Colorado WW Operator D Exam Questions & Answers

______ = BOD, lbs/day / MLVSS, lbs - ANSWERSF/M ratio In a conventional activated sludge plant, oxygen demand is highest - ANSWERSAt the head end of the tank Air requirements in an activated sludge tank are governed by - ANSWERSBOD and the desired removal efficiency, Volatile suspended solids concentration in the aerator, Suspended solids concentrations of the primary effluent It is not necessary to be a skilled microbiologist or to be able to identify or count individual species. Rather the operator needs only to recognize major groups of organisms such as: - ANSWERSFilamentous bacteria, rotifers, protozoa In addition to high energy costs, excess DO levels can cause - ANSWERSDamage to floc particles due to turbulence Which of the following are key factors in activated sludge nitrification? Check all that apply. - ANSWERSMCRT, Alkalinity and pH, Temperature, DO, TKN loading An activated sludge that settles poorly and has an SVI 250 mL/g is described as what? - ANSWERSBulking Which of the following is a modification of the activated sludge process? - ANSWERSAll of these answers are correct Taking samples at different locations along the length and the width of a reactor (aeration tank) as well as at different depths and analyzing them for solids concentration will verify whether or not you have....? - ANSWERSProper mixing in the tank CCSS stands for: - ANSWERSClarifier core suspended solids Because nitrifiers grow slower than other bacteria, sludge ages longer than ____ days are often needed. - ANSWERS5 days During plant rounds, an operator notices that the secondary effluent is cloudy. The operator should: - ANSWERSCheck the dissolved oxygen level in the aeration tank Given the following data, determine the excess solids (in lbs) that should be wasted from this activated sludge system. Target F:M = 0.6 per day, MLVSS = 2500 mg/L, BOD loading= 18,140 lb/day, Volume of aeration basin = 2 million gallons - ANSWERS11,467 lb Conditions in which oxygen is absent but nitrate is present are referred to as what? - ANSWERSAnoxic What characteristics are associated with quality activated sludge? - ANSWERSBrown color, some dissolved oxygen content, and good settling The activated sludge process removes soluble BOD from wastewater by - ANSWERSAbsorption Why is the sludge returned from the secondary clarifier to the aeration tank in activated sludge used for nitrification? - ANSWERSTo provide microorganisms If fine-bubble diffusers are used to introduce air into a biological reactor, the surface of the tank will typically have what type of appearance? - ANSWERSMildly agitated, partially covered with light foam In an anoxic activated sludge process, oxygen for facultative bacteria is provided by...? - ANSWERSNitrate, NO3 A small area of dark gray/black sludge in an aeration tank can be due to aeration equipment failure or ____. - ANSWERSThe introduction of a septic sidestream When doing a 30-minute activated sludge settleability test, a 1000ml Imhoff cone should be used. - ANSWERSFALSE In a conventional activated sludge process, how much oxygen is required per lb. of BOD removed? - ANSWERS0.8 to 1.2 lb oxygen /lb BOD Which of the following conditions would least likely contribute to rising sludge in secondary clarifiers? - ANSWERSClarifier hydraulic loading In an activated sludge process bacteria release chemicals called ________ that break down the food particles that are adsorbed to the cell wall so that they can be absorbed by the microorganism. - ANSWERSEnzymes Acids should never be added to chlorine solutions because they - ANSWERSCause chlorine gas to be released Chloramines are ____? - ANSWERSCombined chlorine What are the characteristics for chlorine as used in pollution control? - ANSWERSChlorine gas is toxic, corrosive, and heavier than air Chlorine applied minus ____ equals chlorine residual - ANSWERSChlorine demand Unlike chlorine, UV does not leave what in treated water? - ANSWERSA residual Coliform bacteria are: - ANSWERSIndicators A _____ residual is attained after breakpoint chlorination. - ANSWERSFree If you need a chlorine residual of 1 mg/l, how many pounds of chlorine must be applied each day if the flow is 2.5 mgd and the chlorine demand is 15 mg/l? - ANSWERS334 lb/d A total residual is also referred to as a ______ residual. - ANSWERSCombined Total and fecal coliform are pathogenic. - ANSWERSFALSE _________ = flow, mgd x chlorine dosage, mg/L x 8.34 lb/gal. - ANSWERSFeed Rate/Dose (lbs/day) Sodium hypochlorite is