Effect of Increasing Streptomicin Loading Rates on the Removal of Toxicity in Sequential Anaerobic ABR/ Aerobic CSTR Reactor System

Research Article

Austin Chem Eng. 2019; 6(2): 1068.

Effect of Increasing Streptomicin Loading Rates on the Removal of Toxicity in Sequential Anaerobic ABR/ Aerobic CSTR Reactor System

Tuzun S* and Sponza DT

1Faculty of Engineering Dokuz Eylul University, Turkey

*Corresponding author: Tuzun S, Faculty of Engineering Dokuz Eylul University, Buca- Izmir Turkey

Received: March 25, 2019; Accepted: May 20, 2019; Published: May 25, 2019


In this study, the anaerobic treatability of streptomycin was investigated in a sequential Anaerobic Baffled Reactor (ABR)/Completely Stirred Tank Reactor (CSTR) system. The ABR reactor was operated continuously through 83days using glucose as primary substrate with constant streptomycin concentration of 200mg/L. 200mg/L streptomycin gives an additional COD concentration to total COD thought continuous operation. 200mg/l of streptomycin gave approximately a COD of 131.38mg/L. The effects of decreasing Hydraulic Retention Times (HRT) (38.4-19.2-12.8-9.60-7.68 days) on COD, antibiotic removal efficiencies and gas productions in anaerobic baffled (ABR) reactor were investigated at constant streptomycin concentration of 200mg/L. Moreover, the effects of decreasing HRT on the change of, Volatile Fatty Acid (VFA) accumulation were investigated in the effluent and in the compartments of ABR reactor.

 In this study, to toxic effect of streptomycin concentration on methane Archaea was investigated using Anaerobic Toxicity (ATA) test under batch conditions in the beginning of the study in order to determine in the IC50 (the streptomycin concentration which caused 50% decreases in the methanogenic activity) value of the streptomycin. The IC50 value for streptomycin was found as 292.06mg/L. In the continuous operation of APR reactor, for maximum COD efficiency (E=90%) and methane percentage (58%) the optimum streptomycin concentration and streptomycin loading rate were found as 200mg/L and 0.180kg/L day, respectively. The total COD removal efficiencies changed between 81% and 95% at different HRTs (38.4-19.2-12.8-9.60-7.68 days) in anaerobic/aerobic reactor system. The maximum COD removal efficiencies at constant streptomycin (200mg/L) concentration were obtained as 89% and 95% in the ABR and CSTR reactor effluents at a HRT of 19.2 days. Maximum total gas, methane gas productions and methane percentage were found as 504 l/day, 446.4 l/day and 58%, respectively at a HRT of 9.60 days. Before a HRT of 9.60 days, the daily total gas, ethane gas productions and methane percentage decreased through HRT. Maximum total gas, methane gas productions and methane percentage were found as 504L/day, 446.4L/day and 58%, respectively, at a HRT of 9.60 days. 259.2L/day total gas, 187L/day methane gas and 42% methane percentage were obtained at a HRT as long as 38.4 days. This indicated the inhibition effect of HRT on methane Archeae. In the continuous operation of APR reactor, for the Total Volatile Fatty Acids (TVFA) values in the effluent of the ABR reactor were found as zero when the HRTs decreased from 38.4 days to 7.68 days. TVFA concentration was higher in the first compartment that other compartments in ABR. TFVA concentration decreased from 608mg/l to 26mg/L in the first compartment when the HRT decreased from 38.4 days to 19.2 days. The effluent TVFA concentrations were approximately zero at all HRTs. Bic.Alk. Concentrations were lower in the first compartment than that the others compartments. This indicates the utilization of alkalinity to buffer the (TVFA) and CO2 produced from the anaerobic co-metabolism of streptomycin and COD. In anaerobic reactor system the TVFA/Bic.Alk. Ratio gives necessary information to determine the stability of the anaerobic reactor. If the TVFA/Bic.Alk. Ratio is lower than 0.4, the reactor is stable [1]. The TVFA/Bic.Alk. Ratio varied between 0.099 and 0.005 in effluent as the HRTs were decreased from 38.4 days to 7.68 days. The antibiotic removal efficiencies at constant streptomycin (200mg/L) concentration were obtained as 66% and 74% in the ABR and CSTR reactor effluents at a HRT of 12.8 days. The total maximum streptomycin removal efficiency was 74% in the sequential reactor system at an influent streptomycine concentration of 179.57mg/L at a HRT of 12.8 days. In this study, it was found that the “streptomycin” antibiotic was mainly degraded (59.79mg/L) in anaerobic ABR reactor while the remaining part of this antibiotic (47.54mg/L) was removed in the aerobic CSTR reactor. In this study, the acute toxic effect of synthetic wastewater containing streptomycin was investigated, separately, through anaerobic/aerobic degradation at decreased HRTs (38.4-19.2-12.8-9.60-7.68 days) using Daphnia magna test. The acute toxicity test results performed with Daphnia magna showed that the EC50 values decreased from influent 400mg/L to 132mg/L, and to 20mg/L in the effluents of ABR and aerobic reactor at a HRT of 38.4 days. The total acute toxicity reduction in sequential ABR CSTR reactor effluent was 95%.

