Wisconsin Department of Natural ResourcesWastewater Operator CertificationAdvanced Activated Sludge Study GuideDecember 2010 EditionSubclass CWisconsin Department of Natural ResourcesBureau of Science Services, Operator Certification ProgramP.O. Box 7921, Madison, WI 53707http://dnr.wi.govThe Wisconsin Department of Natural Resources provides equal opportunity in its employment, programs, services, and functions underan Affirmative Action Plan. If you have any questions, please write to Equal Opportunity Office, Department of Interior, Washington, D.C.20240. This publication is availab le in alternative format (large print, Braille, audio tape. etc.) upon request. Please call (608) 266-0531for more information.Printed on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 EditionPrefaceThis operator's study guide represents the results of an ambitious program. Operators ofwastewater facilities, regulators, educators and local officials, jointly prepared the objectives andexam questions for this subclass.How to use this study guide with referencesIn preparation for the exams you should:1. Read all of the key knowledge’s for each objective.2. Use the resources listed at the end of the study guide for additional information.3. Review all key knowledge’s until you fully understand them and know them by memory.It is advisable that the operator take classroom or online training in this process before attemptingthe certification exam.Choosing A Test DateBefore you choose a test date, consider the training opportunities available in your area. A listingof training opportunities and exam dates is available on the internet at, keywordsearch "operator certification". It can also be found in the annual DNR "Certified Operator" or bycontacting your DNR regional operator certification coordinator.AcknowledgementsThis Study Guide is the result of the efforts of the following workgroup individuals:Chris Marx, Chilton WWTPMatt Schmidt, Green Bay MetroJoe Flanagan, Blanchardville WWTPGary Hanson, AEComDoug Nelson, Ruekert & MielkeJim Shaw, ITT SanitaireDan Tomaro, Wastewater Training SolutionsCurtis Nickels, WIDNR-PlymouthHannah Fass, WIDNR-MadisonAmy Schmidt, WIDNR-MadisonJack Saltes, WIDNR-MadisonPrinted on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 EditionTable of ContentsChapter 1 - Theory and PrinciplesSection 1.1 - DefinitionsSection 1.2 - Microbiological PrinciplesSection 1.3 - Process Variationspg. 1pg. 1pg. 4Chapter 2 - Operation and MaintenanceSection 2.1 - DefinitionsSection 2.2 - MethodsSection 2.3 - Equipmentpg. 5pg. 8pg. 10Chapter 3 - Monitoring, Process Control, and TroubleshootingSection 3.1 - DefinitionsSection 3.2 - Sampling & TestingSection 3.3 - Data Understanding & InterpretationSection 3.4 - Side Streams/Recycle FlowsSection 3.5 - Performance Limiting FactorsSection 3.6 - Corrective 4 - Safety and RegulationsSection 4.1 - Personal SafetySection 4.2 - Regulationspg. 22pg. 23Chapter 5 - CalculationsSection 5.1 - Sludge Age CalculationsSection 5.2 - Food to Microorganism Ratio CalculationsSection 5.3 - Sludge Volume Index CalculationsSection 5.4 - Wasting Rates on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 EditionChapter 1 - Theory and PrinciplesSection 1.1 - Definitions1.1.1Define Hydraulic Retention Time (HRT)The period of time that wastewater remains in a tank. This is important because treatmentprocesses require sufficient time for the wastewater to be treated.Section 1.2 - Microbiological Principles1.2.1Describe the growth curve in the activated sludge process.The principle role microorganisms have in the activated sludge process is to convertdissolved and particulate organic matter, measured as biochemical oxygen demand (BOD),into cell mass. In a conventional activated sludge process, microorganisms use oxygen tobreak down waste so it can be used as food for their growth and survival. Over time and aswastewater moves through the aeration basin, food (BOD) decreases as microorganismsutilize it in the presence of oxygen for growth and reproduction with a resultant increase incell mass (MLSS concentration). This is known as the Growth Phase, where excess food(BOD) is available allowing for optimal bacterial cell growth with the uptake of oxygen. Asfood (BOD) is used and decreases, growth declines (Declining Growth Phase) and bacteriaeventually reach a level production. This is known as the Stationary Phase. As the food(BOD) is used up and decreases over time to very low levels, microorganisms will then usestored