Chlorination in Waterworks Operation Waterworks Operations I WQT 111 Chlorination http://www.c3.org/chlorine_knowledge_center/history.html http://www.wrb.state.ri.us/programs/eo/historydrinkingwater.htm http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html

Week Objectives Comprehend “the basics” of chlorine chemistry Reading assignment: Water Treatment , Chapter 7: Disinfection Comprehend “the basics” of chlorine chemistry Understand the advantages and disadvantages of chlorine Understand the history of chlorine via a timeline Understand Breakpoint Chlorination Curve Calculate C•T values

Key Words Chlorine Residual- Measurable chlorine remaining after the demand is satisfied. Chlorine Demand- The amount of chlorine destroyed by reaction with Fe, Mn, turbidity, organics, and microorganisms in the water. Free Chlorine Residual- point past breakpoint where HOCl (hypochlorous acid) and OCL- (hypochlorite ion) form. 25 times more powerful than combined chlorine for disinfection Combined residual chlorine: chlorine combined with organics or ammonia. NH2Cl (monochloramine) and NH(Cl)2 (dichloramine) N(Cl)3 (nitrogen trichloride)

Key Words Breakpoint chlorination: The point at which near complete oxidation of nitrogen compounds are reached . Any point beyond breakpoint is mostly free chlorine (HOCL and OCL-) C•T (concentration and contact time): Effectiveness of chlorination is dependant on chlorine concentration and contact time. Sterilization: The destruction of all living things in a sample Disinfection: The removal or inactivation of disease causing (pathogenic) organisms Chlorine Demand= Chlorine Dose- Chlorine Residual

The destruction of the larger portion of microorganisms with the probability that all pathogens are killed is called Digestion Disinfection Dilution Sterilization Disposal

Proper disinfection kills all organisms? True False

Chlorine applied minus ____ equals chlorine residual Chlorine dose Chlorine demand Combined chlorine Free chlorine Total chlorine

CL2 Demand= Cl2 Dose- Cl2 Residual? True False

A low chlorine dose w/ longer the contact time can have the same disinfecting power as a high chlorine dose with a short detention time? True False

The amount of chlorine destroyed by reaction with Fe, Mn, turbidity, organics, and microorganisms in the water? Free Chlorine Residual Chlorine Demand Chlorine Residual

Measurable chlorine remaining after the demand is satisfied. Chlorine Demand Chlorine Residual

HOCL? Hypochlorous acid Hypochlorite ion Dichloramine

HOCL? Common at pH < 6 Most powerful/effective disinfectant All of the above

NH2Cl Monochloramine Combined Residual Chlorine Not as effective as a disinfectant as hypochlorus acid All of the above

Sterilization only removes pathogenic organism from a water sample? True False

Chlorine Advantages Chlorine provides a strong residual in the distribution system. Chlorine can be easily converted to chloramines which also provide a strong residual and do not produce by-products. Chlorine is easy to apply. Can use it in liquid, solid, or gas form Chlorine is a relatively inexpensive disinfecting agent. Chlorine is effective at low concentrations.

Chlorine Disadvantages When chlorine reacts with organic material its' concentration is reduced and trihalomethanes(THM's), haloacetic acids (HAA5), chlorite (when chlorine dioxide is used) and bromate (when ozone is used) are disinfection-by-products (DBP's). These compounds are carcinogenic. Chlorine provides poor Cryptosporidium and Giardia control. Effectiveness varies depending on turbidity, [ammonia], pH, etc. Chlorine is a dangerous and potentially fatal chemical if used improperly

According to the Stage 1 Disinfectant/Disinfection Byproducts Rule which of the following are considered haloacetic acids (HAA5) DPBs disinfectant byproducts? Monochloroacetic acid Dichloroacetic acid Monobromoacetic acid All of the above

An advantage of chlorine is that it can be a liquid, solid, or a gas? True False

Chlorine can completely remove Giardia and Cryptosporidium from water? True False

