Chemical Engineering Journal 241 (2014) 184–189

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Chemical Engineering Journal

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Combined ozone oxidation and biological aerated filter processes fortreatment of cyanide containing electroplating wastewater

1385-8947/$ - see front matter � 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.cej.2013.09.003

⇑ Corresponding author. Address: Room 301, College of Environment and Energy,South China University of Technology, Guangzhou Higher Education Mega Center,Guangzhou 510006, China. Tel.: +86 20 13802767806; fax: +86 20 85640936.

E-mail address: cexjwang@scut.edu.cn (X. Wang).

Jiaqi Cui a, Xiaojun Wang a,⇑, Yanlei Yuan a, Xunwen Guo a, Xiaoyang Gu b, Lei Jian b

a College of Environment and Energy, South China University of Technology, Guangzhou 510006, Chinab HuaLu Environmental Technology Co., Ltd., Guangzhou, China

h i g h l i g h t s

� The combined process of BAF–O3–BAF was suitable for treating cyanide containing EPWW.� BAF can tolerate higher cyanide toxicity than some other bioreactor.� High removal efficiencies were obtained with low influent BOD5/TN in BAF.� The addition of glucose into raw EPWW could increase the efficiencies of BAF.� Cyanide compounds of EPWW could be used as the nitrogen source for the microbes.

a r t i c l e i n f o

Article history:Received 18 June 2013Received in revised form 20 August 2013Accepted 1 September 2013Available online 8 September 2013

Keywords:CyanideElectroplating wastewaterOzoneBiological aerated filter (BAF)Biodegradation treatment

a b s t r a c t

In this study, combined ozone oxidation and biological aerated filter (BAF) processes treating cyanidecontaining electroplating wastewater was investigated. The combined process of first BAF–ozone–secondBAF (BAF1–O3–BAF2) was proved the optimal combined way. Under the optimal condition of 100 mg/Lozone dosage, BAF1 HRT (hydraulic retention time) 9 h and BAF2 HRT 6 h, the CN�, COD (chemical oxygendemand), Cu2+ and Ni2+ removal efficiencies were 99.7%, 81.7%, 97.8% and 95.3%, respectively and theeffluent CN�, COD, Cu2+ and Ni2+ concentrations of 0.16 mg/L, 55.0 mg/L, 0.38 mg/L and 0.41 mg/L,respectively satisfied the discharge standard for electroplating (China). The results show that BAF1 cantolerate higher cyanide toxicity than some other bioreactors. Furthermore, the addition of glucose intoraw electroplating wastewater (EPWW) could increase contaminants removal efficiencies of BAF1. Cya-nide compounds of EPWW could be used as the nitrogen source for the microorganisms.

� 2013 Elsevier B.V. All rights reserved.

1. Introduction

Cyanide is well known for its toxicity and it is an EnvironmentalProtection Agency (EPA) designated priority pollutant, yet iswidely used in electroplating industry due to its strong complica-tion and activation ability. Other industries such as gold mining,photo-processing, petrochemical industries, coke-processingplants, metal finishing units and synthetic fiber production alsogenerate large amount of cyanide containing wastewater [1]. Toprotect the environment and human beings from the hazards ofcyanide, effluents containing cyanide must be well treated priorto discharge [2].

The most commonly adopted method for cyanide-contaminatedwastewater treatment is the alkaline chlorination oxidation pro-

cess [1,3]. Although this method can be very efficient in removalof cyanide, it results in highly toxic intermediates (e.g. cyanogenschloride) and suffers from excess hypochlorite which is toxic toaquatic life [4]. Another common method is chemical precipitationby ferrous sulfate due to its low cost and wide availability, but itproduces significant amount of hazardous sludge [5]. Other chem-ical and physical processes, like activated carbon adsorption andion exchange, also can be employed to degrade cyanide and its re-lated compounds; however, they are often expensive and complexto operate. Biological process has been used in variety of wastewa-ter treatments due to its economic advantages, yet a new technol-ogy for cyanide treatment. Several researchers have applied thebiological process to remove or degrade cyanide compounds, andreported that cyanide compounds could be utilized as nitrogenand carbon source and degraded by the microorganisms such asfungus, bacteria and algae [6–8]. However, it is well documentedthat cyanide compounds, especially at high concentration and con-taining heavy metals, are toxic to the bio-sludge and microorgan-isms [9]. Therefore, a new treatment method is necessary, which

Table 1The characteristics of raw wastewater.

