Textile wastewater treatment using magnetic powder activated carbon biogranules

Abstract

Biogranulation technology is novel in the field of biological wastewater treatment with high removal potential as well as providing economical and technical advantages. This technology has been widely tested in the degradation of various types of wastewater owing to its unique sludge properties and high biodegradability potential. Despite its unique characteristics, the major drawback of biogranulation is the long start-up period. This study investigated the possibility of developing biogranules with magnetic powder activated carbon (MPAC) in treating synthetic textile wastewater. This study was aimed at enhancing biogranules development process with better characteristics and high removal performance. At early stage of this study, the effects of magnetic field and MPAC on the initial process development of biogranules were studied using one factor at a time (OFAT) and response surface methodology (RSM). The cultivation of biogranules was then investigated using two laboratory scale sequencing batch reactors (SBR) under intermittent anaerobic and aerobic conditions. Reactor R1 acted as a control system while reactor R2 was added with MPAC. The reactors were designed with 3 L of total working volume and operated at 50% volumetric exchange rate. These biogranules were cultivated with a mixture of textile mill and municipal wastewater sludge. The systems were fed with synthetic textile wastewater. Removal performances, structural aspects and formation of MPAC biogranules were examined based on physical, biological and chemical properties. Batch test results showed that static magnetic field induction and MPAC gave significant positive effect on improving the initial biogranulation process. After 60 days of development stage in the SBR system, the average size of the biogranules increased, reaching 2.0 mm ± 0.5 with an average settling velocity of 44 m/h and sludge volume index (SVI) of 34 mL/g. Total biomass concentration was 8.2 g/L, which was observed to be beneficial for the performance of the system. The extracellular polymeric substances (EPS) of newly developed biogranules were also measured in this study. The total EPS content for these biogranules was 0.083 g. SBR system containing MPAC biogranules showed the best removal performance when operated with 24 hours hydraulic retention time (HRT) with an intermittent of anaerobic (18 hours) and aerobic (6 hours) reactions. The highest removal performance for color, ammonia, TOC and COD were 83%, 98%, 95% and 97%, respectively. The final stage of the study involved the development of an artificial neural network (ANN) for the prediction of the biogranules performance at different HRT and reaction phases. The ANN model has successfully predicted the color removal performance with regression (R2) of 0.9923 and mean square errors (MSE) of 2.75e-05. This study demonstrated that the addition of MPAC in the development of biogranules has demonstrated significant improvement in the physical, biological and chemical characteristics of the newly developed biogranules. The addition of MPAC could shorten and improve the biogranulation development where MPAC acts as the support media for microbial attachment during the development of biogranules.