Chlorine Disinfection Timeline 500 BC- Boiling of water recommended by Hippocrates 1879- Chlorine was applied as a disinfectant for the first time (England). 1893-First time chlorine applied on a plant scale basis (Hamburg, Germany). 1903- First time chlorine gas was used as a disinfectant in drinking water (Middlekerke, Belgium). 1908- The first full scale chlorine installation at a drinking water plant in the United States was initiated in this year. (Bubbly Creek Filter Plant in Chicago)

Chlorine Chemistry Timeline 1744- S.W. Scheele, a Swedish chemist, discovers chlorine. 1810-Chlorine was identified as a chemical element by Davey and called Chlorine (chlorous) due to its pale yellow/green color 1909 Liquid chlorine bleach becomes available after the Niagara Starch Co. in NY develops a production method. 1914-Wallace and Tiernan develop chlorine gas feed equipment 1914 CR Cox describes experiments with chlorine that are called “double chlorination” (Discovered breakpoint) 1928 The Olin Corporation begins production of High Test Hypochlorite dubbed “HTH” http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html#History

Chlorination Methods Timeline 1939- A.E. Griffin explains “Breakpoint Chlorination” 1942-Henry Marks invents the amperometric chlorine residual analyzer. 1973-JJ Rook discovers chloroform (trtihalomethane) in drinking water in New Orleans and Corvallis. 1974- the SDWA is passed into law by congress. 1986 -The Surface Water Treatment Rule requires disinfection of all surface water and groundwater under the influence of surface water (GWUISW) 1986- USEPA approves four methods of drinking water disinfection. Disinfection C•T requirements for each disinfectant are established to insure inactivation of Giardia and viruses -Chlorination, Chloramines, Ozone, UV light 2003- USEPA approves UV disinfection for Crypto http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html#History

SDWA Amendments December 16,1998 promulgated Disinfection Byproduct Rule (DBPR): Stage 1 DBPR **Stage 2 in the works!** MCLs for trihalomethanes, haloacetic acids, bromate, and chlorite. Maximum residual disinfectant level goals (MRDLs) were also finalized for chlorine, chloramines, and chlorine dioxide. “Community water systems and non-transient non-community systems, including those serving fewer than 10,000 people, that add a disinfectant to the drinking water during any part of the treatment process.” MRDLGs for chlorine (4 mg/L), chloramines (4 mg/L), and chlorine dioxide (0.8 mg/L); MCLs for total trihalomethanes - a sum of the four listed above (0.080 mg/L), haloacetic acids (HAA5) (0.060 mg/L)- a sum of the two listed above plus monochloroacetic acid and mono- and dibromoacetic acids), and two inorganic disinfection byproducts (chlorite (1.0 mg/L)) and bromate (0.010 mg/L));

SDWA Amendments January 2002 May 1996- Information Collection Rule (ICR), occurrence data for DBPs and precursors, microbials, water quality parameters, and treatment plant parameters. Used to develop the Stage 2 DBPR and the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). Interim Enhanced Surface Water Treatment Rule -Applies to systems serving 10,000 or more people Long Term 1 Enhanced Surface Water Treatment Rule -strengthen microbial controls for small systems (i.e., those systems serving fewer than 10,000 people.) January 2002

SDWA Amendments January 5, 2006 Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). All public water systems with surface water or groundwater under the influence of surface water. LT2 rule reduce illness linked with the contaminant Cryptosporidium and other disease-causing microorganisms in drinking water. Targets Cryptosporidium treatment requirements to higher risk systems. Targeting additional Cryptosporidium treatment requirements to higher risk systems Requiring provisions to reduce risks from uncovered finished water storage facilities Providing provisions to ensure that systems maintain microbial protection as they take steps to reduce the formation of disinfection byproduct

Chlorine was first used as a disinfectant in Europe in the late 1800s? True False

Ozone, UV light, Chlorination, and Chloramines are 4 EPA approved disinfection methods? True False

Chlorine (Cl2) Widely distributed element Most important use is bleach Toxic, noncombustible, yellow-green gas with a pungent, irritating odor and strong oxidizing effects 2.5 times as dense as air! Slightly soluble in water Combines with water to form hypochlorous acid (HOCl) and hydrochloric acid (HCl) Highly corrosive causes injury when the gas reacts with moisture in the body

