Ae35171177

Unity Oviasogie Int. Journal of Engineering Research and Application www.ijera.com
Vol. 3, Issue 5, Sep-Oct 2013, pp.171-177
www.ijera.com 171 | P a g e
Aeration Treatment of Membrane Concentrates Of TMP
Wastewater
Unity Oviasogie*
*Water Resources and Engineering Management Pfaffenwaldring 7, 70569 Stuttgart, Germany.
ABSTRACT
The aim of this research paper is to investigate the chemical oxygen demand (COD), biological oxygen demand
in 5 days (BOD5), suspended solids (SS) denoted as “food” (F) to biomass (M; microorganism) ratio (F/M), by
targeting varying rate of influent stream. The experiment initially consisted of two acrylic cylinders with cone-
shape bottom with an inner diameter of 20 cm and 65 cm, respectively. The setup is fitted with a heater and
aeration system. Temperature of wastewater range is maintained at 30 – 36 degree Celsius to promote the
growth mesophilic microorganism. COD had its highest elimination rate on day 39 at 83% at an influent rate of
13.96 litres per day. COD mf result showed the highest elimination rate on day 39 at 78% with influent rate of
13.96 litres per day. Biological oxygen demand in 5 days (BOD5; BSB5) result showed the highest elimination
rate on day 43 at 94% with influent rate of 19.98 litres per day. The suspended solids (AFS; SS) result showed
the highest elimination rate on day 39 at 98% with influent rate of 13.96 litres per day. The results attained from
absorbance denoted as DFZ436, DFZ525, DFZ620 exhibits the highest elimination rate on day 44 at 72%, 78%
and 59% respectively with a constant influent rate of 19.98 liters per day
Keywords: Biological Oxygen Demand (BOD5); Chemical Oxygen Demand (COD); Continuous Biological
Treatment (CBT); Suspended Solids (SS, AFS); Sequential Batch Reactor (SBR); Thermal Mechanical Pulping
(TMP)
I. INTRODUCTION
Directive 2008/1/EC on integrated pollution
prevention and control covers industrial plants for the
production of pulp and paper and cardboard with a
production capacity exceeding 20 tonnes per day
[1].The application of European Union (EU) policies
on the pulp and paper sector and heighten awareness
of the challenges waste management. The application
of biological waste management process is common
in the pulp and paper industry, but some drawbacks
are associated with these methods. Challenges
include, the large area required for the aerobic
process, the difficulty in controlling the population of
microorganisms and the rigorous control parameters
i.e. pH, temperature, DO and nutrients. In addition to
biological treatment process is the optimization of
physical filtration of wastewater through the
application of continuous pressure to drive water
molecules through a membrane that is not permeable
to the target substances. The application of membrane
filtration by ultrafiltration (UF) and nanofiltration
(NF) to pulp and paper manufacturing and treatment
process reduces dissolved substances i.e. organic and
inorganic, microorganisms and color. Ultrafiltration is
considered an important treatment step in the
hierarchy of conventional industrial thermal
mechanical pulping wastewater treatment schemes. It
is the main membrane process employed by the pulp
and paper industry and serves as the primary steps in
membrane treatment process [2]. The effectiveness of
ultrafiltration process is measured by its extraction of
large molar mass of ligneous substances, a compound
found in TMP wastewater. Nanofiltration removes
most of the organic load and also the multivalent
ions, such as calcium, iron, aluminum, silicon,
magnesium and sulfate. [3][4]. Nanofiltration is
applied in the treatment of thermal mechanical
pulping or TMP and Deinking wastewater in order to
attain high retention of lignin before immediate
continuous biological treatment by means of
activated or aerated sludge in an aerobic
environment. The efficiency gains can be attributed
to the efficacy of ultrafiltration method in removing
higher molar mass compounds and microorganism,
thereby accelerating the efficiency of nanofiltration in
the consequent filtration step. It is also widely
believed that the choice of specific membrane filters
and their design also have an influence on energy
requirements and overall efficiency thereby removing
problematic constituents of industrial wastewater
from the pulp and paper. The aim of this paper is to
investigate the efficacy of aerobic activated sludge
system in the continuous biological treatment of TMP
concentrate wastewater from the pulp and paper
industry.
