Management of concentrate from desalination plants

282 Pages·2020·24.425 MB·English

by  Nikolay Voutchkov

Management of
Concentrate From
Desalination Plants
Elsevier
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Management of
Concentrate From
Desalination Plants
Nikolay Voutchkov
Gisela Noelle Kaiser
Contents
Preface.....................................................................................................................ix
Acknowledgments.................................................................................................xiii
CHAPTER 1 Introduction to concentrate management....................1
1.1 Currentstatus of desalination........................................................1
1.2 Enablingconditions for desalination.............................................7
1.3 Overview ofexistingconcentrate management practices.............8
1.4 Concentrate management regulations............................................8
References....................................................................................12
CHAPTER 2 Desalination plant discharge characterization.........13
2.1 Desalination plant waste streams.................................................13
2.2 Concentrate...................................................................................14
2.3 Spent pretreatment filter backwashwater...................................17
2.4 Chemicalcleaning residuals........................................................20
References....................................................................................23
CHAPTER 3 Surface water discharge of concentrate...................25
3.1 New surface water discharge.......................................................25
3.2 Potential environmental impacts..................................................27
3.3 Concentrate treatment priortosurface water discharge..............54
3.4 Design guidelines for surface water discharges..........................56
3.5 Costs for new surface water discharge........................................60
3.6 Codisposal with wastewater effluent...........................................64
3.7 Codisposal with powerplant cooling water................................67
References....................................................................................75
CHAPTER 4 Case studies for surface water discharge.................79
4.1 Introduction..................................................................................79
4.2 Surface water discharge case studies...........................................79
References..................................................................................129
CHAPTER 5 Discharge to sanitary sewer.....................................131
5.1 Description.................................................................................131
5.2 Potential environmental impacts................................................131
5.3 Effect on sanitarysewer operations...........................................131
5.4 Effect on wastewater treatment plantoperations......................132
5.5 Effect on water reuse.................................................................133
v
vi Contents
5.6 Design andconfiguration guidelines.........................................134
5.7 Costs for sanitary sewer discharge............................................135
References..................................................................................136
CHAPTER 6 Deep well injection...................................................137
6.1 Description.................................................................................137
6.2 Potential environmental impacts................................................141
6.3 Criteria and methods for feasibility assessment........................142
6.4 Design andconfiguration guidelines.........................................142
6.5 Injectionwell costs.....................................................................145
6.6 Deep well injectioncase study..................................................147
References..................................................................................148
CHAPTER 7 Land application.......................................................151
7.1 Description.................................................................................151
7.2 Potential environmental impacts................................................155
7.3 Criteria and methods for feasibility assessment........................156
7.4 Design andconfiguration guidelines.........................................160
7.5 Land application costs................................................................167
References..................................................................................171
CHAPTER 8 Evaporation ponds....................................................173
8.1 Description.................................................................................173
8.2 Potential environmental impacts................................................178
8.3 Criteria and methods for feasibility assessment........................178
8.4 Design andconfiguration guidelines.........................................180
8.5 Evaporation pond costs..............................................................183
References..................................................................................185
CHAPTER 9 Zero-liquid discharge concentrate disposal
systems......................................................................187
9.1 Overview....................................................................................187
9.2 Disposal system technologies....................................................188
9.3 SWROsystemsfor increased recovery and brine
concentration..............................................................................198
9.4 Potential environmental impacts................................................202
9.5 Criteria and methods for feasibility assessment........................203
9.6 Design andconfiguration guidelines.........................................204
9.7 Zero-liquid discharge costs........................................................204
9.8 Case studies................................................................................206
References..................................................................................207
Contents vii
CHAPTER 10 Beneficial use of concentrate..................................209
10.1 Technologyoverview.................................................................209
10.2 Extractionofminerals from concentrate...................................213
10.3 Feasibility of beneficial reuse....................................................220
References..................................................................................220
CHAPTER 11 Regional concentrate management..........................223
11.1 Types ofregional concentrate management systems................223
11.2 Use ofbrackish water concentrate inSWROplants.................224
11.3 Joint desalinationand reuse.......................................................226
References..................................................................................230
CHAPTER 12 Nonconcentrate residuals management..................231
12.1 Spent pretreatment backwash water..........................................231
12.2 Chemicalcleaning residuals......................................................242
Reference...................................................................................243
CHAPTER 13 Selection of concentrate management approach....245
13.1 Concentrate management alternatives.......................................245
13.2 The future of concentrate management.....................................251
13.3 Concluding remarks...................................................................253
References..................................................................................256
Appendix 1:Abbreviations...................................................................................257
Appendix 2:Units..................................................................................................261
Glossary.................................................................................................................263
Index......................................................................................................................271
Preface
This book provides an overview of the alternatives for management of concen-
trate generated by brackish water and seawater desalination plants, as well as site-
specific factors involved in the selection of the most viable alternative for a given
project, and the environmental permitting requirements and studies associated
with their implementation. The book focuses on widely used alternatives for dis-
posal of concentrate, including discharge to surface water bodies, disposal to
wastewater systems, deep well injection, land application, evaporation, beneficial
reuse, and zero-liquid discharge. Direct discharge through new outfalls, discharge
throughexistingwastewatertreatmentplantoutfalls,andcodisposalwiththecool-
ing water of existing coastal power plants are described, and design guidance for
the use of these concentrate disposal alternatives is presented with engineers and
practitioners in the field of desalination in mind. Key advantages, disadvantages,
environmental impact issues, and possible solutions are presented for each dis-
charge alternative. Easy-to-use graphs depicting construction costs as a function
of concentrate flowrate are provided for all key concentrate management
alternatives.
