Cp

Da

b

c

a

ARRA

KWFCPC

1

mnlw(tnwFlf

gpr2oaeFf

0d

Resources, Conservation and Recycling 55 (2011) 1139– 1145

Contents lists available at ScienceDirect

Resources, Conservation and Recycling

journa l h o me pa ge: www.elsev ier .com/ locate / resconrec

onservation of resources in the pulp and paper industry derived from cleanerroduction approach

arja B. Zarkovic a,∗, Vladana N. Rajakovic-Ognjanovic b, Ljubinka V. Rajakovic c

Belgrade Polytechnic College, University of Belgrade, Brankova 17, Belgrade, SerbiaFaculty of Civil Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, Belgrade, SerbiaFaculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade, Serbia

r t i c l e i n f o

rticle history:eceived 12 December 2010eceived in revised form 3 July 2011ccepted 7 July 2011

a b s t r a c t

This paper analyses the utilization of water and recycled fiber from waste paper for the production inone Serbian cardboard mill. Water and fiber consumption, wastewater generation and its characteristics,as well as sludge recirculation were monitored during production of various paper types, with differentgrade and weight. The aim was to evaluate production rationality and running stability concerning water

eywords:ater

iberonservationaper mill

and fiber utilization and possibilities for their conservation. Cleaner production measures inside themill and in the effluent treatment plant were suggested for the improvement of wastewater qualityand water conservation. Savings in water and fibers were estimated, with the respect to economic andenvironmental aspects of proposed cleaner production measures.

© 2011 Elsevier B.V. All rights reserved.

leaner production

. Introduction

The main feedstock in the paper production is lignocellulosicaterial – cellulose pulp, agricultural residues, waste paper, and

on-wooden materials. Beside this, the paper production requiresarge amounts of fresh water – up to 60 m3 t−1 of produced paper,

ith the generation of large quantity of heavily polluted effluentThompson et al., 2001; Gupta, 1997). The volume and the pollu-ion load of generated effluent depend on production technology,ature and purity of the feedstock, additive usage, the extent ofater reuse and the efficiency of water recycling (Tiku et al., 2007).

rom the view of the limited global resources and increasing popu-ation and industrialization, recovery of water and cellulose fibersrom the production process presents imperative for all paper mills.

Cleaner production is “the continuous application of an inte-rated preventive environmental strategy applied to processes,roducts, and services in order to increase eco-efficiency and toeduce risks to humans and the environment” (Abbasi and Abbasi,004). Some cleaner production approaches involve modificationf existing systems and processes, others involve entirely newnd innovative manufacturing methods or services that overcome

xisting technologies in terms of their environmental performance.or instance, lot of efforts have been made to reduce usage ofresh water and water system closure in the pulp and paper pro-

∗ Corresponding author. Tel.: +381 11 24 10 990; fax: +381 11 38 09 731.E-mail address: darjaz@sezampro.rs (D.B. Zarkovic).

921-3449/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.resconrec.2011.07.003

duction in past years (Pokhrel and Viraraghavan, 2004; Zarkovicet al., 2004). European Union Environmental Directive for Pulp andPaper Production commits producers to decrease fresh water con-sumption, which should be done by water recirculation and systemclosure (IPPC, 2001). Serbia’s national paper and cardboard millswill be faced to more stringent environmental pollution permits,requested from the European norms. National regulatory standardsfor wastewater discharge (NRS, 1978), based on category of recip-ient’s quality, are still valid and in usage.

For a few years, in the production of packaging paper, some millshave been running with a totally closed water system includingdifferent processes for water treatment in internal water cycles,so called ‘kidneys’ (Hamm and Schabel, 2007; Bulow et al., 2003).For some integrated paper mills, internal measures in the paperproduction (installation of additional vacuum extraction tanks,reduction of seal water utilized in the vacuum pumps and reductionof fresh water usage in felt showers) could be sufficient to obtainhuge savings in water, raw material and energy (Avsar and Demirer,2008).

Recycled fibers (RCF) from recovered paper are commonly usedin the paper and board production. This alternative source of fiberis rewetted in papermaking process and conveyed to pulp aftermulti-level cleaning, removing inks, adhesives, and other contam-inants. Paper and cardboard are made from pulp by deposition of

fibers and fillers (mineral additives used to improve paper opacity,strength, and smoothness) from a fluid paper suspension. Remov-ing of water from the pulp by pressing and drying is achieved in thesieve section of the paper machine. Primary or secondary sludge

1 ation

fi

ftwtsi2

di

•

•

2

2

csde

a

2

wc(i“

140 D.B. Zarkovic et al. / Resources, Conserv

rom effluent treatment plant inside the mill, can also be re-usedn paper production as raw material (Ochoa de Alda, 2008).