i. Membrane Resistance and Reduction of
Efficiency
The widespread application of membrane
treatment processes has been very efficient in
reducing toxic emissions to the water bodies. The
tendency of the membranes to become fouled, or
RESEARCH ARTICLE OPEN ACCESS

blocked, by colloidal and other substances in
wastewater is unavoidable. Fouling is not only
limited to colloidal constituents. Biological fouling
has steadily become an increasing issue in membrane
treatment process. This occurs when various
microorganisms can become deposited on membrane
surfaces. The bioavailability of nutrients and alkaline
environment may promote growth of microorganism
and cause membrane fouling. [5]
ii. Continuous Biological Treatment (CBT) of
TMP Membrane Concentrates with Aerated
Sludge System
The continuous biological treatment (CBT)
system is continuously supplied dissolved oxygen as
part and parcel of the activated sludge process. The
wastewater in the aeration tank (see Figure 2) was
provided oxygen at a minimum of 2 mg/min (peak
aeration at 5mg/min) to meet the sludge demand and
promote microorganism growth and BOD, COD
degradation [3]. The efficacy of activated sludge in
industrial wastewater treatment is proving widely
because of its effectiveness in reduction of measured
wastewater parameters of interest in the effluent. Its
high removal rate of toxic substances and efficacy
has made the activated sludge treatment system an
efficient means of emission reduction, water
conservation and management. Aerobic treatment of
activated sludge systems increases degradation of
total, settled and soluble COD in the effluent with
high organic loading rate and low nutrient levels
[6].The high organic degradation during the course of
aerobic treatment leads to an increase in the sludge
production. It is best to monitor the sludge in the
clarifier and withdraw occasionally to prevent excess
suspended solids (SS) in the effluent.
The continuous biological treatment (CBT)
reactor (as seen Figure 2) is used in all the
experimental runs. The CBT reactor is composed of a
reactor (aeration tank), sedimentation tank
(denitrification tank or clarifier) and reverse sludge
recycling system. For example, mixed liquor
suspended solids (MLSS) is the mixture of
wastewater and microorganism in the activated
sludge in the aeration tank until the adequate F/M
ratio is reached. Continuous aeration by dissolved
oxygen (DO) is used to promote microorganism
growth through biological reaction. The MLSS is
later separated to a liquid and solid phase in the
sedimentation tank where the aeration is turned off to
promote denitrification. The supernatant flows out of
the top of the sedimentation tank as effluent while the
settle solids at the bottom is recycled back to the
aeration tank with the assistance of a vacuum pump.
Volume recovery (VR) of wastewater is
symptomatic after membrane filtration. Volume
recovery factor in relation to membrane technology is
characteristic of feed volume used to study the
membrane performance during ultrafiltration and
nanofiltration. For example, ultrafiltration process
yields a VR of about 0.9 or 90% of permeate leaving
10% reject [4] [8].
II. MATERIALS AND METHOD
Two stage membrane filtration processes
was used to obtain concentrated wastewater. Ultra
filtration materials and methods were used to obtain
10% concentrated reject which was subjected to
subsequent nanofiltration to attain 18% concentrated
reject, and then stored separately. The treated influent
was a mix of 10% and 18% permeate representative
of the 2 stage filtration process as shown in Figure 1.
Figure 1: 2-Stage Membrane (UF-NF) filtration
process
The experiment was performed in a (CBT)
reactor (Fig. 2) in a laboratory in WWTP Büsnau.
