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(11)
(11) Wastewater Collection and Treatment
| Question | Answer |
|---|---|
| Extraneous Flow | Refers to stormwater or groundwater that unintentionally enters the wastewater collection system |
| Separated Sewer Systems (SSS) | Stormwater and sewer are conveyed through separate pipe networks |
| Combined Sewer Systems (CSS) | Both stormwater and sewage are conveyed in the same pipe network |
| Sanitary Sewer Overflows (SSOs) | Occurs when infiltration or inflow exceeds the system's capacity, resulting in the unintended release of untreated sewage into the environment, posing severe health and environmental risks. |
| Combined Sewer Overflows (CSOs) | Occur when the combined flow of stormwater and sewage overwhelms the system, causing untreated sewage and stormwater to discharge into the environment and water bodies. |
| Conservation of Mass Principle | States that mass is neither created out of nothing nor destroyed but can be transferred from one form to another. |
| Peak Wastewater Flow Rate | The highest expected flow rate in the system over a given period |
| Dry Weather Flow (DWF) | The total wastewater flow rate during periods of little or no rainfall |
| Wet Weather Flow (WWF) | The total wastewater flow rate during periods of moderate to heavy rain |
| Linear Projection Model | A simple approach to population growth in which the future population is estimated based on a constant growth rate over time |
| Growth Ratio Constant Model | Relates the population growth of a smaller region to that of a larger region, using a proportional relationship |
| Log/Exponential Growth Model | Population growth is proportional to the current population, leading to exponential increases over time |
| Percent Growth Model | Assumes that population increases by a percentage over each time period |
| Saturation Growth Model | Accounts for the eventual slowing of population growth as it approaches a maximum capacity or saturation level |
| Unit Process | Describes a contained, closed batch treatment process in which a specific goal of treatment is achieved. |
| Total Solids | Represent all the solid material in the sample, both suspended and dissolved. |
| Total Suspended Solids (TSS) | Are the particles suspended in the sample that do not dissolve |
| Total Dissolved Solids (TDS) | Are the dissolved materials in the sample that remain after filtration |
| Volatile Dissolved Solids (VDS) | Are the portion of the dissolved solids that volatize upon ignition |
| Fixed Dissolved Solids (FDS) | Are the remaining nonvolatile portion of the dissolved solids |
| Physical Treatment | Fundamental process in wastewater treatment systems that is aimed at removing suspended solids from the water |
| Drag Force | Is a resistance to motion experienced by a falling body through a fluid |
| Hydraulic Loading Rate | Called overflow velocity, is a vertical velocity that can be calculated by dividing the flow rate by the surface area of of the settling tank |
| Type I Settling: Discrete Settling | Most simplest form of settling; there is a reduction in flow speed to allow dense particles to settle manually to the bottom of the clarifier tank |
| Detention Time | The time a particle spends in a tank |
| Biochemical Oxygen Demand (BOD) | A measure of the dissolved oxygen used to sustain carbon-based life forms |
| Chemical Oxygen Demand (COD) | Is the amount of oxygen consumed by chemical reactions required to break down soluble and insoluble organic matter in wastewater |
| Theoretical Oxygen Demand | Is the oxygen demand as calculated from theoretical chemically balanced equations |
| Agglomeration | The formation of flocs |
| Flocs | Are clusters of particles that come together due to this neutralization, increasing in size and mass |
| Intake | The first stage in a wastewater treatment plant, where water or wastewater is drawn from the conveyance systems |
| Wet Well | A chamber pit in a pump station designed to temporarily store wastewater, stormwater, or sewage before it is pumped to a treatment facility or higher elevations |
| Microscreens | A specialized type of fine screen, are often used to filter residual solids from treated effluent |
| Comminutors | Include screens to capture debris as it passes through the flow channel and shred the debris to reduce its size |
| Macerators | Simple devices design to cut or chop solids into smaller pieces without the use of screens |
| Stilling Wells | Serve to dampen fluctuations in the water surface, providing stable and accurate water level measurements at these critical points |
| Horizontal Grit Chamber | Is a wastewater treatment unit designed to remove dense inorganic particles, such as sand and gravel, from the wastewater stream |
| Primary Treatment | Follows the completion of preliminary treatment and focuses on the physical removal of suspended particles by sedimentation |
| Type II Settling: Uniform/Flocculant Settling | Employs flocculants to aggregate particles together. The particles change shape and density due to aggregation, causing particles to settle under their own weight |
| Type III Settling: Zone Settling/Thickening | As the concentration of particles in a suspension increases, particles become so closely spaced that they no longer settle independently. Instead, the high concentration causes the entire suspension to settle as a blanket, with increased drag forces. |
| Hindering | High concentration causes the entire suspension to settle as a blanket, with increased drag forces leading to reduced settling velocity |
| Type III Settling: Zone Settling/Thickening | The formation of distinct zones within the settling suspension |
| Type IV Settling: Compression Settling | Weight of overlying settling solid material compresses the already settled material, which creates a denser sludge as this drives out water from the voids. |
| Iso-Percent Curve (Bounding Equal Percentage Curve) | The percentage of removal for Type 2 settlement is plotted on a graph of depth and time producing a curve |
| Attached Growth System | Bacteria grow on solid surfaces such as rocks or plastic media |
| Sloughing | Drawback of attached growth systems is that the inner layers of bacteria may not receive sufficient oxygen or nutrients, limiting their activity, and thus these bacteria will be weakened and can detach from surfaces and flow out with the treated effluent |
