Liquid / Solids Separation in Wastewater Treatment & Biosolids Dewatering

Home , Belt filter, Dissolved air flotation, Filter press, Vacuum ceramic filter

LIQUID / SOLIDS SEPARATION IN WASTEWATER TREATMENT & BIOSOLIDS DEWATERING

Chemical Products Lab Testing Plant Trials

LIQUID / SOLIDS SEPARATION APPLICATIONS

Influent Water Clarification Process Water Recycling Primary Wastewater Clarification Secondary Clarification Sludge Thickening Sludge Dewatering LIQUID / SOLIDS SEPARATION UNIT OPERATIONS

Clarifiers (Many Types) WATER Filters (Many Types) OR WASTE Dissolved Air Flotation Units WATER Induced Air/Gas Flotation Units Belt Presses Centrifuges SLUDGE Screw Presses DEWATERING Plate and Frame Presses Vacuum Filters (Rotary & Horizontal)

LIQUID / SOLIDS SEPARATION PRODUCT TYPES

Coagulants (+) Low Mol Wt Organic Inorganic Blended Flocculants (+ , ---, 0 ) High Mol Wt Dry Emulsion Solution OilOil----FreeFree Flocculants COAGULANTS AND FLOCCULANTS

Act on Insoluble Particles in Water Oils, Grease, Blood, Insoluble Organics, Clay, Silicates, Metal Oxides/Hydroxides Dirt, Dust, Rust & Metal Filings

Can Act on Charged Organic Compounds Anionic Surfactants, Soaps & Dispersants

Do Not Act on Most Dissolved Solids Salts, Acids, Nonionic Surfactants, Ammonia or Soluble Organic Compounds such as Sugar, Alcohols, etc.

SUSPENSION CHEMISTRY

THE KEY TO EFFECTIVE LIQUID / SOLIDS SEPARATION SUSPENDED SOLIDS VARIABLES

Surface Charge MOST Charge Density Particle Size IMPORTANCE Composition Particle Density

Particle Shape LEAST

MICROSCOPIC FORCES

ELECTROSTATIC

BROWNIAN

VAN DER WAALS

GRAVITY Colloidal Particle in Water +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ Almost all Particles +++ +++ +++ +++ of Industrial Interest +++ Have a Negative +++ +++ Surface Charge. +++ +++ +++ +++ The Particle is +++ +++ +++ +++ Surrounded by an +++ +++ Equal Number of +++ +++ Positive Counterions. +++ +++ +++ +++ +++ +++ +++ +++ +++

PARTICLES IN WATER REPEL EACH OTHER +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ + +++ +++ +++ +++ ++ +++ +++ +++ Colloidal Particle in Water +++ +++ +++ +++ RATIO +++ +++ +++ OF EXCESS +++ +++ +++ CATIONS +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ EQUAL +++ +++ NUMBER +++ +++ OF POSITIVE AND NEGATIVE +++ CHARGES +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++ DISTANCE FROM PARTICLE

ADSORPTION OF CATIONIC POLYMER NEUTRALIZES CHARGES AND COLLAPSES FIELDS

Van der Waals Force of Attraction Now Stronger Than The Electrical Force of Repulsion NEUTRALIZED PARTICLES COAGULATE

2 STOKE’S LAW: ν = 2Gr (ρ − ρ οοο) / 9η

ν = SETTLING RATE G = GRAVITATIONAL CONSTANT r = RADIUS OF PARTICLE ρρρ = DENSITY OF PARTICLE ρρρo = DENSITY OF LIQUID ηηη = VISCOSITY OF LIQUID

BIGGER SETTLES FASTER Effect of Decreasing Particle Size

MATERIAL DIAMETER SETTLING TIME (in mm) PER METER

Gravel 10 1 second Course sand 1 10 seconds Fine sand 0.1 2 minutes Silt 0.01 90 minutes Bacteria 0.001 1 week Colloidal particles 0.0001 2 years Colloidal particles 0.00001 20 years Colloidal particles 0.000001 200 years

