Wastewater treatment

1. Novel Technology for
Industrial wastewater
Xiang-fei Lyu

2. Chapter 2. Membrane technologies for
Industrial Wastewaters Treatment
Contents
Introduction.
Classification of the Membrane for Separation
Electrodialysis
Reverse Osmosis
Nanofiltration
Microfiltration
 Ultrafiltration

3. 2.1 Introduction
In water and wastewater treatment, membrane technology, a
term that refers to a number of different processes using
synthetic membranes to separate chemical substances, has been
recognized as the key technology for the separation of
contaminants from polluted sources thus purifying original waters.
Membranes are selective barriers that separate two different
phases, allowing the passage of certain components and the
retention of others. The driving force for transport in membrane
processes can be a gradient of pressure, chemical potential,
electrical potential or temperature across the membrane.
Membrane processes rely on a physical separation, usually with no
addition of chemicals in the feed stream and no phase change,
thus stand out as alternatives to conventional processes (i.e.
distillation, precipitation, coagulation/flocculation, adsorption by
active carbon, ion exchange, biological treatment…) for the
chemical, pharmaceutical, biotechnological and food industries.

4. Industrial wastewater has many types in large quantity
and it is very harmful. If the wastewater can be treated
, it would not only preserve the resource ,but also
protect the environment because the wastewater
contains some deleterious substances such as oil
,metallic ions , phenol and etc. The membrane technology
bears splendid significance in the industrial wastewater
treatment . In early 1970s, RO membrane began to make
the electric plating wastewater recycled; Charged UF
membrane turned the electro coating system in
automatic company into clean producing line. The
wastewater treatment with membrane recycled the
wastewater in dyeing process; UF membrane is a key
technology for the reuse of oil wastewater.
2.1 Introduction

5. Advantage：
Disadvantage：
 High performance
 Compact units: less space needed than conventional
treatment schemes
 Simple operation
 Membranes available can be used to separate many
kinds of contaminants
 Disinfection can be performed without chemicals
Membrane fouling
Production of polluted water (from backwashing)
Membranes have to be replaced on a regular basis

6. 2.1 Introduction
2.1.1 What Are Membranes?
Membranes are thin films of synthetic organic or
inorganic (ceramic) materials, which can bring about
a very selective separation between a fluid and its
components. The fluid may be a gas or a liquid but in
Environmental Engineering we are more concerned
with water and wastewater.

7. What’s a membrane
Semi-permeable barrier
 Good selectivity
 High Flux
Anti Fouling properties
Membrane operations depend on
• membrane material science
• driving force chemical
engineering
2.1 Introduction

8. Driving
Force
Pressure
Difference
Concentration
Difference
Electrical
potential
difference
Temperature
Difference
Membrane
Operations
Microfiltration
Ultrafiltration
Nanofiltration
Reverse osmosis
Gas separation
Dialysis
Pervaporation
Osmosis-FO
Gas separation
Electro-dialysis
Electro-osmosis
Membrane
Distillation
Exclusion
mechanism
Size exclusion Solubility Charge
Heat of
evaporation
2.1.2 Membrane technology
Engineering approaches for the separation of substances
with the help of semi-permeable membranes
2.1 Introduction

9. 2.1.3 Membrane structure
Porous Structure
Dense
Structure
Solution-Diffusion
mechanism
No pores
Gas Separation
Osmosis – FO - RO
Solubility
differences
Darcy’s Law
Filtration
2.1 Introduction

10. Membrane for UltraFiltration
: asymetric structure
Thin layer
 selectivity
Macrovoids
Highly
interconnected
pores
 Flux
 Mecanical
property
Membrane morphologie
1
2.1 Introduction

11. 2.1.4 Membrane modules
Thin sheet Hollow fibers
Tubular
membrane
Spiral wound module
2.1 Introduction

13. 2.2 Classification of the Membrane for Separation
2.2.1 Electrodialysis membrane
Electrodialysis: the phenomenon
that the charged solute particles
transport through the membrane
under the electric field.
Electrodialysis membrane: the
membrane used during the
electrodialysis process.
https://www.youtube.com/watch?v=QNX150DtnMc

14. 2.2 Classification of the Membrane for Separation
2.2.1 Electrodialysis membrane
• originally used for
seawater desalination
• Now，widely used in
chemical industry, light
industry, metallurgy,
papermaking,
pharmaceutical industry.
Preparation of pure water
and waste treatment in
environmental protection ,
such as alkali r e c o v e r y ,
electroplating wastewater
treatment ，and recovery of
valuable substances from
industrial wastewater

15. 2.2 Classification of the Membrane for Separation
The pore size of a membrane is generally indicated indirectly by
membrane manufacturers, through its molecular weight cut-off
(MWCO) which is usually expressed in Dalton (1 Da = 1g mol-1) .
MWCO is typically defined as the molecular weight of the smallest
component that will be retained with an efficiency of at least 90%.