Parameter Maximum Minimum Discharge standard

COD (mg/L) 329 250 80BOD5 (mg/L) 20.1 16.5 –pH 8.05 7.95 6–9CN� (mg/L) 49.0 26.5 0.3TN (mg/L) 289 266 20Cu2+ (mg/L) 19.5 14.0 0.5Ni2+ (mg/L) 9.80 7.82 0.5

J. Cui et al. / Chemical Engineering Journal 241 (2014) 184–189 185

not only can completely remove cyanide but also economicallyoperate and no secondary pollution produced.

Ozone is known as one of the most powerful oxidizing agentswith a standard redox potential of 1.24 V in alkaline solutions [10].Cyanide oxidation with ozone is rapid, and complete decompositionof cyanide can be obtained without undesirable by-products [11]. Inthis study, ozone oxidation was used as pretreatment process to re-duce the toxicity of cyanide and improve wastewater biodegradabil-ity. After ozone pretreatment the cyanide and organic matter werefurther removed by biological aerated filter (BAF), which containsinert media for attached growth of biomass and depth filtration ac-tion of suspended solids [12,13]. BAF is an alternative to the tradi-tional activated sludge process which eliminated the requirementof secondary clarification for biological treatment. Furthermore,the attached growth on inert granular media in BAF allows for higherconcentration of active biomass than in a suspended growth acti-vated sludge system so that the size of reactor can be reduced[14]. The results of this study derived from a lab-scale test could pro-vide significant information for industrial applications.

2. Materials and methods

2.1. Wastewater source and characteristics

The raw wastewater was cyanide containing electroplatingwastewater (EPWW) from an electroplating industrial park locatedin Zhaoqing city, Guangdong province, PR China. Electroplatingwastewater contains heavy metal cyanide complex, all of whichare difficult to remove by biological methods. Original and treatedwastewater samples were collected daily in clean 100 mL plasticcontainers. The characteristics of the wastewater and dischargestandard for electroplating (China) are summarized in Table 1.

2.2. Experimental installation

Schematic diagram of experimental process was shown inFig. 1. The main reactors were made of unplasticised polyvinylchloride. The three reactors were cylinder with diameters of100 mm. The first biological aerated filter (BAF1) was 1600 mmheight, with a working volume of 4.5 L. The second biological aer-ated filter (BAF2) was 1200 mm height, with a working volume of3.0 L. The ozone reactor was 1500 mm height, with a working vol-ume of 3.8 L. The reactors were packed with diameter size 3–5 mmceramic granular media. The media height of three reactors was900 mm, 600 mm and 700 mm, respectively. Both BAFs were oper-ated in up-flow mode, and the gas–water ratio was 10:1.

The influent was pumped to the bottom of BAF1 by peristalticpump. The effluent flowed automatically to ozone reactor, thento BAF2. The effluent of BAF2 was collected in effluent tank thatcould be used to backwash the BAFs once 2 weeks. The accumu-lated suspended solid (SS) and the excess biomass could be re-moved in time. And through the change of the pipes and valves,the combined process could be transformed between O3–BAF1–BAF2 and BAF1–O3–BAF2.

2.3. Experimental procedure

2.3.1. Single ozone oxidation experimentsIn order to study the feasibility of cyanide oxidation by ozone,

some tests of single ozonation using cyanide containing EPWWwere performed at various cyanide and ozone concentrations.The experiments were carried out in ozone reactor with a maxi-mum ozone production of 3 g/h. The model of the ozone generatorwas CH-ZTW3G from Guangzhou Chuanghuan Co., Ltd., (China).

Eq. (1) shows the relationship between CN� removed and O3

consumption in the ozone reactor. According to Eq. (1), the theo-retical mass ratio of O3 to CN� is 4.29:1. So the different mass ratiosof O3 to CN� were chosen for experiments: 1.17, 2.34, 3.51, 4.68,5.85 and 7.02.

