what is wastewater? - mariana islands water operator ... oxygen: a crucial parameter • strength of...

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Introduction to Introduction to Wastewater Wastewater Treatment Treatment

For Water OperatorsFor Water Operators

CNMI Division of Environmental Quality

& Commonwealth Utilities Corporation

August 11, 2010

Wastewater 101 Agenda

• Classroom– Wastewater characteristics

– Wastewater treatment processes

Solids treatment and disposal– Solids treatment and disposal

– CUC treatment plants

• Field Trip

What is wastewater?

• Water used for any purposes picks up contaminantsand requires disposal.

Sources of wastewater: “Domestic” Sources of wastewater: “Industrial”

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Sources of wastewater: “stormwater” Why do we treat wastewater?

• Prevent the spread of disease

• Protect the environment and “down t ”stream” users

For our purposes:

• WASTEWATER CONTAMINANTS:

5 t i– 5 categories:

• Stuff that sinks

• Stuff that is dissolved• Stuff that floats

• Stuff that is suspended• Pathogenic microorganisms

Microorganisms

– Useful microorganisms

– Pathogenicorganisms

Microorganisms

Useful microorganisms– Bacteria

– Protozoa

– Algae

– higher life forms

BACTERIA:our workhorses

• 3 types, based on Oxygen use:– Aerobic

• Need oxygen• Fast, good for wastewater treatment• Low odor

Anaerobic– Anaerobic• No oxygen• Slow, not as good for wastewater treatment, good for

digestion of sludge (septic tanks)• Stinky!

– Facultative• Can live with or without oxygen• Used in wastewater lagoons

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OXYGEN:a crucial parameter

• Strength of wastewater is measured by – BIOCHEMICAL OXYGEN DEMAND

OXYGEN• Septic sewage:

– No oxygen.

– Black in color

– Rotten egg odor: hydrogen sulfidey g

– Corrodes steel, dissolves concrete

– Very difficult to treat

• Keeping sewage fresh:– Quick delivery

– Aeration (O2)Source: Milton Village, UK

Biological Oxygen Demand (BOD)

• The quantity of oxygen used

in the biological oxidation of

organic matter– 5 days

– 20°C

• Ranges:– Raw domestic sewage: 100 – 300 mg/L

– Primary effluent: 50 – 150 mg/L

– Secondary effluent: 15 – 30 mg/L

Wastewater treatment

• 3 basic treatment processes:– Physical treatment

• Preliminary treatment

• PRIMARY treatmentPRIMARY treatment

– Biological treatment• SECONDARY treatment

• ADVANCED SECONDARY and TERTIARY treatment

– Chemical Treatment• Disinfection

Wastewater treatment

• Ancillary processes:– Solids treatment

• stabilization

• dewateringdewatering

HEAVY DUTY InfluentEffluent

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Wastewater Treatment

• Preliminary treatment:The process of grinding material that can clog equipment, removing rags with screens, and the removal of grit. Premilinary treatment is commonly a part of primary treatmentprimary treatment.

• Primary treatment:The first major (sometimes only) treatment in a sewage treatment works. This process takes place in a rectangular or circular tank and allows those substances in wastewater that readily settle or float to be separated from the water being treated.

Source: Arasmith & Ploetz

Wastewater Treatment

• Secondary treatment:A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. Usually a biological treatment processa biological treatment process.

• Tertiary treatment:Any process of water renovation that upgrades treated wastewater to meet specific reuse requirements. May include general cleanup of water or removal of specific parts of wastes insufficiently removed by conventional treatment processes. Typical processes include chemical treatment and pressure filtration.


