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Performance Evaluation of Activated Sludge Process for Treating Pharmaceutical Wastewater Contaminated With Β-Lactam Antibiotics

ABOU-ELELA S. I.1 AND EL-KHATEEB M. A.1,2*
  1. Water Pollution Research Department, National Research Center, Dokki, Cairo, Egypt
  2. Faculty of Sciences and Arts, Chemistry Department, Al Qurrayat, Aljouf University, KSA
Corresponding Author: EL-KHATEEB M. A, E-mail: elkhateebcairo@yahoo.com
Received: 24 November, 2014 Accepted: 20 December, 2014

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Abstract

The aim of this work is to evaluate and assess the performance of an activated sludge process for the treatment of pharmaceutical wastewater contaminated with β-lactam antibiotics. The pharmaceutical plant produces β-lactam antibiotic derivatives (syrup, tablets and capsules). The wastewater was highly contaminated with high concentrations of organic and inorganic pollutants as presented by COD (980 mg/L), BOD (585 mg/L) and TSS (86). Also, the wastewater was contaminated with antibiotic residues (Amoxicillin, Ampicillin and Dicloxacillin at concentrations of 99.4, 70.6, and 119.4 mg/L, respectively). Treatment of wastewater using an activated sludge process indicated that the β-lactam antibiotic constituents were degraded up to 98%. In addition, the removal rates of COD and BOD reached 88.4% and 94.8%, respectively. In conclusion the β-lactam wastewater can be treated successfully using an activated sludge process without any adverse effect on its performance.

Keywords
Aerobic treatment, Activated sludge, β-lactam, Wastewater, Antibiotics, Pharmaceutical industry

INTRODUCTION
The pharmaceutical industry produces wastewater containing a high strength of organic pollutants. The wastewater contaminants include antibiotics as well as analgesic and anti-inflammatory drugs. Wastewater containing antibiotic resistance plasmids represents a threat to public health if it is discharged into the environment and combined with pathogenic bacteria (Rahube and Christopher, 2010). Consequently, treatment of pharmaceutical wastewater is necessary to protect the environment from the release of residual antibiotics. Despite their low concentrations these contaminants can threat human health and the environment, particularly water resources (Abou- Elela et al., 2012). these contaminants include β -lactam antibiotics, a broad class that include amoxicillin (AMOX), ampicillin (AMP), penicillin (PEN G), oxacillin (OXA), cloxacillin (CLOX)) and cephalosporins. They are the most widely-used group of antibiotics available (Gulkowska et al., 2008). The β- lactam ring (6-aminopenicillanic acid) is responsible for the antibacterial activity and variable side chains account for the major differences in their chemical and pharmacological properties. All penicillins are acidic drugs that could be degraded in neutral or basic solutions (Maurer, 2008). The degradation opens the β-lactam ring resulting in inactivation of the antibiotic. The β-lactams are widely used for their antimicrobial activity against both Gram-positive and Gram-negative organisms.
There are concerns about β-lactam residues in food because of the potential for allergic reactions in sensitive individuals and production of bacterial strains that are resistant to important classes of antibiotics (Launay, et al., 2004 & Lubelchek and Weinstein, 2008). A high percentage of antibiotics consumed by humans and animals in hospitals or by prescription are excreted unchanged via urine and feces into domestic sewage and are discharged to wastewater treatment plants (WWTPs) (Börjesson et al., 2009). In WWTPs these compounds are partially removed and there is a potential for residues to be released through the WWTP effluent into the aquatic environment (Watkinson et al., 2009). Thus, the origin of antibiotic contamination in surface and groundwater is considered to be point and non-point source discharges of municipal and agricultural wastewater (Halling- Sørensen et al. 1998 & Li et al. 2008).
The main objective of this work is to investigate and assess the performance of an activated sludge process for the treatment of wastewater containing β-lactam antibiotics while assuring the quality of the treated effluent and its compliance with the National Environmental Regulatory Standards.

MATERIALS AND METHODS

Industrial Auditing
The pharmaceutical plant under consideration produces β-lactam antibiotics in the form of dry syrup, tablets, capsules and injectable powder. The main active raw materials used are amoxicillin trihydrate, dicloxacillin and anhydrous Ampicillin, while sugar, flavors, starch, and coloring materials are used as inactive ingredients. Wastewater was discharged at a flow of 20 m3/day to a nearby basin, without any treatment. The sources of wastewater are mainly from the washing water of manufacturing vessels and floor washing.

Sampling Location and Collection
Composite wastewater samples were collected from the end-off-pipe in the plant and during the working shifts to represent the actual quality and quantity of the wastewater.

Analyses
Physico-chemical characteristics of the collected wastewater and the treated effluent were determined by analysis of pH, chemical oxygen demand (total CODtot), (soluble CODsol), biological oxygen demand (BOD5), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), total phosphorus (TP), hydrogen sulphide and oil&grease. Sludge was analyzed for total solids (TS) and volatile solids (VS). Determination of amoxicillin, ampicillin and dicloxacillin in the raw wastewater and treated effluent were measured according to Vishal et al. (2011); Mahgoub and Aly (1998) and Patel et al. (2012), respectively. All the analyses unless otherwise specified, were carried out according to standard methods for water and wastewater (2005).

