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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”
2
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
3
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
4
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.
Source: Arasmith & Ploetz
Preliminary Treatment
• Headworks
Source: Arasmith & Ploetz
Preliminary Treatment
• Grinding– comminutors
Source: www.jwce.com“Muffin Monster” channel grinders
Source: www.waterandwastewater.com
Preliminary Treatment
• Grinding– barminutors
Source: Arasmith & Ploetz
Muffin Monster Chain & Rake Monster
Source: www.jwce.com
Preliminary Treatment
• Grit Channel
Source: Indiana University of Pennsylvania
5
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
Source: Arasmith & Ploetz
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
6
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
7
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
Source: Arasmith & Ploetz
Types of Secondary Treatment Processes
• Fixed Film Media
• Lagoons & Wetlands
• Activated Sludge
Source: Arasmith & Ploetz
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)
Source: Arasmith & Ploetz
Trickling Filters
Source: Arasmith & Ploetz
Malakal Wastewater Treatment Plant - Palau
Source: CNMI DEQ
Malakal Wastewater Treatment Plant - Palau
Source: CNMI DEQ
8
Malakal Wastewater Treatment Plant - Palau
Source: CNMI DEQ
Trickling Filters• Zoogleal film
Source: Arasmith & Ploetz
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
Source: Arasmith & Ploetz
Trickling Filters• Piping & Recirculation
Source: Arasmith & Ploetz
RBCs – Rotating Biological Contactors
• Same treatment method as trickling filter
• Popular small plant option
Source: www.gm.ca
RBCs – Rotating Biological Contactors
• Multiple Contactors
9
Lagoons Ponds or Lagoons
Source: Arasmith & Ploetz
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%
Source: Arasmith & Ploetz
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
10
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
Source: Arasmith & Ploetz
• Activated sludge process
Effluent
AirClarifier
Activated Sludge - Description
Return Activated Sludge
EffluentInfluent
Waste Activated Sludge
Aeration Tank
11
Activated Sludge - Description
• 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
Source: Arasmith & Ploetz
Activated Sludge - Process
Source: Arasmith & Ploetz
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
Activated Sludge - Process
• Young Sludge under the microscope:– Increase in number of ciliates & stalked ciliate
protozoa, feeding on bacteria
Source: University of California at Los Angeles
Activated Sludge - Process
• Young Sludge & Settling– Does not settle easily – “bulking sludge”
– Tends to fill clarifier & go over weirs
– “straggle floc”
12
Activated Sludge - Process
• 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
Activated Sludge - Process
• 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
Activated Sludge - Process
• Old sludge
Under microscope:
– Very little protozoa activity
– Maybe some rotifers & wormsy
Source: Environmental Leverage , Inc.
Activated Sludge - Process
• Old Sludge: settling– Settles quickly but does not agglomerate well
– Small particles remain & are carried over into effluent
– “pin floc”
Source: Environmental Leverage , Inc.
• Old Sludge: denitrification– rising sludge
Activated Sludge - Process
Source: Environmental Leverage , Inc.
13
Activated Sludge – Process Control
• Settleometer & sludge age
Source: Arasmith & Ploetz
Activated Sludge – Process Control
• 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
Source: Arasmith & Ploetz
Activated Sludge - Aeration Systems
• Diffusers: on bottom of tank
• Fine Bubble Diffusers:
Source: Arasmith & Ploetz
Activated Sludge - Aeration Systems
Coarse Bubble Diffusers:
Source: Arasmith & Ploetz
• Blowers – 2 types:– lobe (most common)
– centrifugal
Source: Arasmith & PloetzActivated Sludge - Aeration Systems
Source: Aerzen USA Corp.
14
Activated Sludge - Aeration Systems
• Mechanical Aeration Systems• At surface of tank
• Four types of mechanical
Turbine Aerator:
ypaeration systems:
• Propeller
• Aspirator
• Turbine
• Jets
Source: Arasmith & Ploetz
Activated Sludge - Aeration Systems
• Aspirator Aerator
Source: Environmental Expert.comSource: MAOF Madan
Activated Sludge - Aeration Systems
• Jet Aerator
Source: Mixing Systems, Inc.
Activated Sludge - Aeration Systems
• 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)
15
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
Membrane Biological Reactors (MBR)
Source: King County, WA
Source: Zenon Technologies
Membrane Biological Reactors (MBR)
• 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
Membrane Biological Reactors (MBR)
• 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
16
Methods of Disinfection
• Ozone – O3
disinfection
Petro StoppingPetro Stopping Center on-site wastewater treatment system, Kingman, AZ:
Photo: Ozone Water Systems, Inc.
Methods of Disinfection
• Ultraviolet (UV) disinfection
Rota Resort wastewater treatment & reuse plant:
Photo: CNMI DEQ
Methods of Disinfection
• 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
17
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
Illustrtion: Kimon Zentz, ARC Publications
18
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:
Photo: City of Santa Fe, NM
Anaerobic DigestionGas flare:
Photo: City of Santa Fe, NM
Lime Stabilization
Lime stabilization tank:
Photo: City of Santa Fe, NM
Solids Conditioning & Dewatering
• Dewatering:– Purpose:
• Remove water from sludge
• Reduce handling costs
19
Solids Conditioning & Dewatering• Drying Beds
FILL TO 18 INCHES
Illustrtion: Kimon Zentz, ARC Publications
Solids Conditioning & Dewatering• Drying Beds
Photo: Humboldt University
Solids Conditioning & Dewatering
• Vacuum Filter
Solids Conditioning & Dewatering• Solid-Bowl Type Centrifuge installation
Photo: pollutionsolitions-online.com
Solids Conditioning & Dewatering
• Screw Press
Photos: Goble-Samspon Associates Inc.
Solids Conditioning & Dewatering• Belt Filter Press
Photos: Andritz AG
20
Sludge disposal
• Dedicated land disposal site:
Photo: City of Santa Fe, NM
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.
21
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
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