ENE Exam 4
Pretreatment
3 processes: 1. Bar Racks/Bar Screens 2. Grit Chambers/Grit Tanks 3. Equalization Removes material that may cause operational problems.
Of 25 most frequently detected ground water contaminants...
9 are INORGANIC (lead, chromium, zinc) Rest are ORGANIC (TCE, PCE, benzene, toluene)
Saturated Zone
A layer of permeable rock or soil in which the cracks & pores are COMPLETELY FILLED with water.
Primary Sedimentation
Removes suspended solids and floating organic material (called scum) to reduce the suspended solids load for subsequent treatment processes.
Primary Treatment
Removes wastes in settling tank (primary clarities). Wastewater is held for several hours while particles settle to bottom. Removal by mechanical scrapers. Skimming of top to remove risen grease. Removes ~60% of SS, and ~35% of BOD5
MRDLG
Maximum Residual Disinfectant Level Goals.
MRDL
Maximum Residual Disinfectant Level. The highest level of a disinfectant allowed in drinking water without causing an unacceptable possibility of adverse health effects.
Dispersed/Suspended Growth
Microbes are suspended in liquid wastewater ie: Activated Sludge, Oxidation Ponds
Fixed/Attached Growth
Microbes grow on a surface. ie: Trickling Filters, Rotating Biological Contactors
Source Reduction and Reuse
Reducing amount of toxicity of materials bc they become MSW (change in design). Reusal (bottles).
On-Site Wastewater Treatment
"Conventional Septic Systems" in the U.S., 25% of the population uses these. 1. Septic Tank 2. Leach/Absorption/Drain Field
Phosphorus range to be kept to prevent algal blooms.
(0.01 - 0.015) mg/L
Carbonate Hardness
(CH): Ca2+ and Mg2+ associated with bicarbonate (HCO3-) and carbonate (CO32-)
Noncarbonate Hardness
(NCH): Ca2+ and Mg2+ associated with other ions (Cl-, NO3-, SO42-)
Total Hardness
(TH): Sum of all polyvalent cations, amount of calcium/magnesium ions.
Remediation Methods
1. Pump & Treat Technology 2. Soil Vapor Extraction 3. Air Sparging Systems 4. In Situ Bioremediation 5. Permeable Reactive Barriers
2 systems that work to stop spread of waterbourne diseases
1. Safe Drinking Water Act 2. Clean Waters Act
Water Treatment Process
1. Screening 2. Primary Sedimentation 3. (i) Rapid Mixing (ii) Coagulation/Flocculation (iii) Secondary Sedimentation
Radionuclides
- Alpha Particles - Radium 226 and 228 - Beta Particles/Photon Emitties - Uranium
Hydraulic Gradient
- Dimensionless value (l/l) - Refers to slope of water table - Calculated with hydraulic head values: vertical distance from reference plane (often at sea level) to water table
Secondary Treatment
- Microorganisms degrade and breakdown the organic material - BOD and SS removal beyond that achieved in primary treatment - Requires healthy microorganisms Processes: 1. Activated Sludge/Oxidation Ponds (suspended/dispersed growth. 2. Trickling Filters, Rotating Biological Contractors (fixed/attached growth) Removes ~90% of both SS and BOD5
Hydraulic Conductivity
- Property of geological material - Measure of how easy it is to obtain flow of water through porous media (sand/gravel/etc.) - Units: l/time
Sources of Acid Rain and Acid Deposition
- SO2 in coal forms sulfuric acid - NOx from vehicle's combustion forms nitric acid
Septic Tank
- Solids settle - Solids undergo anaerobic digestion (degradation w/out O2) - Excess liquid drains into leach field
Examples of municipal solid waste
- Yard trimmings - Food scraps - Plastics - Paper and cardboard
Disinfectant By-Product
1. HAA5: Sum of 5 Haloacetic Acids 2. TTHM: Total Trihalomethane 3. Bromate and Chlorite
Primary Standards Classifications
1. Microbiological Contaminants 2. Disinfectants 3. Disinfectant By-Product 4. Inorganic's 5. Organic's 6. Radionuclides
Standard Categories of the Safe Drinking Waters Act
1. National Primary Drinking Water Regulations (Primary Standards) 2. National Secondary Drinking Water Regulations (Secondary Standards)
Subtitle D
Addresses non-hazardous waste.
