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Removal of heavy metal from industrial wastewater |
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Researchers at Universiti of Tenaga Nasional, Malaysia,
embarked on a study to interpret the biosorption process and
then develop a cost-effective technology to treat heavy
metals-containing industrial wastewater. A new composite
biosorbent was prepared by coating chitosan on to acid-treated
oil palm shell charcoal (AOPSC). Chitosan loading on the AOPSC
support is about 21 per cent by weight. The shape of the
adsorbent is nearly spherical, with particle diameter in the
range of 100~150 µm.
Results have shown that the use of chitosan-coated AOPSC for
removal of chromium ions is environment- friendly, technically
viable and quite efficient. Moreover, being composed entirely
of agricultural and fishing industry waste, it helps in
reducing waste generation. The adsorbent can be regenerated
using sodium hydroxide and as such can be reused. This
adsorbent can be a good candidate for adsorption of not only
chromium ions but also other heavy metal ions in wastewater
stream.
Contact: Saifuddin M. Nomanbhay, Chemistry Unit, Dept. of
Engineering Sciences, College of Engineering, the Universiti
of Tenaga Nasional, 43900 Kajang Selangor, Malaysia. Tel: +60
(3) 8928 7285; Fax: + 60 (3) 8921 2116
E-mail:
saifuddin@uniten.edu.my
Website:
www.ejbiotechnology.info |
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Oxidation of reactive blue dye wastewater |
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Pre-ozonation has been found to be effective in decolourizing
and raising the biodegradability of textile dye wastewater
while lowering pollution load. However, the cost of ozonation
is high due to poor gas-liquid mass transfer and
self-decomposition reactions. Ozonation efficiency can be
increased by in situ generation of ozone and reacting it
immediately with the wastewater contaminants.
In the United States, researchers at Kansas State University
have developed a novel porous electrode system for the
generation and reaction of ozone with contaminants in aqueous
phase. The in situ ozone generator is based on a novel type of
corona discharge tube design, wherein the discharge gap is
kept juxtaposed to the tubular pathway through which the
treatment fluid is passed. Ozone is generated around the
periphery of the porous electrode tube and diffuses
immediately into the contaminated fluid flowing inside the
tube. The inner porous ceramic tube is grounded and the outer
glass electrode positively charged to enable corona discharge.
Contact: Mr. Alexander P. M./Mr. Kishora K. Panda, Civil
Engineering, Kansas State University, Fiedler Hall, KS 66506,
Manhattan, United States of America.
Website:
www.aiche.confex.com |
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Biological process for nitrogen removal |
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Several nitrification/denitrification methods are available
for ammonia and nitrate removal from municipal and industrial
wastewater. There are, however, few such methods for the
removal of these ions from metal-processing and finishing
wastewater. Researchers at Rhodes University, South Africa,
examined a biological process for this purpose. The system
comprises an aerobic continuously stirred tank reactor (CSTR)
followed by an anaerobic packed column. It was tested using
wastewater effluent of a metal-processing operation. The
proprietary system was inoculated using humus sludge from a
municipal trickling filter, and a period of approximately four
weeks was required for a denitrifying biofilm to develop.
Results have shown that ammonia removal occurs readily in the
CSTR while nitrite oxidation was slower to develop. The CSTR
was found to be suitable for ammonia oxidation: up to 89 per
cent ammonia removal was achieved. The gravel-packed column
reactor was not found to be suitable for nitrate removal in
the configuration used (maximum 15 per cent removal
efficiency). Critical parameters for denitrification include
nitrate concentration, temperature, mean cell retention time
and influent flow rate.
Contact: Ms. Joanna E. Burgess, Dept. of Biochemistry,
Microbiology and Biotechnology, Rhodes University, Grahamstown
6140, South Africa.
Website:
www.wrc.org.za
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Advanced treatment for textile wastewater |
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In China, researchers have studied a method that integrates
electrochemical oxidation and membrane filtration to treat
wastewater from the textile industry. The team employed a
modified transfer-flow membrane (TFM) module, with fibres
welded in an arc shape to raise mechanical properties of the
fibres as well as enhance the TFM module’s specific membrane
surface. The research focused on evaluating performance of the
arc-shaped TFM module to demonstrate these sequences of
electrochemical oxidation coupled with membrane filtration
processes and to develop a potential dye-house wastewater
treatment system.
Two testing sequences of electrochemical oxidation and
membrane filtration were studied in a sequential batch order.