manufactured by the reaction of gaseous or liquid chlorine with a solution of _________ _________ to produce a liquid containing NaOCl. - ANSWERSSodium hypochlorite At concentrations less than _____, chlorine gas is not detectable by the human sense of smell. - ANSWERS1 ppm A treatment plant uses sulfur dioxide to dechlorinate effluent. An operator needs to adjust the sulfonator so that the dosing concentration is 1.5 mg/l more than the chlorine residual. Based on the following information, what should the sulfonator feed rate be: design flow = 5 mgd; chlorine dosage rate = 4 mg/l; chlorine residual = 0.9 mg/l - ANSWERS100 lb/day The UV dose represents the product of the rate of energy emission (lamp intensity) and the time the organisms are exposed to the germicidal energy at 254 nm. This can be expressed by the equation: - ANSWERSDose = intensity x time (d=It) The amount of chlorine used per day from a 1 ton cylinder is normally determined by - ANSWERSWeighings Ultraviolet disinfection is becoming more popular because UV systems - ANSWERSEliminate safety concerns about handling chlorine If a 100-mgd flow of wastewater is dosed at a rate of 12 mg/l, what should the chlorine-reed setting be to the nearest 100 lb/d? - ANSWERS10,000 Coliform bacteria are: - ANSWERSMore resistant to chlorination than pathogenic bacteria After chlorine, what is the most common effluent wastewater disinfection technique or agent used in the US today? - ANSWERSUltraviolet radiation Calculate the chlorine demand given: flow rate = 120 mgd; chlorine feed rate = 8000 lb/d; chlorine residual = 1.0 mg/l after contact time. - ANSWERS7 ppd The fusible plug on a chlorine cylinder melts at about ______ degrees. - ANSWERS150 - 162 One volume of liquid chlorine will yield about ____ volumes of chlorine gas. - ANSWERS450 The two qualities in a final effluent that most affect performance of ultraviolet disinfection system are UV transmission and ____________. - ANSWERSSuspended Solids Which of the following would be the safest action to take in the event of a major chlorine container leak? - ANSWERSCall the fire department _____(which can be used for disinfection) may be mechanically produced by photochemical or electrical methods resembling the natural processes. - ANSWERSOzone, O3 The destruction of the larger portion of microorganisms with the probability that all pathogens are killed is called - ANSWERSDisinfection Chlorine gas is _____ times heavier than air. - ANSWERS2.5 The fusible plug on a chlorine cylinder melts at about ______ degrees. - ANSWERS150 - 162 One volume of liquid chlorine will yield about ____ volumes of chlorine gas. - ANSWERS450 Proper disinfection kills all organisms. - ANSWERSFALSE If a 100-mgd flow of wastewater is dosed at a rate of 12 mg/l, what should the chlorine-reed setting be to the nearest 100 lb/d? - ANSWERS10,000 Exhaust air from a chlorine tank room should be taken from where? - ANSWERSFloor level Invisible light waves used for disinfection are called what? - ANSWERSUltraviolet In disinfection, compounds of organic or inorganic nitrogen and chlorine are called __________. - ANSWERSChloramines In a conventional effluent chlorination system the chlorine residual measured is mostly in the form of _____________. - ANSWERSMonochloramine Ultraviolet light at a wavelength of ___nm has the ability to kill microorganisms without significantly altering the physical and chemical properties of the wastewater effluent. - ANSWERS254 Under normal conditions, the maximum amount of chlorine gas that can be drawn from a 150-lb cylinder is - ANSWERS40 lb/day Chlorine applied minus ____ equals chlorine residual - ANSWERSChlorine demand The chlorine demand at your plant suddenly increases significantly. This change is most likely due to _______. - ANSWERSNitrification beginning to occur at the plant A _____ residual is attained after breakpoint chlorination. - ANSWERSFree One ton chlorine cylinders: - ANSWERSUse the bottom valve only with chlorine evaporators In the process of UV disinfection, the final effluent is irradiated by light at a wavelength of - ANSWERS254 nm A total residual is also referred to as a ______ residual. - ANSWERSCombined A chlorine demand test will show the: - ANSWERSAmount of chlorine required to give a desired residual after a given time As water temperatures decrease, the disinfecting action of chlorine: - ANSWERSDecreases The maximum rate for withdrawing gaseous chlorine from a 1-ton tank at room temperature is - ANSWERS15 lb/h Coliform bacteria are: - ANSWERSIndicators