Common Errors in CT Calculations and Tracer Studies: Surface ...

Common Errors in CT Calculations and Tracer Studies: Surface ...

DISINFECTION Overview What is disinfection? Types of disinfectants

Forms of chlorine NSF/ANSI Standard 60 Disinfection requirements for surface water CTs Tracer Studies and Contact Time Impact of disinfectants on organics What is disinfection? Process of killing microorganisms in water that might cause disease (pathogens) Should not be confused with sterilization which is the destruction of all microorganisms Two types: Radiation (UV)

Chemical (chlorine, chloramines, chlorine dioxide, ozone) Ultraviolet light Works by subjecting water to ultraviolet (UV) light rays as water passes through a tube Drawbacks: Interfering agents such as turbidity can screen pathogens from the UV light Effective against Giardia and Cryptosporidium but not viruses at normal doses No residual is present in the water to continue disinfecting throughout the distribution system For this reason, chlorination for residual maintenance

is required when UV is used The state maintains a list of approved UV units on its website NSF 55 units not allowed for SW treatment (only allowed for GW TC+ with small distribution) UV reactors at a large water system

Quartz UV bulb sleeve Chemical Disinfection Chlorine Chloramines Chlorine dioxide Ozone

Chlorine The most widely used form of disinfection Also used as an oxidizing agent for iron, manganese and hydrogen sulfide and for controlling taste and odors Effectiveness as a disinfecting agent depends on factors such as pH, temperature, free chlorine residual, contact time and other interfering agents Forms of Chlorine

Sodium Hypochorite Onsite generated sodium hypochorite Calcium Hypochlorite Chlorine Gas Sodium hypochlorite The liquid form of chlorine Clear and has a slight yellow color Ordinary household bleach (~5% chlorine by solution) is the most common form Industrial strength: 12% and 15% solutions

Sodium hypochlorite (continued) Can lose up to 4% of its available chlorine content per month; should not be stored for more than 60 to 90 days Very corrosive; should be stored and mixed away from equipment that can be damaged by corrosion Diaphragm Pump/Tank for Chlorine On-site generated sodium hypochlorite 0.8% sodium hypochlorite is produced on demand by combining salt, water & electricity

Electrolysis of brine solution produces sodium hydroxide and chlorine gas, which then mix to form sodium hypochlorite Hydrogen gas byproduct; vented to atmosphere Alleviates safety concerns associated w/ hauling and storing bulk chlorine Higher initial cost, high power cost Mixed oxidants (proprietary) Electrodes for onsite chlorine generation Calcium hypochlorite

The solid form of chlorine Usually tablet or powder form Contains ~65% chlorine by weight White or yellowish-white granular material and is fairly soluble in water Important to keep in a dry, cool place More stable than liquid Used by small systems w/ low flows or no power

Calcium hypochlorite erosion feeder Calcium hypochlorite hopper interior Chlorine gas (Cl2) 99.5% pure chlorine yellow-green color 2.5x heavier than air Liquified at room temperature at ~107 psi hence the pressurized cylinders actually contain liquified chlorine gas. Liquified Cl2 is released from tanks as chlorine gas, which is then injected into the water stream. usually used only by large water systems

Smaller systems may find initial cost of operation prohibitive 1-ton chlorine gas cylinders 1-ton chlorine gas cylinders Note: scales used to weigh cylinders (to tell when they are empty) 150-lbs chlorine gas cylinders Spare tank on hand

Chain to secure tank in place Tanks clearly marked Chloramines Chlorine + ammonia = chloramination Two advantages to regular chlorination: produce a longer lasting chlorine residual (helpful to systems with extensive distribution systems)

may produce fewer by-products depending on the application Disadvantage: Need a lot of contact time to achieve CTs compared to free chlorine (300 times more) which is why not used for primary disinfection Requires specific ratio of chlorine to ammonia or else potential water quality problems Ammonia for making chloramines Ozone

Colorless gas (O3) Strongest of the common disinfecting agents Also used for control of taste and odor Extremely Unstable; Must be generated on-site Manufactured by passing air or oxygen through two electrodes with high, alternating potential difference Large water system ozone

