Development of aerobic granular sludge for removal of pollutants from textile wastewater

Abstract

The textile industry is renowned for its significant contribution to global economic growth. However, the textile manufacturing processes generate vast quantities of wastewater containing various pollutants that pose substantial environmental and health risks. Traditional wastewater treatment methods struggle to efficiently remove the complex and diverse contaminants like color, organic pollutant and suspended particlesfound in textile wastewater. Therefore, alternative treatment technologies, such as aerobic granular sludge (AGS), have gained increasing attention due to their potential for enhanced pollutant removal and process stability in the field of textile sectors. This study presents a comprehensive investigation of the application of aerobic granular sludge for the treatment of textile wastewater. The primary objective of this study is to assess the performanceand feasibility of AGS systems to achieve efficient and sustainable textile wastewater treatment.In this study, wastewater from a knit dyeing textile industry was collected to use as raw textile wastewater (RTWW) for feeding in the AGS reactor. The wastewater quality of RTWW was analyzed in the environmental laboratory and found average data for color ~3300 Pt-Co @455 nm, COD ~1000 mg/L and TSS ~120 mg/L. The geometry for the AGS reactor was selected at H/D of 5.0 and operational philosophy for AGS reactor was followed by steps of sequential batch reactor (SBR). The AGS reactor was initially fed with 1000 mL of RTWW and 1000 mL of activated sludge as seed. The activated sludge was collected from the aeration tank of a textile industry effluent treatment plant where the MLSS was 4600 mg/L at the starting of the reactor operation. In this study, total fifty-eight cycles were conducted in the AGS reactor including granulation phase, reactivation phase after idle period and An-Ae SBR operation phase. Hydrodynamic shear force at 2.4 cm/s ~ 3.6 cm/s and short settling time at 5 minutes ~ 3 minutes were considered as selection pressures for development of AGS from seed flocculant sludge. This investigation found the successful growth of AGS in the batch reactor, with granule sizes ranging from 1mm to 3 mm. The SEM analysis was also performed in this study to examine the morphology of the granules, where it was evident that granular sludge and flocculant sludge differed greatly from one another. The effluent treated by AGS was examined in BUET environmental laboratoryto assess the potential of AGS for treating real textile wastewater. The tests were done in different conditions of operation including granulation phase, reactivation phase after idle period and An-Ae SBR operation phase. The results were observed more than 70% removal of color, COD and more than 95% removal of TSS from RTWW. The AGS capability to treat RTWW was also examined after resuming from the idle period lasted for two months. The results of color, COD and TSS removal were found as good as earlier of idle phase. In the study, the elimination of contaminants from textile wastewater using the AGS granules was also demonstrated by the FTIR spectra analysis.