Preliminary Treatment

• Headworks



• Grinding– comminutors

Source: www.jwce.com“Muffin Monster” channel grinders

Source: www.waterandwastewater.com


• Grinding– barminutors


Muffin Monster Chain & Rake Monster

Source: www.jwce.com


• Grit Channel

Source: Indiana University of Pennsylvania

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Preliminary Treatment• Aerated Grit Chamber

Source: T.L.M. Engineers (G.S.H.) Ltd

www.telem.co.il

Flow Measurement

• Parshall Flumes(with ultrasonic height measurements – no stilling wells)

Source: Indiana University of Pennsylvania

Primary Treatment• Primary Treatment:

– Comes after preliminary treatment

– Circular or rectangular tanks

– Removes settleable & floatable solids

– Also known as sedimentation or clarification

– Many small plants do not use primary treatment, or use microscreens as equivalent


Primary Treatment• Theory of settling:

– Settled particle size depends on detention time

• Longer time = smaller (& more) particles removed

– Detention time depends on size of clarifier and flowDetention time depends on size of clarifier and flow

SETTLING ZONE

SLUDGE

INF

LU

EN

T Z

ON

E

EF

FL

UE

NT

ZO

NE

Primary Treatment• Rectangular Clarifiers

Source: www.garlandmfg.com

Primary Treatment• Rectangular Clarifiers

Source: www.environmentalleverage.com

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Primary Treatment

• Rectangular Clarifiers

Source: www.environmentalleverage.com

Primary Treatment• Circular Clarifiers

MECHANICAL DRIVE

Source: www.westpromachinery.com

Primary Treatment

• Circular Clarifiers

Source: www.cwftx.net

Source: www.ndsd.org

SCUM BOXSCUM BOX

EFFLUENT WEIREFFLUENT WEIR

BAFFLEBAFFLE

HYDRAULIC SLUDGE HYDRAULIC SLUDGE REMOVALREMOVAL

On-Site Treatment Systems• Septic Tank

Source: Clearford Industries Inc.

www.clearford.com

On-Site Treatment Systems• Septic Systems may achieve “secondary”

treatment quality:

– Both physical and biological treatment• Anaerobic digestion of solids in tank

– Solids require removal every 3 years or more

• Biological treatment of dissolved and suspended contaminants in soil

Septic System in limestone:

SEPTIC SYSTEMWELL

G R O U N D W A T E R

L I M E S T O N E

CNMI Division of Environmental Quality 2005 BGB

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REVIEW

• Primary Treatment Plants:– Grinding, grit removal, primary sedimentation

• Secondary Treatment Plants:– Primary plus biological treatment

• Uses aerobic bacteria to reduce the organics and develop a sludge that can be settled easily

• Sludge = biomass


Types of Secondary Treatment Processes

• Fixed Film Media

• Lagoons & Wetlands

• Activated Sludge


Trickling Filters

• Process: Fixed Film Media– Aerobic biological slime does the work

M di• Media:– River rock (usually 10 feet or less in depth)

– Crushed stone

– Synthetic media (20 feet or more in depth)


Trickling Filters


Malakal Wastewater Treatment Plant - Palau

Source: CNMI DEQ


Source: CNMI DEQ

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Source: CNMI DEQ

Trickling Filters• Zoogleal film


Trickling Filters

• Theory – Removes nonsettleable suspended & dissolved

organic matter

– Biological slime on filter media consumesBiological slime on filter media consumes organics

– Produces a settleable sludge

– Zoogleal film• Bacteria, protozoa, fungi, algae


Trickling Filters• Piping & Recirculation


RBCs – Rotating Biological Contactors

• Same treatment method as trickling filter

• Popular small plant option

Source: www.gm.ca

RBCs – Rotating Biological Contactors

• Multiple Contactors

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Lagoons Ponds or Lagoons


Ponds or Lagoons

• Treatment Process– Symbiotic relationship between bacteria and algae

• Night time:– Bacteria use D O made– Bacteria use D.O. made

during day; emit CO2

– Good to check D.O.

before sunrise – if

too low, supplemental

air may be required

Ponds or Lagoons

• Operating zones (Facultative pond)– Anaerobic – bottom 20%

– Facultative

– Aerobic – top 80%


Ponds or Lagoons

• Classification of ponds

– Aerobic Ponds• Shallow (< 4 feet deep)

• D.O. throughout depth of pond

• Usually requires additional air– Surface aerators or diffusers

– Facultative Ponds• Most common type

• 4 to 6 feet deep

Ponds or Lagoons

• Classification of ponds (continued)

