CEEN 572Environmental Engineering Pilot Plant Laboratory

Introduction

Instructor: Prof. Tzahi Cath (tcath@mines.edu)TA: Tori Billings (vbilling@mymail.mines.edu)

Course objectives Apply knowledge and understanding of water

treatment processes to a real-world problem Enhance students ability to apply math, science, and

engineering concepts and skills to the analysis, design, and optimization of drinking water treatment systems

Teach students to effectively communicate the results of their technical work through professional quality written reports and oral presentations

Enhance teamwork skills through team project assignments

Course organization Meeting time Wed 4-5:30 pm and Fri 1-4 pm in the IETL

(CO 166 or Golden Water Treatment Plant) Course webpage:http://inside.mines.edu/~tcath/courses/CEEN572_pilot/ Office hours: CH 128 by appointment Textbook: No specific textbook recommended. Course

webpage is resource

References for CEEN 572 HDR Engineering Inc. (2001). Handbook of Public Water Systems. 2nd Edition. John

Wiley & Sons, Inc. American Water Works Association (1999). Water Quality and Treatment. Fifth

Edition. McGraw-Hill. American Water Works Association (1998). Water Treatment Plant Design. Third

Edition. McGraw-Hill. Faust. S. and Aly, O. (1999). Chemistry of Water Treatment. 2nd Edition. Lewis

Publishers. Qasim, S. R., Motley, E. M., Zhu, G. (2000). Water Works Engineering. Planning,

Design & Operation. Published by Prentice Hall PTR MWH (2005). Water Treatment: Principles and Design. 2nd Edition. John Wiley &

Sons, Inc. Howe, K. and Clark, M. (2002). Coagulation Pretreatment for Membrane Filtration.

AwwaRF Report AWWA (2005). Microfiltration and Ultrafiltration Membranes for Drinking Water.

Manual of Water Supply Practices M 53.

Grading CEEN 572 Laboratory reports and presentations 25% Participation and peer evaluation

30% Project Presentation

15% Final Report (WRITING…)

30%

What do I need to know? Fluid Mechanics: Bulk fluid properties, mass

conservation equations, laminar/turbulent flow regimes, reactor flow models

General knowledge in conventional water treatment (also prerequisites): CEEN 470 (ESGN 453); CEEN 471 (ESGN 453); CEEN 570 (ESGN 504); CEEN 571 (ESGN 506)

or consent of the instructor

Golden Water Treatment Plant

Conventional Water Treatment

Golden Water Treatment Plant

PRESEDIMENTATION & STORAGE

PONDS RAW WATER PUMP STATION

RAW WATER FROM CLEAR

CREEK

KMnO4 (PRE-OXIDATION)

SETTLER

FLOC AID

FERRIC SULFATE

SODA ASH

SPLIT TRAIN (RAPID MIX, FLOCCULATION, SEDIMENTATION)

RAPIDMIX

FLOCCULATION

NaOHCl2

CLEARWELL

Cl2

HIGH SERVICEPUMPS

DISTRIBUTION SYSTEM

MULTIMEDIA FILTRATION

Golden Water Treatment Plant

Golden Water Treatment Plant The Golden water treatment plant has just upgraded

the multimedia filters: New underdrain (leopold® vs. gravel/rocks)

http://www.xylemwatersolutions.com/scs/usa/Documents/LB003-1326_Leopold_TypeS_Underdrain_Brochure_sm.pdf

Dual media vs. mixed media New sand

Conventional filtration vs. greensand filtration To satisfy Level 3 Partnership for Safe Water, the

settled turbidity should be <1 NTU and filtered turbidity < 0.1 NTU

Understanding the Problem In recent years, and especially during the last

rain/flood event, the Golden water treatment plant was overwhelmed with high TOC (DBP precursor…) and taste & odor compounds in the source water

Last year we explored dosing of powdered activated carbon (PAC) in the flocculation basing to adsorb TOC.

Another common approach (that Golden already implement) is enhanced coagulation, which involves simultaneous acidification of the source water… BUT…, it is not simple…

Research Questions1. How and where else can we control source water pH to

optimize TOC/NOM removal?

2. How do we control water stability while changing chemical treatment?

How can we achieve the above without compromising oxidation (KMnO4) for Mn removal and disinfection (Cl2) for pathogen removal?

3. How pH control will affect sludge production and characteristics and filter performance?

Golden’s Desired Solution Recarbonation/pH control of water with CO2

Develop and conduct bench scale study Develop and conduct pilot scale study Test impacts of different operating conditions

What research/teaching infrastructure is available to us?