Large water system ozone Ozone contactors Ozone is to reactive to store, so liquid oxygen is used for making ozone Ozone advantages Short reaction time enables microbes (including viruses) to be killed within a few seconds Removes color, taste, and odor causing compounds Oxidizes iron and manganese

Destroys some algal toxins Does not produce halogenated DBPs Ozone disadvantages Overfeed or leak can be dangerous Cost is high compared with chlorination Installation can be complicated Ozone-destroying device is needed at the exhaust of the ozone-reactor to prevent smogproducing gas from entering the atmosphere and

fire hazards Ozone disadvantages (continued) May produce undesirable brominated byproducts in source waters containing bromide No residual effect is present in the distribution system, thus postchlorination is required Much less soluble in water than chlorine; thus special mixing devices are necessary Chlorine dioxide Advantages More effective than chlorine and chloramines for inactivation of viruses, Cryptosporidium, and Giardia

Oxidizes iron, manganese, and sulfides May enhance the clarification process Controls T&O resulting from algae and decaying vegetation, as well as phenolic compounds Under proper generation conditions halogen-substituted DBPs are not formed Easy to generate Provides residual Chlorine dioxide (continued) Disadvantages Forms the DBP chlorite Costs associated with training, sampling, and laboratory testing for chlorite and chlorate are high

Equipment is typically rented, and the cost of the sodium chlorite is high Explosive, so it must be generated on-site Decomposes in sunlight Can lead to production noxious odors in some systems. NSF/ANSI Standard 60 Addresses the health effects implications of treatment chemicals and related impurities. The two principal questions addressed are: Is the chemical safe at the maximum dose, and Are impurities below the maximum acceptable levels? NSF approved sodium hypochlorite

Disinfection Requirements for Surface Water Surface Water Treatment Rule (SWTR) requires 3-log reduction of Giardia using a combination of disinfection and filtration 2.0 to 2.5-log removal is achieved through filtration 0.5 to 1.0-log inactivation is achieved through disinfection Determines which column of EPA tables used to calculate CTs (0.5 or 1.0-log) What are CTs?

Its a way to determine if disinfection is adequate CT = Chlorine Concentration x Contact Time Do not confuse CT and Contact Time How do we calculate CTs? We use the EPA tables to determine the CTs needed to inactivate Giardia (CTrequired) We need to know pH, temperature, and free chlorine residual at the first user in order to use the EPA tables. Then we compare that with the CTs achieved in our water system (CTactual)

CTactual must be equal to or greater than CTrequired Tracer Studies and Contact Time: Used to determine contact time (T) which is used in calculating CTs Determines the time that chlorine is in contact with the water from the point of injection to the point where it is measured (sometimes referred to as the CT segment) May be at or before the 1st user May be more than one CT segment Estimates of contact time are not allowed for calculating CTs for surface water! The degree of short-circuiting is only approximately known until a tracer study is conducted.

What effects short-circuiting? 1)Flow rate 2)Flow path Mackey Creek (gravity flow to plant) The CT segment is from where chlorine is added here: 4,000 g raw water tank Raw NTU

Slow sand filter Cell #1 Slow sand filter Cell #2 25hp booster pump Flow, NTU

Sodium hypochlorite 210,000 g clearwell/reservoir 36,000 g raw water tank Cl residual, pH, temp, flow Intake/pump station Breitenbush River

Distribution system Mackey Creek (gravity flow to plant) Thru the clearwell, to where chlorine residual is measured here: 4,000 g raw water tank Raw NTU

Slow sand filter Cell #1 Slow sand filter Cell #2 25hp booster pump Flow, NTU Sodium hypochlorite

210,000 g clearwell/reservoir 36,000 g raw water tank Cl residual, pH, temp, flow Intake/pump station Breitenbush River Distribution system

Mackey Creek (gravity flow to plant) 4,000 g raw water tank Raw NTU Slow sand filter Cell #1 Slow sand filter Cell #2

So if we were conducting a tracer study, this is the segment we would be looking at and determining the contact time T for. 25hp booster pump Flow, NTU Sodium hypochlorite

