Overview of Leachate Treatment Technologies -Pros, Cons, Costs, Concerns

IVAN A. COOPER, P.E., B.C.E.E. CIVIL AND ENVIRONMENTAL CONSULTANTS, INC.

Outline

► Overview of Select Conventional Treatment Technologies ► MBR Biological Treatment ▪ Technology summary ▪ Common operational challenges

► Selection Criteria and How to Select a Process? ► Costs

Aerobic Biological Treatment Technologies Commonly Used for Leachate Treatment

Attached Growth Activated Sludge

Static Fixed Film Dynamic Fixed Film

Suspended Growth Activated Sludge

Continuous Batch

Trickling Filters Web Media

BAF A2O Submerged Deep Bed Filters

RBC Plastic Seaweed

IFAS MBBR

Oxidation Ditch Conventional AS Extended Aeration

MBR Step Feed Timeswitch Bardenpho

Ludzak Ettinger Sharon In-Nitri

Bioaugmentation (BAR) Bioaugmentation

Enhanced (BABE) UCT/MUCT

SBR MBR

MBR Process

► Used at many landfills ► Equalization is VERY

important ► Requires aeration and

membrane separation ► In-Tank or External

Membrane? ► System Control by

wasting, aeration ► Sludge

Production/Solids Management

► Maintenance needed on membranes

► High quality effluent

Membrane Biological Reactor (MBR)

► It is still activated sludge (yes it is true !!!) ► Replace clarifier with ultrafiltration (UF) membranes ▪ 0.01 to 0.10 micron filter ▪ Much higher biomass concentration

o 10,000 to 15,000 mg/L VSS ▪ More work in smaller aeration tank volume ▪ No settling issues

► Hollow fiber/Ceramic Membrane (in Tank) ▪ Modules submerged in tank ▪ Immersed in mixed liquor, permeate drawn through the tubes

o Access issues o “Desludging”

► Tubular Membranes (out of Tank) ▪ Cross flow external filtration in modules

o Membrane flux is higher

MBR Technology

Internal MBR

Internal MBR Operation Modes

Activated Sludge Basics ► AERATION TYPES

▪ Diffused aeration – coarse bubble/fine bubble ▪ Jet aeration ▪ Turbine aeration ▪ Surface aeration

► Organic (COD) and nitrogen (ammonia) biodegradation

▪ Heterotrophic organisms - COD degraders ▪ Autotrophic organisms – Ammonia degraders

► Importance of Bench/Pilot Scale test ▪ Toxicity? ▪ Oxygen Uptake ▪ Nitrification Rate ▪ Sludge production – cell production vs. energy (heat released) ▪ Membrane flux rate ▪ Cleaning cycle frequency

Leachate Activated Sludge Basics

► Loading - F to M ratio (food to microorganism ratio) ▪ 0.10 to 0.40 (10 lbs of BOD (COD) / 100

lbs microorganisms) ► Sludge Age – 10 to 50 days typical ▪ Avg. time solids are in the aeration

system ▪ Sludge age and F to M ratio – Inversely

related ► Nitrifiers ▪ Minimum sludge age for nitrification ?

o What is the nitrification rate – Varies!! ▪ pH (Very Important !!!!)

o 7.5 to 7.8 ▪ Temperature-Even More Important

o Autotrophic bacteria dieoff over ~100 degrees F

Leachate Activated Sludge Basics

► Single Stage AS ▪ COD and nitrogen removal in same system

o COD/Ammonia ratio (Very important !!!!) ▪ What if influent COD/ammonia ratio changes ?

o COD: N increases over about 10 or 15:1, then Population of nitrifiers going down (nitrifiers get crowded out)

► Two Stage AS ▪ Two AS systems, two Membrane Systems

o Separate sludge system o Different microbial populations in each stage

▪ More robust for leachate treatment

Free Ammonia Inhibition

Membrane Biological Reactor (MBR) – Temperature Design Concerns ► Temperature – Hot ▪ Too hot in the summer !!!! ▪ Heat of Biological Oxidation

o 2,700 to 3,200 calories/g of COD oxidized o Max temp. for nitrifiers (< 38oC)

▪ Design for heat removal o Surface aerator o Evaporative cooler o Heat exchanger and cooling towers

► Temperature – Cold ▪ Too cold in the winter !!!!!

o Heat of Biological Oxidation not enough? o Interim heating o Steam injection

Temperature Design Range

► Why mesophilic 68°F (20°C) and 113°F (45°C) versus thermophilic (125 – 150 deg F)? Materials Of Construction Corrosion UF, other equipment shut down Foaming Speed of reaction Nitrification (95-100°F)

Temperature Model for Design

STEADY-STATE TEMPERATURE MODEL Modification of original temperature model developed by Y.

Argaman and C. E. Adams, Jr., WEFTEC 2004 paper written by Victor J. Boero

The model can be used for completely mixed basins, totally or partially above ground, covered or not, aerated (diffused air or surface aeration) or not, with steam addition or not.

Based on steady-state heat and mass balances for air and water.