The wastewater was delivered to WWTP Büsnau by
Pulp and Paper mills around Baden Württemberg,
Germany. The CBT apparatus consists of two 50
liters volume capacity acrylic cylinders with an inner
diameter of 20 cm and 65 cm with cone-shape
bottom, and attached to water heater and aeration
system. The temperature of wastewater ranges
between 30 – 36 degree Celsius and thermostat are
used to continuously to maintain constant and
optimal temperature to promote the growth of
microorganism. Metabolic rate of all biological
systems is affected by temperature. Biochemical
reactions proceed more rapidly with increasing
temperature. The treatment efficiency of anaerobic
processes compared with aerobic processes is
particularly sensitive to operation below optimum
temperatures, because of the significantly lower
substrate removal rate constants discussed above.
Considering the relatively high temperatures of many
pulp and paper mill process streams (50 to 85 degrees
C), operation of anaerobic treatment systems in the
optimum range of 55 to 60 degrees Celcius for
thermophilic bacteria has been investigated, but as
yet has not been found to be effective. Mesophilic
temperature range (30-35 o
C) was found to be most
effective.
Nutrients, phosphorus (P) and nitrogen (N)
were added to influent wastewater prior to the onset
each experimental run. Phosphorus was added in the
form potassium dihydrogen potassium phosphate
(KH2PO4) and nitrogen in the form of urea
(NH2CONH2) at a dosing ratio 100C:5N:1P. [6]

Nitrogen (N) and phosphorus (P) are essential
nutrients required for the growth of microorganism
which in turn synthesize new biomass. Beside the
widely used nutrients, nitrogen and phosphorus.
Microorganism also requires available macronutrients
(S, K, Mg, Ca, Fe, Na, and Cl) and micronutrient
(Co, Ni, Zn, Mn, Mo and Se) for growth. Nutrients
in the form of ammonium NH2NH4 and di-hydrogen
potassium phosphate KH2PO4 are added to the
influent wastewater based on measured BOD5
concentration at the start of each run.
Bulking, characterize by floating sludge
blanket, is a commonly known operational problem
in activated sludge plants treating pulp and paper
wastewater. The best way to deal with bulking is
longer adaptation time (long sludge age) which
promotes optimal microorganism, and daily discharge
through sampling of MLSS and MLVSS. This help in
monitoring suspended solids (SS) in the system. The
sludge volume index (SVI) was measured in 250-500
mL graduated glasses by settling samples, with
known SS, for 30 minutes (German ATV DVWK-
131A 2002) as shown in Table 1. Total Suspended
Solids (t ss) is defined as those solids which are
retained by a filter paper and dried to constant weight
at 103-105 degrees Celsius. A modification of filter
paper was used to collect particulate and dried. The
filter paper is left to dry for 24 hours and desiccated
for 2-3 hours minimum then weighed.
Figure 2: Continuous Biological Treatment (CBT)
TMP influent wastewater pH varied from 4
to 9. Therefore buffers were employed in regulation
to desired pH of 6-9 value for each respective
experiment. The acid and base buffers used are
Sulfuric acid (H2SO4) 1M and Sodium Hydroxide
(NaOH) 32%. Influent wastewater pH value of the
was adjusted from 4 to range of 7-8 at the beginning
of each experiment and readjusted as needed to
maintain the optimal range through the experimental
period Dissolved oxygen (DO), pH, and temperature
in the reactors were measured typically on a daily
basis. In the laboratory studies DO was measured
using a YSI Jenway 9300 DO-meter, pH and
temperature were measured using a Hanna
Instrument 6028 pH meter.
Dissolved oxygen (DO), pH and temperature
were measured every experimental day and sample
was taken before mixture at the start of each
experimental day at the top of the aeration tank
(reaction tank) for measurement of MLSS and
MLVSS. The measurement of effluent parameters
chemical oxygen demand (COD), soluble chemical
oxygen demand (COD mf), biological oxygen demand
(BOD5), suspended solids (SS, AFS), and absorbance
(DFZ) was performed through sampling, at a
minimum rate of three times every week.