CSM-Golden Pilot Plant

Mini-Pilot Treatment System

Mini-Pilot Flow Diagram

FeedTankKMnO4

Flocculation Basin

turbidimeter

pH

Chlorine

pH adjustment

Overflow Coag.

BackwashLines

BackwashWaste

V-1

V-2

V-3V-2

V-5V-4

V-10

V-14V-13

V-12V-11

V-9V-7 V-8V-6

Bench Scale Systems Jar tester…

Team Assignments Compile information on relevant federal and state regulations

for TOC/NOM, DBPs, T&O, turbidity, manganese removal, and filtration conditions related to surface water treatment plants. Prepare presentation for January 16

Compile data from Golden water treatment plant and prepare a presentation and discussion for our meeting on January 16

Conduct review on conventional treatment processes for TOC and T&O form surface water, with a focus on pH control with CO2 for improving coagulation

Develop draft experimental plan for pilot scale study using the IETL filtration pilot systems

CO2 Carbonation/Recarbonation Used mainly in conjunction with chemical softening

of hard water CO2 (carbonic acid) is a weak acid… CO2 might impact water stability… Different reactor might be used for application

http://www.eco2tech.com/works.php https://www.youtube.com/watch?v=6thCFEWWSrw

Lab Safety for CEEN 572:General Laboratory Rules Use safety glasses at all times in the laboratory

You must use safety glasses during transport of chemicals between labs Use laboratory coats when working in the laboratory

Don’t use them outside of a laboratory (except when moving between labs)

Use gloves when handling chemicals (see label and MSDS) Remove gloves when leaving the laboratory

Biological and chemical materials must be transported between laboratories: with secondary containment (e.g., bucket or cart with raised sides) with lab coat and gloves with safety glasses worn

Lab Safety for CEEN 572:General Laboratory Rules Closed-toed shoes must be worn at all times Hands must be washed with soap before leaving the laboratory No food, beverages, or cosmetics are allowed at any place within the

laboratory Hair that is long enough to reach the shoulders must be tied back All containers of samples or chemicals must be labeled All benches and hoods must be kept free of clutter, dust, and residue

from any spills All benches must be wiped clean after use All sinks must be kept free of glassware and instrumentation All instrumentation, particularly balances, must be thoroughly cleaned

after use

Lab Safety for CEEN 572 (cont.)Waste Disposal All chemical waste must be disposed of in designated waste containers All containers must be labeled with contents and date Contact wastes: collect in designated yellow buckets

Individual Responsibilities Notify the supervising faculty of any medical conditions that could be

affected by carrying out laboratory activities Notify the supervising faculty of any safety concerns Observe the above laboratory rules Assist other laboratory users in observing general rules Immediately clean routine spills Immediately report non-routine spills to the supervising faculty and to EHS Memorize locations and uses of all exits, eye-wash stations, showers, fire

alarms, and emergency phones

Lab Safety for CEEN 572:Golden Water Treatment Plant Over the years we have established VERY GOOD relationships with the

city of Golden (!!!) You will get access to the water treatment plant.

THIS IS NOT OBVIOUS AND REQUIRE CAREFUL AND OUTMOST PROPER BEHAVIOR

Announce visiting plans Report in and out Don’t take things without permission Return things to their place Use of lab Hygiene

Semester Schedule

http://inside.mines.edu/~tcath/courses/CEEN572_pilot/

Overview of Conventional Water Treatment

FlocculatorRapid mix

Coagulation/Flocculation

Turbidity and NOM in Water:Surface Phenomena Electrostatic force

principal force contributing to stability of suspension electrically charged particles

Van der Waals force attraction between any two masses opposing force to electrostatic forces

Satisfy Electroneutrality

Double Layer Model of Colloidal Particles

Forces Acting on Colloids

Destabilization Mechanisms Compression of the double layer (DLVO Theory)

increasing the ionic strength

Compression of Double Layer

Destabilization Mechanisms Compression of the double layer (DLVO Theory)

increasing the ionic strength Adsorption and charge neutralization

adding a coagulant (metal salt)

Charge Neutralization

Destabilization mechanisms Compression of the double layer (DLVO Theory)

increasing the ionic strength Adsorption and charge neutralization

adding a coagulant (metal salt) Enmeshment in a precipitate (“sweep-floc coagulation”)

high coagulant dose (metal salt) coagulant forms insoluble precipitates dominant mechanism applied (pH 6-8)