Chlorine - Toxicity Major route of toxicity is inhalation Solutions that generate chlorine can be highly corrosive to skin or GI tract Strong oxidizing capability Produce major tissue damage

Chlorine - Toxicity Hypochlorous acid Penetrates cells and react with cytoplasmic proteins, enzymes Form N-chloro derivatives that destroy cell structure Can alter DNA replication of viruses Estimated lowest lethal concentration 30-min exposure is 430 ppm -- 1000 ppm Fatal within minutes

Chlorine is a toxic, corrosive, gas? True False

Which of the following is a correct set of characteristics for chlorine as used in disinfection? Chlorine gas is colorless, flammable, and heavier than air Chlorine gas is colorless, flammable, and lighter than air Chlorine gas is greenish-yellow (amber) in color, flammable, and lighter than air Chlorine gas in greenish-yellow (amber) in color, toxic, lighter than air, and noncorrosive Chlorine gas is toxic, corrosive, and heavier than air

Protective Equipment Variety of rubber and plastic materials resist chlorine Wear protective clothing appropriate to the type and degree of contamination Use air-purifying or supplied-air respiratory equipment Chlorine-resistant plastic sheeting and disposable bags useful in preventing spread of contamination

Protective Equipment

Chlorine Chemistry Molecular Chlorine: Cl2 Chlorine Atom: Atomic Number 17 Atomic Weight 35.45 g Molecular Chlorine: Cl2 Yellow-green gas (above 100 ppm) Chemical Classification -"Oxidizer“, "Reactive“ ********Two SMCL's apply to chlorine: 4 mg/l for Cl2, and 250mg/l for Cl-** New MCL under consideration

Chlorine Chemistry Properties Dry liquid: 100% gas Powder: Calcium Hypochlorite- 30, 65, 70% chlorine Liquid: Sodium Hypochlorite: 5-15% chlorine Density = 2.5 times as heavy as air, Irritant Boiling point -29.9 oF Freezing point -149.76 oF 1 part of liquid will produce 450 parts of gas Maximum solubility: 1% at 49.2 oF Slightly soluble in water Temperatures below 49.2 will result in chlorine ice Insoluble in water at 212oF.

Where should sodium hypochlorite (liquid bleach) be stored? Away from flammable objects, as it is a fire hazard Away from equipment that is susceptible to corrosion closed containers at room temperature for no longer than 6 months Near the chemical feed pump day tank, to lessen operator handling risks

Chlorine as a powder can have purities of 30, 65, and 70%? True False

Sodium hypochlorite is manufactured by the reaction of gaseous or liquid chlorine with a solution of _________ _________ to produce a liquid containing NaOCl. Sodium hydroxide Potassium hydroxide Potassium bisulfite Sodium azide

Which form of hypochlorite is the most dangerous to handle? Sodium Fluoride Calcium Chlorine

Chlorine gas is _____ times heavier than air 2.5 2.0 3.5 1.5

Chlorine Chemistry When Cl combines with water it produces hypochlorous acid (HOCl) and hydrochloric acid (HCl). Cl2 + H2O HOCl + HCl hypochlorous acid and hypochlorite (OCL-) ion vary with pH. Both HOCl and OCl are good disinfecting agents, but un-ionized hypochlorous acid (HOCl) is 100 times more effective than hypochlorite (OCl-) HOCL is stable below pH 6 http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html

Hypochlorous acid is the most powerful disinfectant associated with chlorine? True False

pH Impact on Free Chlorine http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html

What compound is first formed when chlorine is applied to water? Hypochlorous acid Hydrochloric acid Chloramines Free chlorine ions

Chlorine will destroy bacteria most rapidly at what pH? 7.5 8.5 9.5 10.5

Chlorine Chemistry in Water Start with chlorine gas Cl2 + H2O HOCl + HCl 2. If the pH of the water is greater than 8, the hypochlorus acid (HOCl-) will dissociate (break) to yield hypochlorite ion. HOCl H+ + OCl– @pH>8 3. pH is less than 7, HOCl will not dissociate. HOCl HOCl @pH<7 Free residual hypochlorous acid (HOCl) is more 1000 times more effective than combined residual monochloramine http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html