Results have shown that fibres welded in an arc shape enhance
the mechanical properties of the fibres effectively. Also,
electrochemical oxidation and membrane filtration are feasible
as sequential methods. Electrochemical oxidation has high
removal efficiency (89.8 per cent) of the wastewater’s
chemical oxygen demand (COD), while the membrane filter can
almost totally – nearly 100 per cent reduction – remove the
total suspended solids (TSS) and turbidity (98.3 per cent
elimination) in it.
Contact: Mr. Yaobo Fan, Research Centre for the
Eco-environmental Sciences, Chinese Academy of
Sciences, Shuangqing Road 18, Beijing 10085, China; Or Mr.
Xuejun Chen, Shanghai Jiaotong University, Dongchuan Road 800,
Shanghai, 200240, China.
Website:
www.wrc.org.za |
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Wastewater treatment plant for electronics
industry |
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The chemicals used by each printed circuit board (PCB) shop
differ. As such, each generate different liquid waste with
metals and other contaminants. Kurion Technologies Ltd., the
United Kingdom, offers a range of standard stand-alone
technologies that can be combined to treat different types of
wastewater from the manufacturing facilities.
The simplest treatment is a metal precipitation process
designed to meet discharge limits. This “end-of-pipe” concept,
the lowest capital cost option, utilizes proprietary two-step
reaction system in combination with cyclone settlement
technology. Limits of 1.0 ppm copper and 0.4 ppm lead are
achievable. Additionally, up to 0.1 ppm copper and 0.1 ppm
lead is feasible with IX polishing technology. Much more lower
limits can be realized by special chemistry and waste
segregation techniques.
Kurion’s batch treatment system or TREAT-RESIST treats other
wastes such as permanganate of dry film stripper and developer
dumps. Metal recovery and sludge minimization combined with
guaranteed effluent compliance is feasible. Treatment of
copper solution is accomplished by recirculating the fluid
through an electrowinning cell, thus depositing copper on to
the cathodes. Kurion has developed a plate-out cell suitable
for treating a variety of spent solutions. Typically, over 90
per cent of the metal is recovered from each individual bath.
Other systems from Kurion include:
- IX/ER system for copper recovery from rinses and low
copper ores;
- The lead-resin system, a cost-effective option to treat
lead bearing rinses; and
- Electroless Nickel IX wastewater treatment plant for the
treatment of electroless nickel. The ion exchange process
employs a proprietary resin to capture nickel to comply with
discharge limits below 0.5 ppm.
Contact: Kurion Technologies Ltd., 43, Brunel Close,
Drayton Fields Industrial Estate, Daventry, Northants NN11
8RB, United Kingdom. Tel/Fax: + 44 (1327) 876 600/705 131
E-mail:
info@kurion.co.uk
Website:
www.kurion.co.uk |
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Cryomagnets for wastewater treatment |
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A purification system developed by Prof. Shigehiro Nishijima
and others at Osaka University, Japan, utilizes cryomagnets to
treat wastewater from recycled paper plants. In this process,
magnetite or iron oxide particles added to the wastewater
react with impurities in the waste-forming magnetic compounds.
The compounds are then attracted to a stainless filter under
the intense magnetic force of a niobium titanium cryomagnet
when the wastewater passes through the filter. Both the size
and cost of the new system are less than half that of existing
units, typically based on activated sludge method.
Website:
www.uknow.or.jp |
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Extracting metal fluoride from waste |
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R&F Co. Ltd., Republic of Korea, offers technology to recycle
fluorine-containing wastewater produced by the semiconductor
industry. In this procedure, a metal fluoride reactor tank is
constructed as part of the existing wastewater treatment
process, which produces metal fluoride through precipitation
and filtration. Additional metal fluoride is obtained by
eliminating fluoride ions left from the filtered water,
utilizing calcium hydroxide sludge. Fluorine ion
concentrations less than 3 ppm can be achieved. High-purity
metal fluoride thus reclaimed could be used as a solvent for
fluoride glass, a solvent for metal fluoride welding rods and
as an electrode material for lithium batteries.
Contact: R&F Co. Ltd., 1-139, College of 220 Kung-dong,
Yusong-gu, Daejeon city, Republic of Korea. Tel: +82 (42) 8216
692; Fax: +82 (42) 8221 331
E-mail:
bjs123@empal.com
Website:
www.rnf21.co.kr
Website:
www.eng.me.go.kr |
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Treating industrial/municipal wastewater |
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Waterleau, Belgium, is offering a so-called hybrid system that
combines the benefits of conventional wastewater treatment and
SBR methods. Lucas®, a cyclic activated sludge system, in its
basic configuration comprises three reactors, all with a
similar design and equipment. The reactors are interconnected
through openings in common walls. Influent can be sent to each
reactor, just as the effluent can be discharged from them
individually. In each basin, the desired process environment
can be created – aerobic, anoxic, anaerobic or sedimentation
state. Individual inlets and outlets can be automatically
closed/opened. Influent is fed directly to the reactors. Each
basin includes a combined feeding-and- aeration phase, an
aeration phase and a sedimentation phase. Thus, each reactor
is subsequently:
- Fed and aerated;
- Aerated; and
- Not aerated in order to facilitate sedimentation.