2CN� þ 5O3 þH2O ¼ 5O2 þ N2 þ 2HCO�3 ð1Þ

Ozone decomposes in the aqueous phase at a rate that dependsmainly on the pH of the solution [10]. The ozone decomposition isinitiated by hydroxyl ions according to Eq. (2) [15]. So the effect ofinitial wastewater pH was studied.

O3 þ OH� ¼ HO�2 þ O2 ð2Þ

2.3.2. Combined processes experimentsTwo combined ways included O3–BAF1–BAF2 and BAF1–O3–BAF2

were investigated to compare the feasibility of them. The activatedsludge used for BAF start-up was obtained from a domestic waste-water treatment plant. In the start-up stage, the feed steam wasthe diluted cyanide electroplating wastewater which was addedwith glucose (without nitrogen and phosphorus source). The CODconcentration was maintained around 400 mg/L. Subsequentlythe influent CN� concentration increased each day by adjustingto the proportion of actual wastewater, until removal efficiencyof CN� in BAF was below 50%, which indicated that the start-uphad finished. All experiments were performed at 25 ± 5 �C. Experi-ments with different ozone dosages (80, 100, 120, 125 and 150 mg/L) and hydraulic retention time (HRT, 7.5, 10 and 15 h) werestudied.

2.3.3. BAF1 experimentsSakai et al. [16] concluded that an influent biochemical oxygen

demand to total nitrogen ratio (BOD/TN) exceeding 4.9 was neces-sary for obtaining favorable biodegradation using an oxidationditch with intermittent aeration. Wang and Liu [17] reported thatan increase in TN removal efficiency from 58.1% to 87% by addingsodium acetate into the process to enhance the influent BOD/TNratio from 2.89 to 8.32. Fujiwara et al. [18] demonstrated a modi-fied influent BOD/TN ratio larger than 4 could result in more organ-ic matter and TN removal efficiency.

In this study, considering the raw wastewater characteristics,BOD/TN ratio was lower than 0.1 that is shown in Table 1. Some ef-forts were made to improve the BOD/TN ratio for increasing bio-degradation rate by adding external carbon source [17]. Sodifferent dosages (100, 200, 300, 400 and 600 mg/L) glucose wasadded in raw wastewater to study the effect of BOD/TN ratio totreatment efficiency of BAF1.

2.4. Analytical methods

During the study, Chinese standard methods for water andwastewater was used for analyzing chemical oxygen demand

Fig. 1. Schematic diagram of the experimental installation.

186 J. Cui et al. / Chemical Engineering Journal 241 (2014) 184–189

(COD), five-day biological oxygen demand (BOD5), total cyanide(CN�), total nitrogen (TN), copper (Cu2+), nickel (Ni2+) and pH ofthe water samples. COD was measured by dichromate method,BOD5 by inoculation method with a BOD5 measurementequipment (CY-II, Taihong medical equipment Co., Ltd., China),CN� by isonicotinic acid–pyrazolone spectrophotometric method,TN by the potassium persulfate UV spectrophotometric method,Cu2+ by sodium diethydlthiocabamate spectrophotometric meth-od, Ni2+ by dimethylglyoxime spectrophotometric method. ThepH value and temperature were measured by a digital pH meter(PHSJ-4A, INESA Scientific Instrument Co., Ltd., China) and a tem-perature meter.

3. Results and discussion

3.1. Single ozone oxidation experiments: effect of m(O3):m(CN�) andpH

In these tests EPWW of pH 8.02 containing 28.7 mg/L CN�,15.9 mg/L Cu2+ and 8.15 mg/L Ni2+ was treated. And caustic soda(NaOH) was used to adjust the initial wastewater pH. Fig. 2 showsthe removal of contaminants by single ozone oxidation under theconditions of different m(O3):m(CN�) and pH. The higher the ozonedosage fed to the reactor, the higher CN�, Cu2+ and Ni2+ removalefficiencies. It is concluded that m(O3):m(CN�) increase was effi-cient in decreasing effluent CN� concentrations. But the ratio in-crease was efficient only until 4.68. This result was in accordancewith the theoretical m(O3):m(CN�) ratio according to Eq. (1). Be-sides, the removal efficiencies decreased with the increase of theinitial pH. It is suggested that the initial pH had an effect on con-taminants removal, especially on Cu2+ and Ni2+. It shows that hea-vy metal cyanide complexes were oxidized by ozone to heavymetal ions. Then, under high pH condition, these ions were re-moved through combining with hydroxyl ions as hydroxides.Economically considering, pH of 11 and m(O3):m(CN�) of 4.68were chosen as the optimal treatment condition using singleozone. Under this condition, the effluent CN�, Cu2+ and Ni2+ resid-

ual concentrations were 0.20 mg/L, 0.53 mg/L and 0.87 mg/L,respectively.