Which of the following is true about chlorine chemistry? pH < 7 favors hypochlorous acid pH >8 hypochlorite ions form which can still disinfectant HOCL is 100 times more powerful then OCL- All of the above

HOCL is 1,000 times more powerful then monochloramine? True False

Basic Chlorine Compounds Chlorine Demand: chlorine reacted with Clay, silt, iron, manganese, bacteria Combined Chlorine Residuals Chloramines: chlorine reacted with Inorganic ammonia compounds (NH3) Organic nitrogen proteins (amino acids) Less DBP Weak against virus and protozoa

Chlorine demand is satisfied at the point when The reaction of chlorine with organic and inorganic materials stops Free chlorine residuals reach 2.5 mg/L An odor of chlorine is present Chlorine reaches the last tap

Cl:NH3 and pH Impact in Water If ammonia (NH3) is present in water, the hypochlorus acid (HOCL) will react to form one kind of chloramine depending on the pH, temperature, and reaction time. 2. Monochloramine and dichloramine are formed at pH 4.5 - 8.5 3. Monochloramine is most common @pH>7.5; Cl2:NH3 <5:1 4. pH 4-5-7.5, Cl:NH3 > 5:1 -Monochloramine converts to dichloramines 5. pH < 4.5, Cl2:NH3 ~15:1 -Trichloramine which produces a very foul odor. http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html

Chlorine-Ammonia (chloramines) Chlorine- Ammonia reactions are governed by: Rates of formation of mono and dichloramine. pH Temperature Time Cl:NH3 ratio Fact: High Cl:NH3 ratio, low temp & pH favor dichloramine Combined Available Chlorine- chlorine existing in the water in chemical combination with ammonia-nitrogen or organic nitrogen http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html

Chloramines in Water 3. pH 4.5-8.5; pH 8.0-8.5 Monochloramine: NH3 + HOCl NH2Cl + H2O 2. pH 4.5-8.5; pH 4.5-8.0 Dichloramine: NH2Cl + 2HOCl NHCl2 + 2H2O 4. pH <4.5 Trichloramine: NHCl2 + 3HOCl NHCl3 + 3H2O Chloramines are an effective disinfectant against bacteria but not against viruses. Add more chlorine to the wastewater to prevent the formation of chloramines and form stronger disinfectants. http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html

Add the Extra Free Chlorine (HOCL) 5. Additional free chlorine (HOCL or OCL-) reacts with chloramine to produce hydrogen ion, water , and nitrogen gas which will come out of solution. In the case of the monochloramine, the following reaction occurs: 2NH2Cl + HOCl N2 + 6HCl + H2O Added free chlorine reduces the concentration of chloramines in the disinfection process. Instead the chlorine that is added is allowed to form the stronger disinfectant, hypochlorus acid. http://ewr.cee.vt.edu/environmental/teach/wtprimer/chlorine/chlorine.html

If abundant (15 times) Cl is around and the pH < 4 If abundant (15 times) Cl is around and the pH < 4.5 Trichloramine is the most likely chloramine to form? True False

Which of the following impact chloramine disinfection? pH Temperature Time All of the above

Ammonium nitrogen and chlorine

Taste and Odor Problems Free (HOCL) 20 mg/L Monochloramine 5 mg/L Dichloramine .8 mg/L Trichloramine .02 mg/L

Chlorine Chemistry Summary Cl2 + H2O HCl + HOCl Chlorine Hydrochloric Hypochlorous Ca(OCl)2 (aqueous) Ca2+ +2 OCl- Calcium Hypochlorite Hypochlorite NaOCl2 (aqueous) Na+ + OCl- Sodium Hypochlorite Hypochlorite HOCl H+ + OCl- Hypochlorous Hypochlorite HOCl + NH3 NH2Cl + H2O Hypochlorous Ammonia Chloramine

Chlorine Residual Analysis Starch Iodide Titration: common in wastewater Amperometric Titration: common in wastewater with cloudy or turbidity problems DPD colorometric- common in water and wastewater. Measures free residual or combined residual.