Al2(SO4) 3

+

Sweep-Floc Coagulation

Al2(SO4) 3

+ +

Al2(SO4) 3

Sweep-Floc Coagulation

colloids are enmeshed

Restabilization

Destabilization Mechanisms Compression of the double layer (DLVO Theory)

increasing the ionic strength Adsorption and charge neutralization

adding a coagulant (metal salt) Enmeshment in a precipitate (“sweep-floc

coagulation”) high coagulant dose (metal salt) coagulant forms insoluble precipitates dominant mechanism applied (pH 6-8)

Interparticle bridging synthetic organic polymer

Solubility of metals salts:

Operating range

Destabilization of colloidal particlesMetals salts used for destabilization: aluminum sulfate (alum) aluminum chloride ferric sulfate ferric chloride ferrous sulfate

Factors Affecting Coagulation Alkalinity/pH NOM Turbidity Temperature

pH and Coagulation The pH at which coagulation occurs is the most

important parameter for proper coagulation performance, as it affects: Surface charge of colloids Charge of NOM functional groups Charge of the dissolved-phase coagulant species

e.g., Alum Al3+, Al(OH)2+, and Al(OH)4-

Surface charge of floc particles Coagulant solubility

Overall stoichiometric reaction

Al3+ + 3H2O <-> Al(OH)3(am) + 3H+

Fe3+ + 3H2O <-> Fe(OH)3(am) + 3H+

H+ will react with alkalinity

FeCl36H2O + 3HCO3- <-> Fe(OH)3(am) + 3Cl- + 3CO2 + 6H2O

Al2(SO4)314 H2O + 6HCO3- <-> 2Al(OH)3)(am) + 3SO4

2- + 6CO2 + 14H2O

Fe(SO)49H2O + 6HCO3- <-> 2Fe(OH)3(am) + 3SO4

2- + 6CO2 + 9H2O

Stoichiometry of Metal Ion Coagulants

Coagulation Using Different Coagulants

Design of coagulation processes The design of coagulation process involves:

Selection of proper coagulant chemicals and their dosing Design of rapid mixing and flocculation basins

Coagulation (chemical conditioning) Flocculation (physical conditioning)

Sedimentation

Sedimentation Removal of largest particles for increased filtration

run times Achieves about 1-log removal (90%) of particles Extra buffering for raw water upset Required in treatment of many surface waters

Mechanism and Types of Sedimentation Physical treatment process that utilizes gravity to

separate solids from liquids Types of sedimentation

Type I: discrete settling (i.e., settling of silt; pre-sedimentation)

Type II: flocculant settling (i.e., coagulated surface water) Type III: hindered settling/zone settling (i.e., upper

portion of sludge blanket in sludge thickener) Type IV: compression settling (i.e., lower portion of a

gravity sludge thickener)

Gravity filters:• 2-3 m head• housed in open

concrete or steel tanks• large and small systems

Pressure filters:• higher head• housed in closed steel

vessels• costly; small systems

Media Filtration

Granular Media Filtration Theory Particles being captured can be 100-1,000 times

smaller than the pores Obviously not straining

Mechanisms of Filtration Transport to the Media Surface Attachment

Transport Mechanisms During Granular Media FiltrationA. SedimentationB. InterceptionC. Brownian Diffusion

Collector

A

B

C

Disinfection – Chlorine/ClO2

Water Stability

Water Stability Tendency to either dissolve or deposit certain

minerals in pipes, plumbing, and appliance surfaces:

Water that tends to dissolve minerals CORROSIVE Water that tends to deposit minerals SCALING

Water Stability - Corrosion Loss of an electron of metals reacting with water or

oxygen Corrosive chemicals include the following classes:

acids bases ("caustics" or "alkalis") dehydrating agents (e.g., phosphorus pentoxide, calcium

oxide) halogens and halogen salts (e.g., bromine,

iodine, zinc chloride, sodium hypochlorite) organic halides and organic acid halides acid anhydrides some organic materials such as phenol

Water Stability - Corrosion Adverse effects:

Dissolve Ca and Mg but also harmful to metals (lead & cupper)

Regulation require utilities to test dissolved lead and copper in drinking water

treatment technique

Water Stability - Corrosion

Water Stability - Scaling Saturation conditions Deposition of mineral film Some scaling is good to prevent corrosion

of metallic surfaces Excessive buildup (i.e., CaCO3, CaSO4) Rapid deposition:

Damages appliances (water heaters, laundry machines, dish washers…)

Increases pipe friction Clogs pipes

Langelier Saturation Index (LSI) LSI = pH: measured pH of water pHs: pH at CaCO3 saturation pHs =

calcium and alkalinity are in mol/L pK2, pKs – constants dependent on TDS and

temperature of the water

(pK2 – pKs) + pCa2+ + pAlk

pH – pHs

Water Stability – Saturation Index Calculations

Water Stability – LSI Measurement Langelier Saturation Index (LSI)

LSI = pH – pHs

LSI < 0 corrosive tendency LSI > 0 scaling tendency Desired LSI: 0 to +0.2

Limitations - magnitude does NOT indicate severity of the tendency!