Biological Treatment
Biological degradation of β-lactam wastewater using activated sludge was carried out using a system similar to that described by Abou-Elela et al. (2009). Before starting the aerobic treatment, the COD, TKN and TP contents were analyzed to insure the C:N:P ratio and to add supplemental nutrients (if needed). Table 1 shows that, there were no need to add nutrients. For the enrichment of heterotrophic and nitrifying bacteria (Nitrosomonas plus Nitrobacter), sludge from an activated sludge wastewater treatment plant located at North Cairo was loaded into two growth columns with 2.5 liters capacity each. The columns were operated using air pumps with two outlets to provide aeration rates around 2-3 mg O2/L. The columns were fed with settled sewage from a nearby sewage network. The initial concentration of the mixed liquor suspended solids (MLSS) within the columns was adjusted to 3 g/L with almost 75% volatile matter, while 150 mg/L sludge withdrawal was carried out daily to give a sludge residence time (SRT) of 20 days. Gradual addition of β-lactam wastewater to the aerated column was carried out to adapt the mixed liquor to the industrial wastewater. At the starting period of the treatment process the ratio of β- lactam wastewater to sewage was 1:2 for a period of one week, and then increased to 1:1 in the second week. Full feeding with β-lactam wastewater was done in the third week.
Adaptation of the mixed liquor to the experimental conditions was continued for another two weeks until it reached the steady state conditions. Samples were taken during the first six hours and after 24 hours to determine the exact time for the treatment of wastewater. During the adaptation period (5 weeks), COD and TSS concentrations as well as the pH-value were monitored. Also, microscopic examinations of the existing microorganisms were depicted. After mixed liquor adaptation, a growth curve for the COD and TSS removal rates was generated.

RESULTS AND DISCUSSION

Wastewater Characteristics
Average values from analyses of the industrial wastewater are shown in Table (1). pH was slightly acidic and ranged from 5.3 to 6.9. The organic loads represented by CODtot, CODsol and BOD reached 1168, 1023 and 700 mg/L with average values of 980, 725 and 585 mg/L, respectively. According to Table 1 most of COD contributed from the soluble part. The total COD was 980 while, the dissolved part was 725 mg/ L. Consequently, about 74% of COD was in the dissolved form. Average concentrations of nitrates, nitrites, ammonia and TKN were 2, 0.06, 1 and 36 mg/L, respectively. The wastewater contained average concentrations of 99.4 mg/L Amoxicillin, 70.6 mg/ L Ampicillin and 119.4 mg/L Dicloxacillin.

Adaptation of Biological Culture to Wastewater
After an adaptation time of five weeks and during the period of this study, microscopic examination showed that many tolerant species of microorganisms belonging to fauna, namely; Insect larvae, Vorticlla (ciliate, Protozoa), Paramecium (Ciliate, Protozoa) and others related to flora, namely; Microcystis sp. and Euglena spp. Were present in the mixed liquor. This indicated that these microorganisms can grow well at these conditions.
Daily measurements of influent and effluent COD were carried out until the system reached steady state conditions as indicated by consistent COD concentrations in the treated effluent.
The CODtot, CODsol and TSS concentrations in a tested sample were reduced from 586.7, 477.0 and 245.3 to 94.7, 71.7 and 47.7 mg/L, respectively. Effluent pH tended to increase after biological treatment. This may be attributed to biodegradation of β-lactam to compounds containing hydroxyl and ammonium groups. Also, the nitrates concentration in the treated effluent increased from 0.3 to 14.4 mg/L, while the concentration of ammonia decreased from 6.7 to 2.8 mg/L, including partially nitrifying conditions.

Determination of the Optimum Operating Conditions Required for Biological Treatment
A growth curve was carried out to determine the optimum detention time for biological degradation using 100% β-lactam wastewater. Raw industrial wastewater was fed to the aerated column. The effect of different contact times between 0 and 24 hrs was examined. Samples were collected and analyzed for COD and TSS. Figures 1, 2 show that the best removal rate of COD (total and soluble) and TSS were achieved after 24 hr detention time. Their corresponding residual values were 117 and 18 mg/L, while their corresponding removal rates were 83.2% and 78.8%, respectively.
The pH of the treated wastewater increased to the alkaline range (from 6.9 ± 0.2 to 8.2 ± 0.2).

Treatment of Industrial Wastewater
After the adaptation period, the industrial waste water from the β-lactam plant was fed to the biological treatment unit. The system was operated at the pre-determined detention time of 24 hrs. The performance of the treatment process was recorded in Figure (1, 2). High removal of COD and BOD were achieved; average removal values were 88.1 and 94.8% with residual concentrations of 116.5 and 30.3 mgO2/ L, respectively. Also, a slight increase in the pH value to the alkaline range took place. This may be attributed to the biodegradation which opens the β-lactam ring to give slightly alkaline by-product compounds (Li et al., 2008). The β-lactam ring is considered a relatively unstable compound (Christian et al., 2003). This was confirmed by analysis of β-lactam concentrations before and after treatment. Almost 99% removal of Amoxicillin, Ampicillin and Dicloxacillin were achieved with corresponding average residual concentrations of 11, 8 and 14 mg/L, respectively as shown in Table 2.

CONCLUSIONS
Treatment of pharmaceutical wastewater contaminated with β-lactam antibiotics did not impair the performance of the activated sludge process and produced a high quality effluent. Complete removal of β-lactam compounds were achieved and the quality of the treated effluent complied with the National Environmental Regulatory Standard for wastewater discharge into public sewerage network.

ACKNOWLEDGMENT
The research team gratefully acknowledges the keen interest of the management of Misr Co. for pharmaceutical industry, Cairo, Egypt for their unlimited support and assistance during the period of this study.

Tables at a glance
Table icon Table icon
Table 1 Table 2

Figures at a glance
Figure 1 Figure 2
Figure 1 Figure 2

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