– Aerated Facultative Ponds• Used when not enough land available, or high BOD wastes

• Reduces stabilization time from 8-12 weeks, to 1-3 weeks

• Can accept wastes with 10x organic loading than regular ponds

– Anaerobic Ponds• 12 feet deep or more

• Very odorous

• Can be effective, especially with some industrial wastes

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Constructed Wetlands

• Two types:– Free water surface (FWS) wetlands

• Easier to construct & operate

• Requires most land

• Attracts birds (bad near airport)

• Breeds mosquitos

– Vegetated Submerged Bed (VSB)

• Higher removal efficiencies

• Requires less land

• Fewer mosquito & bird problems

Free water surface (FWS) wetland:

Malakal Wastewater Treatment Plant, Palau

Vegetated Submerged Bed (VSB) wetland:

Source: EPA

Vegetated Submerged Bed (VSB) wetland:

Marpi Landfill Facility, Saipan, CNMI

Activated Sludge - Description

• A suspended film, aerobic, secondary, biological treatment process

• Favorable conditions maintained to create an active biological mass called activated sludge

• Consists of one or more tanks called aeration basins, followed by secondary clarifier

• Contents of aeration basins called mixed liquor –measured by mixed liquor suspended solids -MLSS


• Activated sludge process

Effluent

AirClarifier


Return Activated Sludge

EffluentInfluent

Waste Activated Sludge

Aeration Tank

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• Balancing food & microorganisms• Operator must achieve balance between incoming

waste (“food”) and sludge mass (microorganisms)

• Imbalance can cause sludge that will not settle lproperly

• The basic cycle:• Microorganisms pick up food in aeration tank

• Microorganisms digest food in clarifier & rest

• Microorganisms returned to aeration basin to eat again


Activated Sludge - Process



• As bacteria grow:– They secrete a

slime layer that contains polymers

P l h l f d– Polymers help food stick to bacteria

– Also helps bacteria stick together in clumps of food & bacteria –agglomeration

Source: University of California at Los Angeles

Activated Sludge – Process Control

• Efficiency of process depends on high quality sludge– Settles well

– microorganisms allowed to digest & rest before return

– Sludge age = time sludge is in the system


• Young Sludge under the microscope:– Increase in number of ciliates & stalked ciliate

protozoa, feeding on bacteria

Source: University of California at Los Angeles


• Young Sludge & Settling– Does not settle easily – “bulking sludge”

– Tends to fill clarifier & go over weirs

– “straggle floc”

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• Normal growth phase– Bacterial energy more evenly divided between

reproduction & movement

– Slime layer decreases in size, contains more polymer

• Under microscope: – An abundance of free swimming & stalked ciliates, a

few rotifers


• Normal sludge appearance– Light to dark brown

– Small amount of crisp, white foam

Source: Environmental Leverage , Inc.

Activated Sludge - Process• Normal Sludge & Settling

– Agglomerates immediately upon discharge to clarifier

– Settles evenly

– Forms a discrete interface near the top

– Releases clear water as it settles, like a sponge


• Old sludge

Under microscope:

– Very little protozoa activity

– Maybe some rotifers & wormsy



• Old Sludge: settling– Settles quickly but does not agglomerate well

– Small particles remain & are carried over into effluent

– “pin floc”


• Old Sludge: denitrification– rising sludge



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• Settleometer & sludge age



• Controlling the activated Sludge Process

– The operator has control of:• Rate of sludge wastingRate of sludge wasting

– Sludge age

• Rate of return sludge– MLSS

• Dissolved Oxygen in aeration basin– Not much control – equipment limited

– Just keep above 1 mg/L

Activated Sludge - Aeration Systems

• Purpose of aeration:• Provides dissolved oxygen for microorganisms

• Mixes mixed liquor

• Two types of aeration systems:• Diffused air

• Mechanical aeration systems



• Diffusers: on bottom of tank

• Fine Bubble Diffusers:



Coarse Bubble Diffusers:


• Blowers – 2 types:– lobe (most common)

– centrifugal

Source: Arasmith & PloetzActivated Sludge - Aeration Systems

Source: Aerzen USA Corp.

