Wastewater Engineering
tertiary treatment
The third level of sewage treatment; chemicals are used to remove all harmful chemicals and bacteria.
biological filter
A natural filtering system consisting of helpful bacterial colonies that convert pollutants in water to harmless nitrate
Cl2 vs. N a OCl
Cost,, N a OCl more expensive. Cl2 more stable. No Risk management for N a OCl. Safety training--much more with Cl2. Containment and Scrubbers required for Cl2.
A change in the pH of digesting sludge in anaerobic digester is the best early warning indicator of potential digester upset.
False
A grab or composite sample may be used interchangeably for all laboratory tests
False
A rise in DO will be accompanied by a drop in pH in a facultative wastewater treatment pond that is operating normally
False
Acre-feet is a measure of a wastewater treatment pond's surface area
False
Anaerobic bacteria prefer to live and reproduce in an environment containing free molecular oxygen
False
Mechanical aerators are often used to provide supplemental oxygen in a facultative pond
False
Most wastewater treatment plants have a separate Industrial wastewater collection system
False
Organic loading to stabilization pond is pounds of BOD per day per 1000 cubic feet of pond volume .
False
Sodium Thiosulfate is routinely used to dechlorinate a secondary wastewater effluent prior to its discharge into the receiving water
False
The glass tube on the front of a chlorinator cabinet, called a rotometer, measures the chlorine feed rate in units of pounds per million gallons of flow.
False
V notch weirs attached to a primary effluent launder measure the flow rate.
False
Wastewater ponds are usually started during the cold winter months in order to take advantage of oxygen's greater solubility in cold water as compared to warm water
False
A facultative pond is normally aerobic throughout its entire depth
False It's aerobic on top and anaerobic on the bottom
Comminutors cup up or shred large objects normally found in raw wastewater and remove them from the wastewater flow
False they cut up and shred but DO NOT REMOVE them.
Storm waster runoff flowing into a sewer through a flooded or unsealed manhole is referred to as INFILTRATION
False Infiltration from ground , Inflow from top
ammonium
NH₄⁺ fuel of nitrification process
nitrite
NO₂⁻ produced by nitrosomonas
Nitrate
NO₃⁻ produced by nitrobacter
Advantages of UV
No Cl2 residual, reduction in chemical costs, Less safety training, Avoids problems with nitrified effluent
ORP probe position
Show example of Q * T/A
Nitrification
The biological oxidation of ammonia/ammonium to the nitrite ion , and to the nitrate ion using the bacteria, nitrosomonas and Nitrobacter.
cm2 centimeters squared
The cross sectional area that effluent flows through. UV dosage is proportional to this area. UV lamps bundled in narrow channels.
sulfides
compounds that consist of one or more elements combined with sulfur
denitrification
conversion of nitrates into nitrogen gas
nitrobacter
converts nitrite to nitrate
primary treatment
first step of sewage treatment; eliminates most particulate material from raw sewage using grates, screens, and gravity (settling). Physical/Mechanical process
CEPT or advanced primary treatment
involves application of F e Cl3 and Polymer. Dosage and point of dose are important considerations
Alkalinity
level of alkaline in a substance; pH 7.1-14. A buffer against rapid increases in acidity
Cl2 or sodium hypochlorite
oxidizers that oxidize dissolved sulfides to harmless sulfur, thus removing hydrogen gas
Mechanical filter
physical barrier to particles
point-source pollution
pollution that comes from a specific site
nitrogen fixation
process in which bacteria convert nitrogen gas into nitrogen compounds plants can use to make proteins
chemical process
process that happens in the water or soil in the presence of other chemicals, no organisms are required
eutrophication
rapid growth of algae in bodies of water, due to high levels of nitrogen and often phosphate
ORP probe position
reactions with NH3 are not instant--allows time from point of addition of Cl2 and site of ORP probe to allow reactions to complete.
Ferrous chloride
reacts with dissolved hydrogen to form insoluble ferrous sulfides that precipitate out. Also removes H2S.
RAS
recirculation aquaculture system
CEPT energy savings
reduce organic loading to Activated sludge, Less air required. Reduction of DAFs in service. Loading to digester increased for gas production.
ORP probe
reduces the amount of Cl2. Cl2 by-products are toxic to bio-assy.
anoxic sediments
sediments lacking any oxygen.
negative feedback system
system that works to maintain the system as is, or maintain equilibrium.