The investigated mill produces coated and uncoated cardboardrom recycled fibers (waste paper). The mill is located in cen-ral Serbia and provides water from the Sava river. The quality ofater and sediments of Sava and Danube is of significant impor-

ance. Water from these rivers is a source of drinking water supplyystems and possible anthropogenic contamination is related tondustrialization and inputs of sewage water (Crnkovic et al.,008).

Eco-efficiency of water and fiber utilization in paperboard pro-uction is the crucial interest of this study, which was conducted

n order to:

evaluate the utilization of water and fibers in various paper gradeproduction and to comply with economically and environmen-tally sustainable production andpropose and summarize technical measures for water and fiberconservation, based on cleaner production concept.

. Cardboard production and water system

.1. Production profile of the investigated mill

The mill has average daily output of 300 t of coated and uncoatedardboard with different weights. Main feedstock materials areorted and unsorted waste paper (recycled fibers), fillers, CaCO3,ifferent additives, sludge from the effluent treatment plant (ETP),tc.

Several cardboard grades with weights from 230 to 500 g m−2

re commonly produced, as shown in Fig. 1.

.2. The water system in the analyzed cardboard mill

The analyzed water system (shown in Fig. 2) is partially closed,ith an average water consumption of 24 m3 t−1. Primary recir-

ulation of water is provided on the paper machine sieve sectionlabeled in Fig. 2 as “sheet formation”). Secondary recirculationnvolves the dissolved air flotation (DAF) unit (labeled in Fig. 2 assave all – DAF”). Re-use and recirculation of water that is puri-

Fig. 1. Structure of various cardboard grades and

and Recycling 55 (2011) 1139– 1145

fied by the ETP (as a tertiary recirculation) has not hitherto beenrealized (Nassar, 2003).

The largest part of the fresh water is used in sheet formationon the cardboard machine (200 m3 h−1) and the smallest quan-tity is used in stock preparation (90 m3 h−1 for thickening). Whitewater from sheet formation and spent water from the thickenerare treated in the DAF unit. The treated water is used for differentoperations in stock preparation for pulping and multi-level clean-ing. Spent water from stock preparation (84 m3 h−1) and the papermachine (196 m3 h−1) are treated on ETP and discharged into theSava River.

2.2.1. Effluent treatment plantThe ETP presents physico-chemical treatment that includes

several successive processes, which provide for the removal ofsuspended solids, colloids, floating matter, color and toxic sub-stances by sedimentation enhanced by coagulants and flocculants.The overall objectives of the ETP are to separate the wastes fromthe water for disposal elsewhere and to produce an effluent whichcan be discharged to a receiving water body without pollution. Sep-arated solid waste, which is not suitable for reuse immediately, istemporary disposed.

Wastewater treatment in the ETP includes the addition of chem-icals to enhance the primary treatment: Al2(SO4)3 as coagulantand polyacrylamide (PAM) as a coagulation aid (flocculant). Theusual doses of Al2(SO4)3 are 400 mg L−1 and 3 mg L−1 for PAM. Thetype and doses of the chemicals were determined in a preliminaryinvestigation, when the company had a higher specific water con-sumption and a lower production capacity. The ETP was projectedfor 300 m3 h−1 of wastewater and 1500 mg L−1 of suspended solids.

Primary or mechanical wastewater treatment by gravity forcesis carried out for the removal of plastic and polystyrene pieces andsuspended solids, such as fibers, bark particles and inorganic parti-cles (fillers, lime particles, etc.). Particles which settle on the bottomof the primary clarifier form a sludge, which has to be evacuated andpotentially reused. This is achieved by pumping, in circular clarifiersin combination with bottom scraping. The sludge is normally low

in dry solids content, approximately 2% and has to be dewatered,if final disposal will be solution. Sludge from the primary clarifierhas suitable properties to be reused in the production process, formiddle layer of cardboard.

representative scope of production profile.

