NSERC Chair in Water Treatment

Membranes in Drinking Water Treatment

Peter M. HuckProfessor and NSERC Chairholder in

Water TreatmentUniversity of Waterloo, Canada

Topics for discussion

Introduction

Goals and processes for treatment

Membrane fouling reduction

Orientation

NSERC Chair

Senior research professorship supported jointly by NSERC (Natural Sciences and Engineering Research Council of Canada), the University of Waterloo and ‘industrial’ partners (NSERC matches industrial cash and in-kind)

Part of Department of Civil and Environmental Engineering

Granted in five year terms

Support for students, staff, research costs

Centre of Expertise

Some 4th Term Statistics (2008-2012)

Now in Year 18 of 20

Major themes – chemical and (micro)biological contaminants• Source water and treatment

10 on-site students (6 Ph.D.), 2 off-site

Usually one post-doc

Technical and administrative professionals

Eighteen ‘industrial’ partners• Municipal water works, consultants, etc.

NSERC Industrial Research Chair Partners

Current Major Areas of Research

Emerging microbial contaminants

Membranes

Evaluating point-of-use treatment

Trace chemical contaminants• e.g pharmaceuticals and endocrine disruptors

• Adsorption, oxidation, membranes

Membranes – fouling

Biological pre-treatment to reduce fouling

Goals for treatment

Removal of particles (including pathogenic micro-organisms)

Removal of TOC (‘background’ organic matter)• e.g. from leaves, soil, algae, wastewater

Disinfection/inactivation

Removal of chemical contaminants • e.g. pesticides, pharmaceuticals, volatiles

Goals for treatment - 2

Biological stability• Avoiding bacterial regrowth in distribution system

Chemical stability• Corrosion, precipitation in distribution system

Maintaining aethetic quality to the consumer’s tap

Future trends in treatment

Reduction in chemical usage -> tends to favour membranes

Reduction in carbon footprint – ‘green’ technologies

Simple and secure treatment -> also tends to favour membranes

Some additional trends

Desalination – where feasible

Partial reuse -> dual systems (risk management)

Reduced consumption

Membranes

What’s a membrane?

Usually, a sheet of polymer with very fine holes

Push/pull the water through, keep out (most of the) contaminants

• ‘Rejection’ depends to a big extent on size of the holes (pores), the chemical composition of the membrane, characteristics and size of the contaminants and some operating factors (e.g. flowrate)

Membrane types

Microfiltration

Ultrafiltration

Nanofiltration

Reverse osmosis

Capabilities of membranes

UFUF

NFNF

RROO

MMFF

Particles, algae, protoz-oans, bacteria

Macromolecules, viruses

Multi-valent ions,

TOC

Monovalent ions (Na+, Cl-)

Water molecules

Pore sixe

0.1 -1µm

1-100nm

~ 1nm

<1nm

ZeeWeed® Membranes (GE-Zenon)

Module ZeeWeed ®- 500

Nanofiltration – spiral-wound modules

Ceramic membranes

Development of Alternative Membrane Integrity Detection Tools for Low

Pressure Membranes Treating Filter Backwash Water

M.E. Walsh1, M.P. Chaulk2 & G.A. Gagnon1

1Department of Civil Engineering, Dalhousie University 2Zenon Environmental Inc.

AWWA WQTCNovember 2005 Québec City, QC, Canada

Project Objectives

Evaluate current integrity test methodologies for UF membrane treatment of WTP residual streams

• Particle counting & turbidity measurements

Explore alternative indirect integrity test methods

• DOC and color

Capability for detecting “precursor” signals to breaches in a membrane operating system (chronic increases in dissolved material (i.e., NOM)

Integrity Trials

FBWW

Creation of Challenge Conditions

Extended run period without chemical cleaning

• Simulate initial stages of failure in membrane operating system

• Accelerated fouling rate

• Degradation of membrane fibers

Flux – a key parameter

Flow of water per unit membrane surface area and time (e.g. litres per square metre per hour – lmh)

CAPITAL COSTS

Fouling – the enemy of flux

New membrane Membrane after fouling

Effect of fouling on flux

Caused by particles, organics and other substances in incoming water

Extent of fouling determined by• Concentration and type of incoming foulants• Pre-treatment• Membrane operating and cleaning conditions

Fouling

Grand River drainage basin

Some biofiltration basics

Biological processes

• Attachment

• Detachment

• Biodegradation

• Growth

• Decay

Hozalski et al., Water Research, 2001

Process schematic for biofiltration pre-treatment for UF

Grand River 3 - DOC characterization*

Building blocks

*Liquid Chromatography-Organic Carbon Detection (TU Berlin)

TOC/DOC about 6 mg/L

Impact on fouling

Impact on fouling - 2

Impact on fouling - 3

Hallé et al. ES&T, 2009

Pilot confirmation

Possible process train

(Roughing filtration) → Biofiltration → UF →

(Disinfection)

Membrane types

Microfiltration (MF)

Ultrafiltration (UF)

Nanofiltration (NF)

Reverse osmosis (RO)

Some membrane applications in Australia

Source: Google Maps

Example of a two-stage system for water reuse – Perth, Australia

Perth - 2

Biofouling of high pressure membranes

In long term operation, biofouling (growth of biofilm on the membrane) a serious operational issue

Desalination in Adelaide

Pretreatment - 1

Pretreatment - 2

Hands-on testing

Possible process train

(Roughing filtration) → Biofiltration → UF →

RO → (Disinfection)

Some future work

Biofiltration and low pressure membranes• Net removal of biopolymers

• Particulate removal

Biofiltration and high pressure membranes (desalination)• Removal of easily biodegradable carbon (AOC) to very low levels

Biofiltration as membrane pre-treatment in water reuse

Concluding remarks

Challenging issues in drinking water treatment and provision

Membranes important

Rapid biofiltration (without coagulation) effective to reduce organic fouling of UF membranes

• Robust, simple, ‘green’

• Potential for RO (biofouling), water reuse pre-treatment

Acknowledgments

NSERC, Canadian Water Network, GE, Region of Waterloo

NSERC Chair partners

www.civil.uwaterloo.ca/watertreatment