18. 2.2 Classification of the Membrane for Separation
2.2.2 Reverse Osmosis
RO membranes are dense membranes that do not have distinct
pores. It is a pressure-driven process (between 20 and 80 MPa)
that rejects smallest contaminants and monovalent ions (<350
Da) from solutions. The mass transfer in RO is due to solution-
diffusion mechanism, size exclusion, charge exclusion and
physical-chemical interactions between solute, solvent and the
membrane.

19. 2.2 Classification of the Membrane for Separation
2.2.2 Reverse Osmosis
The RO process consists of a feed water source, a feed
pretreatment, a high pressure pump, RO membrane modules, and, in
some cases, post-treatment steps.

20. 2.2 Classification of the Membrane for Separation
2.2.2 Reverse Osmosis
The opposite process of
osmosis : a pressure greater
than the osmotic pressure is
imposed on the concentrated
solution, causing water flowing
through the membrane from
concentrated solution to the
dilute one ,as a result , the
concentration of the
concentrated solution is
greater.
Reverse osmosis membrane:
the membrane used during
the reverse osmosis

21. 2.2 Classification of the Membrane for Separation
2.2.2 Reverse Osmosis
• Applications include
• power
• plant cooling water
and sewage treatment
• seawater desalination
• brackish water
desalination
• large municipal and
industrial wastewater
treatment.
Reverse osmosis technology
is the most advanced and
efficient separation
technology .
Widely used to remove
water soluble salts、colloids
、 organics、bacteria、
microorganisms and other
impurities,
W i t h l o w e n e r g y
consumption and pollution、
advanced technology、easy
operation and maintenance

22. 2.2 Classification of the Membrane for Separation
2.2.3 Nanofiltration
Nanofiltration is a pressure-driven (uses pressures between 4 and
20 MPa) membrane-based separation process in which particles and
dissolved molecules with molar masses between 350 and 1000 Da
are retained. Nanofiltration is a relatively recent membrane
filtration process developed in the mid-1980s and is used most
often in surface water and fresh groundwater treatment, with the
purpose of softening (polyvalent cation removal) and removal of
disinfection by-product precursors such as natural organic matter
and synthetic organic matter (herbicides, pharmaceuticals, etc.)
Nanofiltration is also becoming more widely used in food processing
and other applications such as fractionation of oligosaccharides,
green biorefinery, coffee extract concentration, etc.

23. 2.2 Classification of the Membrane for Separation
2.2.3 Nanofiltration
Nanofiltration membrane modules:

24. 2.2 Classification of the Membrane for Separation
2.2.3 Nanofiltration
Nanofiltration membrane modules:

25. 2.2 Classification of the Membrane for Separation
2.2.3 Nanofiltration
The NF separation mechanism:
The NF separation mechanism can be identified as a sum of convection and
diffusion transport mechanisms,
** Convective transport of ions with the water flux through the
membrane is caused by the pressure difference between feed and
permeate sides.
** diffusive transport is a consequence of the concentration
gradient as achieved by the rejection of solutes Electromigration is
caused by a “streaming potential” difference across the membrane.
** streaming potential is caused by the electric current generated by the
convective flow of a fluid that is necessarily charged through the pores of
a charged membrane
** For uncharged molecules, sieving or size exclusion is primarily
responsible for separation and is controlled by molecular size in solute
form.

26. 2.2 Classification of the Membrane for Separation
2.2.3 Nanofiltration
The NF separation mechanism:
** Multivalent ,viruses , bacteria , suspended solids are removed by
Nanofiltration.

27. 2.2 Classification of the Membrane for Separation
2.2.3 Nanofiltration
Effectiveness of NF:
Micro-pollutants like herbicides and insecticides, as well
as low-molecular components like colorants and sugars
can be very successfully blocked using a Nano-filtration
membrane.
NF can be implemented for removing the following
parameters (removal yield indicated in brackets):
-Dissolved matter (>75%).
-Harmful micro-organisms, e.g. bacteria, protozoa,
algae, fungi (>90%).
-Persistent organic matter (50-75%).
-Organic compounds (50-90%).
-Nutrients (incl. phosphates).
- Metals (50-90%).
-Inorganic salts (e.g. sulphates).

28. Applications of NF:
1 Industrial applications:
* Food and dairy sector.
* Edible oil processing sector.
* Petroleum industry.
* Drug industry.
* Paper pulp industry
2-Water treatment.
3-Desalination of water.
4-Water softening.
2.2 Classification of the Membrane for Separation
2.2.3 Nanofiltration

29. Advantages:
 Lower discharge volumes, lower retentate
concentrations than RO for low value salts.
 Reduction salt content and dissolved matter
 content (TDS) in brackish water.
 chemical-free. e.g. needs no salt or
 Chemicals during operation.
 pH of water after Nano-filtration is normally
non-aggressive.
2.2 Classification of the Membrane for Separation
2.2.3 Nanofiltration

