ceen 572 environmental engineering pilot plant laboratory introduction instructor: prof. tzahi cath...
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CEEN 572Environmental Engineering Pilot Plant Laboratory
Introduction
Instructor: Prof. Tzahi Cath ([email protected])TA: Tori Billings ([email protected])
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)