In conclusion, ozone oxidation was proved feasible to the cya-nide containing EPWW treatment. However, there were two unde-sirable problems. Firstly, the optimal ozone dosage was so largethat the treatment cost was high. Secondly, in order to achievethe optimal pH, high dosage NaOH was needed to add into theraw wastewater. Then, after treatment, extra acid was necessaryto adjust the effluent pH to be neutral for discharge. Thus furtherincreased the treatment cost. Aiming at these problems, combinedozone and BAF processes were proposed. Firstly, in the combinedprocess ozone was used as pretreatment. This could significantlydecrease the ozone dosage. Secondly, it has been reported that un-der acid and neutral conditions ozone can mainly react directlywith organic compounds and under alkaline conditions ozonecan mainly decompose to OH radicals (�OH), which react with thetarget compound [13,19].The initial pH of wastewater was about8.00, which suited the cyanide and organic compounds oxidationby ozone and biological treatment conditions well, therefore, theinitial pH was not changed for the combined process.

3.2. Combined processes experiments: effect of ozone dosages, HRT andcombined ways

3.2.1. Combined process of O3–BAF1–BAF2Because of the toxicity of cyanide to microorganisms and the

refractory contaminants contained in the EPWW, ozone wasconsidered to be set before biological treatment process (thetwo-stage BAF). In this way, ozone was used to diminish the toxic-ity and recalcitrance of the EPWW due to its strong oxidizing prop-erty. Table 2 presents the concentration changes and the removalefficiencies of contaminants along the treatment process underdifferent ozone dosages and HRT. During the experiments, ozoneconcentrations varied between 100 mg/L and 150 mg/L and HRTof BAF varied from 7.5 h to 15 h. Every experiment ran for 6 days,wastewater samples were analyzed everyday and the data in thetable was the 6-day average. It can be seen that the removal effi-

Fig. 2. Removal of contaminants by single ozone oxidation.

J. Cui et al. / Chemical Engineering Journal 241 (2014) 184–189 187

ciencies of CN�, COD, Cu2+ and Ni2+ increased as the ozone dosageincreases and increased with HRT, too. The highest CN�, COD, Cu2+

and Ni2+ removal rates of 99.9%, 80.1%, 98.6% and 95.6%, respec-tively were detected under ozone dosage of 150 mg/L and HRT of15 h. But the optimal condition taking account of running costand discharge standard was found at ozone dosage of 125 mg/Land HRT of 15 h. Under this condition, the effluent CN�, COD,

Cu2+ and Ni2+ concentrations of 0.13 mg/L, 71.6 mg/L, 0.35 mg/Land 0.46 mg/L, respectively satisfied the discharge standard forelectroplating (China).

Most CN�, Cu2+, Ni2+ (94.5%, 88.8% and 79.2%, respectively) anda portion of COD (43.2%) were removed in the ozone reactor. This isattributed to the dissociation of the coordinate linkages in thecomplex by ozone oxidation. And it is known that cyanide can beoxidized by molecular ozone in a two-step reaction [10]:

CN� þ O3 ¼ CNO� þ O2 ð3Þ

2CNO� þ 3O3 þH2O ¼ 2HCO�3 þ N2 þ 3O2 ð4Þ

with the removal of cyanogens, metal ions were removed throughcombining with hydroxyl ions as precipitation of hydroxides. Then,in BAF the contaminants were removed by attached microbe onmedium and filtration. Moreover, it has been reported that somemicroorganisms can produce extracellular polymers during organ-ism growth [20]. Since the bio-films attaching to the ceramsite werecomposed of microorganisms, it was well considered that the secre-tions produced during their metabolism acted as biological floccu-lants that could adsorb and flocculate the heavy metal ions andthe suspended solids to achieve Cu2+, Ni2+ and COD removal andto improve biological oxidation [21].

