Wastewater Operator Certification Information

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Terms

CWA – Clean Water Act passed in 1972   NPDES – National Pollutant Discharge Elimination System – permit good for 5 years ( must reapply 180 day prior to expiration date ) PE – Population Equivalency – how plants are designed – design for 20 years future growth PE, capita = (Flow, MGD)(BOD, mg/L)(8.34lb/gal) 0.17 lbs/BOD/capita/day * An operator should be present during construction to become familiar with the plant, including the equipment, machinery and the operation of it. Provides you with the opportunity to relate your plant to the drawings.

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Overview

Collection Systems  Rain Water I & I  Wastewater Flow  Preliminary Treatment  Secondary Treatment  Solids Handling  Tertiary Treatment  Laboratory  Safety

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Rain Water Inflow and Infiltration (I&I)

Enters collection system through cracks and holes in pipes, open cleanouts, cross connections, manholes, #1 cause – leaking pipe joints  Can cause hydraulic overload at WPCF, decreased capacity due to sand and grit accumulation, lift station pump failures and overflows, increased operating costs  Accounts for 30% of wastewater flow

Liftstations

 Must maintain a velocity of 2ft per second to stop solids from settling and H 2 S from forming, when unable to reach that velocity build a lift station – lift flow to a higher elevation where it can again flow by gravity  Has forced ventilation to prevent toxic gas fume build-up  Most common is air-lift pump

Wastewater Contents

       Domestic waste is 99.9% water Contains pathogenic (disease causing) bacteria, viruses, cysts that can cause Typhoid, Cholera, Dysentery, Polio and Hepatitis Floatable – floats to surface (scum & grease) Settleable – settles to bottom Suspended – won’t float or settle (same weight as water) Dissolved – such as food dye Colloidal – finely dissolved that remains in suspension causing turbidity (cloudiness) due to its size and electrical charge

Raw Wastewater Solids Composition

Wastewater is 99.9% water Dissolved solids makes up the highest percent of solids Dissolved and Suspended Solids make up Total Solids

Preliminary Treatment

        To remove material that can damage or plug up equipment – grit, rags, plastics, sticks, etc.

Flow Equalization / Surge Basins Bars Screens / Bar Racks Moving or Rotating Screens Shredding / Grinding Grit Chambers / Channels Odor Control Pumps (not considered treatment, but located in head works of plant)

Pumps

Impeller vane damage

Cavitation  The formation of partial vacuums in a liquid by a swiftly moving solid body (as a propeller) or by high-intensity sound waves  The pitting and wearing away of solid surfaces (as of metal or concrete) as a result of the collapse of these vacuums in surrounding liquid

Sedimentation and Floatation

 Sedimentation and Floatation happens in both Primary and Secondary (or final) clarifiers  Purpose – to remove settleable and floatable solids from raw ww – Organic solids have high oxygen demand (BOD)  Primary Clarifiers follows grit removal – Velocity 1.0 to 2.0 feet per minute  Secondary Clarifier follows any biological treatment

Primary VS Secondary Sludge

      Primary is denser (heavier) Primary is darker in color (dark chocolate) Effluent (liquid on top) is gray in color Secondary is lighter is color (milk chocolate) Secondary is mainly microorganisms (lighter) Effluent is clear

Rotating Biological Contactor (RBC)

   Mechanical or air operated drive units rotate the media through wastewater Biomass is attached to the moving media (attached growth) 40% of the media is immersed in ww

Covered RBCs

Sequencing Batch Reactors (SBR)

   Treatment is carried out in a single tank through sequencing stages Handles periodic flows or batch dumps with ease Especially well suited for industries – Automatic control through Programmable Logic Control (PLC) – Stable due to high sludge age and long retention time – Less costly to build – no need for sludge handling – can be sent directly to drying beds or composting process

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BOD/N/P

The ratio of biochemical oxygen demand to nitrogen to phosphorus should be 100/5/1. If the organic loading rate increases the appropriate N & P need to be added at a point where the incoming wastewater is highly mixed to provide nutrients needed by the microbes. The pounds of N & P required per day will be about 10% of the organic solids (dry weight) produced every day. The P required will be one-fifth of the N requirement. The amount of P & N added daily are equal to the difference between the quantity required and the quantity in the waste. Aqueous ammonia or anhydrous ammonia may be added to provide the nitrogen. Phosphate fertilizers or phosphoric acid from a waste acid facility may be used to provide P.

