Water and Wastewater Treatment Processes, Exams of Nursing

Download Water and Wastewater Treatment Processes and more Exams Nursing in PDF only on Docsity! OIT Exam Questions and Answers What are colloids? - Very small particles suspended in water which are resistant to settling. What is turbidity measured in? - Nephelometric Turbidity Units (NTU) What is the turbidity measurement that is visible to the naked eye? - 5 NTU What is an important indicator of treatment efficiency and particularly the efficiency of filters and disinfection processes? - Turbidity Why are particles that cause turbidity harmful? - They can hide or entrap harmful organisms so that the disinfectant is unable to reach them. It calls increases CL demand which can be carcinogenic What are the 2 types of sampling? - Grab samples and composite samples What are grab samples and when is it used? - A single sample taken at one place and time. Used when water quality and quantity are not variable What is a composite sample and when is it used? - A series of samples taken over a period of time which are combined to form a single sample. Necessary if water quality changes greatly over time. What is voltage? - Electrical potential or potential difference between two points. Indicated the strength of the "push" on current What is current and what are its units? - Flow off electric charge. Measured in amperes What is the typical rate of change (Hz) or alternating current? - 60 cycles per second What happens when wires or appliances carry more than their rated capacity of current? - May overheat and cause fires. Circuit breakers stop this What is the equation for voltage? - V=IR What is Power (P), what is is measured in and what is the formula? - The rate at which work is done or energy is produced. Measured in Watts P=VI What is the symbol for flow and what is the formula for it? - Flow (Q) Q= AV What can flow provide info on? - Dentention time in tanks, flow between various processes or sections, chemical feed rates, etc. What are the types of flow measurement determined by? - Whether water is flowing in a closed pipe of an open channel What is used to measure flow in an open channel? - Weirs or flumes. Flow is determined by the height of water at a particular point How are centrifugal pumps classified? - By their shapes What are radial vane, Francis vane, mixed flow and axial flow examples of? - Centrifugal pumps How do positive displacement pumps work? - Push fluid mechanically. Starts with a suction valve and discharge valve open What are screw, gear, piston, diaphragm, and progressive cavity examples of? - Positive displacement pumps What are packing glands? - Seals which prevent the pumped fluid from leaking from a pump and prevent air from entering What is the name of the seals which prevent the pumped fluid from leaking from a pump and prevent air from entering - Packing glands What types of pipes can be used? - -cast iron (CI) -ductile iron (DI) -steel and reinforced concrete (CP) -asbestos cement (AC) -plastic (PVC, HDPE, ABS) -copper What is the most common type of pipe used in water systems? - Cast iron, but PVC and HDPE are used more recently for smaller pipes What factors determines the type of pipe used? - -economy -surrounding soil -strength and anticipated life of pipe material What is the main use of a gas valve? - Isolation (not used to control flow) What is the main use of a Butterly valve? - Isolation, automatic control, throttling What is the main use of a globe valve? - Isolation in small size, flow control in large sizes, pressure reducing What is the main use of a ball and plug valve? - Isolation What is the main use of a check valve? - Backflow prevention, preventing pumps from reversing when power is stopped What is the main use of air release and vacuum relief valves? - To release or admit air into a piping system What is the main use of pressure-reducing valves? - To allow water to flow from a higher pressure area to a lower pressure area What is included in the multi-barrier approach? - -selecting the best source -protecting the source from contamination -operating and maintaining an appropriate and effective treatment process -monitoring -preventing water quality deterioration in the distribution system -responding to adverse conditions or emergencies What are the steps included in a "conventional" drinking water treatment? - coagulation, flocculation, sedimentation, and filtration What are the steps included in a "direct" drinking water treatment? - coagulation, flocculation, and filtration What are the steps in chemically- assisted filtration? - Filtration preceded by coagulation and flocculation Why my groundwater filtration systems have simpler treatment facilities? - Due to the quality of the source water What is included in the pre-treatment phase of drinking water treatment and why? - -water passes through screens to ensure large debris does not damage pumps and other equipment -may also require pre-sedimentation period to remove large particles (sand) -may also be dosed with chlorine to remove odours, inactivate pathogens/algae, or to control zebra mussels (pre-chlorination) What is pre-chlorination? - When chlorine is added in the pre-treatment phase in drinking water treatment Why is turbidity harmful? - It can shield microorganisms from inactivation and the colloidal particles resist settling What happens during coagulation and what is formed? - Chemicals (coagulants) are added to the water to enable the removal of suspended and dissolved matter. What is the name of the process used to clean media