210,000 g clearwell/reservoir 36,000 g raw water tank Cl residual, pH, temp, flow Intake/pump station Breitenbush River Distribution system

Tracer studies (continued): Different methods: 1. If water is pumped from the clearwell at different rates depending on time of year, do tracer study at each of those flow rates 2. Do at typical winter/summer peak hour demand flows 3. Otherwise use worst-case scenario parameters: Highest flow rate out of clearwell (conduct during peak hour or conditions that simulate e.g. open a hydrant) Keep flow rate constant Keep clearwell water level close to normal minimum operating level

Tracer studies (continued): Must redo if peak hour demand flow increases more than 10% of the maximum flow used during the tracer study Community water systems with populations <10,000 and non-profit non-community systems can use the circuit rider to perform a tracer study Must submit a proposal to DWS for approval prior to conducting the tracer study (even if using the circuit rider). Exercise #1 Tracer studies

Exercise #1: Tracer studies Directions: Look at the diagram and answer the questions. Figure 1: Water Treatment Plant Smith Creek NTU, flow Slow sand filter #1 Slow sand filter #2

NTU NTU Chlorine injection Two houses Flow control valve: 270 gpm max Reservoir 75,000 gal.

16.1 max volume Clearwell 220,000 gal 10.5 min volume Flow To distribution Questions: If this was your treatment plant, highlight the part of the plant where you might conduct a tracer study. In a worst-case scenario tracer study, what would the flow rate be? In a worst-case scenario tracer study, what would the clearwell level be? Exercise #1: Tracer studies

Directions: Look at the diagram and answer the questions. Figure 1: Water Treatment Plant Smith Creek NTU, flow Slow sand filter #1 Slow sand filter #2 NTU

NTU Chlorine injection Two houses Flow control valve: 270 gpm max Reservoir 75,000 gal. 16.1 max volume

Clearwell 220,000 gal 10.5 min volume Flow To distribution Questions: If this was your treatment plant, highlight the part of the plant where you might conduct a tracer study. In a worst-case scenario tracer study, what would the flow rate be? 270 gpm In a worst-case scenario tracer study, what would the clearwell level be? 10.5 feet How info from tracer study is

used to calculate CTs Use the time T from the tracer study on the monthly reporting form in the Contact time (min) column Use the smallest T (highest flow) if the tracer study was done at multiple flow rates This may not be your exact time, but it represents your worst case (as long as the peak flow is less and clearwell volume is more than they were at the time of the tracer study) How info from tracer study is used to calculate CTs (cont.)

Or, once you know the time T from the tracer study, you can back-calculate to determine the baffling factor of the clearwell Baffling factor (%) = Time (min) x Flow During Tracer Study (gpm) Clearwell Volume During Tracer Study (gal) T can be adjusted based on flow (at <110%) with the following equation: T = Current clearwell Volume (gal) x Baffling Factor (%) Peak Hourly Demand Flow (gpm) If tracer study includes pipeline segments or multiple tanks, contact the state for guidance on using baffling factors

Impact of chlorine and ozone on organics Disinfectants can react with organics to form disinfection byproducts Chlorine: TTHMs & HAA5s Ozone: Bromate Pre-chlorination TOC OPERATIONS Overview Proper instrument sampling locations

Proper treatment plant sampling locations Turbidity Chlorine residual TOC Instrument calibration Turbidimeters Chlorine analyzers Chemical feed pumps Operations & Maintenance Manuals Proper instrument sampling location Data provided by instruments provides the basis for

assessing water quality important to get it right! Common problems Sampling location Measurement techniques Calibration frequency and approach Possible solutions May require investigations (special studies) Modifications to sample lines

Establish guidelines on sample line cleaning Establish calibration procedure Proper treatment plant sampling locations: Turbidity Raw turbidity Applies to all SW systems Location: pre-treatment Frequency: no regulatory requirement but need to know for proper treatment plant operation Individual filter effluent (IFE) turbidity