| Suspended Growth System | Bacteria are freely suspended in the wastewater, where they feed on harmful bacteria. |
| Activated Sludge | Settled solids which is sludge, contain live bacteria |
| Returned-Activated Sludge | Treatment system is set up so that some of the activated sludge is returned to the start of secondary treatment |
| Waste-Activated Sludge | Activated sludge that is not returned |
| Mixed Liquor Suspended Solids (MLSS) | Includes suspended solids in the aeration tank (both organic and inorganic) |
| Mixed Liquor Volatile Suspended Solids (MLVSS) | The portion of mixed liquor suspended solids that is organic and thus can be volatized by heat |
| Continuous Stirred Tank Reactor | A model of a reactor in which the influent material is assumed to be completely and homogenously dispersed throughout the reactor, and the effluent concentration is the same as the concentration in the reactor. |
| Plug Flow Reactor | A reactor model in which wastewater moves through the reactor in the form of discrete pulses, sperate from each other |
| Batch Reactor | A reactor model similar a continuous stirred tank reactor, to as mixing is achieved by complete stirring; influent and effluent are not one continuous flow. |
| Lag Phase | The bacteria have just been introduced in the aeration tank and are still acclimatizing to the new environment |
| Accelerated Growth Phase | The bacteria have started to acclimatize to the new environment |
| Log Growth Phase | The bacteria have acclimatize to the new environment |
| Decelerated Growth Phase | The bacteria are so numerous that they start to compete for available sources (oxygen and nutrients) |
| Stationary Growth Phase | There is no increase in the population of the bacteria |
| Death Phase | The available resources have been consumed, and the bacteria start dying off or feeding on themselves |
| First-Order Reaction | The rate of growth is directly proportional to the amount of available bacteria |
| Dilution | The rate at which wastewater or bacterial cultural is replaced or refreshed in a continuous flow system. |
| Substrate | The organic or inorganic material that the microorganisms consume as a source of energy and nutrients in biological processes, commonly measured in wastewater treatment as BOD or COD. |
| Yield Coefficient | Is a dimensionless number that describes the amount of biomass produced per substate utilized |
| Specific Substrate Utilization Rate | Is the rate at which substrate is utilized per unit of biomass produced. |
| Specific Growth Rate | Is the constant rate at which biomass is increasing in a population |
| Solids Retention Time | The average amount of time that microorganisms are kept in a wastewater treatment system |
| Food-To-Microorganisms (F/M) | Represents the balance in a treatment system between the biomass (microorganism) and the organic material or "food" (substrate) available for the microorganisms. |
| Sludge Volume Index (SVI) | A measure of the volume occupied by one gram of sludge after 30 min of settling |
| Organic Loading Rate (Volumetric Loading) | Is the mass of BOD applied to a given aeration basin per day. |
| Nitrates | The end product of nitrification, are formed when nitrites are fully oxidized |
| Nitrites | Are intermediates in the nitrification process, created during the oxidation of ammonia, and are typically unstable, quickly converting to nitrates in the presence of oxygen |
| Nitrification | Is an oxidation reaction where ammonium is oxidized to nitrite which is further oxidized to nitrate |
| Denitrification | Is a reduction reaction where nitrates are reduced to nitrogen gas which is then released into the atmosphere |
| Sludge | A residual mixture of solids and water produced at any stage of wastewater treatment that has not undergone processes to reduce pathogens or vector attraction |
| Thickening | Increasing the solid content of the sludge by removing a portion of the liquid |
| Gravity Thickening | Relies on gravity to settle solids at the bottom of a tank, separating them from the liquid |
| Dissolved Air Flotation | Introduces microscopic air bubbles that lift lighter sludge particles to the surface, forming a sludge layer that be skimmed off |
| Centrifugation | Involves spinning the sludge at high speeds to separate solids from liquids using centrifugal force |
| Belt Thickening | Uses a continuous belt filter to remove water through a combination of pressure and gravity |
| Rotary Drum Thickening | Rotates sludge in a perforated drum, allowing water to drain and leaving behind concentrated solids. |
| Supernatant | When the digestion process produces gas (biogas) and the sludge is stabilized inside the tank. During this process, the liquid that forms above the sludge. |
| Aerobic Digestion | Involves the oxidation of biodegradable matter and microbial cellular material by aerobic microorganisms |
| Centrifugation | A mechanical process used to separate solid particles from liquid in sludge by applying centrifugal force |
| Incineration | Process involves subjecting sludge to high temperatures in specially designed furnaces to reduce its volume and eliminate harmful pathogens |
| Commonly Used Disinfection Agent | Chlorine |
| Commonly Used Disinfection Agent | Ozone |
| Commonly Used Disinfection Agent | Ultra-Violet (UV) |
| Commonly Used Disinfection Agent | Lime |
| UV Dose | The level of UV exposure microorganisms in wastewater receive before dying off to acceptable levels |
| Chlorine Demand | Difference between the amount of chlorine added to wastewater and the amount of chlorine remaining at the end of the contact period |
| Breakpoint Chlorination | Chlorinating wastewater to the point when all chloramines in the wastewater are completely destroyed |
| Advanced Treatment (Tertiary Treatment) | Provides a final level of purification of effluent beyond primary and secondary treatments |
| Downflow Roughing Filters | Water flows from the top down through the filter layers |
| Upflow Roughing Filters | Water enters from the bottom of the filter and flows upward through the filter media |
| Horizontal Flow Roughing Filters | Water flows horizontally through a series of filter compartments |
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