Wastewater Engineering

V notch weirs attached to a primary effluent launder measure the flow rate.

False

A major purpose of preliminary treatment is to protect pumps and other equipment from plugging, waring or possible damage

True

The units ppm and mg/L are considered to be equivalent for wastewater calculations.

True

A Parshall flume is often found in the "headworks" area of a wastewater plant.

True

Chlorine demand = Chlorine dose -- Chlorine residual

True

A "launder " in a primary clarifier is a trough used to convey flow

True

Most wastewater treatment plants have a separate Industrial wastewater collection system

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

The F to M ratio is an important consideration in the operation of an activated sludge wastewater plant.

True

Organic loading to stabilization pond is pounds of BOD per day per 1000 cubic feet of pond volume .

False

A change in the pH of digesting sludge in anaerobic digester is the best early warning indicator of potential digester upset.

False

A one acre wastewater treatment pond operated at a depth of 3 feet holds approximately1 million gallons

True

A grab or composite sample may be used interchangeably for all laboratory tests

False

The volatile acid concentration is an important lab test used to monitor an anaerobic digester

True

Photosynthesis is an essential part of the biological activity occurring in a facultative wastewater treatment pond.

True

A properly operating grit chamber should yield grit that is high in fixed solids ( inorganic material) and low in volatile solids

True

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.

MCRT refers to the average number of days that a "cell" or "Organism" spends in an activated sludge system.

True

Settling and scum removal are both important to the success of primary treatment

True

In some primary clarifiers water or air sprays may be used to push scum toward the scum removal point

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

Operators may use sludge blanket levels in primary clarifiers to adjust sludge pumping rates.

True

Uneven weirs may result in short circuiting in a primary clarifier

True

Raw sludge pumped from a primary clarifier generally contains about 3 - 6% total solids

True

PRIMARY EFFLUENT is the wastewater flowing into an aeration tank in a conventional activated sludge wastewater treatment plant

True

Daily visual observations of a wastewater treatment pond's color and surface condition should be routine for pond operation

True

Acre-feet is a measure of a wastewater treatment pond's surface area

False

A facultative pond is normally aerobic throughout its entire depth

False

It's aerobic on top and anaerobic on the bottom

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

The minimum operational depth of a facultative wastewater treatment pond is considered to be 3 feet

True

A progressive cavity pump is often used to pump raw sludge.

True

A rise in DO will be accompanied by a drop in pH in a facultative wastewater treatment pond that is operating normally

False

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

Mechanical aerators are often used to provide supplemental oxygen in a facultative pond

False

Sodium Thiosulfate is routinely used to dechlorinate a secondary wastewater effluent prior to its discharge into the receiving water

False

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

Pre-chlorination is used for odor control at wastewater treatment plants.

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

In an anaerobic digester, some organic matter in raw sludge is converted to other organic compounds and to gases

True

An air-lift pump is often used to pump return activated sludge in a so-called "package Plant".

True

The presence of hydrogen sulfide CANNOT always be always be detected by its characteristic odor

True

A flame arrestor is a safety device commonly associated with an anaerobic digester

True

Anaerobic bacteria prefer to live and reproduce in an environment containing free molecular oxygen

False

The underdrain of a trickling filter both drains and allows ventilation to the typical standard rate trickling filter

True

A graduated cylinder may be used to measure the settleability of mixed liquor

True

nitrification

the process by which nitrites and nitrates are produced from ammonium by bacteria in the soil

denitrification

conversion of nitrates into nitrogen gas

nitrogen fixation

process in which bacteria convert nitrogen gas into nitrogen compounds plants can use to make proteins

nitrosomonas

Bacteria that convert ammonia into nitrite

nitrobacter

converts nitrite to nitrate

run-off

water that flows over the ground surface rather than soaking into the ground

eutrophication

rapid growth of algae in bodies of water, due to high levels of nitrogen and often phosphate

point-source pollution

pollution that comes from a specific site

nonpoint-source pollution

water pollution that does not have a specific point of origin

primary treatment

first step of sewage treatment; eliminates most particulate material from raw sewage using grates, screens, and gravity (settling). Physical/Mechanical process

secondary treatment

Treating wastewater biologically, by using microorganisms to decompose the suspended organic material; occurs after primary treatment

tertiary treatment

The third level of sewage treatment; chemicals are used to remove all harmful chemicals and bacteria.

positive feedback system

a change that amplifies rather than reverses the change

negative feedback system

system that works to maintain the system as is, or maintain equilibrium.

equilibrium

a state of balance

biological process

a process occurring in living organisms

chemical process

process that happens in the water or soil in the presence of other chemicals, no organisms are required

physical process

things being filtered by physical barriers like sand and stones

nitrogen cycle

the transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere

BOD

biolochemical oxygen demand, amount of dissolved oxygen needed by aerobic decomposers to break down organic materials

DO

Dissolved oxygen, gaseous oxygen in the water

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.

Alkalinity

level of alkaline in a substance; pH 7.1-14. A buffer against rapid increases in acidity

Nitrate

NO₃⁻ produced by nitrobacter

nitrite

NO₂⁻ produced by nitrosomonas

ammonium

NH₄⁺ fuel of nitrification process

Mechanical filter

physical barrier to particles

biological filter

A natural filtering system consisting of helpful bacterial colonies that convert pollutants in water to harmless nitrate

RAS

recirculation aquaculture system

Aerobic bacteria

bacteria that use oxygen for cellular respiration

anoxic sediments

sediments lacking any oxygen.

anaerobic bacteria

bacteria that do not require oxygen to survive

sulfides

compounds that consist of one or more elements combined with sulfur

hydrogen sulfide

a sulfide having the unpleasant smell of rotten eggs

Calcium Nitrate

Trade Name "Bioxide". Nitrate ion provides chemically combined O2. Bacteria use it instead of sulfate that produces H2S. Releasing harmless Nitrogen gas.

Ferrous chloride

reacts with dissolved hydrogen to form insoluble ferrous sulfides that precipitate out. Also removes H2S.

Hydrogen Peroxide

(50%) strong oxidizer. Reacts with dissolved gasses to oxidize them to harmless sulfur, indirectly removing hydrogen gas.

Cl2 or sodium hypochlorite

oxidizers that oxidize dissolved sulfides to harmless sulfur, thus removing hydrogen gas

Hydrogen Sulfide

Can be oxidized to sulfuric acid in the slime layer in a concrete pipe--destroys concrete

(mW) milliwatts

Power output of UV lamp. Dosage directly proportional to output of UV lamp.

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.

cm2 centimeters squared

The cross sectional area that effluent flows through. UV dosage is proportional to this area. UV lamps bundled in narrow channels.

Considerations for UV disinfection

Clarity of Water, Cleanliness of lamps, water hardness

Advantages of UV

No Cl2 residual, reduction in chemical costs, Less safety training, Avoids problems with nitrified effluent

CEPT or advanced primary treatment

involves application of F e Cl3 and Polymer. Dosage and point of dose are important considerations

CEPT energy savings

reduce organic loading to Activated sludge, Less air required. Reduction of DAFs in service. Loading to digester increased for gas production.

CEPT benefits

Reduces H2S in digester gas. Reduces struvite in digester,, belt presses and centrifuges.

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.

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.

ORP probe

reduces the amount of Cl2. Cl2 by-products are toxic to bio-assy.

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.

ORP probe position

Show example of Q * T/A

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.

Nitrification

The biological oxidation of ammonia/ammonium to the nitrite ion , and to the nitrate ion using the bacteria, nitrosomonas and Nitrobacter.

Denitrification

the biological reduction of nitrate to nitrite and then to nitrogen gas