Wastewater Treatment Exam Solutions: Texas Water Code Guide, Exams of Biology

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TCEQ Wastewater License

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What are the steps of the Water Use Cycle? - answer Environment --> Water Treatment --> Water Distribution System --> Customer Use --> Wastewater Collection System --> Wastewater Treatment --> Environment What are the benefits of the collection system? - answer - Removal of health hazards

• Prevention of odors and flies
• Cleanliness and appearance
• Comfort and convenience Septic vs. Fresh wastewater? - answer Septic wastewater doesn't contain dissolved oxygen and is difficult to treat. Fresh wastewater contains dissolved oxygen and is easier to treat, which results in higher quality effluent Inflow - answer Surface runoff that enters the collection system Infiltration - answer Groundwater that enters the collection system through holes, cracks, etc. What is the average domestic contribution to the collection system? (Per person/day) - answer 100 gallons per day What are the four wastewater characteristics? - answer Physical, Chemical, Bacteriological, and Radiological Domestic wastewater is ___% water and ___% solids - answer 99.9% water, 0.1% solids

Settleable solids - answer Suspended solids that will settle when wastewater flow is still or slow moving What is the pH scale range? - answer 0 (most acidic) to 14 (most basic), 7 is neutral Does septic or freshwater have a lower pH? Why? - answer Septic has lower pH due to volatile acids formed from wastewater decomposition What is Hydrogen Sulfide (H2S)? When does it occur? - answer A colorless, toxic, and flammable gas that resembles the smell of rotten eggs. It results from the bacterial breakdown of organic matter in the absence of oxygen. It is heavier than air. What is Methane? (CH4) What percentage of methane is in digester gas? - answer A colorless, odorless, and highly flammable gas. Methane is an asphyxiant and is lighter than air. Digester gas contains 65% methane and is used for heating fuel or operating equipment. What is carbon dioxide? (CO2) - answer A colorless, odorless gas that has a suffocating effect. When inhaled at higher than normal concentrations, it can produce a sour taste in the mouth and a stinging sensation in the nose and throat. What is carbon monoxide? (CO) - answer A colorless, odorless, and tasteless gas Why is oil and grease a concern if present in wastewater? - answer It may cause explosions, fires, line blockages, and odor What are chlorides and why are excessive chlorides in wastewater bad? - answer Excessive chlorides interfere with treatment processes, especially trickling filters. They also affect laboratory tests.

How did the state get its authority to control water pollution? - answer The Environmental Protection Agency (EPA) delegated that authority to the individual states. What is the EPA's primary wastewater legislation? - answer The Federal Water Pollution Control Act of 1972. As amended in 1977, this law commonly became known as the Clean Water Act What did the Clean Water Act do? - answer - Created pollution control programs

• Made it unlawful to discharge a point source into navigable waters without a permit
• Funded construction of wastewater treatment plants When can TCEQ revoke an operator's permit? - answer If the operator:
• violates the permit
• falsifies records
• states misleading information on the licensing application
• or causes other violations What is an accidental discharge? When must TCEQ be notified about it? - answer An act or omission through which waste or other substances are inadvertently discharged into water in the state. TCEQ must be notified within 24 hours if one occurs. What is an unauthorized discharge? - answer Any discharge of wastewater into or adjacent to waters in the state at a location not permitted as an outfall. Ex: SSO At what population does a city may have to establish a water pollution control and abatement program? - answer 10,000 or more Lift stations are built when wastewater is: - answer - Raised to a higher elevation

• Pumped over a hill
• Lifted at a plant for gravity flow TCEQ's goals regarding water pollution control are: - answer - To maintain state water quality
• To promote wastewater collection and disposal systems
• To use all reasonable methods to implement the state water plan The TCEQ may assess administrative penalties up to $______ per day for each violation - answer $25, Required records, such as flow and effluent quality, must be kept for ___ years. Sludge records must be kept ___ years. - answer 3, 5 Reports, including Discharge Monitoring Reports and Monthly Effluent Reports, are to be submitted to the TCEQ no later than the __ of the _____ month. - answer 20th, following About ___ pounds of BOD are contributed daily by each person (The BOD population equivalent) - answer 0. Any plant with a design flow above ___ MGD is required to install instrumentation for continuous flow totalizing - answer 0.5 MGD What does preliminary treatment do? - answer It protects the treatment system from large obstructions in the raw influent, unnecessary wear on process equipment, and fluctuations of flow and pollutant strength What does primary treatment do? It should remove what percentage of settleable solids, suspended solids, BOD, and total organic matter? - answer Primary treatment is the removal of settleable solids from the raw wastewater It should remove:

What is the purpose of Return Activated Sludge (RAS)? - answer Pumps continuously send RAS to the aeration tank, which reseeds the biological reaction in the aeration tank and removes accumulating sludge from the clarifier What is F/M? - answer The ratio of the amount of food applied per day to the microorganisms in the aeration tanks What is Gould Sludge Age? - answer How long, in days, a pound of solids stays in the aerator What is Mean Cell Residence Time? - answer Estimates how long the living cells are kept in the plant What are the five important controls for activated sludge plants? - answer

• Dissolved Oxygen
• Aerator solids levels
• Solids quality
• Rate of return sludge
• Wasting rate What would be the cause of rising sludge and gas bubbles in the final clarifier? - answer Denitrification (This one is opposite) A = Influent B = Aeration Tank C = Clarifier D = Waste Activated Sludge E = Return Activated Sludge - answer What does A-F represent?