EFFECT OF COAGULATION AND FLOCCULATION

MANY FEWER SMALL LARGE OPTIMUM MIXING FOR CLARIFICATION APPLICATIONS

COAGULANT FLOCCULANT NO MIXING EFFLUENT

STATIC MIXER LIQUID INFLUENT FAST SLOW SLUDGE

CHARGE BRIDGING SETTLING NEUTRALIZATION + OF FLOCS + FLOC INTER-PARTICLE GROWTH COLLISIONS

COAGULATION PROCESS

Adsorption of Cationic Coagulant Neutralizes Negative Surface Charges

Reduces Electrical Barrier

Allows Van der Waals Forces to Predominate Interparticle Collisions

Brownian Motion

Mixing Energy Primary Particles Stick Together FLOCCULATION

+++ ===

SOLIDS FLOCCULANT FLOC

COAGULATION AND FLOCCULATION

Coagulation

Charge Neutralization

Rapid Mixing (High Shear)

Promotes Interparticle Collisions Flocculation

Bridging of Microflocs

Slow Mixing (Low Shear)

Builds Floc Size TYPICAL CLARIFICATION PROGRAM

Add Cationic Coagulant to Neutralize Anionic Charges on Particles Add Anionic Flocculant to Bridge Neutralized Particles

NOTES: (1) Coagulants should be be pre-diluted in water for best results (2) Flocculants MUST be pre-diluted in water for any results (3) Add cationic coagulant as far back in the line as possible (4) Do not add anionic flocculant too close to cationic coagulant

Primary / Secondary Wastewater Treatment System

FINAL OR 2’ EFFLUENT 1’ EFF AERATION WASTE SECONDARY PRIMARY BASIN CLARIFIER CLARIFIER MIXED LIQUOR WATER

RETURN ACTIVATED SLUDGE (RAS) WASTE ACTIVATED SLUDGE (WAS)

PRIMARY SLUDGE SLUDGE DIGESTER or HOLDING TANK

LIQUID PHASE SLUDGE SLUDGE CAKE FILTRATE, CENTRATE, PRESSATE DEWATERING POLYMER CHEMISTRY

VERSATILITY IS A MUST

COAGULANTS EPI / DMA POLYMER AKA EPICHLOROHYDRIN ---DIMETHYLAMINE

OHOHOH CHCHCH 333

------CHCHCH ---CH ---CHCHCH ---N- NNN+++ ------[]222 222 n --- CHCHCH 333 ClClCl

CAS NUMBER: 42751-79-1

POLY [DADMAC] POLYMER AKA POLY DIALLYLDIMETHYL AMMONIUM CHLORIDE AKA POLY [DMDAAC]

------CHCHCH ---CH ---- CH ---CHCHCH ------[ 222 222 ] n HHH222CCC CHCHCH 222

NNN+++ ...... ClClCl ---

HHH333CCCCHCHCH 333

CAS NUMBER: 26062-79-3 INORGANIC COAGULANTS

Aluminum Sulfate: Al 222(SO 444)))333 Aluminum Chloride: AlCl 333 Polyaluminum Chloride (PAC) Aluminum Chlorohydrate (ACH) Ferric Chloride: FeCl 333 Ferric Sulfate: Fe 222(SO 444)))333 Ferrous Sulfate: FeSO 444 Sodium Aluminate: Na 222AlAlAl 222OOO444

HYDROLYSIS OF ALUMINUM (III)

1,1 1,0 1,4

1,2

Log Soluble [Al] SolubleLog 1,3

2 3 4 5 6 7 8 9 1011 System pH HYDROLYSIS OF IRON (III)

