# Zero Liquid Discharge Capability, Experience, and Overview

Principal Technical Consultant 

### Dan Sampson 

### Introductions
 

### Brief Overview of WorleyParsons Experience
 

## ZLD Overview

 Background

 Process building blocks



###  Process considerations 

# Meeting Agenda

### Dan Sampson

 Principal Technical Consultant

– Power/Water/Wastewater



###  30+ Years

 ZLD experience

− Design (modeling, options evaluation, cost estimates)

− Procurement (specification, bid evaluation, equipment due diligence, installation)

− Operation (initial commissioning, operating procedure development, operating plant support)

− Maintenance (troubleshooting, cleaning ) 

# Introductions

# Water/Wastewater Capabilities

 Identifying future water needs

 Demand forecasting

 Water security

 Water assessment

 Strategic planning  Identifying potential water supplies

 Quantifying sustainable yields from natural, municipal & industrial sources

 Water modeling  Linking resources to needs

 Sustainability assessment

 Regulatory compliance  Developing & implementing water strategies

 Water reuse and recycling

 Desalination

 Inter
- catchment transfers

 Demand & leakage management

 Wastewater minimization/ZLD  Eco Nomics TM

 Sustainability being the key decision and planning tool

# Water/Wastewater Capabilities ( con’t )

 Water Source(s)

 Qualifying Source Water Quality

 Quantifying Source Water Quality  Water Purification

 Design

– Conceptual, Detailed,

 Technical Support

– Troubleshooting, Evaluation for Performance & Cost

 Ion Exchange

 Reverse Osmosis  Wastewater Treatment

 Design

– Conceptual, Detailed

 Technical Support

– Troubleshooting, Evaluation for Performance & Cost

 Water Reuse & Recycling

 Environmental Compliance

 ZLD system design, specification, commissioning, and troubleshooting

# ZLD Experience

# ZLD Background

 

### Feed water sources

 Traditional Plants

- incoming water concentrates in cooling tower, demin systems, and/or process wastewater

 Oil and Gas

– drilling and completion of wells, hydraulic fracturing, EOR, oil sands steam generation, oil sands hot water treatment, upgrading  

### Environmental concerns

 High TDS discharge

 Ion

- specific limits may be exceeded

 Organic contaminants  

### ZLD

 Water leaves site only as a gas (steam or water vapor)

 Dissolved solids concentrated until only solid waste remains

# What ZLD is Not

– A Wastewater 

# Treatment System

 

### Wastewater treatment systems receive different streams with variable flow and chemistry  

### Treat wastewater to provide an 

### acceptable effluent  

### ZLD systems MUST operate with constant chemistry and flow

 Do not turn up or down well

 Do not turn on or off well

 Cannot tolerate deviations from design chemistry

 Cannot receive waste streams other than those for which they were specifically designed

 MUST be monitored continuously 

### No such thing (water would leave only as a vapor or steam)  

### Can’t treat sanitary or cleaning 

## wastes  

### Can’t treat oily waste  

### Chemistry and/or contaminants may 

## limit concentration

 Usually nitrates or total organic carbon

 Could be anything, though

 “Bleed” often required

− Small liquid stream with highest concentration of contaminant

− Hauled off as liquid waste



###  Lots of onsite liquid storage/handling 

# What ZLD is Not

– Not Really 

# Zero Conventional plant (no ZLD)

 Unrecoverable water losses (evaporation, process consumption) can’t be reclaimed

 Unrecoverable losses often the majority of plant water usage 

# What ZLD is Not

– A Water Conservation 

# System

# What ZLD is Not

– A Water Conservation System
ZLD with maximum conservation/reclamation

 Water usage lowers from 2127 to 1812 gpm (14.8% reduction)

Much better options to conserve water:

• Air

- coolers (90% conservation)

• Recycled water (100% conservation) 

### Combined cycle plant Operations Supervisor: “We run a chemical plant that happens to produce power.”  

### ZLD is a chemical process with stringent chemistry and flow limits

 Designed to recover specific salts

 Cannot tolerate variation in flow or chemistry, so large buffer tanks required

 Chemical feed often required to balance chemistry (often requires thousands of pounds of other salts, in various forms)

 Pure water and moist salt cake are products  

### Some liquid waste usually has to be hauled off

- site 

# What ZLD is

– Targeted Salt and Water 

# Recovery System

# ZLD Process Building Blocks

 

### 5 Basic Processes

 Initial Concentration

 Pretreatment

 Intermediate Concentration

 Thermal Concentration

 Solid Waste Production  

### Processes may overlap or be eliminated entirely  

### Cost of concentration generally proportional to TDS in concentrated streams

 E ssentially free in cooling towers

 As high as $40/gal in final step  

### Volume of water to be concentrated lowers with each step of the process  

### Designs often focus on moving evaporation to the “front end” (less expensive)

# Initial Concentration

 

