Waste Water Pt 1
3.7A What two basic types of bacteria are present in an anaerobic digester?
1- a group that eats organic sludge to form organic acids and carbon dioxide gas (acid formers) and 2. a group that breaks down organic acids into simpler compounds and forms methane and carbon dioxide gas (gas formers)
5.7A What safety items should be considered when reviewing plans and specifications for clarifiers?
1. Clarifiers must be equipped with adequate access by stairs, ladders, ramps, catwalks, and bridges. Be sure railings meet state and OSHA requirements. 2. Catwalks and bridges must have floor plates or grates firmly secured and equipped and toeboards and nonskid surfaces. 3. Adequate lighting must be provided. 4. Launders, channels, and effluent pipelines that carry flow from the clarifier to another conduit, channel or structure must have safety grates over the entrance. 5. In a circular clarifier, turntables, adjustable inlet deflection baffles, and return sludge control valves must have safe access 6. Adequate guards must be placed over chain drives, belts, and other moving parts. 7. Safety hooks, poles, or floats should be stationed at strategic locations near every basin to rescue anyone who falls into a basin 8. Do not allow any pipes or conduits to cross on topic of catwalks or bridges 9. Adequate offset of drive units, motions, and other equipment must be provided to allow unobstructed access to all areas
5.1A List the significant items to check before start-up of a circular clarifier.
1. Control gates for operation 2. Clarifier tan for sand and debris 3. Collector drive mechanism for lubrication, oil level, drive alignment, and complete assembly 4. Gaskets, gears, drive chain sprockets, and drive motor for proper installation and rotation 5. Squeegee blades on the collector plows for proper distance from the floor to the tank 6. All other mechanical items below the waterline for proper installation and operation 7. Tank sumps or hoppers and return lines for debris and obstructions 8. Tank strucure for corrosion, cracks, and other indications of structural failure
4.4H List the possible safety hazards an operator may encounter when working around a cyclone grit separator.
1. Electrical hazards, 2. slowly moving screw conveyors and other equipment, 3. lifting heavy parts or materials, 4. slippery surfaces.
8.0E What factors could cause an unsuitable environment for the activated sludge process in an aeration tank?
1. High concentration of acids, bases, and other toxic substances 2. Uneven flows of wasterwater 3. failure to supply enough oxygen
5.9B What abnormal operating conditions might the operator of a combined sedimentation-digestion unit encounter?
1. Inflows are higher than design flows 2. Solids loadings are high 3. Toxic substances or high or low PH liquids are released into the collection system.
8.3E What terms or structures should be inspected during a pre-start inspection?
1. Inlet structure 2. Oxication ditch structure 3. Rotor 4. Adjustable weir 5. Clarifier structure and piping 6. Return sludge and waste sludge systems
4.4J List the maintenance steps for a grit washer.
1. Inspecting the facility for corrosion damage 2. Examining moving parts for wear 3. Repairing or replacing any worn or corroded parts 4. Painting any parts that could corrode 5. Oiling and greasing equipment in accordance with plant O&M manual and the manufacturer's instructions.
5.9C List the major maintenance items for a combined sedimentation-digestion unit.
1. Lubricate all equipment in accordance with manufacturers' recommendations 2. If a tool or object falls into the clarifier, stop rotation and remove the tool or object 3. If the scraper mechanism stops moving, determine the cause and remove it before attempting to start the mechanism again
8.3D What are the 2 primary objectives of start up?
1. Make certain that all mechanical equipment is operating properly 2. Develop a proper microbial floc (activated sludge) in the oxidation ditch
8.3B List the major components of an oxidation ditch treatment process.
1. Oxidation Ditch 2. Rotor 3. Level control weir 4. Final settling tank 5. Return sludge pump 6. Excess sludge handling facilities
4.6A What items would you check when reviewing the plans and specifications for racks and screens?
1. Room for a rake when removing screenings and space so the rake handle will not hit any buildings, overhead wires, light posts, or overhead lights. 2. Provision for a good standing place that will not become slippery. 3. Some place to drain and store the screenings 4. Need for a screw press to dewater screenings. 5. A disposal site for the screenings 6. Sufficient number of channels and capacity of racks and screens and provision to handle peak storm flows 7. A sufficiciet number of standby units. 8. Adherence to the Operation and Maintenance (O&M) requirements of the facilities 9. A hoist to remove screenings, if necessary 10. Dock facility for loading containers of screenings on a truck for disposal. 11. Adequate water under sufficient pressure for hosing down machinery and area 12. Sufficient spare parts in accordance with manufacturer's recommendations
4.5A What kind of problems could be created for the operator when screens or comminutors are overloaded or bypassed?