D.B. Zarkovic et al. / Resources, Conservation and Recycling 55 (2011) 1139– 1145 1141

s are

3

3

vaowpmdd

Efplwasaptg(

twiiSggpa

Fig. 2. The water system in the cardboard mill – dotted line

. Instrumentation and operating conditions

.1. Water issue

Water samples were collected during commercial production ofarious cardboard grades and average daily production of 300 t. Theverage water consumption was 24 m3 t−1 of product. The periodf the examination was from January to July 2009. This periodas sufficient to take into account all possible fluctuations in theroduction process and all kind of working routines which ulti-ately affect the effluent and sludge quality. Production in mill was

ynamic, sometimes with several changes in production programuring one day (various paper grades and weights).

Raw wastewater was collected from the equalization tank ofTP, before the addition of chemicals. Treated water was collectedrom the discharge pipe, as effluent to river. Wastewater from stockreparation and wastewater from cardboard machine were col-

ected separately. Inlet and outcome stream of present DAF unitere also considered. All samples were taken three times per day,

nd the mean values of analyzed parameters were taken as repre-entative. Water samples were collected in situ, handled carefullynd analyzed in the chemical laboratory within 3 h. Wastewaterarameters were determined according to Standard Methods forhe Examination of Water and Wastewater (APPHA, 1998). Inor-anic anions were determined by ion chromatography methodZarkovic et al., 2009).

Specific wastewater generation, SWG (expressed as wastewa-er volume per tone of dry product, m3 t−1) and TSS content inastewater present common parameters which should be mon-

tored according to NRS and BAT norms. These parameters presentndirect tool for monitoring of the water and fiber utilization.WG and TSS were analyzed and summarized for various paper

rades of the same weight and various weights of one chosen paperrade (grade A as the most commonly produced). Wastewater fromaper production was considered as wastewater from two sep-rate processes – stock preparation (SP) and cardboard machine

for the cleaner production measures (Zarkovic et al., 2011).

(CM), as well as common wastewater, which represent the inlet toETP.

Total suspended solids parameter (TSS) presents all suspendedsolids with a diameter larger than 1 �m (fibers, fillers, etc.) andcould be used as a control parameter for evaluating fiber utilizationand potential loses in raw material.

4. Results and discussion

All the available information sources (raw material purchaserecords, product quantities, water usage and wastewater dischargedata, sludge characteristics and its recycling data, etc.) were used togather the data for the materials balances. Average water usage perunit production and SWG were calculated by utilizing data gath-ered in the preliminary investigation of the mill. Present waterconsumption was found to be 24 m3 t−1 of the produced cardboard.

4.1. Wastewater character

Table 1 presents the results of wastewater characterization forchosen parameters.

Data in Table 1 show huge variations for almost all parameters,which is due to the changes in raw material used (different grades ofwaste paper, with or without addition of recycled sludge from ETP),different product type (paper grade and weight), addition of chemi-cals etc. Further, data in Table 1 indicate heavily loaded wastewater,with high content of organic matter (expressed as COD and BODparameters), high value of total suspended solids and ammoniacontent. Wastewater was relatively stable, in a pH range between7.0 and 7.7, which means neutral to slightly alkaline.

Recorded TSS values (mean value and maximum recorded valuein examined wastewater) were 3993 and 8495 mg L−1, respectively.

Relatively high TSS values might be a consequence of pure fiber andfiller retention on sieve section of paper machine, which results intheir high content in process water, and consequently in commonwastewater. Fibers and fillers in wastewater present pure lost for

1142 D.B. Zarkovic et al. / Resources, Conservation and Recycling 55 (2011) 1139– 1145

Table 1Characteristics of the raw wastewater.

No. Parameter (in mg L−1, except pH value) Na Range Mean ± s.d.b

1 pH 30 7.0–7.7 7.3 ± 0.222 Chemical oxygen demand, COD 28 3770–9330 5539 ± 4123 Biochemical oxygen demand, BOD 28 816–2495 1372 ± 1084 Total suspended solids, TSS 29 603–8495 3993 ± 2165 Settleable solids, SS 30 40–850 480 ± 58

ta

4

vp

epophotdbmwtfa

v

wpcwa(tsctt

Fg

of larger quantities of fillers. Sludge recirculation is the most com-monly used in the case of paper grade C, which is usually producedas heavy-weight cardboard, with thicker middle layer. Percentage

a Number of days with 3-times sampled wastewater.b Confidence limit for 95% probability level.

he mill, and they should be retained and separated from wastew-ter.

.2. Wastewater generation and TSS content

Wastewater generation in different production stages and forarious paper grades of constant weights (average 350 g m−2) isresented in Fig. 3.