CF, DF & membranes only Location: after each individual filter Frequency: continuous (every 15 minutes) Know what the triggers are! IFE Triggers (Conventional/Direct) Report the following events immediately and conduct a filter profile within 7 days (if no obvious reason exists) if the IFE turbidity is: > 1.0 NTU in 2 consecutive 15-min readings > 0.5 NTU in 2 consecutive 15-min readings within 4 hours of being

backwashed or taken off-line Report the following events and conduct a filter self assessment within 14 days if the IFE turbidity is: > 1.0 NTU in 2 consecutive 15-min readings at any time in each of 2 consecutive months. A CPE must be done within 30 days if the IFE turbidity is: > 2.0 NTU in 2 consecutive 15-min readings at any time in each of 2 consecutive months. Proper treatment plant sampling locations: Turbidity (cont.) Combined filter effluent (CFE) turbidity

Applies to all SW systems Location: post all filtration prior to chemical addition and any storage Frequency: CF/DF > 3,300 pop. continuous CF/DF 3,300 pop. every 4 hrs Alternative - daily Proper treatment plant sampling locations: Chlorine residual Location: entry point (EP) to the system EP = post clearwell, at or before 1st user Frequency

Continuous > 3,300 population 1-4x/day for 3,300 population Must maintain minimum 0.2 ppm at all times Proper treatment plant sampling locations: Total organic carbon (TOC) Applicability CF (2.5-log plants): required raw TOC & alkalinity and filtered TOC All others: raw TOC required to qualify for DBP monitoring reduction (>500 population)

Frequency Monthly; may be reduced to Quarterly if filtered TOC is <2.0 ppm for 2 years, or <1.0 ppm for 1 year Quarterly if DBP reduction is granted Proper treatment plant sampling locations: Total organic carbon (TOC) (cont.) Location Raw TOC & alkalinity: pre-treatment Filtered TOC: CFE prior to chemical addition/disinfection <2.0 ppm for 2 years, or

Coagulant <1.0 ppm for 1 year Chlorin e Exercise #2 Proper sampling locations for turbidity, chlorine residual, and TOC Work in groups to determine proper sampling locations on WTP diagrams Exercise #2: Proper sampling locations in a treatment plant for turbidity, chlorine residual, and TOC

Source water Sodium hypochlorite Alum Polymer capability Rapid mix Flow Flocculation Basin Sedimentation Basins Backwash settling

lagoon Transfer pump (up to filters) Flow Sodium hypochlorite Polymer capability Alum capability to recreate floc if needed Rapid sand filter #1 Rapid sand

filter #2 Sodium hypochlorite capability 5 MG Clearwell To distribution system Exercise #2: Proper sampling locations in a treatment plant for turbidity, chlorine residual, and TOC Source water Raw turbidity, raw TOC & alkalinity Sodium hypochlorite Alum Polymer capability

Rapid mix Flow Flocculation Basin Sedimentation Basins Backwash settling lagoon Transfer pump (up to filters) Flow

Sodium hypochlorite Polymer capability Alum capability to recreate floc if needed Rapid sand filter #1 Rapid sand filter #2 IFE turbidity

IFE turbidity CFE turbidity, filtered TOC Sodium hypochlorite capability 5 MG Clearwell Chlorine residual To distribution system Basket strainer w/ auto backwash 12 pipe from river to wet well Flow Filter skid 2: 125 gpm max

Filter skid 1: 125 gpm max (2) 5 hp VT booster pumps lead/lag, 250 gpm each 1400 gallon buffer tank (wet well for booster pumps) Sodium hypochlorite

Soda ash (2) 15 hp variable speed VT booster pumps Flow 72 x 150 pipe used for contact time To distribution system Basket strainer w/ auto backwash 12 pipe from river to wet well

Raw turbidity, raw TOC & alkalinity Flow Filter skid 2: 125 gpm max Filter skid 1: 125 gpm max (2) 5 hp VT booster pumps

lead/lag, 250 gpm each IFE turbidity IFE turbidity CFE turbidity, filtered TOC 1400 gallon buffer tank (wet well for booster pumps)

