Study of a hybrid system : Moving Bed Biofilm Reactor-Membrane Bioreactor (MBBR-MBR) in the treatment and reuse of textile industrial effluents
Textile wastewater often shows high color concentration, containing a large range of organic chemicals, with high chemical oxygen demand as well as hard-degradation materials. Therefore, understanding and developing effective textile industrial wastewater treatment technologies is environmentally im...
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| Format: | doctoral thesis |
| Status: | Published version |
| Publication Date: | 2021 |
| Country: | España |
| Institution: | CBUC, CESCA |
| Repository: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/672347 |
| Online Access: | http://hdl.handle.net/10803/672347 https://dx.doi.org/10.5821/dissertation-2117-351123 |
| Access Level: | Open access |
| Keyword: | Àrees temàtiques de la UPC::Enginyeria civil 628 |
| Summary: | Textile wastewater often shows high color concentration, containing a large range of organic chemicals, with high chemical oxygen demand as well as hard-degradation materials. Therefore, understanding and developing effective textile industrial wastewater treatment technologies is environmentally important. Different treatments such as biological or physico-chemical processes have been studied to treat textile wastewater. Membrane Bioreactor (MBR) technology has been widely applied in textile wastewater treatment and Moving Bed Biofilm Reactor (MBBR) is a relatively novel technology to treat this type of wastewater. Both of them have some deficiencies and limitations during application. Thus, a MBBR-MBR hybrid system could be an attractive solution to the shortcomings of each treatment process. In this thesis, a hybrid MBBR-MBR system has been designed and applied for the treatment of textile wastewater. Additionally, the feasibility of reusing the treated water in new dyeing processes has been studied. The first step of the thesis work has been the comparative study of the treatment of textile wastewater by three treatment processes, conventional activated sludge (CAS), MBR and MBBR, working under the same operating conditions. 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, since it reduced the consumption of electricity and decolorizing agent with respect to CAS. According to the results, the water treated by the MBBR system was reused to make new dyeings and the quality of new dyed fabrics was within the acceptable limits of the textile industry. Combined with the theory and experimental results, a hybrid MBBR-MBR reactor was designed and applied in textile wastewater treatment. The MBBR-MBR system achieved reducing the HRT to 1 day, which is very promising in textile industry comparing with conventional biological treatment. The removal efficiency of COD reached 93%, which is almost the maximum for a biological process treating this type of wastewater, as well as the color removal performance, which achieved 85%. Additionally, 99% of the TSS were removed due to the filtration. Furthermore, new dyeing processes reusing the treated water were performed. Color differences between new dyed fabrics and reference fabrics were found within the general requirement of textile industry (DECMC(2:1) < 1). Additionally, based on the experimental results in the pilot plant, an economic study and LCA analysis were carried out to evaluate the economic and environmental feasibility of the implementation of the hybrid MBBR-MBR on an industrial scale. Economically, MBBR-MBR had lower CAPEX and OPEX than CAS process due to lower effluent discharge tax and the decolorizing agent saved. The result of Net Present Value (NPV) and the Internal Rate of Return (IRR) of 18% suggested that MBBR-MBR is financially applicable for the implantation into industrial scale. The MBBR-MBR system also had lower environmental impacts compared with CAS process in the LCA study, especially in some categories, such as the Climate change, Human Health, Marine eutrophication, and ecotoxicity categories, thanks to the high quality of the effluent treated by MBBR-MBR and the avoiding of using extra decolorizing agent, a compound based on a quaternary amine. |
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