Fig. 3 shows that the most part of the wastewater (ca. 70%) gen-rates in the cardboard machine; the rest origins from the stockreparation. The highest value for inlet to ETP is recorded in the casef paper grade D, which is made of sorted recycled paper (“whiteaper” and wood-pulp), with longer fibers. This might be due to theigher water consumption for showers in the sheet forming sectionf cardboard machine. In this point, water is used to lubricate ando clean forming fabrics and wet press felts to maintain satisfactoryewatering performance. Longer fibers are settling faster and causeetter retention and more intense binding to press felts fabrics. Thisight need more fresh water for felts showering, and cause largerastewater generation. The lowest value for wastewater genera-

ion is recorded for paper grade B, which might be caused by lowerresh water consumption (unsorted waste paper as raw materialnd simplified production for paper grade B).

TSS content in wastewater from different production stages andarious paper grades is presented in Fig. 4.

As presented in Fig. 4, the main source of suspended solids inastewater (mainly presented as paper fibers and fillers) was stockreparation. In general, this stage generates double content of TSSomparing to cardboard machine wastewater. However, summaryastewater (inlet to ETP) had TSS content more similar to wastew-

ter from cardboard machine, because of higher wastewater flow201.5 m3 h−1 compared to 71.7 m3 h−1 from SP). The highest con-ent of TSS (over 12,000 mg L−1) was recorded in wastewater from

tock preparation of paper grade B, which is made of unsorted recy-led paper and board. In that case, fibers are short and can be easilyransferred to wastewater during intense and multi-level purifica-ion in stock preparation. Beside that, raw material for paper grade

ig. 3. Wastewater generation from different production stages in various paperrade production.

B has more impurities which can reach wastewater streams duringstock cleaning. In cardboard machine wastewater, all paper gradeshad similar TSS content (average from 2800 to 4040 mgL−1). Low-est value is recorded in the case of paper grade D, which is made ofsorted recycled paper (“white paper” and wood-pulp), with longerfibers which means better retention and less fibers and other sus-pended solids in wastewater.

4.3. Waste generation and sludge recirculation

In the processing of recovered paper in the mill, various typesof rejects and sludge in varying quantities are collected and haveto be handled. These are treated in the sludge and reject system.A reduction in the quantity of residues to be disposed of can beachieved if similar types of rejects from various process steps inthe stock preparation and the approach flow system are collectedand treated together. Fiber recovery also contributes to minimizethe quantity of residues.

Generated sludge from ETP is usually recycled as raw materialfor middle layer of heavy-weight paper (over 350 g m−2). Charac-teristics of generated sludge on ETP and data of sludge recycling forvarious paper grades are presented in Fig. 5.

As it can be noticed from Fig. 5, paper grade B has the lowestvalues for all parameters – the sludge density, percent solids anddegree of sludge recirculation. This can be explained with the factthat paper grade B is produced from low-quality waste paper, whichcontains more non-fibrous material and whose fibers are short andhard to separate from the water. Paper grade D has extremely highvalue of sludge density, which might be because of the addition

Fig. 4. Average TSS content in wastewater for various paper grade production.

D.B. Zarkovic et al. / Resources, Conservation

Ft

oe

4

rrrttdettt8Gwb

ohwdo

tip

5

wpio

srfihC

tm

ig. 5. Characteristics of sludge and recycling data in various paper grade produc-ion.

f solids in generated sludge is similar for all paper grades (2.5%),xcept for paper grade B which contains less solids.

.4. Effluent treatment efficiency

ETP was the most effective and stable in operation for SS and TSSeduction, with the efficiency ranges 80.2–98.7% and 75.4–99.1%,espectively, and average values 97.1 and 85.8%, respectively. Theseesults were expected, having in mind that ETP is primarily orientedoward removing suspended solids. Mean value for TSS content inhe raw wastewater was 3993 mg L−1, calculated for actual pro-uction and wastewater generation (300 t day−1 and 280 m3 h−1

ffluent flow) it presents 26.8 t of suspended solids per day. Withhe average reduction efficiency of 85.8% on ETP, this would presenthe amount of 23 t of generated sludge per day, or 7.6% of produc-ion. Besides, the maximum value for TSS in raw wastewater was495 mg L−1, that is around 2.5 times higher than average value.eneral remark is that the raw wastewater is overloaded in TSS,hich presents direct loss in fiber, filler and additives, if would not

e returned to production process.Average TSS content in effluent after treatment was 120 mg L−1

r 2.6 kg t−1 produced cardboard. This value was considerablyigher than BAT norms for integrated production of newspaper,riting and printing paper from recycled fibers (0.3 kg t−1). Theseata indicated a need for ETP efficiency increasing and/or upgradingf existing ETP by biological treatment.