1. Sticks and rags can fould the raw sludge pumps for the primary clarifiers. 2. Debris can plug the orifices in trickling filter distributors. 3. Debris can interfere with air diffusers in the aeration tanks of activated sludge plants. 4. Floating debris can appear in the chlorine contact basin and leaves the plant in the final effluent. 5. Solids can plug return sludge pumps and flow-meters in activated sludge plants.
5.1E What types of abnormal conditions could affect clarifier performance?
1. Toxic wastes from industrial spills or dumps 2. Storm flows and hydraulic overloads 3. Septicity from collection system problems
4.4C How can you control the velocity in a grit channel in order to maintain velocities within a range of approximately .7 to 1/4 ft/sec?
1. Varying the number of channels in service in a multiple-channel installation 2. Use of proportional weirs 3. Using bricks or cinder blocks to change the cross-section shape or area of the grit channels. However, this can cause cleaning, maintenance, and operational problems.
5.1B What safety precautions should be taken during starting up a clarifier?
1. Wear a hard hat when down in the tank for protection from falling objects 2. Keeps hands away from moving equipment 3. When working on equipment, be sure to tag and use a lockout device on the main circuit breaker and influent control gates to prevent equipment from starting unexpectedly and causing equipment damage or personal injury
5.2C About what percentage of settleable solids should you expect to be removed by your clarifier?
95 to 99 percent of the settleable solids
1.3A How did many receiving waters become polluted?
A lack of the public's concern for the impact of waste discharges and by discharging wastewater into a receiving water beyond its natural purification capacity.
4.4D A stick travels 20 feet in 40 seconds in a grit channel. A) What is the velocity in the channel? B) What corrective action should be taken, if any?
A) .5/ft/sec B) Increase velocity to keep lighter organic solids moving.
1.0B What does an operator do?
A,B,C collect samples, lubricate equipment, record data
1.0C Who employs treatment plant operators?
A,B,C- cities, sanitation districts, industries
2.2A Several of the following contain significant quantities of organ material. Which are they?
A,C, E- domestic wastewater, paper mill waste, tanning wastes
8.2H Testing the aeration compartment of a package activated sludge plant for solids condition may be accomplished by the settlement test. What is indicated if after 30 min. of settling time? A- The solids in the sample do not settle to the bottom half of the jar and the water above them is cloudy or murky? B. The solids in the sample settle to the bottom of the jar with a clear liquor on top but rise in one hour?
A. a longer aeration period, m ore air, or solids wasting is needed. B. This is usually an indication of too much air or too many solids. Another possible cause could be there are not enough solids under aeration. When this happens the sludge will rise because of the high respiration (breathing) rate of the overtaxed organisms and the rapid DO depletion caused by these organisms in the settling compartments.
8.4A When reviewing package plant plans and specifications what provisions should be made to permit rapid servicing of submerged equipment?
Adequate dewatering systems should be provided to permit rapid servicing of submerged equipment.
5.8A Would you place the flotation process Before or After primary sedimentation?
After
8.0D What happens to the air requirement in the aeration tank when the strength (BOD) of the incoming wastewater increase?
Air requirements increase because more food (wastes) encourages biological activity (reproduction and respiration)
4.1A Which of the following items may be found in a treatment plant influent? cans, toys, rubber goods, pieces of wood, all of the above
All of the above
8.2D In starting a diffused-air type plant with air lift pumps for return sludge, why will the air line valve to the air lifts (pumps) have to be closed until the settling compartment is filled?
All the air will attempt to go to the empty compartment and none will go to the diffusers.
6.2E What is the first thing an operator should do before shutting down a trickling filter?
Always take a few minutes to plan what you are going to do.
2.3B What kind of bacteria causes hydrogen sulfide gases to be released?
Anaerobic bacteria
4.4K Book page 95
Answer page100
6.2C Prepare a checklist of items needing daily inspection durign normal operation of trickling filters.