Atpresent,membrane reverse osmosis(RO)desalination isthefastestgrowing
technology for production of fresh water from saline water sources: desalination
plants use less energy to produce the same volume of fresh water than thermal
desalination facilities. Therefore, this book focuses exclusively on the concentrate
management ofRO desalination projects.
Planning and design for locating, construction, funding, and operation of desa-
lination plants is more complex and demanding than that for conventional water
treatment facilities in terms of professional skills, knowledge and understanding
of the environment, treatment processes, technologies, and equipment employed
in desalination processes. As the advances in desalination technology make desa-
lination more competitive with other alternative sources of water supply, planning
and design, including preparation of accurate cost estimates for construction and
operation of desalination projects becomes of critical importance for identifying
the size and role of desalination in the mix of alternatives that provide a sustain-
able and reliable water supply portfolio for municipal coastal centers around the
world.
This book provides detailed information on how to manage concentrate in the
implementation of seawater RO desalination plants. The book contains 13 chap-
ters, covering current developments in desalination and essential knowledge of
prevailing methods of concentrate management. Easy-to-use formulas and cost
curves are included to facilitate development of estimated volumes and costs
associated with the various typesof concentrate management.
Chapter 1, Introduction to Concentrate Management, provides a brief review
to the current status of desalination worldwide and an overview of the most com-
monly used concentrate management alternatives. With the elevated risk of water
ix
x Preface
scarcity due to climate change and demand growth, desalination is becoming
increasinglypopularfortheproduction offreshpotablewater,especiallyinhighly
urbanized coastal regions. As the number of plants and volumes of desalinated
water increase, assurance must be provided of the environmental sustainability of
such discharges over extended time periods. Potential environmental impacts can
be minimized through treatment of concentrate and optimal discharge configura-
tion and design, either directly into the water body or disposed together with trea-
ted wastewateror cooling water from power plants.
Chapter 2, Desalination Plant Discharge Characterization, presents the key
components of desalination plant waste streams. Discharge from desalination
plants is constituted mainly of RO concentrate, but may also contain significant
volumes of filter backwash water and cleaning solutions used in water condition-
ing and membrane cleaning. The quantity and quality of each source can be cal-
culated based on the plant characteristics. The volume of concentrate is a function
of the plant recovery rate, and given the large volumes discharged, concentrate
management mustbe integral to preliminary design decisions.
Chapter 3, Surface Water Discharge of Concentrate, covers the most common
desalination plant concentrate disposal practice. As the number of developments
and volumes of desalinated water increases, assurance must be provided of the
environmental sustainability of such discharges over extended time periods.
Potential environmental impacts can be minimized through mixing of concentrate
with discharges of wastewater treatment plants or power plant generation stations,
or by the use of diffuser systems for accelerated dissipation of the concentrate in
the marine environment. If properly managed, the footprint of increased salinity
can be minimized resulting in the elimination of potential negative impacts of
concentrate and other desalination plant discharges on the receiving aquatic
environment.
Chapter 4, Case Studies for Surface Water Discharge, includes case studies of
concentrate management practices in Australia, Israel, Spain, and the United
States. Most large plants have direct discharge to surface water bodies. In this
chapter, permitting practices are compared between countries. As the technology
has evolved rapidly over the past decades, standardization within countries is
often still lacking– most countries however have similar permitting requirements
for desalinationplant discharges.
Chapter 5, Discharge to Sanitary Sewer, addresses the disposal of concentrate
to the wastewater collection system as a common practice from small desalination
plants. Typically, small volumes of brine are combined with the influent to large
treatment plants. The cost of discharge relates only to conveyance into the waste
stream and is thus low. Concentrate is managed as industrial effluent with both
quantity and quality regulated to have no negative impact on plant operations.
