Chemical Engineering in Water Infrastructure Projectsmc.hkie.org.hk/Upload/Doc/e59d8165-835b-49c6-9f91...- SWRO/BWRO array - staging and pass(es), modelling - post-treatment - water

香港公開大學THE OPEN UNIVERSITY OF

HONG KONG

Chemical Engineering Series III -Chemical Engineering in Water Infrastructure Projects

Harry LeeSenior Engineer, Arup31 October 2014


HONG KONG

IntroductionWater InfrastructureWater Scarcity and ResilienceSummary and Thoughts


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3 What is Chemical Engineering?


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4

• a branch of engineering that applies the natural sciences and life sciences together with mathematics and economics to produce, transform, transport and allow proper use of chemicals, materials and energy

• emerged upon the development of unit operations and focus on several key principles:

- chemical reaction engineering (reactors)

- separation

- process design, control and safety

- plant design and economics

What is Chemical Engineering?


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5

Obje

ctiv

es

• throughput rate

• process yield

• product purityC

on

stra

ints

• capital costs

• operation and maintenance costs

• available space

• safety concerns

• environmental impact - projected effluents and emissions

• waste production

Oth

er F

acto

rs

• reliability

• redundancy

• flexibility

• anticipated feedstock variability

• allowable product variability

Process Design - Considerations

design of processes for desired physical/chemical/biological

transformation of materials


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• material and energy balances

• thermodynamics

- change in enthalpy: endothermic vs exothermic processes

- phase change(s)

• reaction and reactor

- reaction kinetics: zeroth-/first-/second-order reactions

- batch vs continuous processes

- reactor configurations- continuous stirred-tank reactor (CSTR)- plug flow reactor (PFR)

Chemical Engineering Terminologies (1/3)


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• fluid mechanics (pipe hydraulics)

• heat and mass transfer

• process dynamics and control

• plant/process design and economics

• process safety

- hazard and operability (HAZOP) study

- hazard assessment

- quantitative risk assessment (QRA)



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8

• process integration

- emphasise the unity of the process

- consider the interactions among different unit operations from the outset, rather than optimising them separately

• process intensification

- a set of often radically innovative principles (paradigm shift) in process and equipment design



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9

Block Diagram

• simple diagrams of rectangles and lines indicating major material (or energy) flows

Process Design - Documentation (1/3)


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10

Process Flow Diagram (PFD)

• more complex diagrams of major unit operations and flow lines

• sometimes include material and/or energy balances

• showing typical or design flowrates, stream compositions, stream/ equipment pressures and temperatures


Example PFD on fluid catalytic cracking

[http://chemengineering.wikispaces.com]


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11

Piping and Instrumentation Diagram (P&ID)

• valving along with instrument locations and process control schemes

• pipelines with piping class and pipe size

Specifications

• written design requirements of all major equipment items


Example P&ID on membrane desalination process

[http://www.projenex.com/]


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13 Water Supplies Department (Fresh Water)


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14 Drainage Services Department (Sewage Treatment)


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15 Design with Water (Arup)

Fundamental water &

sanitation services


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16

Chem

ical

Engin

eeri

ng • throughput rate

• process yield

• product purityW

ater

Tre

atm

ent

• demand forecast of supply zone(s), peaking factors

• raw water quality

• contaminant(s) of concern

• wastage

• drinking water standard

• (residuals quality)

Was

tew

ater

Tre

atm

ent • sewage flow

projections, peaking factors

• load projections

• bypass

• discharge standard

• (residuals quality and recovery)

Translation of Process Design Objectives for Water Infrastructure Projects


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17

• reaction

- contact tanks (chemicals addition, aeration)

- digestion

• separation - mostly solid/liquid

- coarse/fine screening

- (coagulation/flocculation and) sedimentation

- filtration (and adsorption)

- thickening/dewatering

• others

- energy/resource recovery (eg CHP, micro-turbine)

- deodourisation

Common Unit Operations for Water Infrastructure (1/2)


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18 Common Unit Operations for Water Infrastructure (2/2)


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19 Case Study - HATS Stage 2A, Overview

Photomontage of SCISTW after HATS Stage 2A Upgrading Works

© A

rup

HATS Layout Plan

© A

rup

SCISTW prior to HATS Stage 2A Upgrading Works

© A

rup

Harbour Area Treatment Scheme (HATS) Stage 2A

A centralised sewage collection and treatment system for urbanised areas on both sides of Victoria Harbour.