### Occurs in processes, cooling towers, demin systems, or produced water  

### Level of concentration obtainable depends on the incoming makeup 

### water quality and its propensity to form scale or cause corrosion  

### Typical makeup water can be concentrated from 3

- 10 times, raising TDS to 2500

- 8000 ppm  

### Water high in scale

- forming dissolved solids or corrosive ions can be concentrated only a few times prior to being removed from the system via blowdown. Water with low concentration of problem constituents may be concentrated ten or more times prior to removal through blowdown  

### “Front

- end” removal of scale

- forming minerals a good option to 

### maximize initial concentration (may not address corrosion issues)  

### Initial concentration is least expensive and should be maximized

# Pretreatment

 

### VERY broad topic

– pretreatment depends on subsequent processes

 May require filtration, clarifier/softener, ion exchange, biological treatment, oil removal, etc.

 May not be required if initial concentration exceeds 6 cycles or feedwater TDS already high

 “Best” approach requires financial analysis

 IX usually economical only if water is “hardness limited” (NaZ, WAC, or both)  

### TDS in effluent may be unchanged, higher, or lower. Depends on process. May generate solid and/or liquid waste

 Liquid waste generated goes to intermediate or final concentration

 Solid waste hauled off

- site  

### Goals vary, but generally

 Remove TOC, oils, and/or grease

 Remove suspended solids

 R eplace less soluble species with more soluble species

 Stabilize or remove silica

# Intermediate Concentration

 

### Utilizes RO/ED to further concentrate TDS  

### Limited by level of insoluble species in RO reject  

### RO permeate reused, reject goes to final
c oncentration  

### Allows smaller final c oncentration equipment

 Minimizes capital cost

 Minimizes parasitic load  

### R aises TDS

 20,000

- 60,000 ppm range

# Thermal Concentration

 

## Three Options (in various combinations)

 Brine Concentrator

 Crystallizer

 Other evaporation options (ponds, dryers, etc.)  

## BC and Bxtal use thermal energy to evaporate incoming water  

### Distillate recovered for reuse  

## Concentrated slurry sent to solid w aste p roduction  

### Focus shifts from TDS to TS (Total Solids), combination of TSS and TDS  

### Can typically raise waste stream TS to the 150,000 to 500,000 range

# Solid Waste Production

 

### Transforms concentrated brine into a damp solid  

### Requires various combinations of

 Solar evaporation ponds

 Filter presses



###  Centrifuges

 Dryers  

### Solid waste eventually 

## hauled off

- site

# ZLD Process Considerations

 

### Pretreatment Systems

 Clarifiers and Clarifier/Softeners

 Filtration

 Ion Exchange  

## High

- TDS RO Systems  

### Thermal Systems  

### Complexity  

### Degradation  

### Sizing Criteria  

### Manpower

# Clarifiers and Clarifier/Softeners

 

### Inherently difficult to balance  

### Require significant chemical addition and control  

### Generate solid waste  

### Require stable influent and effluent flow  

### May require installation of extremely large 

### “buffer” tanks  

### Blowdown softeners especially difficult

 Must overcome cooling tower dispersant

 Cooling tower treatment chemicals “lost” across the unit and must be added again if effluent recycled to cooling tower  

### Avoid if possible 

### Media or membrane filtration required for High

- TDS RO  

### Large debris (mesh strainers) for thermal concentrators  

### Filtration ahead of RO systems always a problem

 Filters themselves may foul ( uF and mF)

 Filters may not remove TSS (media 

### filters)

 RO membrane fouling results  

### Avoid intermediate concentration 

# Filtration 

### Sodium Zeolite (NaZ) and Weak Acid Cation (WAC) most common  

### Remove hardness to increase High

- TDS RO recovery  

### Generate high

- TDS waste (spent regenerant), must be 

### processed in ZLD  

### Generate large volume of low

- TDS waste (rinses/flushes

- requires 

### complex recovery systems)  

### Regeneration/rinse often challenging and must be optimized. 

# Ion Exchange

# High

- TDS RO

 

### Most “elegant” chemistry  

### Initial modeling often shows lowest cost  

### Implementation extremely difficult

 Adds several pieces of support equipment

 Increased complexity reduces reliability  

### Experience shows poor reliability and high maintenance  

### Almost all sites have to haul

- off water  

### Actual costs much higher than predicted

 Increased operator involvement

 High maintenance

 Water haul

- off  

### May still have a niche, but EXTREMELY difficult to manage  

### Avoid use if at all possible. Install 2x100% 

### trains if used 

### Simplest approach (avoids most pretreatment and all intermediate concentration)

 Easiest operation if ZLD is required  

### Still have issues

 Cleaning (often and expensive)



###  Corrosion (alloy selection very important)

 Capacity (heat transfer surface area and thermal input capacity 

### very important)

 Small failures (seals, instruments, pumps, etc.) common and impact reliability 

# Thermal Systems

# Complexity

 

