Abstract
In this study, three different biological methods—a conventional activated sludge (CAS) system, membrane bioreactor (MBR), and moving bed biofilm reactor (MBBR)—were investigated to treat textile wastewater from a local industry. The results showed that technically, MBR was the most efficient technology, of which the chemical oxygen demand (COD), total suspended solids (TSS), and color removal efficiency were 91%, 99.4%, and 80%, respectively, with a hydraulic retention time (HRT) of 1.3 days. MBBR, on the other hand, had a similar COD removal performance compared with CAS (82% vs. 83%) with halved HRT (1 day vs. 2 days) and 73% of TSS removed, while CAS had 66%. Economically, MBBR was a more attractive option for an industrial-scale plant since it saved 68.4% of the capital expenditures (CAPEX) and had the same operational expenditures (OPEX) as MBR. The MBBR system also had lower environmental impacts compared with CAS and MBR processes in the life cycle assessment (LCA) study, since it reduced the consumption of electricity and decolorizing agent with respect to CAS. According to the results of economic and LCA analyses, the water treated by the MBBR system was reused to make new dyeings because water reuse in the textile industry, which is a large water consumer, could achieve environmental and economic benefits. The quality of new dyed fabrics was within the acceptable limits of the textile industry.
Highlights
As one of the largest industries worldwide, the textile industry produces significant amounts of wastewater
(54 mg/L) and total phosphorous (TP) (11 mg/L), over 90% removal of total nitrogen (TN) and TP was obtained after membrane bioreactor (MBR) and moving bed biofilm reactor (MBBR)
Of MBR and MBBR was gradually reduced to evaluate if the treating efficiency could be maintained while the treating capacity was increased
Summary
As one of the largest industries worldwide, the textile industry produces significant amounts of wastewater. Textile wastewater is generated in different steps during production, such as destarching, mercerization, dyeing, and washing [1], and is known to contain considerable amounts of organic compounds which provide color to the effluent [2]. One of the most applied biological methods in treating textile wastewater is the conventional activated sludge (CAS) process [4,5]. The main objective of the CAS process is to remove organic compounds [6]. The CAS system has disadvantages such as high hydraulic retention time (HRT), problems with sludge settling, requirement of large space [7], and poor color removal efficiency due to the low biodegradability of dyes which can only be partially adsorbed on biomass [8,9,10].
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