Any indication of ponding Filter flies Odors Plugged orifices Roughness or vibration of the distributor arms Leakage past the distributor turntable seal Splash beyond the filter media Cleanup of slimes not on media
2.1A How does water pick up dissolve substances?
As it falls as rain, flows over land, and is used for domestic, industrial, agricultural and recreational purposes.
4.3A How are comminution units different from bar racks and bar screens?
Bar racks and bar screens remove debris from the wastewater while comminution units grind up debris and leave it in the wasterwater.
3.3A Why is grit removed early in the treatment process?
Because it is an abrasive and will rapidly wear out pumps and other equipment.
8.3L Why are more microorganisms (higher MLSS) needed in the ditch during cold weather than warm weather?
Because the colder the water, the less active the microorganisms
6.2B During start-up of a trickling filter, why should the plant effluent be heavily chlorinated?
Because the slime growth is not completely developed and an unstable effluent will be produced. An unstable effluent will exert a pollutional load on the receiving waters. Heavy chlorination is usually used during this time to reduce the pollutional load and the health hazard to some extent.
3.4A Why is a Parshall flume widely used for measuring wastewater flow?
Because their smooth constriction does not offer any protruding sharp edges or areas where wastewater particles may catch or collect behind the metering device.
3.3B What is usually done with grit that has been removed from the wastewater?
Buried to avoid nuisance conditions.
4.2D How can screenings be disposed of?
By covering them with a minimum of 6 inches (15cm) of earth or by incineration.
6.0D How does the trickling filter process work?
By distributing settled wastewater over the filter media. Microorganisms grow on the filter media and convert colloidal and soluble oxygen-demanding substances to forms that will separate from the wastewater being treated.
1.4B How does the operator become involved in public relations?
By explaining the purpose and operation of the plant to visitors, civic organizations, school classes, news reporters, and city or district representatives.
6.0E How does recirculation increase the efficiency of a trickling filter?
By increasing the time of contact of the wastewater by washing off excess growths (sloughing). Sloughing keeps the biological film in an aerobic condition and seeds the lower regions of the filter with active organisms. Sometimes recirculation (recycling) is practiced intermittently, or only during period of low flow to keep rotary distributors in motion, to prevent drying of the filter growths, or to prevent freezing.
5.6C How can "short-circulating" be corrected?
By installing weir plates, baffles, port openings, and by proper design of the inlet channel.
8.2I How can operators avoid being injured on the job?
By practicing safety, avoiding hazardous conditions, and using safe procedures
8.1B How might harmful industrial waste discharges be regulated to protect an activated sludge process?
By preventing discharge to the collection system, requiring pre-treatment, or controlling the discharge in order to protect an activated sludge process.
8.3H How is the DO in the oxidation ditch regulated?
By raising or lowering the ditch outlet level control weir
5.10C How could you maintain a fairly level sludge blanket in the digester portion of an Imhoff tank?
By reversing the direction flow at regular intervals
3.7C List some of the ways to dewater and dispose of digested sludge.
By using sludge (or sand) drying beds, lagoons, centrifuges, vacuum filters, or filter presses. The dried sludge may be used as a soil conditioner or it may be buried.
1.0A Wastewater is the same thing as
C. sewage
4.2B What safety precautions should be taken when cleaning a bar screen?
Check to make sure that your footing will be secure by removing any slippery substances such as water and grease. Be certain there is adequate space to safely lift the screenings and that there is a receptacle for the screenings (debris).
2.3E What is the most frequently used means of disinfecting treated wastewater?
Chlorination
3.9A List as many advanced waste treatment methods as you can remember.
Coagulation-sedimentation (used in water treatment plants), membranes, filtration, adsorption, and electrodialysis. Also reverse osmosis, chemical oxidation, and the use of polymers.
5,8B Give a very brief description of: colloids and emulsion.
Colloids are very small, finely divided solids that remain dispersed in a liquid for a long time due to their small size and electrical charge Emulsion is a liquid mixture of two or more liquid substances not normally dissolved in one another, but one liquid held in suspension in the other.
5.9A What is a combined sedimentation-digestion unit?
Consist of a small clarifier constructed over a sludge digester. Treatment units of this type have been designed and constructed to serve small populations.
5.8D Give a brief description of the vacuum flotation process.
Consists of aerating the wastewater and creating a vacuum to pull out the air, which will carry the solids to the water surface.