### Increased operator involvement (two extra per shift required for complex designs)  

### Maintenance 

### costs increase  

### Reliability decreases  

### Additional 

### spares required (2x100% trains, additional shelf spares)PRE TREATMENT

ANCILLARY TREATMENT (ALTERNATIVE) FILTRATION MAIN TREATMENT

Feed Water Balance Tank INTERMEDIATE BARRIER

Dosing

• PAC

• PACl Dosing

• H 2 SO 4

• NaOCl Disk Filters HARDNESS & HEAVY METALS REMOVAL

Dosing

• SBS

• AS

• H 2 SO 4 MAIN TREATMENT Ion Exchange Units

SW RO System BW RO Feed Tank & Pump Station

REVERSE OSMOSIS

BW RO System SOLIDS DEWATERING Feed pump

Air blower Wastewater (out)

Ultra

- filtration System RO Bypass Dosing

• NH 3

SW RO Feed Tank

& Pump Station

BRINE RECOVERY SYSTEM (ALTERNATIVE) BACKWASH RECOVERY SYSTEM Solids Disposal

Sludge Bag

(Option)

Submerged UF Services Tank

To Irrigation Pond Dosing

• NaOH To Brine Pond 

## Complexity

# Degradation and Redundancy

 

## Design Margin

 Developers may not perform detailed risk analysis

 May buy cheapest system with nameplate capacity to handle the required flow

 Feed water analysis often uncertain

– any deviation from design causes additional loss of capacity

 System almost never meets nameplate  

### Best Case

 Expect 75

- 95% mechanical reliability

 Expect 20% degradation between cleanings (80% of nameplate flow capacity)



###  Effective ZLD capability = 80% x 80% = 64%

 That’s BEST CASE

– more complex designs much worse (more to go wrong)

 So, a 500 GPM ZLD system can reliably handle about 300 GPM

# Sizing Criteria and Spares

 

### Sizing Criteria

– NO exceptions

 Based on max peak flow

 “Simple” designs (thermal o nly)

– 2x60% trains (prefer 2x75%)

 “Complex” designs (WWRO, intermediate concentration)

– 2x100% trains (completely independent)



###  Provides effective capacity of 90

- 150% of nameplate

 “Thermal” only most reliable, so lower redundancy requirement

 Increasing complexity = decreased reliability, more redundancy (additional design margin) required  

## Spares

 Perform single

- point failure analysis

 Purchase additional shelf or installed spares (regardless of design)  

## Risk assessment must be part of initial plant design

– cost analysis should include redundancy

# Manpower

 

### Common mistake

– assume that ZLD can be operated with same staff as a typical water plant

 ZLD Vendor: “The system uses a PLC, so it basically runs itself.”

– n ot accurate.

 ZLD systems much more complex, increased manpower required

 Additional manpower depends on complexity  

### “Simple” ZLD designs require 7

- 9 extra EXPERIENCED people

 One operator 24/7 (dedicated to ZLD system)

 1⁄2 mechanic, 1⁄2 I&C

 Manager (plant chemist or ZLD O&M manager)  

### “Complex” ZLD designs require 12

- 14 extra people

 Two operators (24/7)

 Full time mechanic, full time I&C

 Manager (plant chemist or ZLD O&M manager)  

### No ZLD plant “runs itself”

– vendor sales pitches create wrong 

### impression

 Need at least one experienced person constantly watching the PLC and running chemistry

– no other duties

 At least one other person available to combat problems

# Critical Issues

 ALWAYS get references:

 Talk to others actually operating the equipment you intend to buy

 No references = no sale

 “Emerging” or “new” technology = extreme process risk (pilot test)  

### AVOID use of intermediate concentration

 Looks good on paper, very challenging in the real world

 Pretreatment too complex and unpredictable

 Intermediate concentration technologies also unreliable  Simplify pretreatment

 Avoid pretreatment

 Simple filtration only preferred  Focus on redundancy and capacity

 Brine Concentrator/Crystallizer Sizing: at least 2

- 60% (based on max peak flow) trains

 Complex systems: at least 2x100% completely independent trains

 NO exceptions  Manpower

 Factor into cost analysis

 Include in plant staffing plan

 Dedicated staff provide best reliability  Spares

 Perform single

- point failure analysis

 Purchase shelf spares

# Conclusions

 

### ZLD is LAST resort. Discharge to others if possible. A basic 500 gpm ZLD system will cost 

## about $50 million in NPV over 20 years  

### Avoid use of intermediate concentration. Minimize processes that require chemical feed.  

### Minimize complexity. Simple thermal systems least efficient, but easiest to operate.  

### Move concentration as far back in the system as possible. Concentration in the cooling tower costs 

## nothing and should be maximized.  

### Regardless of vendor claims, ZLD systems are MUCH harder to operate than they claim or you may think.32 KEY CONTACTS

Power/Water/Wastewater :

Dan Sampson, Principal Technical Consultant, dan.sampson@worleyparsons.com ; (707) 643

- 2834 / Mobile: (925) 570

- 0842