DESALINATION PLANTS: WHAT ARE THE OPTIONS MUSHTAQUE AHMED DEPT. OF - - PowerPoint PPT Presentation

BRINE DISPOSAL FROM SMALL SCALE DESALINATION PLANTS: WHAT ARE THE OPTIONS

MUSHTAQUE AHMED

• DEPT. OF SOILS, WATER & AGRICULTURAL ENGINEERING, SQU

ahmedm@squ.edu.om

 Introduction  Brine Production from Desalination Plants  Brine Disposal Methods  Evaporation Ponds  Innovative Concepts  Production of Chemical Products: A Case Study

Outline

 Coastal Plants Practices Ocean Disposal  No. of Inland Plants and Small Plants for Agriculture are Increasing  Brine Disposal from Inland Plants and Agricultural Plants is a Problem – Economically and Environmentally

Introduction

2 Mm3/day 1972 26 Mm3/day 1999 119 Mm3/day 2025

2015, 18,000 desalination plants worldwide, with a total installed production capacity of 86.55 million m3/day

Desalination World-wide

 17,277 Commissioned Desalination plants  80.9 Mm3/day production  59% seawater, 22% brackish water, 9% river and 5% wastewater  Saudi Arabia 9.2 Mm3/day, UAE 8.4 Mm3/Day and Spain 3.8 Mm3/day

Desalination 2013

 90 Mm3/yr in 2006  221 Mm3/yr demand in 2013 (15% annual increase)  Demand is met mostly by large desalination plants  Large number of small desalination plants are in operation in inalnd areas and for agriculture

Desalination Oman

CF = 1/(1-R) CF = Concentration Factor R = Fractional Recovery

Brine Production is Common to all Categories of Desalination

Quality of the feed water The desalination technology used Percent Recovery Chemical additives used

Brine Quality Depends on:

 Pre-treatment wastes  Brine (membrane concentrate)  Cleaning waste  Post-treatment waste  Chemicals such as NaoCl, Free Cl2, FeCl3, Alum, Sodium Hexameta phosphate, EDTA, Citric acid, Sodium polyphosphate

Types of Wastes in RO Plants

 Lined evaporation ponds  Deep well injection  Disposal in surface bodies  Through pipeline to municipal sewers  Concentration into solid salts  Irrigation of plants

Options for Brine Disposal from Desalination Plants

 Volume or quantity of brine  Quality of brine  Location  Availability of receiving site  Regulations  Costs  Public acceptance

Factors Influencing Selection of Disposal Method

 48% disposal to a surface water  23% to a wastewater treatment plant  12% land application  10% deep well injection  6% evaporation ponds

From a survey in the USA (Mickley, 2006)

 Average evaporation rate is used  Lower evaporation due to salinity (70%)  Large area needed  Liners are to be used  Negev desert, 5000 m3/day permeate, 384 m3/day brine (92% recovery), 65,000 m2 evaporation pond, 8.5 cents/m3 of permeate cost for brine disposal  Enhanced evaporation  Cost highly variable

Evaporation Ponds

 Brine is treated further  More water is produced (thermal desalination, ED, RO after removing scale forming constituents)  Dry salts are the final products  High cost  Mostly used in the industries

Zero Liquid Discharge (ZLD)

 Big coastal plants dispose in the sea  PDO (14 plants in 2006), Police, MOH, MOD also own plants  Most inland plants are RO type of small capacities  Disposal in evaporation ponds

Current Status of Brine Disposal Technology in Oman

 Widely used in desalination plants in Oman: Adam, Haima, PDO plants  Brine quality highly variable  Sizes vary: Adam nearly 6 ha  Cost: highly variable (6-54 usd/m2 in 2000)  Lack of regulations  Lack of monitoring

Evaporation Ponds in Oman

Design Evaporation rate for Oman: 2 m/yr Scenario 1: For 40 m3/day plant with 50% recovery, Brine will be 20 m3/day, 6,000 m3/yr (300 day operation), Area needed 3,000 m2 (30m X 100 m), Brine quality: if input 5,000 mg/l, Brine: 10,000 mg/l (total per year 60 tons) Scenario 2: For 40 m3/day plant with 90% recovery, Brine will be 4 m3/day, 1,200 m3/yr (300 day operation), Area needed 600 m2 (30m X 20 m), Brine quality: if input 5,000 mg/l, Brine: 50,000 mg/l (total per year 60 tons) Considerations: Desalination units capability, Energy Cost, Enhanced Evaporation, Operation Life,