Effluent and excess sludge are withdrawn from the reactor
that is in sedimentation. The length of the phases can be
adapted according to hydraulic and organic loading.
Contact: Waterleau, Radioweg 18, B 3020 Herent (Leuven),
Belgium. Tel/Fax: +32 (16) 650 657/663
E-mail:
info@waterleau.com
Website:
www.water-leau.com |
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Desalination of organic wastewater |
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Research has been carried out in China to assess the efficacy
of an evaporation crystallizer for desalinating alkaline
organic wastewater. Researchers devised a wastewater
evaporation-desalination pretreatment method to remove
potassium (K) and sodium (Na) in wastewater that contains
volatile organic compounds (VOCs) before it is passed on to
the incinerator. VOCs in the wastewater volatilize in the
evaporation unit and the ensuing vapours get combusted in the
incinerator. In a simulation, phenol wastewater with sodium
chloride (NaCl) was evaporated and concentrated, and NaCl
crystallized. Results have demonstrated that the higher
initial density of NaCl increases the ratio of volatilization
of VOCs. This is due to the effect of “salting out” – a fall
in the solubility of the non-electrolyte in solution, or more
rigorously, an increase in its activity coefficient – caused
by the salt addition.
When the evaporation speed was increased from 1.67 ml/min to
2.73 ml/min, total removal coefficient of NaCl was 99.88-99.99
per cent. This pretreatment eliminates slag phenomenon caused
by Na and K salts during incineration of wastewater.
Contact: Mr. M.A. Jing-ying, City Construction Department,
Zhejiang College of Construction, Hangzhou 311231, China.
E-mail:
majy75@163.com
Website:
www.zju.edu.cn |
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Purification of tannery effluent |
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At the University of Waikato, New Zealand, a new electrolytic
effluent processor that enables purification of tannery
effluents has been designed by a research team. The
specialized proprietary prototype effluent processor, which is
based on a novel anode design, was tested extensively and
satisfactory results obtained during continuous inline
operation, despite wide variation in the composition of the
inflow. Over 90 per cent removal of chromium from solution,
with similar reductions in turbidity, were achieved at lower
operating cost, residual aluminium and total aluminium
addition than by dosing with usual commercial aluminium-based
flocculants such as poly-aluminium chloride.
While the system performed well under conditions of a real
tannery, the mechanism of operation was difficult to discern
in the field. This was due to the numerous types of compounds
in the effluent and the rapidly varying absolute and relative
levels of the component impurities. Particularly, the
excellent results with low residual aluminium at pH in excess
of 9.5 was unexpected, given the high solubility of aluminium
at that pH. Also, the effect of pulsed voltage waveforms was
trialed at the tannery, but any effects were swamped by the
rapid variations in the effluent content.
Contact: Mr. Alan Langdon, Chemistry Dept., University of
Waikato, Private Bag 3105, Hamilton, New Zealand.
Website:
www.ecsmeet2.peerx-press.org |
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Membrane modules to treat wastewater |
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Koch Membrane Systems Inc., the United States, is offering
PURON® submerged membrane modules for membrane bioreactor (MBR)
treatment of municipal and industrial wastewater. These
technologically advanced membrane modules raise water quality
while needing less space than conventional alternatives.
PURON’s patented module design provides reliable removal of
filtered material. Hollow fibre membranes, 2 mm in diameter
with a pore size less than 0.1 µm, are bundled in a single
header at their lower end. Each hollow fibre membrane filter
is sealed at the upper end and left to float freely. The
filter membrane is coated on a braid, increasing the
mechanical strength of each fibre to ensure that they do not
break or delaminate. Water flows from the outside to the
inside of the filters. Solids and particulates, including
bacteria, are blocked and remain on the outside, while the
permeate is withdrawn from inside the fibres.
Contact: Koch Membrane Systems Inc., 850-T Main St.,
Wilmington, MA 01887, the United States. Fax: +1 (978) 6575
208
E-mail:
info@kochmembrane.com
Website:
www.kochmembrane.com
Website:
www.news.thomasnet.com |
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