What is a trickling filter? - answer A fixed film process where wastewater trickles over media, usually rock or plastic. Wastes are then consumed by layers of bacteria, protozoa, fungi, and other organisms that live on the media. What are the five basic parts in a trickling filter? - answer - Filter floor

• Underdrain system
• Walls
• Filter media
• Distribution arms What is the material that sloughs off the trickling filter that settles in the clarifier? - answer Humus sludge What is super important about the distribution arms on a trickling filter? - answer Orifices or nozzles on the rotating arms should be inspected daily for clogging and cleaned if necessary. There should be no trash or large debris through the filter. How do Rotating Biological Contactors spin? - answer Each unit is driven either by a motor with a gear reducer or by air trapped in air cups In Rotating Biological Contactors, what is the biological growth like? - answer The entire wetted surface area of the disc becomes covered by a 0.05-0.1 inch film of gray to brown biological growth. It contains approximately 50,000 mg/L of solids What can advanced treatment processes do that secondary treatment can't? - answer Advanced treatment processes strive to provide a higher removal level of specific compounds, suspended solids, and oxygen- demanding materials that cannot be achieved through secondary treatment alone. In advanced treatment processes, what is the most important factor affecting filter performance? - answer the quality of the secondary effluent being applied to the filter - low in solids

BOD analysis should begin no later than after __ hours of sampling (after being refrigerated to __C) to be assured of representative results - answer 6 hours, 6 degrees Celsius What is the holding time for TSS after being collected in a wastewater treatment plant? - answer 7 days What is the definition of a flow-weighted composite sample? - answer A combination of portions of samples collected at regular intervals and combined according to flow The Sludge Volume Index (SVI) should range from ________. What does being out of this range mean? - answer 70 to 150. Under 70 = sludge is settling so rapidly that poor clarification will result. Over 150 = there becomes a tendency for the sludge to begin bulking and solids sent over the weir of the final clarifier What is the preferred Guild Sludge Age (GSA) for activated sludge? - answer 5-10 days for conventional and complete mix plants,

25 days for extended aeration plant Operators should be concerned with what four types of microorganisms? - answer Amoeboids, flagellates, ciliates, and rotifers Name the presence of the four different microorganisms in good quality sludge with good settling in order from most prominent to least prominent

• answer 1. Free swimming ciliates

2. Stalked ciliates
3. Flagellates
4. Rotifers
5. Amoeboids At what percentage of exposure can hydrogen sulfide begin to harm you? - answer Exposure for 2-15 minutes at 0.01% impairs the sense of smell.

Exposure to amounts of 0.07-0.1% rapidly causes acute poisoning, paralyzing the lungs What is the most common reason for large amounts of sand, gravel, and grit entering the plant? - answer Storm events What is the relationship between water temperature and capability to hold dissolved oxygen? - answer An inverse relationship. As the water gets colder, it is capable of holding more dissolved oxygen. As it gets warmer, the ability to hold dissolved oxygen decreases The Clean Water Act requires WWTPs to achieve greater than or equal to __% removal of TSS and BOD - answer 85% What is the imhoff cone used to measure? - answer Settleable solids What are different types of preliminary treatment? - answer racks, screens, grinders, grit channels What is grit and why is it removed during preliminary treatment? - answer Grit consists of non-biodegradable particles including sand, , rocks, coffee grounds, etc. It is removed to remove the heavy, inorganic waste that doesn't break down during treatment and to prevent equipment damage. What are coagulants? What is flocculation? - answer Coagulants are chemicals that cause very fine particles to clump together into larger particles Flocculation is the gathering together of fine particles after coagulation to form larger particles What are colloidal particles? What can be used to get rid of them? - answer Very small particles that carry an electric charge which makes it very difficult for them to flocculate and settle. Coagulants can be used to neutralize the charge and enable them to flock together.

Solids remain in an anaerobic digester for ___ days - answer 15-20 days. Each time sludge is pumped into a digester, an equal volume of sludge is transferred to the secondary digester What are four methods of dewatering stabilized sludge? - answer belt press, centrifuge, plate and frame press, drying beds and lagoons What can an operator do to reduce the effluent BOD of a Trickling Filter? - answer Raise recirculation rate. What do evaporators in the chlorine feed system do? - answer Convert liquid chlorine to gaseous chlorine for use by chlorinators What is the purpose of recirculating trickling filter effluent? - answer To keep a constant hydraulic load on the trickling filter The Clean Water Act (CWA) defines secondary treatment as a wastewater treatment plant that consistently produces an effluent that contains no more than _____BOD and ______ Suspended Solids based on a _____day average - answer 30 mg/L, 30 mg/L, and 30 day average What is the best chemical to use for pond odor control? - answer Sodium Nitrate When operating a Rotating Biological Contactor plant to nitrify incoming ammonia, the DO levels in the nitrification stage should be maintained in the range of: - answer 2.0 - 3.5 mg/L. Wastewater flowing through a grit channel should ideally flow at a velocity of: - answer 1 fps. Each stage of the RBC process should have sufficient volume to provide for a contact time of about: - answer 1 hour

When might surface aerators be necessary when operating a pond? - answer During night, during periods of organic overload, and during cold seasons What should an operator do if an anaerobic digester is noticing that the volatile acid/alkalinity ratio is increasing? - answer To cure a souring digester, the operator should reduce the sludge feed and removal rate from the digester and ensure adequate mixing is occurring What does the outlet baffle do on a pond? - answer Prevents surface debris from leaving the pond. Floatable scum is usually removed from wastewater in the: - answer Primary clarifier What must be considered when designing a No Discharge pond system? - answer percolation rates and evaporation rates How can the operator control the scum blanket in an anaerobic digester? - answer proper mixing and heat control What adverse condition may be created if the pressure relief or the air relief operates on an anaerobic digester? - answer an explosive condition can be created by the mixture of methane and air. What problem is indicated by organic material in removed grit? - answer that flow velocities are too low in the grit channel.