Determine if the following water has a corrosive or scaling tendency: Ca2+ = 1.05x10-3 MAlkalinity = 1.2x10-3 MTDS = 120 mg/LpH = 7.73Temperature = 10 C

Classwork

Ryznar Index (RI) RI =

< 5.5 = heavy scale formation 5.5 - 6.2 = some scale will form 6.2 – 6.8 = non-scaling or corrosive 6.8 – 8.5 = corrosive water > 8.5 = very corrosive water

2pHs – pH

Water Stability – RI Measurement

Determine if the following water has a corrosive or scaling tendency: Ca2+ = 1.05x10-3 MAlkalinity = 1.2x10-3 MTDS = 120 mg/LpH = 7.73Temperature = 10 C

Classwork

Treatment Options to Enhance Water Stability Corrosive water

increase pH add hydrated lime Ca(OH)2

add soda ash Na2CO3 or NaOH

Scale forming water lower pH

add acid recarbonation – add carbon dioxide

sequestering agents (i.e., polyphosphates) softening to remove calcium and magnesium

Regulations and Water Quality Standards Federal Requirements State regulations

Golden WTP: Level III Partnership for Safe Water Quality The Partnership for Safe Water is a voluntary effort that encourages public

water systems to survey their facilities, treatment processes, operating and maintenance procedures, and management oversight practices. It is geared toward filter plants that obtain source water from reservoirs, lakes, rivers and streams. The Partnership’s goal is to provide a new measure of safety. The program’s self-assessments identify areas that will enhance the water system’s ability to prevent entry of Cryptosporidium, Giardia and other microbial contaminants into the treated water. At the same time, system staff can voluntarily make corrections that are appropriate for the water system. In essence, the preventative measures are based on optimizing treatment plant performance and thus increasing protection against microbial contamination in the state’s drinking water supplies.

Regulations and Water Quality Standards Federal Requirements

0.3 NTU (95%) not to exceed 1 Fe: secondary maximum contaminant level: 0.3 mg/L Mn: secondary maximum contaminant level: 0.050 mg/L

Complaints received when Mn is > 0.015 mg/L

Golden WTP: Level III Partnership for Safe Water Quality 0.1 NTU (95%) (15 minute intervals) Strict SOP’s for Operations Stringent Reporting Guidelines 2nd plant in State, 7th in the Nation

Clear Creek Watershed

Mn in Raw Surface Water in U.S.(Source: WaterStats)

Avg_Manganese_(mg/L)_Raw_SW

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Percentile

Ave

rage

Mn

Con

cent

ratio

n,

mg/

L Golden’s CurrentAvg. Mn = 0.15 - 0.20

Manganese Chemistry Potassium permanganate (KMnO4)

Oxidant, bactericide, algaecide, deodorizers, used to purify drinking water, treat wastewater

MnCl2 chemical intermediate, catalyst, feed supplement, batteries

MnSO4 fertilizer, varnishes, glazes, fungicide, nutritional supplement

MnO2 batteries, matches, fireworks, amethyst glass, chemical

intermediate

Manganese Chemistry Divalent manganese is a reducing agent

Can lose electrons - become oxidized

Tetravalent manganese is a good oxidising agent

Heptavalent manganese is a powerful oxidising agent Can gain electrons - become reduced

Manganese ChemistryReactions of Manganese Compounds Metal

Oxidizes superficially in air, rusts in moist air Dissolves readily in dilute mineral acids