food in their cells and slowly begin to die. Cell mass (MLSS) will decrease. This isknown as the Endogenous Phase.Figure the relative abundance of activated sludge indicator organisms (protozoa androtifers) relative to sludge age an operator can expect to see under the microscope.When an activated sludge system is first started up, the activated sludge is very young andthin, the organisms an operator would see under the microscope are ameoba and someflagellates. During the Growth Phase, as the mixed liquor suspended solids (MLSS) buildsand sludge age increases, flagellates and free swimmers will be seen. When the mixedliquor suspended solids and sludge age reach an optimum level for treatment, flagellatesdecline, and free swimming ciliates and stalked ciliates will be seen in more abundance. AsPage1of 27Printed on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 Editionactivated sludge gets older, more stalked ciliates and rotifers will be commonly seen. If thesludge gets too old, rotifers and nematodes will dominate.By observing the relative abundance of these indicator organisms the operator will be ableto quickly tell the age and health of his activated sludge. The protozoan species that aremost dominant indicate the environmental conditions occuring in the process, especially therelative age of the sludge. Sludge age is controlled by wasting, the operator can adjust thewasting rate to influence the microbiological population and health of the activated sludgesystem and resultant effluent quality.A protozoan count procedure is used to determine the relative numbers of protozoa in theactivated sludge treatment process. The protozoan species that dominate are very helpfulin assessing the conditions of the activated sludge process. The count examines protozoain the following categories:A. AmoebaB. FlagellatesC. Free-swimming ciliatesD. Crawling ciliatesE. Stalked ciliatesF. Metazoa (rotifers, nematodes, water bear, etc.)See figure for an example count worksheet. The operator is referred to thereferences for Protozoan Count procedures.Figure 27Printed on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 EditionFigure the sludge production (in pounds of volatile matter per pound of BOD removed) in theactivated sludge process.The total pounds of sludge produced per pound of BOD removed can vary considerablydepending on plant specific conditions. The amount of inert total suspended solids must behandled as well as the sludge volatile (biological) matter produced in the process. Totalsludge production can reach 1 pound of total sludge per pound of BOD removed,especially, in facilities without primary clarification or poor preliminary treatment. Sludgehandling facilities must be sized to handle the total sludge production.Typical unit sludge production values for various processes are shown in figure 27Printed on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 EditionFigure the types of protozoa and organisms commonly found in activated sludge andobservable under a microscope.Protozoa are single-celled microscopic organisms, several hundred times larger thanbacteria. It is the protozoa we observe under a microscope since bacteria are actually toosmall to see. There are four types of protozoa commonly found in activated sludge systems.They are identified by their method of movement within the wastewater environment. Thefour types are amoeba, ciliates (free-swimming and stalked), flagellates and suctoreans.Rotifers are multi-celled (metazoa) organisms also commonly found in activated sludgesystems. The relative predominance of these protozoa is commonly associated with theage of the activated sludge.Figure 1.3 - Process VariationsPage4of 27Printed on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 Edition1.3.1Describe conventional (plug flow) activated sludge process.Conventional plug flow activated sludge is a process in which influent and returned activatedsludge enters at the head of the aeration tank and travels through the tank at a constant rateto the point of discharge. The sludge age is generally less than 15 days, usually bestbetween 3-10 days.Figure the extended aeration activated sludge process.Extended aeration uses conventional plug flow patterns, however, the aeration tanks arelarger to provide for over 15 hours of hydraulic retention times (HRT). The sludge age istypically greater than 15 days, usually best between 15-30 days. This results in a highlytreated effluent, and less WAS produced. The oxidation ditch is