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• Mechanical Aeration Systems• At surface of tank

• Four types of mechanical

Turbine Aerator:

ypaeration systems:

• Propeller

• Aspirator

• Turbine

• Jets



• Aspirator Aerator

Source: Environmental Expert.comSource: MAOF Madan


• Jet Aerator

Source: Mixing Systems, Inc.


• Brush Aerator• Used in “oxidation ditch” plants

Source: Mixing Systems, Inc.

Source: CST Wastewater Solutions

“Race Track” configuration

Secondary Clarifiers

• Very similar to primary clarifiers, with a few changes:– Rectangular box trough used in center of tank to increase weir

length (reduce weir loading)

– Or, larger diameter tank

– Sludge removal mechanisms different, depending on treatment process

Source: www.cwftx.net

Activated Sludge – Varieties

• Extended Aeration

• Contact Stabilization

• Nitrification/Denitrification

• Sequencing Batch Reactors• Sequencing Batch Reactors

• Package Plants

• Membrane Bio Reactors (MBRs)

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Membrane Biological Reactors (MBR)

• Activated Sludge system – NOT an R/O system

• Microfilter replaces secondary clarifier:

Source: Hitachi Plant Technologies Ltd.

VACUUM PUMP

1 – 3 psi


Source: King County, WA

Source: Zenon Technologies


• Advantages– Significantly smaller than other systems

– Tolerant of higher MLSS: • 15,000 to 25,000 mg/L (8,000 to 10,000 most cost effective)

• Higher hydraulic loadings (shorter detention time)g y g ( )

• Longer MCRT = less sludge production

– Can operate with low D.O• Nitrification/Denitrification a common addition

– High quality effluent• Turbidity

• Bacteria

• TSS

• BOD Source: Wastewater Engineering

Metcalf & Eddy, 2003


• Disadvantages– Expensive

– Limited Membrane life• Replacement every 3 years

– Complicated operation• Often automated

– Need to control membrane fouling

Source: Wastewater Engineering

Metcalf & Eddy, 2003

Disinfection

GOAL OF DISINFECTION:

– To destroy all disease causing organisms in order to protect downstream users of the water

HOW DO WE MEASUREHOW DO WE MEASURE EFFECTIVENESS:

– Fecal Coliform bacteria

Methods of Disinfection

• Lime– Kills pathogens by raising pH to 11.5 or higher

– Most commonly used for:• screening waste• screening waste

• Digested sludge

• Honeybucket waste

• Sewage spills

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• Ozone – O3

disinfection

Petro StoppingPetro Stopping Center on-site wastewater treatment system, Kingman, AZ:

Photo: Ozone Water Systems, Inc.


• Ultraviolet (UV) disinfection

Rota Resort wastewater treatment & reuse plant:

Photo: CNMI DEQ


• Chlorine – Most common in U.S.– Most commonly used for:

• Drinking water systems• Wastewater disinfection• Swimming pools

– Available as gas, liquid, or powder

Chlorine Facilities

• Contact Chamber– Maximize contact time

– Minimize turbulence

• “Plug flow”g

• 20-30 minutes needed

Chlorine Facilities

Photo: City of Denver, CO

Dechlorination

• Why dechlorinate?– Chlorine is deadly to fish & other aquatic life

– Can kill small fish at 6 µg/L (parts per billion)

• 2 common dechlorination processes:– Sulfur dioxide

• Gas; same equipment as standard gas chlorine system

– Sodium bisulfate• Liquid; same equipment as hypochlorite system – standard

chemical feed pump

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Other Uses of Chlorine

• Odor reduction

• Prevention of corrosion by hydrogen sulfide

• Control of undesirable bacteria at plant

• Prevent sewage from becoming septic• Prevent sewage from becoming septic

Sludge Treatment & Disposal

• Sludge treatment & disposal = solids handling

3 Steps:

– Stabilization – to reduce pathogens & organic content

– Conditioning & Dewatering – to reduce volume

– Disposal – to prevent contamination

Types of Sludge

• Five basic groups:– Primary sludge

– Biological sludges

Scum– Scum

– Screenings

– Lagoon sludge

STABILIZATION: Aerobic Digestion

• Occurs in open, aerated tank called digester

• Common part of activated sludge plant• Stabilization accomplished by aerobicStabilization accomplished by aerobic

microorganisms• Best for secondary sludges• requires about 30 days• 1 to 3% solids