Conventional Activated Sludge

     Detention time – 4 to 8 hours (6 hrs) Sludge Age – 3.5 to 7 days MLSS – 1,000 to 3,000 mg/L DO – 2 to 4 mg/L or ppm – High (>5.0) shear floc, waste energy – Low (<0.5) lead to bulking, poor effluent Mixing – Distributes oxygen evenly – Brings food in contact with microorganisms – Prevents septic conditions on bottom of tank

Nitrification Cycle

Heterotrophic Bacteria –

    Carbonaceous Stage Get energy from the oxidation of organic materials Common bacteria in wastewater This bacteria is responsible for denitrification Form floc – fast growing

Autotrophic Bacteria –

    Nitrogenous Stage Get energy from inorganic materials or from the sunlight (some are algae) Are the nitrifiers Sulfide oxidizing organisms Do not form floc – slow growing

Floc under electron microscope

Sludge Floc

Notice the large thing running through this – that is a filament. The small rice shaped objects are the floc forming bacteria (heterotrophic).

You can clearly make out each floc particle and see pretty clear liquid outside of the floc. There is very little filament outside of the floc and the floc is “roundish” in shape.

Good floc Young – weak lacy Old – dark and falling apart

Primary Pond or Lagoon

Ponds

Secondary or Two Stage Pond This is how it works Tertiary or Three Stage Pond

Feed the Primary Digester with Primary or Secondary (WAS) Sludge Sludge is transferred (pumped) from the Primary Digester to the it is the first digester – creates gas

Chemical Stabilization

 Lime – Addition of lime adds to the overall quantity of solids that must be disposed – High costs  Chlorine – pH will drop <3.5 (acidic) – Lime may be added before dewatering

Sludge Incineration

 Use dewatered sludge  Converts dewatered sludge by combustion to carbon dioxide and water vapor  Reduce volume up to 90%  Most common is MHF (multiple hearth furnace)  Temperature 1,300 – 1,700°F

Only use the chlorine wrench when opening or closing cylinders – open 100%, close then reopen ¼ turn only Train cargo cars (Class C) Fusible plug – center is lead – will melt at 158 to 165ºF to release gas instead of liquid or explosion Trunions – used to turn ton cylinders so the valves are straight vertically when opening Ton (2,000 lb) cyliners (Class B)

Biological Treatment

 Luxury Uptake of Phosphorous – modification of activated sludge   Definitions – Aerobic (oxic): free DO is present – Anoxic: oxygen is deficient or present as combined oxygen in Nitrate (NO 3 ) and Sulfate (SO 4 ) Anaerobic: No oxygen

Safety

 Top three injuries in wastewater in order: – Back – Leg – Hand  Lockout/Tagout – Everyone who is working on that piece of equipment must sign/date/add lock

Lab Miscellaneous

 Meniscus (commonly found in pipettes) – read at the bottom of the curve or the top of the curve    You can preserve a metals sample for 6 months BOD solution water make-up – phosphate buffer, magnesium sulfate, calcium chloride, ferric chloride A bottle containing only dilution water is called a blank

Pretreatment

   Total toxic organics (TTO) refers to the sum of the masses or concentrations of certain toxic organic pollutants found in the regulated discharge at a concentration greater than 0.01 mg/L Inspection – minimum of once per year or as needed Sampling – Significant Industrial User (SIU) at least annually and self monitored semi-annually