▪ This may control the design!!! ▪ Not process kinetics

Advantages / Disadvantages for MBR systems ADVANTAGES

BOD removal – high 90% Oxidation/Nitrification Biological phosphorous removal possible Temperature Dependent

DISADVANTAGES

No color removal – possibly increase by forming colored intermediates

Nutrient removal may require several stages/ May be Land Intensive – based on design

Heterotrophic versus autotrophic populations Energy intensive Close operation attention needed – Cleaning/scale

control/avoid plugging High WAS flows

Key Design Considerations

► Influent Parameter Variability – Flow & Constituents? ► Organic and Nitrogen Loading ► Biological Treatment -Temperature Considerations ► Biological Treatment - Nutrient Deficiency ▪ Nitrogen and Phosphorus

► TDS ▪ Biological inhibition/Oxygen transfer ▪ Effluent limits (future?) ▪ Corrosion

► Fouling/Scaling ► Odors ► Sludge processing ▪ Labor required

Pretreatment Process Flow

Jet Aeration Example MBR System ► Jet Aeration Systems Often

Used for Leachate Treatment

► External Circulation Pumps

► Blowers (VFD)

Construction Progress – March 2014 – Aeration Tanks

Startup – May 2014

Startup Challenges – September 2014

► Operator Training ► Foam ► Temperature ► Pump Issues ► Scaling – Piping and UF

Foaming Challenges ►Foaming ▪ Foaming varies with f/m ▪ Controls:

o Spray water = more to UF o Harnessing a portion of the

jet mix recycle as a continuous knockdown spray;

o Incorporating a knockdown defoamer (antifoam) NON-SILICA BASED! injection into the continuous spray feed pipe;

o functional foam level sensor incorporating to control the defoamer feed.

Biological Fouling of UF ► Fouling Solutions

▪ Mineral Scale ▪ Calcium carbonate scale – Acid

cleaning step ▪ Biofouling ▪ Caustic clean helps remove

biofouling ▪ Two biological fouling

mechanisms ▪ Soluble Microbial Product (SMP)

o Cells Lysis – release internal contents

▪ Extracellular Polymeric Substance (EPS)

o Polysaccharides (Goo) ▪ Control by proper nutrients –

P/N/micronutrients ▪ Check lab vacuum filtration rates

o Flux rate o Example – reduced from 3

minutes to 10 seconds for 100 ml sample

Biological Treatment - Common Operational Problems ► What is the process control method ? ▪ F to M, Sludge Age, Wasting, None ?

► Rapid Loading Changes ▪ Remember Equalization? ▪ Foam

► Poor Flux Rate ▪ Track filtration time in lab ▪ Nutrient deficiency (phosphorus) ▪ Too high F to M (too much COD) ▪ Low dissolved oxygen (DO)

► Winter temperature ▪ The design basis (i.e., 25oC) ? ▪ No temperature control

► Free Ammonia Inhibition

Ultrafilter Operation ►External MBR Ultrafilters ▪ Excellent quality effluent ▪ Requires monitoring pressure

drop and cleaning (120 psi – 80 psi)

▪ Initially plant staff ran below recommended pressure drop; elements clogged.

▪ Additional system training helped operations

▪ Scale formation – added soda ash addition to primary step to remove Ca hardness

▪ Membrane autopsy – Calcium carbonate scale controlled by acid cleaning. Calcium sulfate more difficult to remove.

Effluent Acceptance by POTW

► BOD: ▪ 30,000 mg/l 34 mg/l = 99.932% removal

► COD ▪ 55,000 mg/l 2,200 mg/l = 96% removal

► Metals – All under limits Metals Permit, mg/l Acceptance Test, mg/l ▪ Arsenic 0.4 0.0529 ▪ Chromium 5.0 0.0298 ▪ Copper 2.7 0.247 ▪ Iron 150 2.7 ▪ Lead 0.4 0.0082 ▪ Nickel 2.3 0.0359 ▪ Zinc 3.0 0.0595

Comparative Options

New leachate treatment methods Jude Ifeanyichukwu Madu, Sweden, 2008

Comparative Aerobic Technologies Comparison MBBR RBC Activated

Sludge SBR IFAS MBR

Capital Investment

Low to medium

High High Low Medium High

Effluent Quality

Good Fair Good Good Good Excellent

Footprint Low High

High Low Medium Medium

Flow Tolerance

Good Poor

Poor Good Good Fair

Aeration Blowers

Required None Required Required Required

Required

Recirculation pumps

Not required

Not required

Required Not required

Required Required

Chemical usage

Low Moderate Moderate Low Low Moderate

Operator difficulty

Low Low High Low – Moderate

Moderate High

Leachate Disposal Costs Alternatives built on combination of technologies

► Very site dependent / Sewer or direct discharge / Residual management

► Costs from various sources

CONSTRUCTION & O/M Air Stripping $0.01 – $0.03/gal Constructed Wetlands $0.01 - $0.03/gal Phytoremediation $0.01 - $0.03/gal Chemical Treatment $0.02 -$0.05/gal Conventional Activated Sludge (CAS) $0.035 - $0.076/gal MBR/MBBR $0.04 – $0.065/gal SBR (EPA 1998, adjusted) $0.02 - $0.054/gal RO $0.02 - $0.10/gal MBR + RO 0.064 - $0.095/gal Conventional AS (CAS) + RO $0.07 - $0.35/Gal Evaporation $0.03 - $0.09/gal AOP $0.06 - $0.07/gal Hauling (distance/disposal) $0.10 - $0.40/gal

Summary

►Leachate Key Parameters of Interest ►Overview of Select Aerobic Biological

Treatment Technologies ►Overcome Design Challenges ►How to Address Operational Issues? ►Selection Criteria and How to Select a

Process ►Costs

Questions & Discussion

CIVIL & ENVIRONMENTAL CONSULTANTS, INC. (CEC) IVAN A. COOPER, PE, BCEE: ICOOPER@CECINC.COM