30. 2.2 Classification of the Membrane for Separation
2.2.3 Nanofiltration
 Higher energy consumption than UF and MF
(0.3 to 1 kWh/m³).
 Limited retention for salts and univalent ions.
 Membranes are sensitive to free chlorine
(life-span of 1000 ppmh).
 An active carbon filter or a bi-sulphite
treatment is recommended for high chlorine
concentrations.
Disadvantages:

31. 2.2 Classification of the Membrane for Separation
2.2.4 Microfiltration
Microfiltration , also called microporous filtration, which belongs
to the precision filtration, is the membrane separation process
,widely applied in the interception of silt, clay and other particles
and algae, bacteria in solution, while most of the solvent molecule
and the small solute molecules can pass through the membrane.
Porous membrane; particle diameter
0.1 – 10 μm Microfiltration lies
between UF and conventional
filtration.
In-line or crossflow operation.
Screen filters/depth filters Challenge
tests developed for pore diameter and
pore size.

32. 2.2 Classification of the Membrane for Separation
2.2.4 Microfiltration
Membrane materials
• Cellulose acetate/cellulose nitrate
• PAN – PVC
• PVDF
• PS
Modules
•Plate and frame
•Cartridge filters

33. Application of Microfiltration
• Applied in the
removal of ultrafine
particles in solution
larger than 50
micrometers or so .
• The separation
membrane with the
largest scale in sale.
Microfiltration is widely
used in
• the ultrapure water
terminal filter of
microelectronics
industry,
• Also used to detect tiny
impurities in Biomedical
Science and
Sophisticated
technologies,
• is an important tool in
scientific experiments.
2.2 Classification of the Membrane for Separation
2.2.4 Microfiltration

34. 2.2 Classification of the Membrane for Separation
2.2.5 Ultrafiltration
Uses a finely porous membrane to separate
water and microsolutes from
macromolecules and colloids.
Membrane pore diameter 0.001 – 0.1 μm.
Nominal ‘cut off’ molecular weight rating
assigned to membrane.
Membrane performance affected by:
• Concentration polarisation
• Membrane fouling
• Membrane cleaning
Spiral wound UF
module

35. 2.2 Classification of the Membrane for Separation
2.2.5 Ultrafiltration
Membrane materials (Loeb- Sourirajan process)
• Polyacrylonitrile (PAN)
• PVC/PAN copolymers
• Polysulphone
• PVDF (polyvinylidene difluoride)
• PES (polyethersulfone)
• Cellulose acetate (CA)
Modules
• Tubular
• Plate and frame
• Spiral wound
• Capillary hollow fibre

36. 2.2 Classification of the Membrane for Separation
2.2.5 Ultrafiltration
Ultrafiltration is used to retain particles of colloidal size
under pressure , while water and small molecule solutes
is permitted to get through the membrane.

37. Application of ultrafiltration
For 0.1-0.01 microns in diameter
• widely used in
• the preparation of drinking
water,
• food industry,
• pharmaceutical industry,
• industrial wastewater
treatment, metal
processing,
• biological products,
• oil paint processing and
other fields.
such as
Surface Water Treatment,
Sterile liquid food
manufacturing,
Ultrafiltration purification
2.2 Classification of the Membrane for Separation
2.2.5 Ultrafiltration

38. 2.2 Classification of the Membrane for Separation
Future of membrane application in water treatment
The essence of membrane technology is a highly effective
material. The material should provide high flux , high selectivity
and so on. In the wastewater treatment , we often encounter
hazardous condition. Under such kind of circumstances , organic
membrane sometimes cannot meet the requirement . Consequently
, more attention is paid to the inorganic membrane now that
has fulfilled a considerable progress in these years with a rate of
30 %. Currently China can produce tube ceramic membrane on
industrial scale. With the decrease of water resource and the
increase of water pollution , it is definitely that the membrane
technology , the separation technology of the lowest energy cost ,
will realize a brilliant future. RO , NF ,UF , MF , ion - exchange ,
dialysis etc which are mainly used in water treatment will be the
center of membrane technology.

39. 2.2 Classification of the Membrane for Separation
Future of membrane application in water treatment
The essence of membrane technology is a highly effective
material. The material should provide high flux , high selectivity
and so on. In the wastewater treatment , we often encounter
hazardous condition. Under such kind of circumstances , organic
membrane sometimes cannot meet the requirement . Consequently
, more attention is paid to the inorganic membrane now that
has fulfilled a considerable progress in these years with a rate of
30 %. Currently China can produce tube ceramic membrane on
industrial scale. With the decrease of water resource and the
increase of water pollution , it is definitely that the membrane
technology , the separation technology of the lowest energy cost ,
will realize a brilliant future. RO , NF ,UF , MF , ion - exchange ,
dialysis etc which are mainly used in water treatment will be the
center of membrane technology.

40. Class Assignment
Reading the book Page 206 to 243 ： MICROWAVE-
AND ULTRASOUNDASSISTED SURFACTANT
TREATED ADSORBENT FOR THE EFFICIENT
REMOVAL OF EMULSIFIED OIL FROM
WASTEWATER
Reading some articles and Finishing a report about
membrane technologies for wastewater treatment