1,0 1,1

1,2 1,4 Log Soluble [Al] SolubleLog 1,3

2 3 4 5 6 7 8 9 1011 System pH

DEPRESSION OF SYSTEM pH WITH ALUMINUM or FERRIC SALTS

DOSAGE OF CALCULATED 28% ACTIVE FINAL pH

1 ppm 5.2

10 ppm 4.2

100 ppm 3.2

1000 ppm 2.2

ASSUMES UNBUFFERED WATER STARTING AT pH = 7.0 ORGANIC COAGULANTS ADVANTAGES OVER INORGANICS

Sludge Volume Reduction Larger, More Stable Floc Less Pinfloc and Carryover Lower Flocculant Requirements Work Over Wide pH Range (2(2----12)12) Do Not Change System pH Lower Caustic Requirements

INORGANIC COAGULANTS ADVANTAGES OVER ORGANICS

Inorganics Can Produce Very Low Turbidity Waters Because the Metal Hydroxides Can Sweep Fine Particles from Suspension Low Price per Pound Looks Very Attractive to Purchasing Agents FLOCCULANTS

NONIONIC MONOMER ACRYLAMIDE

CH 2 = CH - C - NH 2

AM ANIONIC MONOMER ACRYLIC ACID

O _ …… + CH 2 = CH - C – O H

CATIONIC MONOMERS AETAC ADAME.MeCl QQQ-Q---9999

+ POLYACRYLAMIDE

CHCHCH 222 ---CHCHCH- CH ---CHCHCH 222 ---CH ---CHCHCH 222 ---CHCHCH C=O C=O C=O

NHNHNH 222 NHNHNH 2 NHNHNH 222

POLYMER SHORTHAND POLYACRYLAMIDE

HHH

CHCHCH 222 –––C– CCC C=O

NHNHNH 222 n n is about 282,000 @ 20 million Molecular Weight HOMOPOLYMERIZATION YELLOW = ACRYLAMIDE

FLOCCULANTS ARE TYPICALLY 200,000+ MONOMERS

ANIONIC POLYACRYLAMIDE COPOLYMER aka AM/SA ANIONIC POLYACRYLAMIDE

HHH HHH

CHCHCH 222 –––C CHCHCH 222 ---C- CCC C=O C=O

NHNHNH OOO 222 m NaNaNa + n RANDOM COPOLYMER m + n = 1

COPOLYMERIZATION YELLOW = ACRYLAMIDE; RED = ACRYLATE 25% ANIONIC CHARGE COPOLYMERIZATION YELLOW = ACRYLAMIDE; RED = ACRYLATE 50% ANIONIC CHARGE

CATIONIC POLYACRYLAMIDE COPOLYMER aka AM/Q9 CATIONIC POLYACRYLAMIDE

HHH R’R’R’

CHCHCH 222 –––C CHCHCH 222 ---C- CCC C=O C=O

NHNHNH 222 OOO m

(CH 222)))222 + RANDOM COPOLYMER HHH3C NNN CHCHCH 333 m + n = 1 n CHCHCH 333 Cl

COPOLYMERIZATION YELLOW = ACRYLAMIDE; BLUE = CAT 10% CATIONIC CHARGE COPOLYMERIZATION YELLOW = ACRYLAMIDE; BLUE = CAT 25% CATIONIC CHARGE

COPOLYMERIZATION YELLOW = ACRYLAMIDE; BLUE = CAT 50% CATIONIC CHARGE TYPICAL MOL-WT DISTRIBUTION

RESIDUAL THIS PRODUCT WOULD HAVE AN AVG MOL-WT MONOMER OF ~7 MILLION NUMBER OF MOLECULES OF NUMBER

0 1 2 3 4 5 6 7 8 9 101112131415

MOLECULAR WEIGHT IN MILLIONS

TYPICAL MOL-WT DISTRIBUTIONS

CATIONICS ANIONICS NUMBER OF MOLECULES OF NUMBER

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

MOLECULAR WEIGHT IN MILLIONS LINEAR POLYMER STRUCTURE

LIGHTLY BRANCHED POLYMER STRUCTURE HIGHLY BRANCHED POLYMER STRUCTURE

CROSSCROSS----LINKEDLINKED POLYMER STRUCTURE ASHLAND WATER TECHNOLOGIES EMULSION POLYMER PRODUCT LINE 20