3.2.2. Combined process of BAF1–O3–BAF2In order to research the feasibility of high cyanide containing

EPWW treatment by bioprocess and decrease ozone dosage inthe combined process, BAF1 was considered as a part of pretreat-ment before ozone reactor. The concentration changes and the re-moval efficiencies of contaminants in this combined process wereshown in Table 3. The main experimental parameters remainedunchanged, except ozone dosage varying from 80 mg/L to120 mg/L. The data shows that under high cyanide concentration(average 46.3 mg/L) BAF1 could remove a certain contaminants.Because BAF provides enormous surface area for microbe inhabi-tance by filling with granular media, it can tolerate higher cyanidetoxicity than some other bioreactor such as sequencing batch reac-tor (SBR) [9]. It can be seen that a mass of Cu2+ and Ni2+ were re-moved in BAF. That is because the coordinate linkages in thecomplex can be dissociated by attached microbe oxidation, then,the heavy metal ions were adsorbed and flocculated by bio-floccu-lation [21,22]. However, the dominant bacteria in the BAF were notidentified and specified in this study. Therefore, the further re-search regarding the separation and identification of microbes inBAF will be undertaken. This will be conducted to pointedly cultureand domesticate bio-film in BAF when treating cyanide containingelectroplating wastewater.

It also can be seen that the removal efficiencies of CN�, COD,Cu2+ and Ni2+ increased as the ozone dosage increases and in-creased with HRT, too. Out of economic considerations as well,ozone dosage of 100 mg/L, BAF1 HRT of 9 h and BAF2 HRT of 6 hwere chosen as optimal treatment condition. Under this condition,the effluent CN�, COD, Cu2+ and Ni2+ concentrations of 0.16 mg/L,55.0 mg/L, 0.38 mg/L and 0.41 mg/L, respectively also satisfiedthe discharge standard for electroplating (China). But this com-bined way can decrease ozone dosage by 25 mg/L than anotherway.

3.3. BAF1 experiments: effect of glucose addition

The raw EPWW which was added with glucose at the concen-trations of 0, 100, 200, 300, 400 and 600 mg/L to adjust theBOD5/TN ratios of 0.067, 0.44, 0.81, 1.18, 1.55 and 2.29, respec-tively, was used for testing the efficiency of BAF1. The results onthe effect of glucose addition on the efficiency and performanceof BAF1 were shown in Table 4. Low contaminants removal rates

Table 2Removal of contaminants in combined process of Ozone–BAF1–BAF2.

Ozone Dosage (mg/L) Total HRT of BAF (h) CN� (mg/L) COD (mg/L) Cu2+ (mg/L) Ni2+ (mg/L) Total removal efficiencies byOzone–BAF1–BAF2 process (%)

Inf.a O3b Eff.c Inf. O3 Eff. Inf. O3 Eff. Inf. O3 Eff. CN� COD Cu2+ Ni2+

100 15 42.6 6.25 0.24 285 181 79.1 17.9 2.69 0.64 9.02 2.13 0.76 99.4 72.2 96.4 91.610 42.2 6.90 0.98 302 191 87.5 18.4 2.84 0.86 8.87 2.05 0.92 97.7 71.0 95.3 89.67.5 41.8 6.18 1.65 316 192 92.2 16.7 2.53 0.99 9.15 2.24 1.09 96.1 70.8 94.1 88.1

125 15 43.5 2.39 0.13 308 175 71.6 16.3 1.82 0.35 8.08 1.68 0.46 99.7 76.8 97.9 94.310 42.1 1.86 0.27 280 168 76.9 15.6 1.69 0.51 8.46 1.82 0.78 99.4 72.5 96.7 90.87.5 42.8 2.15 0.64 292 174 83.0 16.8 1.79 0.72 8.71 1.79 0.84 98.5 71.6 95.7 90.4

150 15 40.6 0.38 0.05 299 163 59.4 17.4 1.42 0.25 8.38 1.26 0.37 99.9 80.1 98.6 95.610 40.7 0.65 0.08 286 156 62.4 18.2 1.35 0.33 8.16 1.19 0.46 99.8 78.2 98.2 94.47.5 41.7 0.52 0.06 312 165 65.8 18.9 1.50 0.53 8.63 1.38 0.55 99.9 78.9 97.2 93.6

a Inf.: Influent of the combined process.b O3: Effluent of the ozone reactor.c Eff.: Effluent of the combined process.