Beside, TSS reduction efficiency was not stable (varied from 75.4o 99.1%), which might be because of variations of TSS contentn raw wastewater, which influence the coagulation/flocculationrocess.

. Cleaner production measures

Some cleaner production measures for the improvement of theater system and sludge utilization efficiency in the mill were pro-osed during previous investigations (Zarkovic et al., 2011). These

mprovements are oriented in two directions, i.e., in-mill and end-f-pipe measures.

In-mill measures consider adoption of internal water system clo-ure by reduction of fresh water consumption, as well as sludgee-use in stock preparation. These measures resulting in water andber conservation, decreasing wastewater generation, decreasingydraulic load of ETP and pollution degree of raw wastewater (TSS,

OD and BOD content).

End-of-pipe measures are more oriented toward increasingreatment efficiency on ETP which can be obtained through opti-

ization and maximal efficiency achieving in stable operation of

and Recycling 55 (2011) 1139– 1145 1143

existing ETP and possibility for its upgrading toward accomplishingeffluent discharge limits and quality for in-mill re-use.

End-of-pipe measures include providing an equalization basinwith 3-4 hours retention time with mixing facility, dosing of anti-foaming agents, leveling of weirs, implementation of additionalscreening unit and optimization of coagulation–flocculation pro-cess by conducting Jar-tests (Zarkovic et al., 2011; Nandy et al.,2002). One of the observed problems on ETP functioning wasreduced volume available for sedimentation inside the primaryclarifier, in a case of production low-weight cardboard, because ofnon-continuous evacuation of sludge from the bottom of clarifier.This problem could be solved with the system for continuous evacu-ation and re-pumping sludge toward re-use or temporary disposal.Beside that, many different additional options for further treatmentof sludge could be implemented: dewatering, processing in pressesor centrifuges, incineration (which provides net positive heat value)or composting (Kay, 2003).

5.1. Water conservation

Inside the mill, reduction of fresh water is already achieved bythe use of internal fiber recovery unit (DAF – dissolved air flota-tion, so-called save-all). DAF unit clarifies 330 m3 h−1 of whitewater, with dosing 2–4 mg L−1 anionic polymer and TSS removalefficiency of 97%. Clarified water, with 120 mg L−1 average contentof TSS is commonly used for different operations in stock prepara-tion (pulping, multi-level screening and cleaning), as presented inFig. 2. Further fresh water conservation, with additional treatmentunit, could be achieved by using this water as high-pressure showerwater on cardboard machine. It might be a polydisc filter, whichprovides several separated outcomes, including clear filtrate (with60 mg L−1 TSS) and ultra-clear filtrate, with less than 25 mg L−1 TSS.Both filtrates could be used directly instead of fresh water, or indi-rectly, after filtration on existing sand filters. The later could providewater with 5–10 mg L−1 TSS, which might be used for high pressureshower water (under 60 bar) and other purposes instead of freshwater. Clear filtrate (with 60 mg L−1 TSS) could be used directly intechnological process, for shower water under pressure of 25 bar.Both measures would save up to 50 m3 h−1 (about 17%) of freshwater that is used on cardboard machine and for thickening in stockpreparation. However, if clarified water would be recycled for useas shower water directly, with no previous sand filtration, speciallydesigned nozzles on cardboard machine should be required. Thesenozzles must be slightly larger than those using fresh water to avoidclogging by fibers contained in the recycled water.

The main source of suspended solids in wastewater is stockpreparation, which brings 9–12 g L−1 TSS. This problem might besolved with providing one additional purification unit in internalwater cycle – DAF 1 unit, as presented in Fig. 2. This unit wouldpurify dark sieve water from cardboard machine and wastewaterfrom final stages of stock preparation (high density cleaning, finescreening and low density cleaning). DAF 1 unit would purify cca.150 m3 h−1 wastewater, which is double smaller unit than existingDAF. Treated water (with up to 150 mg L−1 TSS) would be usefulfor different in-mill purposes, or further treatment on polydisc fil-ter. With additional DAF unit, income wastewater to ETP wouldbe decreased to 150 m3 h−1. Fresh water consumption would bedecreased for ca. 100 m3 t−1.