Sodium hypochlorite Soda ash (2) 15 hp variable speed VT booster pumps Flow 72 x 150 pipe used for contact time Chlorine residual To distribution system Instrument calibration

Turbidimeters (online, portable or benchtop) Must be calibrated per manufacturer or at least quarterly with a primary standard Formazin solution Stablcal (stabilized formazin) Secondary standards used for day-to-day check Check is used to determine if calibration with a primary standard is necessary Gelex Manufacturer provided (e.g. Hach ICE-PIC) Portable turbidimeter

Instrument calibration Chlorine analyzers Handheld Follow manufacturers instructions Inline Check calibration against a handheld that has been calibrated At least weekly Follow manufacturers instructions if out of calibration Portable colorimeter Instrument calibration

Chemical feed pumps Calibration measures both the speed and the stroke (amount of chemical pumped) so accurate dosages can be calculated Create a pump curve; Set the stroke at half way point On a graph, plot speeds of 10% to 100% on X axis Plot chemical output amount on Y axis (ml/min) Record drawdown in graduated cylinders for 1 minute Instrument calibration (cont.) Chemical feed pumps (cont.) Pump curve is an important tool to identify when a pump may be in need of maintenance or replacement

A smooth pump curve is good (should fit close to a straight line) Must compare information at varying speeds to be a full pump calibration process Suggested frequency: no less than annual Chemical feed pumps Exercise #3 Create a pump curve using made-up data points Directions: Use the data provided in the examples below to create a pump curve. Pump curves should be smooth and fairly linear. A bouncing or jagged pump curve indicates the

pump needs maintenance. Maintenance needed may include cleaning, diaphragm replacement and/or seal replacement. Exercise #3: Creating a chemical feed pump curve Directions: Use the data provided in the examples below to create a pump curve. Pump curves should be smooth and fairly linear. A bouncing or jagged pump curve indicates the pump needs maintenance. Maintenance needed may include cleaning, diaphragm replacement and/or seal replacement. Feed pump #1 pump curve data: Plot the data points on the graph. Does the pump need maintenance? Yes (jagged line) Setting

% Speed 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Time Minutes

3 3 3 3 3 1 1 1 1 1 Volume ml 60

360 420 810 900 450 400 525 530 575 Flow Rate ml/min 20 120

140 270 300 450 400 525 530 575 Feed pump #2 pump curve data: Plot the data points on the graph. Does the pump need maintenance? No (straight-ish, smooth

line) Setting % Speed 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Time Minutes 3 3 3 3 3 1 1 1 1 1

Volume ml 120 270 480 690 960 400 460 500 540 560 Flow Rate

ml/min 40 90 160 230 320 400 460 500 540 560 Bonus question: Referring to feed pump #2 data above, if you normally have your speed set at 50% in order to maintain 1 ppm of chemical, what speed do you need to change it to if you do a new pump

curve and get the following results: Feed pump #2 NEW pump curve data Answer: 60% Setting % Speed 10% 20% 30% 40% 50% 60%

70% 80% 90% 100% Time Minutes 3 3 3 3 3 1 1

1 1 1 Volume ml 60 120 270 480 690 320 400 460

500 540 Flow Rate ml/min 20 40 90 160 230 320 400 460 500

540 Lessons learned from data assessments done in the past Common findings: Most systems have some problems with the way they monitor, record, assemble, and/or report data Operators do not know which data to report and which to exclude Operators do not know how to correctly use their tracer studies/calculate CTs Most system managers and operators are surprised by what they find out from a data assessment

Data assessments (cont.) Even automated systems require a knowledgeable person to correctly assemble data Data assessments often used to justify invalidation of turbidity data which would have triggered a CPE Effective optimization can only be achieved when using valid performance data How can operators become better data managers? Make data reliability a plant goal Only collect data used for process control or

compliance reporting Establish protocols for collection and recording of data Establish a data verification process that can be routinely used to confirm data integrity Turn data into information! Operations & Maintenance Manual Keep written procedures on: Instrument calibration methods and frequency Data handling/reporting Chemical dosage determinations Filter operation and cleaning CT determinations

Responding to abnormal conditions (emergency response plan)

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