Wastewater Operator Grade 1 Exam Notes by Gary Hudson

Grease Traps/Interceptors

Units to cool and congeal grease and oils in waste-stream

Toilet water

Should never be tributary to a grease trap

Inflow pipe

Should be higher than the effluent pipe in a grease trap

Temperature and distance

Affect grease trap performance in relation to the source of FOG

Baffle wall

Wall separating the chambers of a grease trap

Sanitary tees

Allow for visual inspection of influent flow, effluent flow, and cleaner effluent in a grease trap

Septic Tank/Sand Filters

Devices for dosing and filtering wastewater

Automatic siphon

Causes intermittent dosing of wastewater to the sand filter

Ponding

When spaces between sand grains become clogged and wastewater accumulates in a sand filter

Hydrogen sulfide

Gas most commonly associated with septic wastewater

Grit

Heavier inorganic matter that will not decompose

Preliminary Treatment

Units designed to reduce velocity of influent flow and allow solids to settle out

Bar screen

Protects treatment units from large debris or rags in influent water

Grit chamber

Protects treatment units from solids by reducing influent flow velocity

Upstream depth

If 9 inches greater than downstream, indicates a clogged bar screen

Protect downstream processes

Purpose of preliminary treatment (bar screens and grit chambers)

Screening devices

Bar screens with parallel bars at an angle in wastewater stream

Fecal coliform bacteria

Indicates possible presence of pathogens in effluent

Temperature decrease

Leads to decreased biological activity, settling rates, and increased DO

Temperature increase

Leads to increased biological activity, settling rates, and decreased DO

Biochemical oxygen demand (BOD)

Expresses strength of wastewater in terms of oxygen utilized by bacteria under controlled conditions

Anoxic conditions

DO <0.5 mg/l with nitrate present

Difference

Anoxic conditions have nitrate nitrogen present, anaerobic conditions do not

Biochemical oxygen demand

Amount of oxygen utilized by bacteria sampled under controlled conditions

Fresh domestic wastewater

Has musty odor and gray color

Total solids

Dissolved solids + suspended solids

Bakery wastewater

Has high BOD due to presence of flour and starches

Fecal coliform bacteria

Considered an indicator organism

Inorganic matter

Sand, silt, and salt

Organic matter

Decaying leaf

Activated Sludge

Brownish flocculant culture of organisms in an aeration basin

Sludge wasting rate

Adjusted to optimize biomass to organic load FIM ratio

Excessive detention

Causes small floc particles to go over weirs (Pin Floc)

Air diffusion

Provides oxygen to microorganisms, keeps activated sludge solids in suspension, and mixes incoming wastewater and activated sludge solids

Mixed Liquor Suspended Solids (MLSS)

Test performed to control solids in the aeration tank

Good quality mixed liquor

Brownish in color, settles leaving clear supernate, and has some DO

Secondary clarifier

Allows solids to settle

Field test

30 minute settle test to assess solid levels in aeration tank

Nutrients deficient in industrial wastewater

Phosphorus and Nitrogen

Lagoons/Ponds

Systems for wastewater treatment and algae control

Facultative bacteria

Can live under anaerobic and aerobic conditions

Algae population increase

Increases pH of waste stabilization pond

Excessive algae growth

Controlled by limiting sunlight, removing excess solids, and filtering

Cat trails

Root system that can damage lagoon liner

Lagoon temperature decrease

Leads to decreased biological activity, increased DO, and decreased pH

Daylight hours

Higher pH due to photosynthesis and carbon dioxide consumption

Short circuiting of a pond

Caused by excessive weed growth, poor arrangement of inlet and outlet pipes, and an irregular pond bottom

Lagoon sludge accumulation

Approximately 0.2 pounds per pound of BOD removed, higher with excessive algae blooms

BOD loads on receiving streams

Reduced by removal of algae from lagoon effluents

Nighttime operations for lagoons

Lower pH and higher oxygen demand (low DO)

Algae in wastewater pond

Provides a source of oxygen for other biological life

Sampling and Lab Procedures

Methods for collecting and testing wastewater samples

Time interval composite sampler

NOT more representative than flow-proportional composite sample

Fecal coliform test

Correct units are colonies per 100 ml

DO test

Important to avoid entrapment of atmospheric oxygen when collecting sample

Grab samples

Required for DO, pH, and temperature tests

Settleable solids

Measured in an imhoff cone

Settleability

Measured with a settleometer

Kjeldahl

Refers to organic plus ammonia nitrogen

Composite samples

Should be made from grab samples taken at selected intervals, consist of no less than 4 samples per day, and be proportional to the flow at the same time of sampling to be in compliance

Fecal coliform sample

Should be a grab sample preserved with sodium thiosulfate

pH averaging

Impossible

Wastewater Collections

Systems built to carry away disease-producing materials from homes

Infiltration

Occurs through the manhole barrel

Stale septic wastewater

Adjust pumps to cycle more frequently

Solvent odor

Trace odor in collection system to its source and thoroughly ventilate affected lift stations

Disinfection

Process designed to destroy pathogenic microorganisms in wastewater

Saprophytes

Considered essential and beneficial microorganisms in biological wastewater treatment systems

Fecal coliform bacteria

Originate in intestines of warm-blooded animals and are not naturally present in water

Chloramines

Formed by reaction of hypochlorous acid with ammonia

Pathogenic organisms

Disease-causing microorganisms destroyed to prevent spread of disease

Chlorine disinfection

Works better with low pH and high temperature

Chlorine demand

Chlorine dose - chlorine residual

Polymer

NOT a disinfectant for wastewater effluent

Chlorine application

Can be as solid, liquid, or gas

Effluent coliform level increase

Could be caused by short circuiting in contact chambers

Chlorine reaction with water

Forms hypochlorous acid and hydrochloric acid

Sodium hypochlorite

Bleach

Pumps

Devices for moving wastewater

Positive displacement pump

Should NEVER be operated against a closed discharge line

Pump packing

Prevents air from entering pump and keeps pump primed

Centrifugal pump

Not seriously damaged if discharge valve is closed for a short period of time while pump is running

Cavitation

Caused by incorrect head, pump capacity, or suction lift

Pump operation

Best to alternate pumps to reduce wear and tear

Reciprocating pump

Consists of a piston on a motor-driven shaft

Head

Height of water above a point

Flow rates

Expressed as mgd (million gallons per day), not feet per second

Pump packing tightening

Should be tightened down to a drip

Primary sludge pumping

Uses diaphragm or piston pump

Positive displacement pump

Does not have a rotating impeller

Wet well pump control systems

Include electrodes, bubblers, and floats

V-notch weir

Best for measuring low flows

Series electrical circuit

If one unit is burned out, the other units will cease to function

Amps

Electrical component that causes the most harm to the human body

Broken wire

Does NOT affect pump efficiency

Mechanical seals

Should not allow any amount of leakage from the gland

Safety

Guidelines and precautions for working in wastewater treatment

Confined space

Not designed for continuous occupancy and not easy to enter/exit

Gas specific gravity

>1, sinks to the floor

Hazards at WWTP

Pathogenic organisms, areas with oxygen deficiencies, and poisonous chemicals