Table 1: German Standards ATV-DVWK-131A
2002 for Wastewater Analysis
Influent parameter were taken 1 to 3 times
per experimental period dependent on length of the
experimental period and change in biodegradability
of influent concentration, and the availability of staff
to do the extra analysis. Total Kjelhdahl Nitrogen
(TKN) and Total Phosphorus (Ptot) were sampled and
at experimenter’s discretion of F/M results and
amount present in the effluent sample. Sampling of
listed parameters was carried out 1-3 times a week
and daily operation parameters were performed to
ensure the functionality and integrity of the
continuous biological treatment systems. The influent
rate was monitored constantly and changed at
author’s discretion.
Parameters Abbrevia
tion
Uni
t
DIN
Chemical oxygen
demand
COD mg/
L
DIN
38409
Teil 41-2
Soluble chemical
oxygen demand
COD mf mg/
L
DIN
38409
Teil 41-2
Biochemical
oxygen demand in
5 days
BOD5
(BSB5)
mg/
L
DIN
38409
Teil 52
(8-2)
Suspended solids SS (AFS) mg/
L
DIN
38409
Teil 2-2
(5.2)
Mixed liquor
suspended solids
MLSS mg/
L
DIN
38414
Teil 10
Mixed liquor
volatile suspended
solids
MLVSS mg/
L
DIN
38414
Teil 10
Total phosphorus P tot mg/
L
DIN
38405
Teil 11
Total Kjeldahl
nitrogen
TKN mg/
L
DIN EN
25663
pH pH - DIN
38404
Teil 5
Dissolved Oxygen DO mg/
L
DIN EN
25814
Temperature T o
C DIN
38404
Teil 4

III. RESULTS
The growth of microorganism are seen in
four phases; lag, log (growth), stationary and death
phase with slight alteration based on varying
chemical conditions in wastewater. The time needed
to adapt to wastewater characteristics is the lag
period, enzymes and it substrates to produce and
sustain a growth phase (log). This is characterized by
steady predation and succession of competing
microorganism success in adaptation to changing
wastewater parameters, substrate optimization and
metabolism. This success of emerging species leads
to decline in wastewater and death. An increase in the
BOD of a sample due to the pretreatment would
indicate its greater amenability to biodegradation.
Thus, an increase in BOD/COD and BOD/TOC ratios
after pre-treatment is indicative of improved
biodegradability due to an enhancement in the
proportion of COD or TOC amenable to biological
mineralization. The relationship of BOD and
BOD/COD or BOD/TOC are commonly used Kinetic
studies based on Monod model have also been
developed. [9]
In aerobic treatment process,
microorganism, through three main processes;
oxidation, synthesis, and endogenous respiration uses
organic matter (biomass) to produce energy. An
example of this is exhibited by chemoautotrophs,
Nitrosamines in the nitrification process.
Microorganisms, in aerobic environment, ammonia
are converted into nitrate in two steps: conversion of
ammonia into nitrite, and then subsequent oxidation
of nitrite into nitrate by Nitrobacteria. Chemo
heterotrophs microorganism species involved in other
conversions are bacteria, fungi, algae, protozoa and
metazoans (flagellates or ciliates) [3] [9]. Fungi and
algae are competes for food , aerobic suspended
growth process and lower pH gives fungi an
advantage over algae at lower pH yielding lower
algae in the process. Protozoan and metazoans like
rotifers and nematodes’ makes up the secession of the
activated sludge process [9]. The objective of these
organisms revolves around solid formation,
saprophytes, nitrification, predation and secession. A
pH of 6-9 is optimal for carbonaceous removal. A
constant pH range of 7-9 was maintained in all
experimental phases. Although TMP and De-inking
wastewater had a pH of 4 or lower; readjustment of
pH was performed trough addition of Sodium
Hydroxide (NaOH); consequently increasing the pH
to increase microbial growth. An acidic wastewater
characteristic drastically reduces microbial growth;
therefore, antithetical to the activated sludge process
because microorganism cannot survive under high
acidic conditions.