The most important sewage infrastructure in Hong Kong serving ultimately over 5 million population.


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• flow and load projections

• system capacity and process design

• process evaluation (liquid + sludge) and value management

• constraints identification and layout design

• reference design and specifications

• contract packaging and procurement

• construction supervision

• testing and commissioning

Case Study - HATS Stage 2A, Chemical Engineering Inputs


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Case Study - HATS Stage 2A, Layout Design

New facility under

HATS 2A

Existing facilities

New Main Pumping Station

and Interconnection Tunnel

New flocculation and

sedimentation Tanks

Odour Control Enhancements

(including covers to all

sedimentation tanks, channels

and flow chambers)

New Sludge Treatment and

Disposal Facilities

Disinfection facilities

New Control and Expert

System

New Effluent Tunnel and Flow

Chambers

Ancillary Upgrading and

Improvement Works


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22 Case Study - HATS Stage 2A, On-going Construction

September 2014


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23

Obje

ctiv

es

• throughput rate

• process yield

• product purityC

on

stra

ints

• capital costs

• operation and maintenance costs

• available space

• safety concerns

• environmental impact - projected effluents and emissions

• waste production

Oth

er F

acto

rs

• reliability

• redundancy

• flexibility

• anticipated feedstock variability

• allowable product variability

Chemical Engineering for Water Infrastructures (1/2)


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24

• HAZOP study

• environmental study

• chemicals storage and handling

- occupational safety and health

- dangerous goods

• process optimisation and operation management

- energy efficiency/recovery

- chemicals consumption

- asset management

• many other involvements (to be explored)

Chemical Engineering for Water Infrastructures (2/2)


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26 Design with Water (Arup)

Too much water?

Too little water?


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27

• climate change

• diminishing available fresh water resources

• population growth

• water-energy-foodnexus

• watershed management and cooperation (politics)

Challenges

Water-Energy-Food Nexus [IChemE]


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28

Total Water Management (TWM) in Hong Kong 2008

water demand management

• public education on water conservation

• promote water saving features

• active leakage control

• sea water for toilet flushing

water supply management

• protection of water resources

• water reclamation

• new water resources (sea water desalination)


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Chem

ical

Engin

eeri

ng • throughput rate

• process yield

• product purityD

esal

inat

ion

• demand forecast of supply zone(s) - as augmentation

• recoveries through pre-treatment, desalination and post-treatment; function of feed water qualities

• concentrate (brine) discharge

• product water standard(s)

• (residuals quality)

Wat

er R

ecla

mat

ion

• reclaimed water application(s) and demand

• effluent quality - load projections

• return of wastage to inlet of STW/ public sewer

• reclaimed water standard(s), usage-specific

Translation of Process Design Objectives for Desalination and Water Reclamation Projects

[Wiki]


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• separation: removing salt from water

• energy is provided through

- thermal

- mechanical

- electrical

Desalination - Fundamentals

feed water fresh water salt+

ener

gy


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Desalination - Classification

desalination

thermal

heat addition

steamMSF / MED / HDH / MD /

TVC

solarsolar stills /

solar collectors

heat removal freezing

mechanical

MVC

RO

electrical ED / EDR


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• 182MLD desalter, MSF technology

- 15 acres (6.07ha) in 6 production units

- once the largest desalter in the World

- intermittent operation 1975-1982

• site selection

- near Pearl River estuary, clearer and less salty sea water

- proximity to Tai Lam Chung Reservoir

• closed down in 1982

- adequate rainfall, public opposition, high fuel price, committed DJ water

Lok On Pai Desalter (1/2)

[WSD / Wiki / HK Reporter]


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Lok On Pai Desalter (2/2)

[Lok On Pai Desalting Plant, Water Supplies Department (HKU Library)]


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From Thermal to Membrane (1/2) -Process Intensification