4.3D Why is it hazardous to handle mercury? It is poisonous, Breathing fumes may be fatal, Breathing fumes may cause loss of hair and teeth, All of the above
D. Because it is poisonous and breathing the fumes may be fatal or cause loss of hair and teeth.
5.10D Desribe the sludge from an Imhoff tank that is operating properly.
Digested sludge is relatively odorless or has a musty smell and it is black or very dark in color.
2.4A Total solids consist of ____ and ___ solids, both of which contain organic and inorganic materials.
Dissolved and suspended
5.2A List the basic laboratory tests used to determine clarifier efficiency.
Dissolved oxygen (DO), settleable solids, PH, temperature, BOD, suspended solids, chlorine residual (if needed), and coliform group bacteria (if needed)
6.0C What causes the distributor arms or pipes to rotate on a trickling filter?
Due to the force of the wastewater flowing out of the orifices (as with a lawn sprinkler or fire hose), or they may rotate by mechanical means (a motor and gears).
8.2G How frequently should a package activated sludge plant be visually checked by an operator?
Every day
3.1D Why are combined sewers a problem?
Flows sometimes may become overloaded during storms due to inadequate capacity. This could allow partially treated wastes to be discharged into receiving waters as a result of attempting to treat extreme hydraulic (flow) overloads.
3.1B What problems may occur when it takes a long time for wastewater to flow through the collection sewers to the treatment plant?
Hydrogen sulfide gas maya be released by anaerobic bacteria feeding on wastes. This can cause odor problems, damage concrete in the plant, and make the wastes more difficult to treat.
2.1B What are some of the dissolved substances in water?
Hydrogen, oxygen, calcium, carbon, magnesium, sodium, chloride, sulfate, iron, nitrogen, phosphorus, and organic material
4.4I Why is it necessary or desirable to wash grit?
If the organic material is not removed, then odors could develop. If used as fill material, the fill could settle when the organics decompose.
1.4A Why is it important that the operator be present during the construction of a new plant?
In order to become familiar with the plant before the operator begins operating it.
2.5A Why should an operator have an understanding of natural cycles?
In order to control wastewater treatment processes and odors and also to protect receiving waters.
4.1B Why should coarse debris (rocks, boards, metal) be removed at the plant entrance or headworks?
In order to prevent damage to pumps, plugging of pipes, and filling of digesters.
3.5A What is the purpose of flights or plows in a clarifier?
In rectangular tanks it moves scum along teh surface to a scum trough and push sludge along the bottom to a hopper for removal to the sludge handling facility. Plows scrape sludge along the bottom of circular tanks to a hopper for removal.
8.1A What 2 different ways make effluent quality requirements be states by regulatory agencies?
In terms of percentage removal of wastes or allowable quantities of waster that make be discharged
6.1B What are the principal differences between standard-rate and high-rate filters?
Include BOD loading, hydraulic loadings, depth of the media, recirculation, and effluent quality.
8.2E What would you do if the water in the aeration comparment was murky or cloudy and the aeration compartment had a rotten egg odor?
Increase the aeration rate
5.6G What usually is done with the sludge that collects (settles out) in secondary clarifiers (final settling tanks)?
Is disposed of depending on the particular plant design and the characteristics of the sludge. Sometimes, disposal is accomplished by transferring the sludge to a a primary settling tank to be settled with primary sludge. Other times, it is transferred directly to the digestion system.
8.3M Why is a general cleanup each day at the plant important?
It provides a more pleasant place to work and also improves plant performance
4.2E A plants receives a flow of 4.4 million gallons (MG) on a certain day. The day's screenings are calculated to be 11 cubic feet. How many cubic feet of screenings were removed per MG of flow?
Known: Flow, MGD is 4.4 MGD and Screenings removed cu ft/day is 11 cu ft/day. Unknown is screenings removed, cuft/mg. Screenings removed, cuft/day divided by flow, mgd 11 cu ft/day divided by 4.4 MGD is 2.5 cu ft/ MGD
8.2B What are some common characteristics of all extended aeration types of package plants?
Long solids retention times, high mix liquor suspended solids, and low food microorganism ratios
8.3G When an oxidation ditch is operating properly, how should the activated sludge solids appear?
Look like particles with sharply defined edges and should be golden to rich dark brown in color.
4.3C What has replaced mercury seals in comminutors?
Mechanical seals
2.6A What does NPDES stand for?