Increased secession by nuisance
microorganism can be cause of sludge blankets,
forming and excessive sludge bulking. During the
course of the experimental work, experiences with
nuisance microorganism in biological reactor led to
longer adaptation periods and reduced influent rate.
F/M ratio is the relationship of substrate removal to
biomass is often termed the food-to-microorganism
or food-to biomass (F/M) ratio. The influence of the
F/M ratio on the COD load elimination and effluent
COD concentration is to be considered. The F/M
ratio is calculated by the following formula
F/M =
Where:
F: M : food to microorganism ratio (g BOD5/g
MLSS)
V1 : liquid volume of the reactor, V1 = V in +
Vs1 (liters)
V in : volume of the influent (liters)
V s1 : volume of the sludge fed in the reactor (L)
BOD5, in : BOD5 concentration in the influent (mg/L)
MLSS : mixed liquor suspended solids in the
reactor (mg/L)
SS in : suspended solids concentration in the
effluent (mg/L)
T : aeration time (days)
MLVSS instead of MLSS may be more viable in
estimation of the amount of substrate applied on the
amount of active biomass. MLSS was chosen in
accordance with the German Water Quality Standard
(ATV-DVWK-131A, 2002).
The carbonaceous organic matter removal capacity of
the aerobic reactor is expressed by COD
concentration elimination rate. It is calculated by the
formula below:
E = ]
Where:
E : COD elimination rate (%)
COD eff : COD concentration in the effluent (mg/L)
COD R : COD concentration in the reactor (mg/L)
COD R is calculated as follows:
COD R =
Where:
COD in : COD concentration in the influent (mg/l)
COD s : COD concentration in the sludge volume
(mg/l)
Sludge age is calculated according to the formula
below:
t ss =

Where:
T ss : sludge age (day)
MLSS ES: mixed liquor suspended solid in the excess
(mg/L)
V ES : excess sludge flow (liters/day)
V sample : sampling volume per day (liters/day)
SS eff : suspended solids in the effluent (mg/L)
V eff : clear effluent flow decanted from the
reactor (liters/day)
These studies were carried out in a
continuous activated sludge system for short periods
with variable feeds. Sludge Retention Time (SRT)
characteristics are an estimate of the biomass growth
yield on COD indicates slight decrease in yield at
higher temperature operations. The possible
explanation for lower cell yield at higher temperature
is due to higher endogenous respiration which means
more COD is used by cell bacteria for their cell
maintenance (endogenous respiration) and less for
cell growth. COD is the main parameter which is
used to evaluate the carbonaceous organic matter
removal capacity (see Figure 3). COD analysis was
performed on the effluent of every experiment. COD
mf was measured to assess the effect of SS content in
the effluent on the COD elimination [10]. COD mf
analysis was performed in all stages of the
experimental period and served as an indicator of true
COD values. BOD5 was measured to evaluate
whether the effluent was fully biodegraded after the
experiment. And the analysis of Ptot and TKN
(Figures not shown) was performed in order to check
if the nutrients were sufficient for the
microorganisms during the experiment. BOD5, Ptot
and TKN were samples were measured randomly.
Biomass can be found smaller or larger
aggregates of free-living microorganism. SS in the
form of aggregates would interfere with the treated
wastewater effluent quality, as well as the production
process and therefore have to be removed before
reusing the water. The presence of free-living
bacteria may not affect the product quality
negatively, but a high number may decrease the
drainage rate and therefore influence the efficiency of
the treatment process. Therefore, the application of a
functioning clarifier will most likely be needed in all
cases for the optimum removal of SS. The removal
efficiency and the final amount and character of the
remaining suspended solids will probably differ from
case to case.