Evaporation Ponds for Small Plants: Design Consideration

Recovery Rate % Product Water m3/day Brine m3/day Brine m3/yr Evaporati

• n Rate

m/yr Area Needed m2 Brine Quality ppm Total Salt tons Salt Depth cm/yr Cost of Pond usd Comment 50 20 20 6000 2 3,000 10,000 60 1 30,000 Will operate for a long time 90 36 4 1200 2 600 50,000 60 5 6,000 Requires better RO systems, More energy cost 90 36 4 1200 4 (100% increase) 300 50,000 60 10 3,000 Extra cost for enhanced evaporation, deeper ponds, lower operational life, Subsidies!

Evaporation Pond Design Details

Input Water Quality = 5,000 ppm; Recovery Rate = 50%, Input Water Amount = 40 m3/day, 300 days operating, Pond cost 10 usd/m2, Salt weight 2 tons/m3, No enhanced evaporation

 Volume reduction by Forward Osmosis  Salt Lake  Disposal to sea  Centralized collection system  Integrated System – Desal plant-Evaporation Ponds- Salt Harvesting-Solar Ponds-Fish Farming-Salt Lake- Recreation

Other Possibilities

 Fish culture (Baramundi, Red Snapper, Black Bream, Mullet, Tilapia, brine shrimp)  Algae production  Agriculture (salt tolerant crops)  Solar pond  Mineral recovery

POSSIBLE BRINE REUSE POTENTIAL

 Energy is stored in highly dense concentrated brine  10,000 m2 solar pond in Australia produced enough energy to run a 500 m3/day desalination plant for 160 days a year  Solar ponds can produce electricity at 12 cents/kWh

Solar Ponds

Salt Gradient Non-Convective Solar Pond Source: Burston and Akbarzadeh, 1995

 HIGH VALUE SALTS & FERTILIZERS  QUALITY FEEDSTOCK FOR MANUFACTURE OF MAGNESIUM METALS & ALLOYS  INORGANIC FIRE RETARDANTS  BUILDING PRODUCTS  SEALANTS  FLOCCULATING AGENTS

MINERAL RCOVERY (SAL-PROC)

Bahja Nimr Marmul Rima Capacity ML/yr 219 310 548 110 Saline discharge (ML/yr) 75 135 150 45 Brine salinity TDS g/l 23.1 19.4 4.5 25.7 An annual salt load t/yr 1730 2600 680 1160 Specific features very low bicarbonate High bicarbonate, low salinity, low magnesium Low bicarbonate

RO Plant Bahja 1 & 2 Rima Nimr 1 & 2 Marmul 1 & 2 (Treatment Option 1) Gypsum (tonnes) 350 204 475 Sodium Chloride Salt (t) 1000 510 1385 Magnesium Hydroxide (t) 75 68 97 Calcium Chloride 240 295 385 (Treatment Option 2) Precipitated Calcium Carbonate (t) 370 320 532 Sodium Sulphate (t) 225 130 304 Sodium Chloride Salt (t) 1100 560 1850 Magnesium Hydroxide (t) 35 36 51 Bittern (ML) 1.5 1.0 2.5 (Treatment Option 3) Gyps & Magnesium Carbonate Admixture (t) 220 Sodium Sulphate (t) 180 Sodium Chloride Salt (t) 115 Magnesium Hydroxide (t) 37 Calcium Chloride (t) 55

 Resource Recovery  Low cost evaporation ponds  Enhanced evaporation  Effect of brine on soil and groundwater  Beneficial uses of evaporation ponds

Research Needs

• - Various disposal options currently in use
• - Potential for groundwater contamination
• - Leakage in evaporation ponds suspected
• - Very little monitoring and reporting on brine

and disposal systems

• - Specific regulations lacking
• - Mineral recovery is feasible but may not be

economic