National Pollutant Discharge Elimination System
3.10A Does disinfection ususaly kill all organisms in the plant effluent?
No, disinfection is designed to kill or inactivate pathogenic organisms; sterilization kills all organisms in wastewater.
3.6A Would it be a good idea to use trickling filter media of various sizes so it could pack together better?
No. A trickling filter media size should be selected so that the media does not pack together. If the media were packed together, air could not circulate and the organisms on the media would not get enough oxygen.
5.3A How often should sludge be removed from a clarifier?
Often enough to prevent septic conditions or sludge gasification. The proper interval is dependent on many conditions and may vary from 30 minutes to 8 hours, and as much as 24 hours in a few instances. Experience will dictate the proper frequency of removal.
3.4B What are the disadvantages of using weirs to measure influent flows at the head of the plant?
Organic solids may settle out in this area. When this occurs, odors and unsightliness can result. Also, as the solids accumulate, the flow reading may become incorrect.
2.2B List 4 types of pollution
Organic, inorganic, thermal, and radioactive pollution
2.3D What is the term that means "disease causing"?
Pathogenic
8.2J What safety precautions should be taken if you must work alone?
Phone your office at regular intervals and have someone check on you if you fail to report.
3.6C Activated sludge can be pumped from the secondary clarifier to ____ or __________.
Primary clarifier or the waste sludge handling facilities.
5.0A What is the main difference between the sludge from the primary and secondary clarifiers?
Primary sludge is usually denser than secondary sludge.
5.10B How can you force settled material into the digestion compartment?
Pushing it through the connecting slot with a squeegee. Dragging a chain on the flow and allowing it to pass through the slot in another method for removing the sludge accumulation.
5.2B At what two points should samples be collected for measuring clarifier efficiency?
Sample the influent and effluent of the clarifier
4.4A Grit is composed mostly of which of the following substances: grease, sand, rubber goods, eggshells, wood?
Sand and eggshells
3.1C List 3 types of sewers.
Sanitary, storm, and combined sewers
5.1F What steps could be taken to ignore clarifier effluent quality when excessive storm flow infiltration is a frequent problem?
Sealing of the sanitary sewers or use of a flow equalization basin
4.4E Assume you wish to calculate the velocity in the grit channel at your plant's peak flow. Examining the flow charts, you determine that the peak flows are usually about 2.75 MGD. The grit channel is 3 feet wide, and the flow depth is 17 inches at peak flow. What is the velocity in the grit channel under these conditions?
See page 100 in book
5.2D What is the suspended solids removal efficiency of a primary clarifier if the influent concentration is 300 mg/L and the effluent concentration is 12mg/L?
See page 158
5.6D A circular clarifier has a diameter of 80 feet, and an average depth of 10 feet. The flow of wastewater is 4.0 MGD and the suspended solids concentration is 190 mg/L. Calculate the following: 1. Detention Time in hours 2. Weir Overflow Rate in GPD/ft 3. Surface Loading Rate in GPD/sq. ft.
See page 159
5.6E A circular clarifier has a diameter of of 80 feet and an average depth of 10 feet. The clarifier treats 4.0 MGD from the plant inflow plus 1.2 MGD of return sludge flow. The mixed liquor suspended solids concentration is 2,700 mg/L. Calculate the solids loading in lbs/day/sq. ft.
See page 160
4.2A Manually cleaned bar screens should be cleaned frequently to prevent which of the following: The screen from breaking, septic conditions from developing upstream, a shock load on the plant when eventually cleaned, formation of hydrogen sulfide which has a rotten egg odor and causes corrosion of concrete and paints, all of the above
Septic conditions from developing upstream, a shock load on the plant when eventually cleaned, or formation of hydrogen sulfide, which has a rotten egg odor and causes corrosion of concrete and paints. Usually, bar screens are very sturdy and will not collapse under the load from a blockage or an uncleaned screen.
2.4C An Imhoff cone is used to measure ____ solids.
Settleable
8.3I What should be the velocity in the ditch?
Should be maintained between 1.0 and 1.5 FPS
4.4F List the safety hazards that might be encountered while manually cleaning the grit channel.
Slipping or a back injury. Also be aware of dangerous gasses. There have been instances of gasoline or similar material leaking into the sewer and creating a potentially explosive hazard.