a variation of the extendedaeration process.Figure 2 - Operation and MaintenanceSection 2.1 - Definitions2.1.1Define variable frequency drive (VFD).Page5of 27Printed on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 EditionVariable Frequency Drive (VFD) is a system for regulating the rotational speed of analternating current (AC) electric motor by controlling the frequency of the electric powersupplied to the motor.2.1.2Define oxygen transfer efficiency (OTE).Oxygen transfer efficiency is measured by the exchange of oxygen between the gas that isabsorbed in a liquid compared to the amount of gas fed into the liquid. This is normallyexpressed as a percentage.2.1.3Diagram full floor coverage, side roll, and center roll placement of diffusers.Page6of 27Printed on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 EditionFigure 27Printed on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 EditionFigure 2.2 - Methods2.2.1Discuss the factors that most influence energy consumption in a diffused aeration system.A diffused aeration system consumes approximately half of the power consumed in awastewater treatment plant.Equipment:A. Type of aeration system diffusers (ultra fine bubble, fine bubble, coarse bubble)B. Diffuser placement on the tank floor (full floor coverage, side placement or centerplacement)C. System operating pressureD. Oxygen transfer efficiency (following ASCE standard test)Operations:A. Diffuser maintenanceB. Mixed liquor suspended solidsC. Excess process dissolved oxygenThe most efficient aeration system is a combination of fine bubble and high oxygen transferefficiency with the diffusers placed in full floor coverage with a mid-range system pressurePage8of 27Printed on 12/11/12

Advanced Activated Sludge Study Guide - December 2010 Edition(6-8 psi) and annual cleaning. A coarse bubble diffuser system placed in full floor coveragehas low maintenance requirements but a much lower oxygen transfer efficiency (about halfof fine bubble diffusers). Fine bubble diffusers used in a side roll or center roll placementare not any more efficient than a similarly placed coarse bubble diffuser and may requiremore maintenance.2.2.2Outline the start-up procedures for the activated sludge portion of a treatment plant. Prior toany startup activity for new equipment, installation service and training of the plant staff by aqualified person must have been completed.A. Inspect all ground water relief valves operation and insure they are: clean, seat properly,and operate freelyB. Inspect aeration basin for debris and removeC. Check blowers for proper oil level/lubrication and rotationD. Fill aeration basin with "clean" water 6 inches above diffusers and piping. Check airsystem for level and leaks. Tighten, adjust, and repair.E. Inspect final clarifiers for debris and removeF. Check final clarifiers for proper oil level/lubrication and rotationG. Turn on and rotate final clarifiers at least 2 complete rotations checking for properoperationH. Check RAS/WAS pumps for proper oil level/lubrication and rotationI. Start filling the aeration basin at a low flow rate, directing flow away from the air pipingand diffusers to minimize potential damage to the aeration system.J. Start blowers and add seed sludge if available after diffusers are submergedK. Allow flow from aeration basin to overflow into clarifierL. Start sludge collector mechanism when water level reaches the bottom of the weirsM. Open isolation valves (suction and discharge) at the RAS/WAS pumps, purge air frompumps and turn on the pumpsN. Turn on power to RAS and WAS flow metersO. Allow the MLSS to reach the target level before beginning to waste2.2.3List the steps that might be taken to speed-up the formation of sufficient mixed liquorsuspended solids when starting or restarting an activated sludge plant.A. Obtain "seed" activated or return sludge without filamentous organisms from a near-byplantB. Return sludge from the final clarifier should be recirculated at a medium to high rate tobuild-up solidsC. Limit wasting any sludge until a targeted MLSS is established2.2.4List the strategies for dealing with extreme weekly or seasonal fluctuations in loading rates.A. WeeklyIf loadings can be anticipated, adjust mixed liquor suspended solids as needed. If theloading is from industry, consideration should be given to flow equalization at the plantand/or the industry. In addition, consideration should be given to a pretreatment system atthe source to minimize loading rates.B. SeasonalPage9