle flocculators Sedimentation (CH 7; section 7-3) Settling velocity Overflow rate (surface loading rate) Filtration (Ch 7; section 7-7) Mechanisms of filtration Pressure filters Slow sand filters Rapid sand filters Filter backwashing and surface washing Filter media Dual and multi-media filters Chlorination and disinfection (Ch 7; section 7-12) Chlorine chemistry Free chlorine residual Ammonia removal Breakpoint chlorination Disinfection of surface and groundwater The “C.t” concept of disinfection Temperature and pH effects Primary and secondary disinfection Different disinfectants Tri-halo methane (THM) formation A) TRUE / FALSE (If false, explain briefly) The primary objective of a drinking water treatment plant is to remove soluble BOD F Giardia cysts are generally more resistant to chlorination than are bacteria T Free chlorine residuals represent the sum of HOCl and chloramine concentrations F During water treatment, a coagulant is typically added between sedimentation and filtration F The rate at which a particle settles in water is a function of its size T The form of chlorine that predominates at pH = 9, is dissolved chlorine gas F Ozone is a disinfectant that forms long-lasting secondary disinfection residual F An overflow rate, e.g gpm/ft2, can not be expressed in units of velocity F For a plug flow reactor, the detention time is a function of the length of the reactor T During flocculation, the size of the floc increases due to quick mixing F The unit of porosity is gpd/ft2 F The piezometric surface in an unconfined aquifer is commonly below the water table F Secondary treatment of domestic wastewater has been made mandatory by the clean water act F According to the SDWA, maximum contaminant level goal is an enforceable standard which must be achieved by the treatment plants F Direct filtration (without sedimentation) increases the filtration rate F B) Short answer questions Relative to drinking water treatment, give examples of contaminants that commonly have to be removed from: a) Surface water sources (name contaminants) b) Groundwater sources (name contaminants) Briefly describe how a rapid sand filter is backwashed During breakpoint chlorination, what materials consume the added free chlorine? How ammonia is removed from water using chlorination? What are the components of the ground water protection plan under SDWA? What measures can be taken to prevent the formation of THMs during the disinfection process? Why groundwater is not disinfected for Giardia cysts? C) Numerical Problems 1) The settling velocity of an alum floc is approximately 0.0014 ft/s in water at 10 0C What is the minimum detention time (in hours) to settle out this alum floc in an ideal clarifier with a depth of 10 ft? td= L/v= 10/0.0014=7142.86 s = 1.98 h (td ) 2) Two rectangular clarifiers each 27 m long, 5.0 m wide, and 3.8 m deep settle 6000 m3/d of water Calculate the detention time and overflow rate V=1026 m3 td= V/Q=0.171d=4.104h v0=Q/A1=6000/270=22.2m/d 3) What is the major advantage of a dual-media coal-sand filter compared to a conventional plain sand filter? 4) Why chlorination has to be preceded by chemical coagulation followed by granular-media filtration for effective disinfection of surface waters? Some comments…… ** BRING CALCULATORS ** Manage time well during exam……try to answer all the questions ** Always pay attention to units