5.1C What happens when the flights in a rectangular clarifier are not straight across the tank?
Sludge will be piled higher on the trailing side or the flights will hang up and cause severe damage or personal injury
5.6F Why are secondary clarifiers needed in secondary treatment plants?
The biological treatment processes following the primary clarifier convert more solids to the settleable form and also produce floc containing microorganisms that have to be removed from the treated wastewater. Because of the need to remove these additional solids, the secondary clarifier is considered part of the these other types of processes.
2.3C Where do the disease- causing bacteria in wastewater come from?
The body wastes of humans who have a disease
5.0B What is the main difference between the effluent from primary and secondary clarifiers?
The effluent from the secondary is usually clearer than the primary effluent.
4.3B What are the advantages of comminuting machines over screens?
The elimination of screenings disposal, flies, and odor problems. A disadvantage is that plastic and wood may be rejected and must be removed manually.
3.10B Which would provide better chlorine contact, a 10,000 gallon cubical tank or a length of 10-inch pipe flowing full and containing the same volume as the cubical tank?
The pipe would provide better chlorine contact because water cannot short-circuit (take a short route) through a pipe, while it might not move evenly through a tank and thus some of the water would have a shorter contact time.
6.2D What may happen to a clarifier effluent if the clarifier is not operated within design hydraulic loadings?
The solids in the clarifier will become septic and cause a poor effluent. When the hydraulic loading is too high, some solids may be washed out the of the clarifier.
6.2A Prepare a checklist of items that should be inspected before a trickling filter is placed in service.
The type and amount of oil used in all oil reservoirs Examine the distributor arms for rotation and level Inspect the adjustable distributor orifice settings Remove debris from the underdrain system Touch up any damage to painted surfaces Examine all valves for seating and smooth operation Remember to remove any trash on or in the media
2.5B What can happen when nutrient cycles are disrupted and there is no dissolved oxygen in the receiving water?
These waters become septic, stink, and look terrible.
4.1C What items of equipment are used to remove rocks, pieces of wood, metal, and rags from wastewater?
They are removed using racks, screens, comminutors, and grit removal devices.
3.5B What happens to the sludge and scum collected in a primary clarifier?
They are usually pumped to sludge handling facilities such as digesters.
3.6B Why is a secondary clarifier needed after a trickling filter, rotating biological contractor, or aeration tank?
To allow organisms in treated wastewater to be removed by settling.
8.3C Why should operators avoid walking on top of oxidation ditch side walls?
To avoid slipping and falling into the ditch
3.7B Why are digesters mixed?
To bring food and organisms together, provide a uniform temperature, and prevent the formation of a scum blanket.
5.3C How can floating material (scum) be kept from the clarifier effluent?
To collect scum, a baffle is generally provded at some location int he tank. Primary clarifiers often have a scum collection area where the scum is skimmed off by some mechanical method, usually a skimming arm or a paddle wheel. If mechanical methods are not provided, hand tools may be used, such as a skimming dipper attached to a broom handle.
6.0B What is the purpose of secondary treatment?
To convert dissolved or suspended materials into a form more readily separated from the water being treated. This process produces an overall plant removal of suspended solids and BOD of 90% or more.
2.4B Why is it necessary to measure settleable solids?
To determine the efficiency of settling basins. This amount must also be known to calculate loads on settling basins, sludge pumps, and sludge handling facilities for design and operational purposes. (You should have recognized the need to know the efficiency of settling basins)
5.1D Describe a good operational strategy for a clarifier.
To develop and implement a good preventive maintenance program, to closely monitor operating conditions, and to respond to any lab results that indicate problems are developing.
8.3A Why are the ends of oxidation ditches well rounded?
To prevent eddying in dead areas
8.2C Why should package plants have cathordic protection?
To prevent rust, corrosion, and pitting of metal surfaces and contact with wastewater
4.4B why bother to remove grit?
To prevent wear in pumps, plugged lines, and the occupation of valuable space in digesters.
1.3B Why must municipal and industrial wastewaters receive adequate treatment?
To protect receiving water users
8.0C Why is air added to the aeration tank in the activated sludge process?
To provide oxygen to sustain the living organisms as they oxidize wastes to obtain energy for growth. The application of air also encourages mixing in the aerator.
5.8C Why is the flotation process used in some wastewater treatement plants?