[ GWI / DesalData.com / roplant.org ]

• less energy-intensive: no heating or phase changes

• dedicated research & development in membrane science and technology

• continuous process development / optimisation

• competitive membrane prices

• dimensional standardisation

• other market factors


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35

• pressure exchangers (work exchangers)

- directly transfer pressure from the brine to the feed

• turbine systems (Pelton wheel or turbocharger systems)

- convert potential energy from the brine to mechanical energy either supplied to the SWRO high pressure pump as auxiliary power supply or directly to the feed

From Thermal to Membrane (2/2) -Energy Recovery

Dual Work Exchange Energy

Recovery (DWEER) supplied by

FlowserveIsobaric PX supplied by ERI

Pelton Wheel

Turbo Charger Francis Turbine

//upload.wikimedia.org/wikipedia/commons/d/d1/Francis_Turbine_High_flow.jpg

//upload.wikimedia.org/wikipedia/commons/d/d1/Francis_Turbine_High_flow.jpg


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• 240m3/day capacity

• 3×3 configuration

- 3 pre-treatment- submerged UF- pressurised UF

- dual media filter

- 3 RO membrane brands

• process optimisation

• post-treatment study

• cost estimation

Hong Kong Pilot Desalination Plant (1/2) - Unit Operations and Process Configuration

[WSD Pilot Plant Study, Executive Summary]


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37

Hong Kong Pilot Desalination Plant (2/2)

Tuen Mun (2004-2005)

• estuary water (Pearl River)

• considerable seasonal variations in

wet season

• generally less saline

Ap Lei Chau (2006-2007)

• oceanic water (South China Sea)

• relatively stable and consistent

water quality year-round

• relatively more saline


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38 From very sophisticated system…


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39… to system that meets the basic need of people in developing regions.


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40

• site selection

• source water quality characterisation

• environmental study, pilot study

• process design and configuration, energy consideration

- intake and pre-treatment

- SWRO/BWRO array - staging and pass(es), modelling

- post-treatment

- water chemistry and chemical dosing

- waste and brine management

• life-cycle costing (CAPEX and OPEX)

Chemical Engineering for Water Resilience (1/4) Planning and Design


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41

• testing and commissioning

• plant utilisation

• (unit) production cost

• (product) water quality compliance

• process control and automation

• system reliability and diagnosis

• improvement works and prioritisation

• knowledge transfer and operator on-the-job training

Chemical Engineering for Water Resilience (2/4) O&M Strategy


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42

• H3BO3H2BO3+ HBO3

2+ BO33+

- 4-8mg/L (typical sea water)

- 0.3mg/L (WHO1993)

- 0.5mg/L (WHO2004)

• implications to SWRO

- non-ionic species in normal pH range

- maximum 80-90% removal in first-pass

• solutions

- blending with catchment/DJ water (technical limitation)

- first-pass RO alkalisation (precipitation and/or scaling)

- partial/full second-pass RO ($$$)

Chemical Engineering for Water Resilience (3/4) Boron Mitigation Study

[Huehmer et al (2006) Boron Mitigation Strategies in Seawater Desalination]


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Chemical Engineering for Water Resilience (4/4) The Chemical Engineer | Issue 804, June 2008

“During [the Lanarca plant’s] eight years of operation, we followed a defined plant

operation strategy involving four main steps: optimisation, standardisation,

stabilisation, and innovation… In each step, distinct chemical engineering

principles can be used to ensure that the plant performs optimally.”

“…faced with a substantial growth in the desalination industry… action must be

taken by IChemE and the chemeng community to grasp this opportunity and

meet the demand with a supply of well-educated and skilled engineers.”