Keywords: Aerobic Continuous Stirred Tank Reactor System (CSTR); Anaerobic Baffled Reactor (ABR); Daphnia magna; Streptomycin; Toxicity


Antibiotics are an important group of pharmaceuticals in today’s medicine. In addition to the treatment of human infections, they are also used in veterinary medicine such as streptomycin. Bacteria that are resistant to antibiotics are present in surface water [2]. Antibiotics are found in ground water at concentrations below than 10µg/L. The source of antibiotics in ground water originating from the leaching the fertilized fields with animal slurry and from the waters passing through the sediments [2].

The anaerobic treatability studies concerning the pharmaceuticals and antibiotics are limited with few studies: The performance of an Upflow Anaerobic Filter (UAF) treating a chemical synthesis-based pharmaceutical wastewater was evaluated under various operating conditions [3].The performance of an Up-flow Anaerobic Stage Reactor (UASR) treating pharmaceutical wastewater containing macrolide antibiotics was investigated [4].The performance of a lab-scale hybrid Up-flow Anaerobic Sludge Blanket (UASB) reactor, treating a chemical synthesis-based pharmaceutical wastewater, was evaluated under different operating conditions. This study consisted of two experimental stages: first, acclimation to the Pharmaceutical wastewater and second determination of maximum loading rate (OLR) 1kg COD/m3d [5]. A four-compartment Periodic Anaerobic Baffled Reactor (PABR) was run in a ‘clockwise sequential’ switching manner continuously fed on Chinese traditional medicine industrial wastewater [6].

The Anaerobic Baffled Reactor (ABR) is high rate anaerobic reactor offering two-phase separation with a single vessel. The literature survey shows that there is a lack on the anaerobic treatment of streptomycin and chloramphenicole by ABR. In other words, no study was found in the literature for the ABR reactor treating the wastewaters containing streptomycin.

Streptomycin is an antibiotic drug, the first of a class of drugs called amino glycosides to be discovered, and was the first antibiotic remedy for tuberculosis. Streptomycin was first isolated on October 19, 1943 by Albert Schatz, a graduate student, in the laboratory of Selman Abraham Waksman at Rutgers University. The chemical identities of the streptomycin and physical and chemical characteristics of the streptomycin, in Tables 1,2, respectively [7].

It has been known for more than six decades that certain fungi and bacteria are capable of producing chemical substances, which have the capacity to inhibit the growth of, and even to destroy, pathogenic organisms. Only within the last twelve or thirteen years, however, have antibiotics begun to find extensive application as chemotherapeutic agents. Among these, penicillin and streptomycin have occupied a prominent place. Penicillin is largely active against gram-positive bacteria, gram-negative cocci, anaerobic bacteria, spirochetes and actinomycetes; streptomycin is active against a variety of gram-negative and acid-fast bacteria, as well as against gram-positive organisms, which have become resistant to penicillin.

Since the discovery of streptomycin, the production and clinical application of this antibiotic have had a phenomenal rise. The streptomycin producing strain of Streptomycin griseus was isolated in September 1943, and the first public announcement of the antibiotic was made in January 1944. Before the end of that year, streptomycin was already being submitted to clinical trial. Within 2 years, the practical potentialities of streptomycin for disease control were definitely established.

Material and Methods

Experimental setup

A schematic of the lab-scale sequential ABR and CSTR reactors used in this study are presented in Figure 1. The effluent of the anaerobic ABR reactor was used as the influent of aerobic CSTR reactor. The ABR reactor was rectangular box having the dimensions 20cm wide, 60cm long and 40cm high. The ABR reactor with the active reactor volume (38.4L) was divided into four equal compartments by vertical baffles. Each compartment was further divided into two by slanted edge (45°C) baffles to encourage mixing within each compartment. Therefore, down-comer and up-comer regions were created. The liquid flow is alternatively upwards and downwards between compartment partitions. This provided effective mixing and contact between the wastewater and biomass at the base of each upcomer. In other words, during upflow, the waste flow contact with the active biomass and it is retained within the reactor providing a homogenous distribution of wastewater. An additional mixing was not supplied to the compartments of the reactor. The width of the downcomer was 4cm and the width of the up-comer was 11cm. The passage of the liquid from each compartment to another was through an opening with size 40 mm ×10 mm that located about 80mm from the top of each compartment. The liquid sampling ports were located at 40mm back of the effluent opening of each compartment. The sludge sampling ports were also located in the center of the compartments and 80mm above from the bottom of the each compartment. The influent feed was pumped using a peristaltic pump. The outlet of the ABR was connected to a glass U-tube for controlling the level of wastewater. The produced gas was collected via porthole in the top of the reactor. The operating temperature of the reactor was maintained constant at 37±1°C by placing the ABR reactor on a heater. A digital temperature probe located in the middle part of the second compartment provided the constant operation temperature. This provided a homogenous temperature in whole compartments of ABR reactor. The aerobic CSTR reactor consisted of an aerobic (effective volume=9L) and a settling compartment (effective volume=1.32L).