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