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44

• a dependable source

• effective approach on overall water efficiency with dual benefits

- reduce fresh water demand

- reduce effluent discharge to environment

• public acceptance

- Singapore (NEWater, indirect potable reuse)

- California (aquifer recharge, indirect potable reuse)

- Windhoek, Namibia (direct potable reuse)

- Hong Kong (non-potable uses)

Water Reclamation - General Perspective


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45

[Modified from Takashi Asano, “Water from (waste)water – the dependable water resource”, 2001 Stockholm Water Prize Laureate Lecture]

Urban Water Usage and Quality Profile

1) different starting points and end points

2) different process designs and technologies

3) paradigm shift: wastewater = used water


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46

the first tertiary STW in Hong Kong

• within a country park

• 500m above sea level

• within water gathering ground of Shek Pik Reservoir

reclaimed water as pilot scheme and education (100-150m3/day)

• toilet flushing

• controlled landscape irrigation

treatment technology

• tertiary treatment (SBR + media filter) and disinfection (UV + chlorination)

Reclaimed water uses within NPSTW

© A

rup

Ngong Ping Sewage Treatment Works (NPSTW)

© A

rup

t


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47

What do you think about large-scale applications of Reclaimed Water (RW) in HK?

Water Reclamation Demonstration Scheme in North District


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• holistic water strategy and thinking

- across the entire water cycle

- fresh water + used water

• next available water source

- ascending life-cycle costs

- match quality with usage

• impact on existing infrastructure(s) and environment

- not only water but also energy/power infrastructures

- centralised vs decentralised approaches

- desal: brine/waste discharge, energy/chemical consumption

- water reclamation: potential risks on “closing the water loop”

How shall the alternative water treatment processes be applied? (1/2)


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49

How shall the alternative water treatment processes be applied? (2/2)

water demand management

• public education on water conservation

• promote water saving features

• active leakage control

• sea water for toilet flushing

water supply management

• protection of water resources

• water reclamation

• new water resources (sea water desalination)

compatible?


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51

1) process maturity: technology advancement over time, market creation, value-adding

• research and development - product, process, service

• proof-of-concept design

• bench-scale

• pilot-scale

• demonstration

• full-scale / commercialisation

2) physical-size: spatial consideration, scale-of-economy

• house-hold

• building-/block-level

• development-level

• district-level

• municipal-/city-level

• portable/mobile units

Scale Approach - Two Dimensions


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• chemical: process system(s), unit operations, instrumentation & control - steady-state, conversion, economic potential

• civil: structures, building, transportation, site development -risks, uncertainty

• mechanical: materials, mechanics, energy - machinery and tools

• electrical: power supply, [process] control, computer programming, [tele-]communication - electricity, electronics

• …environmental, geotechnics, coastal/maritime, hydrology…

• collaboration is the key

Different Disciplines and Focuses


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“Here [in Singapore], water is an issue of life and death. That's always been the message.”

Chew Men Leong, Chief Executive, PUB

Macao Recycled Water Development Plan (2013-2022)• target of 10% of total water

consumption by 2022• price of recycled water: 85% of tap

water

Maritime Administration (CP) and Working Group for the

Promotion of a Water-Saving Society, Macau SAR

The Chinese characters below embedded the relationship of water and politics, precisely:

治水 - Water management水治 - Water politics

Professor Yun Zu-whan, Dept of Environmental

Engineering, Korea University

The Wider Perspective - Water Governance

Channel NewsAsia, 30 July 2012 Keynote speech, the 4th IWA-ASPIRE Conference and Exhibition, Tokyo, 2-6

October 2011

My Blog, Financial Secretary Office, 30 March 2014

“Hong Kong… should not be over-reliant on Dongjiang water, but should bear the responsibility to explore other new water sources, to prepare for the challenges of water supply in the future.”

John Tsang, GBM, JP, Financial Secretary, HKSAR

Government


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• resource recovery

- sludge, MSW, organic (food) waste

• cleaner production

- waste minimisation, life-cycle analysis, eco-design

• advanced/sustainable materials

- nanotechnology, (bio-)composites

• mining, minerals, energy and utility

- from fossils to renewables

• food, beverage, pharmaceutical

Chemical Engineering - Beyond Water Infrastructures


HONG KONG

Chemical Engineering Series III -Chemical Engineering in Water Infrastructure Projects

Harry LeeSenior Engineer, Arup31 October 2014

Documents

Chemical Engineering in Water Infrastructure Projectsmc.hkie.org.hk/Upload/Doc/e59d8165-835b-49c6-9f91...- SWRO/BWRO array - staging and pass(es), modelling - post-treatment - water