To remove colloids and emusions
4.4G What is the purpose of a cyclone grit separator?
To separate grit from organic material and wastewater.
4.0A True or False The wastewater treatment and pollution control industry has a higher accident rate than most other industries reporting to the National Safety Council.
True
4.0B True or False Electrical power must always be shut off before working on equipment.
True
4.0C True or False Operators must wash their hands thouroughly before eating, smoking, or going home.
True
4.2C What should be done first if a problem develops in a mechanically cleaned screen?
Visually identify what appears to be the cause of the problem, then shut off the machine if you must work on the equipment. Any moving equipment is hazardous, regardless of its speed.
8/4B When reviewing oxidation ditch plans and specifications, what considerations should be given to the walkways extended to provide access to the rotor for maintenance?
Walkways with railings must be provided across the aeration channel to provide access to the rotors for maintenance. The normal location is upstream of the rotor. The location should prevent spray from the rotor on the walkway. Approved flotation devices should be provided at strategic locations if accidental entry into the channel is possible.
8.2F If it becomes necessary to waste sludge, how much and when should it be wasted?
Waste about 5% of the solids each week during warm weather operation.
8.OB What is a stabalized waste?
Waste that has been treated or decomposed to the extent that, if discharged or released, its rate and state of decomposition would be such that the waste would not cause a nuisance or odors in the receiving waters.
6.2F What items should be considered when planning to shut down a trickling filter?
What is the incoming flow? How will a shutdown affect the rest of the plant? Are the necessary tools and other needed items available? Are there any other tasks that should be performed while the filter is off the line?
5.3B How can you tell when to stop pumping sludge?
When it becomes thin. Thin sludge can be detected by the sounds of the sludge pump, differences in sludge pumping pressure gauge readings, and sludge density gauge readings, visual observation of a small quantity (gallon or less), and through a sight glass in the sludge line while the sludge is being pumped.
5.6A What is "short-circulating" in a clarifier?
When the flow is not uniform throughout the tank. In this situation, the water flows too rapidly in one or more sections of the clarifier to allow sufficient time for settling to occur.
8.3F During plant start up, when should the rotors be started?
When the water level in the ditch reaching the bottom of the rotor blades
3.8A How are ponds similar to the following: 1. primary clarifiers, 2. anaerobic digesters, 3. trickling filters or aeration tanks?
When wastewater is discharged to a pond, teh settleable solids fall to the bottom just as they do in primary clarifiers. The solids begin to decompose and soon use up all the dissolved oxygen in the nearby water. A population of anaerobic bacteria then continues the decomposition, much the same as an anaerobic digester. Aerobic bacteria, algae, and other microorganisms feed on the dissolved solids in the upper layer of the pond similar to the way they do in a trickling filter or aeration tank.
5.6B Why is "short- circulating" undesireable?
Where the velocity is too high, particles will not have time to settle. Where the velocity is too low, undesirable septic conditions my develop.
8.3K What problems can be caused by ice buildup during cold weather?
Will hinder or stop altogether the proper operation of mechanical parts such as rotors and sludge scraper mechanisms
8.3J What observations should be made daily to help indicate the performance of the oxidation ditch?
color of the mix liquor in the ditch, odor at the plant site, and clarity of the ditch and sedimentation tank surfaces
8.2A How many compartments are there in a typical package extended aeration plant? What is the purpose of each compartment?
either 2 or 3 compartments The purpose of each compartment is: 1. aeration 2. Clarification and settling 3. Aerobic Digestion
2.3A What causes oxygen depletion when organic wastes are discharged to water?
organic wastes in water provides food for bacteria. These bacteria require oxygen to survive and deplete the oxygen int he water in a way similar to the way oxygen is removed from air when people breathe.
6.0A Primary treatment is effective in removing ____ ___, and _____, but is not nearly as effective in removing ___.
settleable solids, scum or floatable solids, lighter suspended solids or dissolved solids
5.10A What are the two components of an Imhoff tank?
settling area and sludge digestion area
6.1A What are the 3 general classifications of trickling filters?
standard rate, high-rate, and roughing filters
3.1A Why should the operator be familiar with the wastewater collection and transportation network?
the operator will be able to spot troubles and take corrective action.
8.0A What is the purpose of the activated sludge process in treating wastewater?
to oxidize and remove soluble or finely divided suspended materials that were not removed by previous treatment.