filters? - Backwashing What happens to the backwash? - Its treated on-site before release back into the environment for it is routed to the sanitary sewer What are some examples of filter used in drinking water treatment other than rapid rate gravity filters? - Pressure filters, slow sand filters, cartridge and bag filters, diatomaceous earth filters and membrane filters What is the most important process in drinking water treatment? - Disinfection- it makes the water safe for consumption What are the 2 things that make up disinfection? - Removal and inactivation How are pathogens removed from drinking water? - Chemically-assisted filtration or equivalent process Is inactivation or filtration done first? - Filtration occurs first so that pathogens are not shielded What is important to ensure while using chlorine for inactivation? - Ensure that the Cl has sufficient time to react with the water and inactivate the pathogens What is chlorine contact time? - The time needed for Cl to be in contact with the pathogens to inactivate them What is an advantage to using chlorine for disinfection over other methods? - Chlorine is able to disinfect long after it was applied What are trihalomethanes? - By products produced when chlorine reacts with organic material What does log mean? - Represents the percentage of removal and is used in place of many-digit numbers What is the CT concept? - Uses the combination of a disinfectant residual concentration (mg/L) and the effective disinfectant time (min) to quantify the capability of a chemical disinfection system CT= (concentration)(time) When is the CT concept not used? - UV systems What oxygen and temperature levels produce the best tasting water? - High O2, low temp What are the most common methods to treat taste and smell? - Sequestering manganese and iron in solution or oxidation and filtration Where are waste residuals produced? - Screene, sedimentation, or clarification process, filter backwash What does the amount of sludge produced depend on? - Amount of suspended matter in source of water and dosage and type of coagulants used What is the minimum pressure that must be kept in the water distribution system at all times and why? - 140kPa: firefighting purposes What is the range of pressure that is usually maintained in the water distribution system? - 250-550kPa What are the main distribution pipes within the water distribution system known as? - Trunk mains Where are distribution pipes buried underneath? - Municipal right-of-ways What are valves used for in distribution systems? - -isolate portions of the system for repair, cleaning, maintenance, or adding additional lines -regulate flow or pressure within a pipe What is it important to to with hydrants? - Open and close slowly Why is it important to maintain positive pressure in distribution systems? - -serve firefighting/customer needs -prevents contamination of the system (can lead contaminated groundwater to enter the pipe through cracks) What is used to provide the community with short term emergency storage of water and to maintain pressure within the system? - Storage tanks and reservoirs. What is comminution? - Process of particle size reduction by chopping or shredding What process reduces particle size by chopping or shredding in wastewater treatment? - Comminution Where do the large particles end up after the screens and shredders in wastewater treatment? - Grit channels or chambers What is the primary clarifier? - Primary settling basins What are the steps in primary wastewater treatment? - -water flows into primary settling basins -velocity is slowed so solids will sink or float -settles/floated material is removed and pumped to sludge facilities -decanted liquid proceeds to secondary treatment What do settling basins rely on? - Gravity What percent of BOD will settling basins remove in wastewater treatment? - 30- 40% What percent of suspended solids will settling basins remove in wastewater treatment? - 40-60% What does secondary treatment in wastewater rely on? - Aerobic bacteria to break down solids and BOD What step in wastewater treatment relies on aerobic bacteria? - Secondary What percent of BOD and suspended solids does secondary treatment remove in wastewater treatment? - 80-99% What is one of the most widely used secondary treatment processes? - Activated Sludge Process (ASP) What are the steps in secondary treatment? - -effluent from primary treatment (or sometimes right from preliminary) water aeration tanks where it is mixed with bacterial mass, known as activated sludge (or biomass) -the biomass consumes the BOD -air must be added to keep bacteria alive using surface aerators or air diffusers -it is then sent to secondary clarifiers where activated sludge and other materials settle out -half sludge: back to aeration, other half: sludge facilities What is mixed liquor? - The mixture of wastewater and microorganisms What is the mixture of wastewater and microorganisms called? - Mixed liquor What is the rotating biological contractor (RBC) process? - -consists of an RBS reactor and a secondary clarifier What is an RBC (rotating biological contractor)? - An attached growth process where biomass grows on the surface of a rotating disk What is an RBC reactor and how does it work? - Consists of a series of closely spaced rotating disks that are partially submerged in the wastewater. Microorganisms on the disk remove organic material from the wastewater. O2 is added. As the biomass increases it is sheared from the media and flows with the wastewater into the secondary clarifier What