5.2. Fiber conservation

Cross media effect of ETP operation is generation of sludge,

which is re-used in production process or evacuated for disposal(with water content of 60–80%). The current average amount offibers and fillers generated as sludge from ETP was 3.1 t day−1. Itpresents pure lost if not recycled as feedstock. Currently, waste

1144 D.B. Zarkovic et al. / Resources, Conservation and Recycling 55 (2011) 1139– 1145

Table 2Estimated costs and benefits of cleaner production measures.

Ser. no. Cleaner production measure Estimated costs, D Actual effects Estimated annualbenefits, D a

1. Re-use of white sieve water for fine screeningin stock preparation

5000 Fresh water conservation (≈20%)Decrease of wastewater generation (≈20%)

13,200985,600

2. Implementation of IV-grade pulp cleaning 10,000 Fiber conservation (≈10%) 286,0003. Additional flotation unit (DAF 1) 250,000 Additional fresh water conservation (≈20%)

Additional decrease of wastewater generation(≈20%)TSS content reduction in effluent (≈30%)

10,500788,50015,200

4. Polydisc filter implementation 150,000 Additional fresh water conservation (≈10%)Additional decrease of wastewater generation(≈10%)

4200314,600

5. Fibermizer implementation (IV-grade pulpcleaning)

20,000 Additional fiber conservation (≈10%) 257,400

6. Thickener and press in III-grade pulp cleaning 25,000 TSS content reduction in effluent (≈20%) 13,8007. Piping re-routing 5000 Auxiliary action –8. Sludge storage tank with mixing facilities and

pumps for continuous sludge re-pumping400,000 Fiber and filler conservation (≈8%) 231,600

9. Total 865,000 Total fresh water conservation (≈50%)Total decrease of waste-water generation (≈50%)Total fiber conservation (≈28%)Total TSS content reduction in effluent (≈50%)

≈30,000≈2,100,000≈700,000≈30,000

river

2

swpffnoduifottub

5

pmtsf

2s2wtp

cpdweato

a According to prices in EU: average 0.025 D m−3 for industry water usage from0 D t−1.

ludge can be almost 90% recycled in the case of producing heavyeight cardboard (over 400 g m−2). But, in the case of low-weightroduct, sludge is disposed as a waste, because there is no needor its re-use in production. Mill does not have dewatering unitor sludge (presses and centrifuges), what should be obtained inext period. One of the measures for fibers and fillers saving wasbtained by decrease their content in raw wastewater. This wasone by increasing efficiency of water purification at save-all DAFnit inside the mill. Previously low efficiency of DAF (60% in retain-

ng fibers and fillers) was increased to 97% by rerouted white waterrom formation section of cardboard machine to DAF and additionf optimal type and dose of flocculant. Beside this in-mill measure,here is a possibility to storage sludge from ETP in special storageanks with mixing facility when it is not re-used in production. Latersage of this sludge for heavy-weight cardboard production, wouldring up to 8% savings in raw material (RCF).

.3. Economic aspects of water and fiber conservation

As presented in previous study (Zarkovic et al., 2011), pro-osed cleaner production measures (as in-mill and end-of-pipeeasures) would be achieved through three successive phases in

he period of next 18 months. Estimated costs and benefits of mea-ures which directly influence water and fiber conservation derivedrom cleaner production approach, are presented in Table 2.

In EU countries taxes for discharged wastewater are around.0 D for each cubic meter of discharged effluent. With the presentituation of water system, average wastewater generation of2.4 m3 t−1 and annual production output of ca. 110.000 t, the taxesould be almost 5 M D per year. With closing up of water sys-

em and decreased consumption at estimated 12 m3 t−1, with sameroduction output, mill would save 2.0 M D per year.

As presented in Table 2, the most significant water and fiberonservation would be achieved from in-mill measures of cleanerroduction strategy achieving (positions 1–7 in Table 2). With con-ucted in-mill measures in the period of 3 months, estimated freshater conservation would be 50%, which would bring annual ben-

fit of 30,000 D . Multiply higher benefit from in-mill measuresnd implementation of sludge storage tank would be achievedhrough fiber conservation (ca. 28%), which would bring benefitf 700,000 D .

