Treatment of textile effluent in a developed phytoreactor with immobilized bacterial augmentation and subsequent toxicity studies on Etheostoma olmstedi fish

Highlights

• A phytoreactor was developed and augmented with immobilized bacteria.

• This consortium showed enhanced treatment than the individual species.

• Oxido-reductases from P. crinitum and B. pumilus could decolorize the effluent.

• Characterization of effluent samples endorsed the efficacy of consortial strategy.

• Toxicity studies revealed the less toxic nature of the consortium treated effluent.

Abstract

A static hydroponic bioreactor using nursery grown plants of Pogonatherum crinitum along with immobilized Bacillus pumilus cells was developed for the treatment of textile wastewater. Independent reactors with plants and immobilized cells were also kept for performance and efficacy evaluation. The effluent samples characterized before and after their treatment showed that the plant–bacterial consortium reactor was more efficient than those of individual plant and bacterium reactors. COD, BOD, ADMI, conductivity, turbidity, TDS and TSS of the textile effluent was found to be reduced by 78, 70, 93, 4, 90, 13 and 70% respectively within 12 d by the consortial set. HPTLC analysis revealed the transformation of the textile effluent to new products. The phytotoxicity study on Phaeseolus mungo and Sorghum vulgare seeds showed reduced toxicity of treated effluents. The animal toxicity study performed on Etheostoma olmstedi fishes showed the toxic nature of untreated effluent giving extreme stress to fishes leading to death. Histology of fish gills exposed to treated effluent was found to be less affected. The oxidative stress related enzymes like superoxide dismutase and catalase were found to show decreased activities and less lipid peroxidation in fishes exposed to treated effluent.

Introduction

Real textile effluents are a complex mixture of organic, inorganic, elemental, polymeric products, acids, base, salts, mordants, fasteners, and detergents predominated by a variety of dyes and coloring agents. The toxicity of dyes and textile effluents is becoming a major threat confronting the modern world as these xenobiotic compounds pollute our valuable water resources [1]. Presence of these dye stuffs in the water bodies decreases the penetration of sunlight which reduces the photosynthetic activity, dissolved oxygen concentration, water quality and depicts toxic effects on the aquatic flora and fauna [2]. The textile wastewaters containing mixture of dyes generally have high BOD, COD, TOC, suspended, and dissolved solids and other toxic chemical compounds. The colored wastewaters released by textile dye processors are not only difficult to treat but also very toxic to all biological forms including humans.

Textile dyes have been proved to be highly toxic to crustaceans like Daphnia magna [3]. Some of the reactive dyes were found to show an increased rate of bladder cancer in dye manufacturing industry workers [4]. Textile paint chemical sprays have been reported to cause a pulmonary disease called ‘Ardystil syndrome’ to many sprayers leading to deaths in Spain and Algeria [5]. The complex structure of aminoazobenzene dyes and their derivatives are able to cause mutations leading to cancer [6]. The studies on Salmonella bacterium and human HepG2 cell line revealed the mutagenic nature of Disperse Blue 291 dye [7], [8]. Malachite Green dye and its metabolite leucomalachite green have also been reported as toxic and persistent in two human cell lines causing hypertrophy and vacuolization followed by necrosis and cirrhosis in hepatocytes of freshwater catfish, Heteropneustes fossilis [9]. The concentrated textile effluents have been found to significantly reduce the red blood cells count in Swiss albino rats [10]. These are just a few examples of toxicity of textile dyes and many more are yet to be found out. Therefore, it becomes very essential to treat textile effluents before their release into the environmental sink.

The modern methods like bio and phytoremediation for textile effluent treatment discourage the employment of physicochemical methods owing to their shortcomings like secondary pollution, cost and efficacies. In biological methods, the use of bacteria, fungi or other combinatorial systems are difficult to be monitored when in situ administration of the pollutant is concerned. Phytoremediation has immerged as a famous, cost effective and ecofriendly treatment method for the treatment of textile wastewaters. Common garden plants like Tagetes patula, Aster amellus, Glandullaria pulchella, Sesuvium portulacastrum and Petunia grandiflora were shown to have tremendous dye degradation potential [11], [12], [13], [14]. The bacterial assisted phytoremediation as recently proposed as a more efficient process also have in situ applicability [15], [16], [17]. In this study, a static hydroponic phytoreactor was developed using Pogonatherum crinitum grass and augmented with immobilized Bacillus pumilus cells for enhancement of efficacy. The bacterium is a natural inhabitant of root zone and therefore can easily survive on exudates released by plants. After the treatment process, the toxicity and risk assessment of untreated and treated real textile effluent on Etheostoma olmstedi fish was performed.