Table 2: Analysis Results of Influent and Effluent
Parameters of TMP concentrate-Aerobic
treatment
Parameter Unit Influent Effluent
COD mg/L 6410 -
6320
2460 - 639
CODmf mg/L 5000 -
4660
2070 - 600
BOD5 mg/L 2240 - 270 - 28
1914
BOD5/COD - 0.34 - 0.30 0.11 - 0.04
SS mg/L 1230 -
1165
310 - 20
Parameter Unit Influent Effluent
DFZ436 1/m 41.5 - 25.4 92.1 - 32.8
DFZ525 1/m 27.4 - 13.7 64.9 - 17.1
DFZ620 1/m 16.5 - 10.7 35.6 - 13.4
TMP concentrate experiment by aerobic
treatment was started on day 33 to 45 on the second
experimentation phase of industrial wastewater
treatment. The results of COD parameter showed the
highest elimination rate on day 39 at 83 % with an
influent rate of 13.6 liters per day. Meanwhile COD
mf also experienced its highest elimination rate the
same day at 78 % also with an influent rate of 13.6
liters per day as shown in Figure 4.
5. VARIABLES AND EQUATIONS
All variables should be italic through the text. All
equations should be placed on separate lines and
numbered consecutively.
The highest elimination rate within the
experimental period was shown in the BOD5
parameter. Results as shown in Figure 5; exhibit the
highest elimination rate on day 43 at 94 % with
influent rate of 19.98 liters per day reinforcing the
efficacy of biodegradability. Suspended solids
denoted as AFS had the highest elimination rate on
day 39 at 98% with influent rate of 13.96 liters per
day as shown in Figure 6. This indicates that there
was almost no suspended solid in effluent sample.
The absorbance spectrum was analysed at three
wavelengths 436, 525, 620 nm, respectively. DFZ436
(Figure 7) showed the highest elimination rate on day
44 at 72% with influent rate of 19.98 liters per day.
The absorbance DFZ525 analysis results (Figure 8)
shows higher elimination rate at a moderate
wavelength on day 44 at 78%, and DFZ620 results
(Figure 9) on the same day 44 at 59%.

0
20
40
60
80
100
0
1000
2000
3000
4000
5000
6000
7000
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Eliminationrate(%)
Concentration(mg/l)
F/M (g BOD5/(g SS. D)
Figure 10: TMP Con-Ana-Aer
Cod effluent CODmf Effluent BOD5 Effluent COD influent COD elimination rate Influent Vol l/d
The food to microorganism (F/M) ratio was
well targeted throughout the TMP concentrate
experimental phase. The results shows that the
highest influent rate at 19.98 liters per day influence
a higher food to microorganism ratio and higher COD
elimination rate.
IV. CONCLUSIONS
Due to environmental regulation, the pulp
and paper industry uses a lower volume of process
water today, and recycles and reuses more water, and
cleans water before releasing it to the environment.
This treatment method is referred to as an end of pipe

technology non-distributed wastewater cleanup and
treatment technologies. The treatments of concern are
physical (dissolved air flotation) and a combination
of physical and membrane treatment (i.e.
ultrafiltration), which remove suspended solids from
the effluent [10]. This is made possible by the
application of membrane technology in the treatment
process. This practice is also a strategy in cost
reduction which is primarily based on the amount of
water consumed. The pulp and paper industry has
made advancement in treatment techniques through
the use of new and applicable technology to reduce
its environmental impacts. The intermittent
application of membrane technology in the treatment
process also plays an important role in decreasing
freshwater withdrawal but increases the toxicity of
permeate retained; Hence, the necessity for
efficacious activated sludge treatment. The activated
sludge, used as inoculum, is collected from the return
sludge of local municipal sewage treatment plant i.e.
WWTP Busnau [11].