Total annual benefits: 2,860,000 D ≈3.0 M D

basin; average 2 D m−3 taxes for wastewater discharge; RCF (raw material) price:

In addition, increasing the water system closure would result inmore efficient fiber recovery (by 8%), increasing production outputfor ca. 12%, decreasing energy consumption by an estimated 15%and reducing wastewater pollution degree (50% for TSS content).All the mentioned effects would result in total savings of almost3.0 M D per year. The estimated investment costs for water sys-tem closure and the presented measures on the ETP would reachca. 865,000 D . It is obvious that the cleaner production in-mill mea-sures for the water system closure and end-of-pipe measures wouldresult in savings in first year, if the prices for water supply andtaxes for wastewater discharge would be at the European averagelevel. At present, the price for water usage in Serbia is more than10 times lower compared to the prices in EU countries; the cal-culated tax for this mill and the actual wastewater pollution loadis 0.05 D m−3 (comparing to 2 D m−3 in the EU). With the currentprices in Serbia, the yearly level of savings for fresh water consump-tion and wastewater discharge would be only 125,000 D . Having inmind the cost of investment (865,000 D ) and the present status ofwater prices in Serbia, the pay-off period would be 7 years, whichis not stimulating for urgent actions.

Several of the suggested improvement options are independent,meaning that a redesigned system can be a combination of oneor more of the different options. The decision to execute a certainaction is dependent upon its economic, environmental, and productquality advantages (Senante et al., 2010).

6. Conclusions

The results of the conducted study indicate a relatively highlevel of fresh water consumption (average 24 m3 t−1), high specificwastewater generation (average 22.4 m3 t−1), insufficient sludgerecirculation ratio and an overload of the ETP in terms of wastew-ater flow and TSS content. The most part of the wastewater (ca.70%) generates in the cardboard machine; the rest origins fromthe stock preparation. The highest value for the inlet to ETP isrecorded in the case of paper grade D, which is made of sorted recy-cled paper (“white paper” and wood-pulp), with longer fibers. The

main source of suspended solids in wastewater (mainly presentedas paper fibers and fillers) was the stock preparation. In general,this stage generates double content of TSS comparing to cardboardmachine wastewater. However, summary wastewater (inlet to the

ation

EbBp

tAohwdo

sttfiIsciitA5sfpdsbtcaeei

twrlidnp

atte

as

D.B. Zarkovic et al. / Resources, Conserv

TP) had TSS content more similar to wastewater from the card-oard machine, because of higher wastewater flow. Paper grade

has the lowest values for all parameters – the sludge density,ercent solids and degree of sludge recirculation.

With the average TSS reduction efficiency of 85.8% on the ETP,his mill generates 23 t of sludge per day, or 7.6% of production.verage TSS content in effluent after treatment was 120 mg L−1

r 2.6 kg t−1 of produced cardboard. This value was considerablyigher than IPPC norms for integrated production of newspaper,riting and printing paper from recycled fibers (0.3 kg t−1). Theseata indicated a need for ETP efficiency increasing and/or upgradingf existing ETP by biological treatment.

Several proposed in-mill and end-of-pipe measures for waterystem closure (with a polydisc filter and a DAF unit and implemen-ation of sludge storage tank on the ETP) provide for a decrease inhe fresh water consumption by ca. 50%, a higher degree of fiber andller recovery (ca. 28%) and a more efficient operation of the ETP.

mplementation of presented measures would be an essentiallytep in achieving national and European norms for wastewater dis-harge and would bring great environmental benefits for the milltself. It was calculated that the estimated investment of 865,000 Dn cleaner production would bring savings of ca. 3.0 M D (accordingo European prices for the fresh water and wastewater discharge).t annual degree, savings would be achieved through 2.5 M D for0% decreased wastewater generation, 735,000 D for 28% fiber con-ervation, 33,000 D for 50% fresh water conservation and 20,000 Dor 50% TSS content reduction in effluent. These actions would beaid-off in 9 months, if the prices of fresh water and wastewaterischarge taxes would be at European average. It is clearly demon-trated that cleaner production pays-off in cardboard production,ecause all the benefits arising from suggested measures exceedheir total costs. With presented measures, it is confirmed thatleaner production approach is a positive process not only fromn environmental point of view, but also economically (Abou-Elelat al., 2008). The saved money could be invested in measures andquipment for handling of waste sludge, when it cannot be re-usedn production (Kay, 2003; Ribeiro et al., 2010).

The obtained results show that the maximum environmen-al benefits are derived from water conservation and decreasedastewater generation (estimated at 2.5 M D annually), while the

emoval of suspended solids from the wastewater contributes theowest percentage to the overall environmental benefits. However,n the present situation in Serbia, where the taxes for wastewaterischarge are several times lower than in EU countries, the eco-omic aspect might be the crucial reason for current investmentassivity.