Table 3Removal of contaminants in combined process of BAF1–Ozone–BAF2.

HRT of BAF (h) Ozone dosage (mg/L) CN� (mg/L) COD (mg/L) Cu2+ (mg/L) Ni2+ (mg/L) Total removal efficiencies byBAF1–Ozone–BAF2 process (%)

BAF1a O3b BAF2c BAF1 O3 BAF2 BAF1 O3 BAF2 BAF1 O3 BAF2 CN� COD Cu2+ Ni2+

9 (BAF1) 80 26.2 1.79 0.54 129 95.0 64.5 2.26 1.19 0.59 1.96 1.05 0.57 98.8 76.0 96.1 93.16 (BAF2) 100 26.4 0.93 0.16 143 89.0 55.0 2.63 0.96 0.38 1.83 0.94 0.41 99.7 81.7 97.8 95.3

120 26.4 0.19 0.05 140 72.0 43.8 2.62 0.79 0.27 2.09 0.84 0.38 99.9 84.6 98.4 95.9

6 (BAF1) 80 29.6 4.45 1.60 168 118 86.3 4.03 1.59 1.09 3.40 1.93 1.18 96.3 70.2 93.7 86.44 (BAF2) 100 32.4 2.90 0.81 170 98.0 72.5 3.89 1.48 0.87 3.04 1.35 0.88 98.2 76.2 94.0 89.6

120 31.5 0.92 0.24 173 89.0 63.1 4.13 1.33 0.81 3.16 1.31 0.81 99.5 78.9 95.0 90.3

4.5 (BAF1) 80 35.8 8.30 3.50 189 139 96.0 5.86 2.18 1.49 4.49 2.61 1.73 92.5 67.6 90.8 79.23 (BAF2) 100 36.6 5.74 1.62 197 124 84.2 6.10 2.21 1.52 4.85 2.30 1.43 96.6 72.0 91.2 83.4

120 36.0 2.49 0.89 199 112 75.8 6.48 1.85 1.29 4.70 2.01 1.16 98.1 75.8 92.4 87.4

a BAF1: Effluent of BAF1.b O3: Effluent of the ozone reactor.c BAF2: Effluent of BAF2.

188 J. Cui et al. / Chemical Engineering Journal 241 (2014) 184–189

were detected using BAF1 to treat raw EPWW. However, the effi-ciency could be increased by supplementation with glucose (or-ganic matters). Also, the efficiency increased with the increase ofglucose concentration (organic loading increasing). The highestCN�, COD, Cu2+ and Ni2+ removal efficiencies of 74.4%, 77.5%,88.1% and 79.9%, respectively were obtained under organic loadingof 1.65 kg BOD5/m3 d.

Due to the high cyanide concentration, the attached bio-filmson the media might be killed and autolysis resulted to decreasethe contaminants removal efficiencies. Also, the Cu2+ concentrationof 17.9 mg/L of the raw EPWW might effect to both efficiency and

Table 4Removal of contaminants in BAF1 using EPWW containing various glucose concentrations

The addition of glucose (mg/L) Organic loading (kg BOD5/m3 d) BOD5:TN CN�

Inf.a

0 0.048 0.067 41.2100 0.32 0.44 40.2200 0.58 0.81 40.8300 0.85 1.18 40.7400 1.12 1.55 39.1600 1.65 2.29 39.9

a Inf.: Influent of BAF1.b Eff.: Effluent of BAF1.

performance of BAF1 [23]. However, cyanide compounds of EPWWcould be used as the nitrogen source for the microorganisms of bio-logical wastewater treatment system [24–26]. But the heavy met-als as Cu2+ of EPWW affected the growth and performance of bio-films. And the lack of BOD5 (organic matters) in the EPWW mightaffect the growth and removal efficiency of bio-films. But the addi-tion of glucose into raw EPWW could increase both organic andcyanide removal efficiencies of the BAF1 resulted by stimulatingthe bio-films growth [27]. So the removal efficiencies were quitelow without glucose addition and it might be the effect of cyanideand some other toxic substance of raw EPWW. However, the rele-

under HRT of 9 h.