Chlorine residual may be determined using the reagent: Diethyl-p-phenylene diamine Ethylene diamine tetraacetic acid Polychlorinated biphenyls Sodium thiosulfate

Which of the following methods is not used to determine chlorine residual? Photometric Iodometric Titrimetric Amperometric

A chlorine demand test will show the: Safe amount of chlorine that may be fed without killing people Number of lbs required to kill 100% of coliforms Amount of chlorine required to give a desired residual after a given time Amount of chlorine required to satisfy the biochemical oxygen demand

Breakpoint Chlorination Breakpoint chlorination: The point at which near complete oxidation of nitrogen compounds are reached . Any point beyond breakpoint is mostly free chlorine (HOCL and OCL-) A. Amount of chlorine required Theory: 7.6 to 15 times the ammonia nitrogen content of the water Practice: up to 25 times the ammonia nitrogen content B. Beyond breakpoint 90% free residual chlorine (HOCL and OCL-) 10% combined chlorine C. Why must breakpoint chlorination be reached? Necessary for the production of free residual chlorine (HOCL and OCL-) Reduces taste and odors Reduces chloramines

What is the process of adding chlorine to water until the chlorine demand has been satisfied called? Contact time Reliquefaction Hypochlorination Breakpoint chlorination

Breakpoint Chlorination Zone I: Chlorine is destroyed by reducing agents such as iron, manganese, clay and silt. Chlorine reduced to chloride Zone II: Chlorine comes into contact with organics and ammonia. Chloroorganics and chloramines are formed. Zone III: Chloroorganics and chloramines are partially destroyed. Chloramines are broken down and converted to nitrogen gas which leaves the system Zone IV: Breakpoint. Beyond this point, free available residual is formed. Some chloroorganics still remain as combined residual. Chlorine demand is difference between applied chlorine and the free chlorine residual at any two points on the breakpoint curve.

In Zone 1 most of the chlorine dose gets used by chlorine demand ? True False

In Zone II chlorine reacts with ammonia to form combined chlorine ? True False

In Zone III some combined chlorine gets broken down to nitrogen gas ? True False

At Breakpoint chlorine added becomes free available chlorine? True False

Disinfection with chlorine may cause the formation of these compounds Disinfection with chlorine may cause the formation of these compounds. They are a result of chlorine binding to naturally occurring organic matter. Trihalomethanes Trichloramines CFCs Chloroalkali salts

DPB (TRIHALOMETHANES) THM: Carcinogenic byproduct of a reaction with chlorine. Form when free chlorine comes into contact with organic compounds. ID by EPA in 1974. A. Four most common THMs MCLS Chloroform 0 mg/L Bromodichloromethane 0 mg/L Dibromochloromethane 0.06 mg/L Bromoform 0 mg/L C. DPB Trihalomethanes, haloacetonitriles, chlorinated acetic acids, chlorophenolds,

Bromoform is a type of trihalomethane? True False

TRIHALOMETHANES X H C X X HCX3 X= Cl, Br, or I Chloroform Bromodichloromethane Bromoform MCL=0.08 mg/L X H C X X HCX3 X= Cl, Br, or I

DPB (TRIHALOMETHANES) D. Water treatment processes that can be used to control THMs. Aeration Feed oxidation chemicals instead of pre chlorination Coagulation, flocculation, sedimentation, and filtration Water softening processes (Ion exchange) Powdered activated carbon. E. Substitute Oxidants for Pre-chlorinations Ozone O3 Potassium permangante KMnO4 Hydrogen peroxide H2O2 hypochlorous acid HOCl Hypobromous Acid HOBr Bromine Br Hypoiodous acid HOI Chlorine Dioxide ClO2 Iodine I2 Oxygen O2

You can aerate or add oxygen to water before chlorination to cut THMS? True False

Chlorine Effectiveness These are all important: pH Temperature Chlorine Demand: suspended solids/nitrite/organics/ reduced chemicals 5. Contact time 6. Concentration 7. Mixing Intensity 8. Type of residual

Chlorine Effectiveness 1. pH (low pH =better disinfection) want pH < 7.5=more hypochlorus acid 2. Temperature (warm temp=better disinfect) chlorine disinfection power doubles every 10 degrees. 3. Chlorine Demand (Low Chlorine demand=better disinfect) Fe+3, Mn+4, HS and turbidity cause chlorine demand 4. Suspended solids/nitrite/organics/ reduced chemicals