The presented in-mill and end-of-pipe measures are identifieds a strategy toward achieving the cleaner production concept inhe examined mill and in similar mills in Serbia. However, it haso be appointed that each cardboard mill has to be analyzed and

valuated by considering its own characteristics.

The final report of this study was delivered to the mill man-gement for consideration and implementation. Achieving the bestolution depends to a large extent on many internal and external

and Recycling 55 (2011) 1139– 1145 1145

conditions of the factory system, management commitment, andthe enforcement of environmental law in Serbia.

Acknowledgements

Authors express their thanks to Ministry of Science and Techno-logical Development of the Republic of Serbia, as countenancer ofthe study Rationalization of water consumption in the paper indus-try, a part of which was this examination. We are also thankful tothe Anahem laboratory for providing the necessary equipment forwater analysis and the mill’s staff for team work and supplyingvaluable information.

References

Abbasi GY, Abbasi BE. Environmental assessment for paper and cardboard industryin Jordan – a cleaner production concept. J Clean Prod 2004;12(4):321–6.

Abou-Elela SI, Nasr FA, Ibrahim HS, Badr NM, Askalany AM. Pollution preventionpays off in a board paper mill. J Clean Prod 2008;16(3):330–4.

APPHA. Standard methods for the examination of water and wastewater. 20th ed.Washington, DC: American Public Health Association; 1998.

Avsar E, Demirer GN. Cleaner production opportunity assessment study in SEKABalikesir pulp and paper mill. J Clean Prod 2008;16:422–31.

Bulow C, Pingen G, Hamm U. Complete water system closure. Pulp Paper Int (PPI)2003(August):14–7.

Crnkovic D, Crnkovic N, Filipovic A, Rajakovic L, Peric-Grujic A, Ristic M. Danube andSava River sediment monitoring in Belgrade and its surroundings. J Environ SciHealth A 2008;43(12):1353–60.

Gupta A. Pollution load of paper mill effluent and its impact on biological environ-ment. J Ecotoxicol Environ Monit 1997;7(2):101–12.

Hamm U, Schabel S. Effluent-free papermaking: industrial experiences andlatest developments in the German paper industry. Water Sci Technol2007;55(6):205–11.

Integrated Pollution Prevention and Control – Reference Document on Best Avail-able Techniques in the Pulp and Paper Industry (December 2001), Europeancommission. Available from: http://eippcb.jrc.es (accessed 23.04.2010).

Kay M. What to do with sludge. Pulp Paper Int (PPI) 2003;August.Nandy T, Kaul SN, Shastry S. Upgrading a paper industry effluent treatment plant

for capacity expansion with recourse to recycling effluent. Resour Conserv Recy2002;34:209–28.

Nassar M. Studies on internal and external water treatment at a paper and cardboardfactory. J Chem Technol Biotechnol 2003;78:572–6.

National regulatory standards. Decree on classification of natural water streams andtheir quality. Official gazette of SFRJ; 1978.

Ochoa de Alda JAG. Feasibility of recycling pulp and paper mill sludge in the paperand board industries. Resour Conserv Recy 2008;52(7):965–72.

Pokhrel D, Viraraghavan T. Treatment of pulp and paper mill wastewater – a review.Sci Total Environ 2004;333:37–58.

Ribeiro P, Albuquerque A, Quinta-Nova L, Cavaleiro V. Recycling pulp millsludge to improve soil fertility using GIS tools. Resour Conserv Recy2010;54(12):1303–11.

Senante MM, Sancho FH, Garrido RS. Economic feasibility study for wastewatertreatment: a cost-benefit analysis. Sci Total Environ 2010;408(20):4396–402.

Thompson G, Swain J, Kay M, Forster CF. The treatment of pulp and paper milleffluent: a review. Bioresour Technol 2001;77:275–86.

Tiku DK, Kumar A, Sawhney S, Singh VP, Kumar R. Effectiveness of treatment tech-nologies for wastewater pollution generated by Indian pulp mills. Environ MonitAssess 2007;132:453–66.

Zarkovic D, Todorovic Z, Krgovic M, Rajakovic L. Determination of inorganicanions in papermaking waters by ion chromatography. J Serb Chem Soc2009;74(3):301–10.

Zarkovic D, Krgovic M, Rajakovic Lj. Rationalization of water consumption in paperindustry. Chem Ind 2004;8:327–37.

Zarkovic D, Todorovic Z, Rajakovic Lj. Simple and cost-effective measures for theimprovement of paper mill effluent treatment – a case study. J Clean Product2011;19:764–74.