(mg/L) COD (mg/L) Cu2+ (mg/L) Ni2+ (mg/L) Removal efficiencies (%)

Eff.b Inf. Eff. Inf. Eff. Inf. Eff. CN� COD Cu2+ Ni2+

26.9 277 113 16.2 2.65 9.12 2.12 34.7 59.2 83.6 76.820.4 372 129 18.2 2.47 8.77 1.94 49.3 65.3 86.4 77.917.3 485 148 17.9 2.22 9.05 1.91 57.6 69.5 87.6 78.915.1 578 169 18.5 2.41 8.28 1.78 62.9 70.8 87.0 78.512.0 680 191 17.5 2.19 8.36 1.72 69.3 71.9 87.5 79.410.2 897 202 18.9 2.24 8.75 1.76 74.4 77.5 88.1 79.9

J. Cui et al. / Chemical Engineering Journal 241 (2014) 184–189 189

vant data for toxicity test of cyanide compounds and other toxicsubstances of EPWW on the bio-films was not collected in thisstudy. Therefore, the further research regarding the toxicity testof cyanide compounds and other toxic substances such as heavymetals will be conducted to further advance the understandingof toxicity of heavy metals and cyanide compounds.

4. Conclusions

The cyanide containing EPWW could be well treated by thecombined process of BAF1–O3–BAF2 under the optimal conditionof 100 mg/L ozone dosage, BAF1 HRT 9 h and BAF2 HRT 6 h. Underthis condition, the CN�, COD, Cu2+ and Ni2+ removal efficiencieswere 99.7%, 81.7%, 97.8% and 95.3%,respectively and the effluentCN�, COD, Cu2+ and Ni2+ concentrations of 0.16 mg/L, 55.0 mg/L,0.38 mg/L and 0.41 mg/L, respectively satisfied the discharge stan-dard for electroplating (China). Furthermore, the addition of glu-cose into raw EPWW could increase contaminants removalefficiencies of BAF1. Cyanide compounds of EPWW could be usedas the nitrogen source for the microorganisms.

Acknowledgements

This work was supported by the National Natural Science Foun-dation (NSFC) of China, Grant No. 5107 8149. We also appreciatedthe electroplating plant in Zhaoqing city, Guangdong province, PRChina, especially their valuable cyanide containing electroplatingwastewater.

References

[1] J.R. Parga, S.S. Shukla, F.R. Carrillo-Pedroza, Destruction of cyanide wastesolutions using chlorine dioxide, ozone and titania sol, Waste Manage. 23(2003) 183–191.

[2] J.M. Monteagudo, L. Rodríguez, J. Villaseñor, Advanced oxidation processes fordestruction of cyanide from thermoelectric power station waste waters, J.Chem. Technol. Biotechnol. 79 (2004) 117–125.

[3] R.R. Dash, A. Gaur, C. Balomajumder, Cyanide in industrial wastewaters and itsremoval: a review on biotreatment, J. Hazard. Mater. 163 (2009) 1–11.

[4] C.M. Kao, K.F. Chen, J.K. Liu, S.M. Chou, S.C. Chen, Enzymatic degradation ofnitriles by Klebsiella oxytoca 71 (2006) 228–233.

[5] V.K. Sharma, W. Rivera, J.O. Smith, B. O’Brien, Ferrate(VI) Oxidation of AqueousCyanide, Environ. Sci. Technol. 32 (1998) 2608–2613.

[6] M. Barclay, A. Hart, C.J. Knowles, J.C.L. Meeussen, V.A. Tett, Biodegradation ofmetal cyanides by mixed and pure cultures of fungi, Enzyme Microb. Technol.22 (1998) 223–231.

[7] M.I. Ezzi, J.M. Lynch, Biodegradation of cyanide by Trichoderma spp. andFusarium spp, Enzyme Microb. Technol. 36 (2005).