As water temperatures decrease, the disinfecting action of chlorine Decreases Increases Remains the same

In the application of chlorine for disinfection, which of the following is not normally an operational consideration? Mixing Contact time Dissolved oxygen pH None of these answers are correct

pH > 8 favors hypochlorite ion which is a more powerful disinfectant than hypochlorous acid? True False

Chlorine disinfection power doubles every 10 degrees? True False

Low chlorine demand is better for disinfection? True False

Chlorine Effectiveness 5. Contact time (longer contact = better disinfection) Varies depending on tank dimensions 6. Concentration (higher concentration=better disinfection) OPTIMIZE THE DISINFECTION PROCESS 7. Mixing Intensity (Rapid Mixing=better disinfection) Rapidly disperse chlorine better kill rate 8. Disinfection CT (higher actual CT=better disinfection) As disinfection CT increases by 50, effective kill increases 10 times (EPA set guidelines)

Longer contact time is better for disinfection? True False

In general high dose concentrations = better disinfection? True False

Slow mixing favors better disinfection? True False

SDWA 99.9% removal of Giardia Lamblia cysts 99.99% removal of Enteric Viruses Disinfection CTs have been established Free chlorine Chloramine Chlorine dioxide Ozone

Log Understanding “log removal” requirements of the Long Term 1 Enhanced Surface Water Treatment Rule First a definition and some examples: Logarithm10: The exponent of the power to which 10 must be raised to equal a given number. Examples: • 102 is equal to 100, the log10 of 100 is 2 • 103 is equal to 1000, the log10 of 1000 is 3 • 102.65 is equal to 446.7, the log10 of 446.7 is 2.65 Log inactivation: A simplified method for expressing the degree to which microorganisms are removed from water. The removal percentage is expressed as the log to the base 10. If 100 Giardia cysts are inactivated so that only 1 remains, what is the percent removal of the microorganism? (100 - 1) x 100 = 99% or 2 log inactivation 100

EPA APPROVED METHODS Disinfection C•T Inactivation of Waterborne Pathogens By Disinfection The EPA has approved 4 chemical oxidizers for drinking water Disinfection: Free Chlorine, (HOCl and OCl-) Chloramine, (NH2Cl) Chlorine dioxide, (ClO2) Ozone (O3) Each of these disinfectants has a proven capability to kill or inactivate waterborne pathogens, including viruses and protozoa cysts. The disinfection power of these chemicals is dramatically different. Disinfection C•T

Four EPA Approved disinfectant chemicals are Free Chlorine, (HOCl and OCl-) Chloramine, (NH2Cl) Chlorine dioxide, (ClO2) Ozone (O3)? True False

Disinfection C•T Requirements Chlorine residual concentrations (mg/L) Contact Time (min) Water Temperature Water pH Disinfection power= [residual chlorine] • time of its contact

Disinfection C•T Calculation C•T= [disinfection concentration mg/L] • contact time (min) C•T units= mg/L• min or mg •min/L Required C•T CTrequired is # established by EPA to provide log inactivation. Based on Giardia cysts. Look up in charts Actual C•T CTactual is # established by multiplying actual chlorine residual by hydraulic detention time and baffle factor.

Disinfection C•T Calculation C•T actual =[Residual chlorine]•hydraulic detention time•baffle factor (table) Hydraulic detention time = volume/flow rate C•Tact/ CTreq= ratio must be > or = to 1. C•Tact/ CTreq>1.0

Disinfection C•T Rules Chlorine residuals used for C•T calculations are measured after contact, but before first customer. 2. Contact times are determined by calculating the hydraulic detention time (HDT) as water flows through pipes and tanks. Based on highest flow of day.

Disinfection C•T Rules 3. Water flowing through pipes provides contact times that are equal to the calculated HDT. Circular or rectangular tanks used for contact time are given only partial credit due to short circuiting.

The objective stated in the syllabus to have an overview of chlorine chemistry and the chlorination process, were met ? Strongly Agree Agree Disagree Strongly Disagree