is the moving bed biological reactor (MBBR) process? - Consists of an aeration basin filled with suspended media and a secondary clarifier. The process is based on the attached-growth principle, and is essentially a combination of suspended growth and attached growth processes. What is the moving bed biological reactor (MBBR) also known as? - IFAS (integrated fixed film activated sludge) What are MBRs (Membrane biological reactor) and how do they work? - Consist of membranes that are submerged in a biological reactor containing suspended biomass. This consumes the BOD as food and the membranes are used to filter out the solids from the effluent. Effluent is drawn through the membranes by vacuum and pumped downstream for disinfection What is the most common method of disinfection? - Chlorination At what concentration is total residual chlorine toxic to aquatic life? - 0.02mg/L How can you produce a non-toxic effluent after using chlorine? - Neutralize it by adding a dechlorinating agent such as sulphur dioxide or sodium bisulphate How long does it take for dechlorination reactions? - Instantaneous What disinfectant method produces no by-products? - UV light How do facultative lagoons work? - Algae use sunlight to convert wastewater nutrients into cell mass. As the algae die, the cells settle to the anaerobic zone where bacteria break them down into methane, organic acids, hydrogen sulphide and CO2 What are the pros and cons of lagoons? - Pros: -economic alternative to conventional treatment Cons: -require a large area of land -less effective during the winter What is a combined sewer? - Pipes that carry both wastewater and storm runoff Why are cross connections between storm sewers and sanitary sewers bad? - Can lead to the discharge or domestic and industrial waste into streams, rivers, and lakes and cause overcharging of wastewater collection systems What are cleaning methods to clean blockages from pipes? - -high velocity jet cleaners -flushing -power rodders -bucket machines What is a surcharge and when does it occur? - When a sewer is hydraulically overloaded (too much wastewater is trying to flow through a sewer) resulting in sewage backing up the collection system What are some contributing factors of surcharging? - -inflow of surface water into sewers -infiltration of groundwater through cracks in the sewer wall What is exfiltration? - The flow of wastewater through cracks in the sewer wall into the ground (can result in groundwater contamination) What is the easiest method of avoiding accumulation of material in the sewer? What happens if this is not done? - Maintain a sufficiently high rate of wastewater flow or periods of high flow If velocity is too low, a buildup of organic materials can produce hydrogen sulphide, methane (CH4) and other dangerous gases. What can hydrogen sulphide and methane do in sewers? - Causes corrosion of sewer lines How and where is home/industry wastewater collected? - By service connections into a lateral or branch sewer Where do main sewers transport waste to? - From branch sewers to larger trunk sewers When gravity isn't able to be used in wastewater transportation, what is used instead? - Lift stations What does a lift station consist of? - Two pumps and an alternative source of power What is a forcemain? - A pressurized pipe Where does wastewater go after a lift station? - Pumped through a forcemain to a treatment facility or to an elevated gravity sewer What are the maintenance accessories points for sewers? - Manholes What must you do before entering a manhole? - -testing for hydrogen sulphide and methane -ensuring there is sufficient O2 Where are alternative sewer collection systems used? - -In small communities where gravity systems can be expensive -places where there is shallow bedrock -high groundwater tables -topography that won't work What are examples of alternative sewer collection systems? - -Septic Tank Effluent Gravity (STEG) -Septic Tank Effluent Pumping (STEP) -grinder pump systems -vacuum pump systems How do alternative sewer collection systems work? - -Use smaller diameter pipes buries below the depth of frost penetration that have a slight slope or follow the surface contour. Determines the organic strength (amount of organic pollution) in wastewater The Higher the BOD, the higher the organic material Why is nitrogen in water harmful? - Nitrites can be toxic to infants What does the presence of nitrogen in water indicate ? - Pollution Why is phosphorous needed in WWT? - It is a requirement for plant and bacterial growth, needed to ensure nutrients for microorganisms What is alkalinity expressed as? - Milligrams per litre as calcium carbonate (mg/L as CaCO3) What could colour in water be a precursor to? - Disinfection by-product formation Who is the harness of water removed by? - The consumer What can the measurements of solids in water do? - Provide a quick indication of water quality What is the name of solids that can pass through an extremely fine mesh filter? - Dissolved solids What are dissolved solids? - solids that can pass through an extremely fine mesh filter What are settleable solids? - Solids which will settle to the bottom of the liquid if left for a period of time How are suspended solids measured? - By entrapment of on a filter How do you measure total solids? - Weighing the residue left when a given volume of water is evaporated What are volatile solids? - Solids which, when a total solid sample or suspended sample is heated to a high temp, are burnt off. These solids approximate the amount of organic material in the water