Landfilling
Before 1979, we only disposed into dumps. Federal Standards: - Location - Liner requirements (overlay 2ft of clay/soil) - Leachate collection and disposal - Operating practices (frequently overlaying) - Groundwater monitoring - Closure and past closure requirements - Financial (long-term)
Composting
Biological decomposition of organic matter into humus (a soil-like material). Can be used as a fertilizer.
Biosolids Management
Biosolids = Residual Solids = Sludge
Total Dissolved Solids
Cannot be removed by filter.
Acid Deposition
Caused by sulfuric and nitric acids resulting in a lowered pH of surface waters. Can be wet (rain/snow) or dry (gas particles) Potential damage to ecosystems: 1. Many species cannot tolerate low pH values 2. Low pH values solubilize metals, resulting in increased toxicity
Rapid Mixing
Coagulant is added and mixed in.
Coagulation
Coagulants - Alum - Ferrous Sulfate - Ferric Chloride
Landfill Operation
Compacted into cells. Cells are covered periodically (layer of soil). When an area is filled with cells other layers can be added on top (lifts).
Equalization
Dampens variation in wastewater flow to WWTP. Wastewater is collected in large basins and pumped out at a constant rate. Improves effectiveness of primary/secondary treatments.
Subtitle C
Defines and regulates hazardous waste.
DNAPL
Dense Non-Aqueous Phase Liquid (denser than water)
In Situ Bioremediation
Designed to biodegrade subsurface pollution. - Bioventing provides O2, results in biodegradation of pollutants - Carbon Addition (Anaerobic Removal) has been successful for bioremediation (TCE/PCE)
Final Treatment
Disinfections commonly by addition of chlorine gas. Kills microorganisms.
Air Sparging Systems
Drive air into saturated contaminant zone.
Integrated Waste Management
EPA recommended... 1. Source Reduction and Reuse 2. Recycling/Composting 3. Incineration/Landfilling
Pump & Treat Technology
Extracting contaminated groundwater and then treating it above ground. Treated effluent can be used for beneficial purposes or returned to the aquifer. Expensive and time consuming.
Secondary Sedimentation
Flocs settle by gravity and are removed.
Confined Aquifer
Found between two confining layers (aquitards).
Permeable Reactive Barriers
Groundwater passes through permeable wall (most commonly a zero valent iron).
Aquitard
Impermeable beds that hinder or prevent groundwater movement.
Nitrogen Removal
It can be in many forms. Blue Baby Syndrome: methemoylobinemia (High NO3-) Removal by: (Biological) 1. Nitrification: Ammonium (NH3+) to nitrate (NO3-) 2. Denitrification: Nitrate (NO3-) to nitrogen gas (Chemical) 1. Ammonia Stripping: Converts ammonia ions (NH4+) to ammonia gas (NH3)
Eutrophic
Lake that's accumulated silt and organic debris. Excess nutrients. High plant productivity.
LFG's
Landfill Gas - treated as waste materials decompose. ~50% methane (CH4) ~50% carbon dioxide (CO2) Can be captured and used to generate energy.
Safe Drinking Water Act
Law established by EPA to set national health-based standards on drinking water. Aimed to protect against naturally occurring and man-made contaminants.
Clean Water Act
Law established by the EPA that regulates pollutant discharge into waters of the U.S. Implements standards and programs to monitor these pollutant discharges. ie: BOD, nutrients, microorganisms
LNAPL
Light Non-Aqueous Phase Liquid (lighter than water)
Oligotrophic
Low nutrient level. Low plant productivity.
