Evaluation of eventual toxicities of treated textile wastewater using anoxic-aerobic algal-bacterial photobioreactor

Effects of a Cellulose Aerogel Template on the Preparation and Adsorption Properties of Coal Gangue-Based Multistage Porous ZSM-5

In this study, a ZSM-5/CLCA molecular sieve was prepared by the hydrothermal method using coal gangue as the raw material and cellulose aerogel (CLCA) as the green templating agent, which not only reduces the cost of traditional molecular preparation but also improves the comprehensive resource utilization rate of coal gangue. Through a series of characterization methods (XRD, SEM, FT-IR, TEM, TG, and BET), the crystal form, morphology, and specific surface area of the prepared sample were tested and analyzed. The performance of the adsorption process of malachite green (MG) solution was analyzed by adsorption kinetics and adsorption isotherm. The results show that the synthesized zeolite molecular sieve and the commercial zeolite molecular sieve are highly consistent. At a crystallization time of 16 h, a crystallization temperature of 180 °C, and an additive amount of cellulose aerogel of 0.6 g, the adsorption capacity of ZSM-5/CLCA for MG was up to 136.5 mg/g, much higher than that of commercially available ZSM-5. This provides an idea for the green preparation of gangue-based zeolite molecular sieves to remove organic pollutants from water. Moreover, the process of adsorbing MG on the multistage porous molecular sieve, which is spontaneous, conforms to the pseudo-second-order kinetic equation and Langmuir isothermal adsorption model.

Bacillus spizizenii DN and microbial consortia biostimulation followed by gamma irradiation for efficient textile wastewater treatment

Textile wastewater still poses a huge environmental problem due to its high water consumption and high effluent release that is full of toxic chemicals. In the present study, different approaches were studied to layout an operating procedure for textile wastewater treatment in order to obtain treated wastewater that is safe for non-potable uses. Our approach depended on (1) co-substrate to biostimulate indigenous microbial textile wastewater community by adding Tryptone Soy Broth (TSB) and TSB supplemented with 1% glucose, (2) co-culture (bioaugmentation) with Bacillus spizizenii DN cells (previously isolated, identified and characterized as efficient decolorizing bacteria), and (3) co-metabolites using Bacillus spizizenii DN metabolites. The obtained results show that using Bacillus spizizenii DN cells resulted in 97.78% decolorization while adding Bacillus spizizenii DN metabolites resulted in 82.92% decolorization, both after 48 h incubation under microaerophilic conditions. The phyla identified for all treatments were Bacteroidota, Firmicutes, and Proteobacteria. The dynamic changes in the bacteria showed that both Clostridium and Acinetobacter disappeared for co-substrate, co-culture, and co-metabolite cultures. While Alkalibacterium and Stenotrophomonas appeared after adding Bacillus spizizenii DN cells, Flavobacterium increased for co-substrate and co-metabolic cultures while iron reducing bacteria appeared only for co-metabolic cultures. The use of 25 kGy gamma irradiation as a sterilization dose post bioremediation ensured safe use of treated wastewater. This was confirmed by cytotoxicity assay; the obtained IC₅₀ tested on BJ fibroblasts obtained from skin showed that gamma irradiated treated wastewater are about 80.1% less toxic than non-irradiated treated wastewater. We conclude that (1) we can use combined bioaugmentation and biostimulation as initial steps for in situ bioremediation in collection tanks and that (2) the proposed protocol for bioremediation of industrial wastewater should be tailored based on the required application and level of safety needed for re-use.

Use of bacterial isolates in the treatment of textile dye wastewater: A review

The textile industry uses large amounts of dyes like reactive, azo, anthraquinone, and triphenylmethane to colour textiles. Dyes that are not used up during the colouration process usually end up in water bodies as waste leading to the pollution of the water bodies. This makes the industry to be one of the major contributors to water pollution in the world. Bacterial agents isolated from various sources like dye contaminated soil and textile wastewater have shown to have the ability to effectively decolourise and degrade these dye pollutants leading to improved water quality. This review discusses bacterial isolates that have been used successfully to degrade and decolourise textile dyes, their mode of dye removal as well as the factors that affect their dye degradation ability. It further looks at the latest wastewater treatment technologies that incorporate bacterial microorganisms to treat dye wastewater.