Aerobic Digestion

Illustrtion: Kimon Zentz, ARC Publications

Aerobic Digestion

• Continuous operation


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Anaerobic Digestion

• Occurs in airtight tank called digester

• Tank is heated

• Stabilization accomplished by anaerobic microorganismsmicroorganisms

• Produces methane gas – can be used for heating tank, generating electricity

• Works for both secondary and primary sludges, and scum

• requires about 20 - 25 days

• 3 to 4% solids

Anaerobic DigestionDigester:

Photo: City of Santa Fe, NM

Anaerobic Digestion

Heat exchangers:

Boilers:


Anaerobic DigestionGas flare:


Lime Stabilization

Lime stabilization tank:


Solids Conditioning & Dewatering

• Dewatering:– Purpose:

• Remove water from sludge

• Reduce handling costs

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Solids Conditioning & Dewatering• Drying Beds

FILL TO 18 INCHES


Solids Conditioning & Dewatering• Drying Beds

Photo: Humboldt University


• Vacuum Filter

Solids Conditioning & Dewatering• Solid-Bowl Type Centrifuge installation

Photo: pollutionsolitions-online.com


• Screw Press

Photos: Goble-Samspon Associates Inc.

Solids Conditioning & Dewatering• Belt Filter Press

Photos: Andritz AG

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Sludge disposal

• Dedicated land disposal site:


Sludge disposal

• Subsurface injection equipment:

Photo: City of Columbia, MO

Photo: City of Santa Fe, NM Photo: Region of Huronia Environmental Services, Ltd.

Sludge disposal

• Disposal in Landfills:

– “Liquids restriction” in federal solid waste regulationsregulations

– minimum 10% solids

– “No Free Liquids” measured by “paint filter test”

• Sludge placed into conical paint filter

• PASS: no drained liquid after 5 minutes

• FAIL: any free liquid in container below filter

Sludge disposal

• Paint Filter free liquids test

– EPA SW-846 method 9095

Sludge disposal

• Other disposal methods:

– Sludge lagoons• Provides some further o des so e u e

treatment, but disposal still required

– Incinerators• Expensive• Permitting & monitoring a

serious challenge• Ash disposal a problem -

metals

Sludge disposal

• Other disposal methods:

– Composting• Can provide a useful product

S il “ d t” t f tili– Soil “amendment”, not fertilizer

• Must be carefully monitored & controlled to meet regulatory requirements

– 131°F (55°C) for 3 consecutive days to kill pathogens

• Requires mixing with a carbon source– Wood chips, shredded paper, etc.

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Sludge disposal

• Composting Palau EQPB

Regulatory Agencies

• USEPA– Permits

• Clean Water Act• NPDES Permits

– “National Pollutant Discharge Elimination System”

Inspection & enforcement– Inspection & enforcement• DEQ

– Permits• Water Quality Standards• Section 401 Water Quality Certification

– Inspection & enforcement– Operator certification

Operator Certification:

• All “OWTS” under “responsible charge” of operator with proper level cert.

• All personnel making process control / system integrity decisionssystem integrity decisions

• Must be “available” for each operating shift

• High school diploma

Operator Certification

Table 1 - Years of Experience Required for Certification at each Classification Level

ClassificationLevel

OIT* Class 1 Class 2 Class 3 Class 4Level

WastewaterTreatment

0 1 3 4 4

WastewaterCollection

0 1 3 4 4

*OIT means Operator-In-Training. An operator certified at the OIT level is a certified operator, but can not be the supervising operator having responsible charge over an OWTS because the certification level is not at the classification level of the OWTS.

Photo: www.theage.com.au

what is wastewater? - mariana islands water operator ... oxygen: a crucial parameter • strength of...

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