Mn(s) + 2H+ Mn2+ + H2

Oxides Most stable MnO2 – Manganese dioxide Lower oxides basic – MnIIO, MnIII

2O3

Higher oxides acidic – MnIVO2, MnVII2O2

Manganese ChemistryReactions of Manganese Compounds

oxidant

Reaction Oxidant needed, mg/mg Mn2+

Alkalinity used, mg/mg Mn2+

Sludge produced, kg/kg Mn2+

O2 2MnSO4 + 2Ca(HCO3)2 + O2 2MnO2 + 2CaSO4 + 2H2O + 4CO2 0.29 1.80 1.58

Cl2 Mn(HCO3)2 + Ca(HCO3)2 + Cl2 MnO2 + CaCl2 + 2H2O + 4CO2 1.29 3.64 1.58

ClO2 Mn(HCO3)2 + 2NaHCO3 + 2ClO2 MnO2 + 2NaClO2 + 2H2O + 4CO2

2.46 3.64 1.58

KMnO4 3Mn(HCO3)2 + 2KMnO4 5MnO2 + 2KHCO3 + 2H2O + 4CO2 1.92 1.21 2.64

Although the mechanism of Mn reaction is not understood completely, the following general expression may be used to describe the oxidation in a Completely Mixed Batch Reactor:

K1, k2 = rate constants of oxidative and autocatalytic pathways, respectively

[Mn2+] = aqueous-phase manganese ion concentration, mol/L[MnO2(s)] = manganese oxide precipitate concentration, mol/L

Manganese ChemistryReactions of Manganese Compounds

Manganese ChemistryReactions of Manganese CompoundsAn alternative rate expression has been presented for the oxidation of Mn2+ to MnO2 using potassium permanganate:

K1 = rate constants of oxidative pathway, 9.55x1012 s-1(mol/L)-2.1

[Mn2+] = aqueous-phase manganese ion concentration, mol/L[KMnO4] = aqueous-phase KMnO4 concentration, mol/L [OH-] = aqueous-phase hydroxide ion concentration, mol/Lk2 = rate constants of autocatalytic pathway, 8.7x103 s-1(mol/L)-1

[Mn2+]e = aqueous-phase Mn2+ ion concentration in finished water, mol/L[MnO2(s)] = manganese oxide precipitate concentration, mol/L

Measures to Improve Manganese Removal Lower Mn levels can be achieved by

adsorption/oxidation process (“Greensand” filtration) than through particle removal

FilterMedia

Mn2+

Mn2+

Natural negative surface charge

HOCl

Mn2+ + HOCl + H2O <-> MnO2(s) + Cl- +3H+

-

-

- ---

HOCl

HOCl

HOCl HOCl

HOCl

HOCl

Mn2+

Mn2+

Mn2+

Mn2+

Mn2+

Mn2+

Mn2+

Measures to Improve Manganese Removal Mn levels in Clear Creek too high during Spring run-

off for adsorption/oxidation to be fully effective (need to be < 0.5 mg/L)

Multiple Barrier Approach Pre-oxidation to create Mn precipitates Coagulation, Floc/Sed and filtration to remove Mn

precipitates Pre-chlorination across filters to polish Mn removals via

adsorption/oxidation process

Oxidation followed by Adsorption & Filtration

SOURCE WATER RESERVOIR

CONVENTIONAL TREATMENT: MIXING, FLOCCULATION, &

SEDIMENTATION

FILTRATIONDISTRIBUTION

SYSTEMFINISHED WATER RESERVOIR

Step 1: Add enough oxidant to oxidize a portion of theMn – allow some to stay in soluble form

Step 2: Particles removedvia standard conventionaltreatment

Step 3: Soluble Mn removed via adsorption onto filter media.Add chlorine onto filters, this “regenerates” media and allows forcontinued adsorption

Maintain free chlorine residual

Viable Oxidants KMnO4 (1.44 mg per mg Mn)

ClO2(g) (0.49 mg per mg Mn)

Cl2(g), or HOCl (1.29 mg Cl2 per mg Mn)

KMnO4 as Oxidant of Choice Fast reaction times at high pH (>8) Overfeeding can cause colored water and higher Mn

concentration Liquid Concentrate

Continuous feeding pump that canbe flow paced

Solid Chemical Mixer

KMnO4 and Cl2 Dosing Strategies Deliberately “Under Dose” KMnO4 to prevent pink

water and leave final polishing to adsorption/ oxidation process

Set KMnO4 to 80-90% of stoichiometric dose Target 0.10 mg/L KMnO4 to ensure no pink color in

finished water Feed enough Cl2 ahead of filters to assure >1.0 mg/L

residual in finished water and maintain high Mn/Fe adsorption affinity of MnO2 coating

KMnO4 and Cl2 Dose Requirements 0.94 mg KMnO4 per mg of Fe+2

1.92 mg of KMnO4 per mg of Mn+2

0.62 mg Cl2 per mg of Fe+2

1.27 mg Cl2 per mg of Mn+2

KMnO4 reacts fast (seconds/minutes) Cl2 reacts more slowly (hours)