Efficiency of sequencing batch reactor for removal of organic matter in the effluent of petroleum wastewater

The main aim of this research was to study the biodegradation of Methyl Tertiary Butyl Ether (MTBE) using aerobic sequencing batch reactor (SBR) at a pilot-Scale. The reactor was made of a 3 mm-thick glass cylinder with an internal diameter of 12 cm and height of 60 cm. SBR operated in five phases. The first phase was filling the reactor for about 10 min. the second phase was the main reactor for biological treatment of petroleum wastewater about 21.55 h. The third phase was the sedimentation (1 h). The fourth phase was decanting from the reactor for about 10 min. The last phase consisted of idle for about 45 min. The experiments showed that the mixed microbial mass is able to degrade high concentration of methanol up to 250 mg/l, and concentration of MTBE up to 70 mg/l for a 24 h cycle. However, the mixed microbial mass is not able to degrade MTBE with concentration more than 70 mg/l. Microorganisms were generally isolated from Fajr petrochemical wastewater treatment plant. Analysis showed that the mixed microbial mass able to biodegradation of COD up to 1350 mg/l in effluent. Aerobic SBR can be used for biological treatment of the petroleum wastewater containing pollutants such as methanol, MTBE with a promising efficiency.


a b s t r a c t
The main aim of this research was to study the biodegradation of Methyl Tertiary Butyl Ether (MTBE) using aerobic sequencing batch reactor (SBR) at a pilot-Scale. The reactor was made of a 3 mmthick glass cylinder with an internal diameter of 12 cm and height of 60 cm. SBR operated in five phases. The first phase was filling the reactor for about 10 min. the second phase was the main reactor for biological treatment of petroleum wastewater about 21.55 h. The third phase was the sedimentation (1 h). The fourth phase was decanting from the reactor for about 10 min. The last phase consisted of idle for about 45 min. The experiments showed that the mixed microbial mass is able to degrade high concentration of methanol up to 250 mg/l, and concentration of MTBE up to 70 mg/l for a 24 h cycle. However, the mixed microbial mass is not able to degrade MTBE with concentration more than 70 mg/l. The contact time, initial COD concentration and solution pH were studied for the removal of MTBE In the SBR reactor.

Experimental features
The main substrate of the synthetic solutions for to feed the SBR reactor, including methanol, TBA and MTBE, along with nutrients (nitrogen and phosphorus), and essential elements (micro elements) was injected to during application of reactor. Data source location Ahvaz city, Khuzestan province, Iran Data accessibility available in this article

Value of the data
Data showed that mixed microbial mass is able to degrade high concentration of methanol and MTBE in petroleum wastewater.
According to data SBR can be used as a biological treatment method to remove MTBE in petroleum wastewater.
Removal of MTBE using SBR has no need for extra tanks, secondary sedimentation and system of returning sludge.

Data
Microorganisms for biodegradation of MTBE were isolated from the real petrochemical wastewater treatment plant. Nutrient injection values were calculated regard to input COD concentration. Table 1 an environment with natural pH is a promising condition for the maximum growth rate of bacteria. Figs. 1-4 show the trend of COD removal by microorganisms in 4 steps. At first step methanol was used as substrate and then in second and third steps, TBA and MTBE was used as substrate, respectively. We also collected data when used reactor for COD removal of real petroleum wastewater. In this study the concentration of COD during the process varied in the range of 313-780 mg/l. At the all four steps, change in the pH of treated wastewater was very low.

Experimental design, materials, and methods
In this study, all chemicals materials were purchased from Merck. Microorganisms for biodegradation of MTBE were isolated from the real petrochemical wastewater treatment plant. The SBR reactor, a cylindrical shape with a thickness of 2 mm, height of 50 cm, diameter of 12 cm and volume of 6.1, was made of glass. It was complemented by two peristaltic pumps for feeding and discharging effluent and excess sludge [1][2][3]. H 2 SO 4 and NaOH were used to adjust pH in neutral state of 7. Present work has shown that an environment with natural pH is a promising condition for the maximum growth rate of bacteria (Fig. 1) [4,5]. 70 mg/l of MTBE was determined as the optimal loading for SBR in this study. The main substrate for feeding the SBR was included methanol, TBA and MTBE along with nutrients (nitrogen and phosphorus). Gas Chromatograph (Agilent model) was used for measuring the MTBE [6][7][8]. Low levels of essential elements (micro elements) were injected to SBR during application. In order to prepare activate and adapted microorganisms, the primary activated sludge (Seed sludge) was collected from the petrochemical Complex [9]. According to Table 2, Chemical oxygen demand (COD) was analyzed with standard methods (3249) for evaluation of efficiency of process [10].