Increased salinity can have potential impact on effluent reuse, especially for
irrigation.
Chapter 6, Deep Well Injection, details how concentrate from desalination
plants could be disposed of in deep confined saline aquifers. The capacity of such
Preface xi
aquifers is limited by permeability and transmissivity, while the underground
injection zone must be compatible with the water quality of the membrane con-
centrate. The injection zone receiving concentrate must also be over 10,000mg/L
TDS. Concentrate may require pretreatment to prevent negative impacts on the
receiving aquifer. Monitoring of groundwater in the area, and pressure in the
aquifer are critical to early identification of leaks and regulating this form of
disposal.
Chapter 7, Land Application, explains how concentrate can be disposed in a
manner which involves either spray irrigation on salt-tolerant plants or infiltration
through earthen rapid infiltration basins. Land application is typically used for
small volumes of brackish water concentrate only and its full-scale application is
limited by climate conditions, seasonal demand and by availability of
suitable land and groundwater conditions. Agricultural applications to vegetation
toleranttosalinity holds promiseof improvingbeneficialuse.
Chapter 8, Evaporation Ponds, describes the circumstances under which con-
centrate can bedisposedtoponds,wherewaterisevaporatedthroughsolarpower,
while the remaining salts are collected periodically in crystalized form and trans-
ported to landfill. Land area needed for the ponds is mainly dependent on the vol-
ume of concentrate and the site-specific evaporation rate. Additional storage
capacity is required to allow for accumulation of the minerals that have crystal-
ized at the bottom of the ponds. Solar ponds are evaporation ponds with an
enhanceddepth which are configured togenerate energy.
Chapter 9, Zero-Liquid Discharge Concentrate Disposal Systems, explores
current developments in reducing both environmental impact and cost of concen-
trate management by substantially reducing concentrate volumes. Zero-liquid dis-
charge technologies convert concentrate to pure water and dry crystals or dense
brine which can be either used for commercial purposes or disposed of to a land-
fill. Process intensification combines a number of existing processes to improve
therecovery,butdisruptivetechnologiesare likelytobenecessarytosignificantly
reducecosts and energy requirements.
Chapter 10, Beneficial Use of Concentrate, builds on zero-liquid discharge in
identifying potential markets for the byproducts derived from the brine such as
high-value minerals and rare metals. Beneficial use of concentrate provides the
opportunity to transform desalination, rendering it far more sustainable by not
only reducing the negative environmental impact of discharge, but by providing
revenuethroughmineral recovery.
Chapter 11, Regional Concentrate Management, introduces the integration of
concentrate from various sources in relatively close proximity to exploit potential
efficiencies. Given the comparatively high cost of concentrate management, bene-
fitscanbeobtainedbyconsolidatingeffluentfromanumberofsourcestoprovide
infrastructure that minimizes environmental impact while taking advantage of
economies of scale. Using a variety of sources and types of effluent (i.e., brackish
and seawater) has the advantage of dilution that can further positively impact the
environment.
xii Preface
Chapter 12, Nonconcentrate Residuals Management, describes the disposal of
nonconcentrate residuals such as spent filter backwash water from seawater pre-
treatment, spent membrane cleaning solutions and other process side streams.
Pretreatment backwash quantity and quality varies depending on whether mem-
brane or granular system is employed. Where quality is not detrimental to the
environment, spent backwash water is blended with concentrate and discharged to
water bodies. Alternatively, on-site treatment is required prior to blending.
Chemicals used to periodically clean membranes result in residual discharge that
typically needs to be either treated and blended with concentrate before disposal,
or conveyedto the nearby wastewater collectionsystem.
Chapter 13, Overview of Concentrate Selection Management Approach, com-
pares the various methods of concentrate disposal and highlights their advantages
and disadvantages. Feasible methods of disposal need to be identified and then
costed for the life of the project. Feasibility is influenced by regulations, environ-
mental sensitivity and physical constraints. Cost of concentrate management is
impacted by the size of the desalination project, source seawater quality, the type
and sensitivity of the marine environment in the vicinity of the discharge, and
preventive or mitigation measures that need to be implemented in order to mini-
mizeenvironmental impacts.
This book is intended for desalination project planners, engineers, and
designers; water utility professionals involved in development of water resource
management plans; equipment and membrane developers; operation and trouble-
shooting specialists; as well as for students and teachers in the desalination field.
It contains need-to-know desalination concentrate management practices and
information, which would benefit practitioners, decision-makers, and scholars
alike.