Denitrification
the biological reduction of nitrate to nitrite and then to nitrogen gas
nitrification
the process by which nitrites and nitrates are produced from ammonium by bacteria in the soil
nitrogen cycle
the transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere
physical process
things being filtered by physical barriers like sand and stones
nonpoint-source pollution
water pollution that does not have a specific point of origin
run-off
water that flows over the ground surface rather than soaking into the ground
Calcium Nitrate
Trade Name "Bioxide". Nitrate ion provides chemically combined O2. Bacteria use it instead of sulfate that produces H2S. Releasing harmless Nitrogen gas.
secondary treatment
Treating wastewater biologically, by using microorganisms to decompose the suspended organic material; occurs after primary treatment
A "launder " in a primary clarifier is a trough used to convey flow
True
A Parshall flume is often found in the "headworks" area of a wastewater plant.
True
A flame arrestor is a safety device commonly associated with an anaerobic digester
True
A graduated cylinder may be used to measure the settleability of mixed liquor
True
A major purpose of preliminary treatment is to protect pumps and other equipment from plugging, waring or possible damage
True
A one acre wastewater treatment pond operated at a depth of 3 feet holds approximately1 million gallons
True
A progressive cavity pump is often used to pump raw sludge.
True
A properly operating grit chamber should yield grit that is high in fixed solids ( inorganic material) and low in volatile solids
True
Although chlorine is a greenish - yellow hazardous gas at atmospheric pressure, some of the chlorine is a liquid when under pressure in a one- ton chlorine container
True
An air-lift pump is often used to pump return activated sludge in a so-called "package Plant".
True
Chlorine demand = Chlorine dose -- Chlorine residual
True
Daily visual observations of a wastewater treatment pond's color and surface condition should be routine for pond operation
True
Either pounds of BOD or COD can be used as a measure of the food applied to the aeration tank of an activated sludge plant
True
In an anaerobic digester, some organic matter in raw sludge is converted to other organic compounds and to gases
True
In some primary clarifiers water or air sprays may be used to push scum toward the scum removal point
True
MCRT refers to the average number of days that a "cell" or "Organism" spends in an activated sludge system.
True
Operators may use sludge blanket levels in primary clarifiers to adjust sludge pumping rates.
True
PRIMARY EFFLUENT is the wastewater flowing into an aeration tank in a conventional activated sludge wastewater treatment plant
True
Photosynthesis is an essential part of the biological activity occurring in a facultative wastewater treatment pond.
True
Pre-chlorination is used for odor control at wastewater treatment plants.
True
Raw sludge pumped from a primary clarifier generally contains about 3 - 6% total solids
True
Settling and scum removal are both important to the success of primary treatment
True
The F to M ratio is an important consideration in the operation of an activated sludge wastewater plant.
True
The lowest concentration of dissolved oxygen in a well-operating facultative wastewater treatment pond typically occurs just before sunrise because algae use up oxygen at night
True
The minimum operational depth of a facultative wastewater treatment pond is considered to be 3 feet
True
The presence of hydrogen sulfide CANNOT always be always be detected by its characteristic odor
True
The underdrain of a trickling filter both drains and allows ventilation to the typical standard rate trickling filter
True
The units ppm and mg/L are considered to be equivalent for wastewater calculations.
True
The volatile acid concentration is an important lab test used to monitor an anaerobic digester
True
Uneven weirs may result in short circuiting in a primary clarifier
True
Hydrogen Peroxide
(50%) strong oxidizer. Reacts with dissolved gasses to oxidize them to harmless sulfur, indirectly removing hydrogen gas.
nitrosomonas
Bacteria that convert ammonia into nitrite
Hydrogen Sulfide
Can be oxidized to sulfuric acid in the slime layer in a concrete pipe--destroys concrete
oxidation
Chemical reaction in which electrons are gained by the oxidizing agent and lost by the substance being oxidized. Lost electrons cause bonds to be broken in the organic matter and thus destroy it.
Considerations for UV disinfection
Clarity of Water, Cleanliness of lamps, water hardness
seconds
Detention time. UV dosage proportional to detention time. Two or more bundles of lamps in a series in a channel allow longer detention time.
Oxidation Potential
Direct measure in millivolts, of the potential for electron transfer to the oxidating agent, Cl2. More Cl2 increases oxidation potential.. More organics lower the oxidation potential.
DO
Dissolved oxygen, gaseous oxygen in the water
(mW) milliwatts
Power output of UV lamp. Dosage directly proportional to output of UV lamp.
CEPT benefits
Reduces H2S in digester gas. Reduces struvite in digester,, belt presses and centrifuges.
positive feedback system
a change that amplifies rather than reverses the change
biological process
a process occurring in living organisms
equilibrium
a state of balance
hydrogen sulfide
a sulfide having the unpleasant smell of rotten eggs
pH
a value that indicated the acidity or alkalinity of a solution on a scale of 0-14, based on the proportion of H+ ions.
anaerobic bacteria
bacteria that do not require oxygen to survive
Aerobic bacteria
bacteria that use oxygen for cellular respiration
BOD
biolochemical oxygen demand, amount of dissolved oxygen needed by aerobic decomposers to break down organic materials