[8] F. Gurbuz, H. Ciftci, A. Akcil, A.G. Karahan, Microbial detoxification of cyanidesolutions: a new biotechnological approach using algae, Hydrometallurgy 72(2004) 167–176.

[9] S. Sirianuntapiboon, K. Chairattanawan, M. Rarunroeng, Biological removal ofcyanide compounds from electroplating wastewater (EPWW) by sequencingbatch reactor (SBR) system, J. Hazard. Mater. 154 (2008) 526–534.

[10] F. Barriga-Ordonez, F. Nava-Alonso, A. Uribe-Salas, Cyanide oxidation by ozonein a steady-state flow bubble column, Miner. Eng. 19 (2006) 117–122.

[11] W. Somboonchai, M. Nopharatana, W. Songkasiri, Kinetics of cyanide oxidationby ozone in cassava starch production process, J. Food Eng. 84 (2008)563–568.

[12] L. Qi, X. Wang, Q. Xu, Coupling of biological methods with membrane filtrationusing ozone as pre-treatment for water reuse, Desalination 270 (2011) 264–268.

[13] X.J. Wang, S.L. Chen, X.Y. Gu, K.Y. Wang, Y.Z. Qian, Biological aerated filtertreated textile washing wastewater for reuse after ozonation pre-treatment,Water Sci. Technol.: J. Int. Assoc. Water Pollut. Res. 58 (2008) 919–923.

[14] Z. Fu, Y. Zhang, X. Wang, Textiles wastewater treatment using anoxic filter bedand biological wriggle bed-ozone biological aerated filter, Bioresour. Technol.102 (2011) 3748–3753.

[15] J. Lin, T. Nakajima, An AM1 study of decomposition of aqueous ozone, J. Mol.Struct.: THEOCHEM 625 (2003) 161–167.

[16] Y. Sakai, M. Wakayama, H. Miyake, A new design method for OD plants, J. Jpn.Soc. Water Environ. 39 (2002) 95–112.

[17] S. Wang, J. Liu, Enhanced biological nutrients removal using an integratedoxidation ditch with vertical circle from wastewater by adding an anaerobiccolumn, J. Environ. Sci. 17 (2005) 894–898.

[18] T. Fujiwara, S. Inamori, K. Nakamachi, K. Ohtoshi, H. Tsuno, F. Nishimura,Operational parameters for simultaneous removal of organics and nitrogenfrom domestic sewage in the high-loading oxidation ditch process, J. Jpn.Sewage Works Assoc. Res. J. 45 (2008) 121–131.

[19] U. von Gunten, Ozonation of drinking water: Part I. Oxidation kinetics andproduct formation, Water Res. 37 (2003) 1443–1467.

[20] T.E. Cloete, D.J. Oosthuizen, The role of extracellular exopolymers in theremoval of phosphorus from activated sludge, Water Res. 35 (2001) 3595–3598.

[21] L. Qiu, J. Ma, L. Zhang, Characteristics and utilization of biologically aeratedfilter backwashed sludge, Desalination 208 (2007) 73–80.

[22] M.D. Mullen, D.C. Wolf, F.G. Ferris, T.J. Beveridge, C.A. Flemming, G.W. Bailey,Bacterial sorption of heavy metals, Appl. Environ. Microb. 55 (1989) 3143–3149.

[23] S. Sirianuntapiboon, T. Hongsrisuwan, Removal of Zn2+ and Cu2+ by asequencing batch reactor (SBR) system, Bioresour. Technol. 98 (2007) 808–818.

[24] S. Ebbs, Biological degradation of cyanide compounds, Curr. Opin. Biotechnol.15 (2004) 231–236.

[25] A. Akcil, T. Mudder, Microbial destruction of cyanide wastes in gold mining:process review, Biotechnol. Lett. 25 (2003) 445–450.

[26] A. Akcil, Destruction of cyanide in gold mill effluents: biological versuschemical treatments, Biotechnol. Adv. 21 (2003) 501–511.

[27] R.S. Bernardes, A. Klapwijk, Biological nutrient removal in a sequencing batchreactor treating domestic wastewater, Water Sci. Technol. 33 (1996) 29–38.