Legally Enforceable SDWA standards
MCL TT MRDL
Not Legally Enforceable SDWA standards
MCLG MRDLG
MCL
Maximum Contaminant Level EPA balances public health benefit against economic/technical considerations.
MCLG
Maximum Contaminant Level Goals Represent no known health effects. It doesn't consider technological feasibility or cost.
Unconfined Aquifer
Next to only one confining layer (aquitard).
NAPL
Non-Aqueous Phase Liquid Organic materials sometimes may not completely dissolve in water.
Secondary Standards
Non-Enforceable. Aesthetic Effects - damage to water equipment.
Incineration
Pros: - Immediate volume reduction - Less land required - Possibility of recovering energy Cons: - Ash management needed - Air pollution - Public perceptions
Acid Rain
Rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water. pH < 5.6
Phosphorus Removal
Removal by chemical precipitation: Alluminum Sulfate Al(SO4)3 Teric Chloride FeCl3
Soil Vapor Extraction (SVE)
Remove organic vapors from unsaturated zone. - Vapors are extracted up and sent to treatment units - Works well with highly volatile contaminants and permeable soils - Can be combined with other methods
Grit Chambers/Grit Tanks
Removes inert dense material (broken glass/silt). "Grit" refers to the fact that these materials are too small to be removed by bar screens.
Screening
Removes larger items.
Bar Racks/Bar Screens
Removes larger objects. Solids material sent to landfill.
Filtration
Removes particles that are too small to be effectively removed during previous steps.
RCRA
Resource Conservation and Recovery Act Regulates solid waste. -Subtitles C/D
Surface Water examples
Rivers Lakes Reservoirs
Total Solids
SS + TDS
Aquifer
Saturated geological layer that is permeable (water can flow through). Found on top of a "confining layer".
Rotating Biological Contactors (RBC's)
Series of discs (~3m dia.) Half of each disc is submerged into water and rotated. Biofilm develops on discs.
Leach Field
Series of trenches that contain PVC pipes and multiple drainage holes. Organics/inorganic's in liquid are degraded in soil and liquid is lost through various processes. ie: evaporation, percolation, plant uptake
Groundwater examples
Shallow wells (< 50 ft deep) Deep wells (> 50 ft deep)
Coagulation/Flocculation
Slow mixing, converts smaller particles into larger particles (flocs).
Suspended Solids
Solids/particles that can be removed by filter (1.7 micrometers)
Activated Sludge
Suspended or dispersed growth. Uses aeration and aerobic microorganisms to help to break down contaminants. Process: In the reaeration tank, microorganisms (activated sludge) consume and oxidize organic material. Wastewater flows to the settling tank.
Microbiological Contaminants
Total coloform. - "Indicator Organisms" bc they indicate fecal and other contaminations - Many of these coloforms are enteric (live in intestines)
Eutrophication
Transition from oligotrophic to eutrophic. Can occur naturally or forced by nature.
Sludge Treatment
Treated sludge/incinerated ash to landfills or used as fertilizers.
TT
Treatment Technique Contaminants may be too difficult to detect. ie: Viruses, cryptosporidium
Trickling Filters
Type of fixed or attached growth. Microbes grow on the surface of "filter medium" (rocks or plastic). Process: Rotating arm sprays primary effluent over filter medium. Biofilm: Layer of microorganisms develops on filter medium. Microbes degrade waste as it passes over.
Disinfection
Use chemicals to kill majority of organisms in water and provide residual disinfection capability to prevent regrowth of organisms in distribution system. Commonly w/ chlorine based chemicals.
Disinfectants
Used to destroy microorganisms in water (to then form disinfectant by-product). Chlorine Dioxide, Chloramines, and Chlorine
Advanced Treatment
Varies, targets Nitrogen and Phosphorus
Unsaturated Zone
a layer of rocks and soil above the water table in which the pores contain air as well as water. aka: Vadose Zone