TMP wastewater stream passing through one
or more membranes and being concentrated in the
stream permeate. The treated effluent is less
concentrated. The experiment utilized the more
concentrated reject. The results, as shown in Figure
3-9, show that the activated sludge system in
combination with continuous biological treatment
was very efficacious in removal of carbonaceous
organic and inorganic matter. With elimination rate
peaking at 98% for certain parameters, the author
concludes that membrane concentrate of industrial
wastewater from pulp and paper industry were
biodegradable under certain optimal conditions i.e.
long sludge retention time (SRT) or sludge age,
constant maintenance of mesophilic temperature, DO,
and daily operations parameters [12]. One of the
major problems encountered during activated sludge
treatment of pulp and paper concentrate is poor
sludge settling characteristics better known as
bulking. Settling ability is dependent on the
structure and type of sludge flocculation, which is in
turn dependent on environmental conditions and
process operating parameters. Therefore, the
temperature effect on sludge settling and a better
understanding of microbial flocculent also becomes
important for improving the performance of these
effluent treatment systems. All experimental
parameters achieved high elimination rate after
continuous biological treatment combine with
activated “aeration” sludge system.
V. REFERENCES
[1] Commission of the European Communities
Brussels, 30.7.2009 Sec (2009) 1111 Final
Commission Staff Working Document
European Industry in A Changing World
Updated Sectoral Overview 2009 Section 26.
Pulp, Paper And Paper Products
[2] J. Nuortila-Jokinen, M. Mänttäri, T. Huuhilo,
M. Kallioinen And M. Nyström; Water Circuit
Closure With Membrane Technology In The
pulp And Paper Industry; Water Science &
Technology Volume 50 No 3 217–227 © IWA
Publishing 2004
[3] Industrial Waste Treatment Handbook Second
Edition By: Woodard & Curran, Inc. © 2006
Elsevier
[4] Jutta Nuortila-Jokinen,Tina Huuhilo, and
Marianne Nyström, Closing Pulp And Paper
Mill Water Circuits With Membrane Filtration
Ann. N.Y. Acad. Sci. 984: 39–52 (2003). ©
2003 New York Academy Of Sciences.
[5] Nuortila-Jokinen, M. Nystron, Comparison of
Membrane Separation Processes in the Internal
Purification of Paper Mill Water. Journal of
Membrane Science 119 (1996) 99-115
[6] Ess Method 340.2: Total Suspended Solids,
Mass Balance, Volatile Suspended Solids;
Environmental Sciences Section Inorganic
Chemistry Unit, Wisconsin State Laboratory of
Hygiene, 465 Henry Mall, Madison, WI 53706
Revised June 1993
[7] S. Contreras, M. Rodrıguez, F. Al Momania, C.
Sansa, S. Esplugas; Contribution of the
ozonation pre-treatment to the biodegradation
of aqueous solutions of 2,4-dichlorophenol;
Water Research 37 (2003) 3164–3171
[8] A.-S. Jönsson, O. Wallberg Cost estimates of
kraft lignin recovery by ultrafiltration
Desalination 237 (2009) 254–267
[9] Goksen Capar, Levent Yilmaz, Ulku Yetis
Reclamation of acid dye bath wastewater:
Effect of pH on nanofiltration performance
journal of Membrane Science 281 (2006) 560–
569
[10] Anantha P.R. Koppol, Miguel J. Bagajewicz,,
Brian J. Dericks, Mariano J. Savelski, On zero
water discharge solutions in the process
industry, Advances in Environmental Research
8 (2003) 151–171
[11] Muhammad Afzal, Ghulam Shabir, Irshad
Hussain, Zafar M. Khalid, Paper and board
mill effluent treatment with the combined
biological–coagulation–filtration pilot scale
reactor; Bioresource Technology 99 (2008)
7383–7387
[12] Vimal Chandra Srivastava, Indra Deo Mall,
Indra Mani Mishra; Treatment of pulp and
paper mill wastewaters with poly aluminium
chloride and bagasse fly ash Colloids and
Surfaces; Physicochem. Eng. Aspects 260
(2005) 17–28

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