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. Graphical abstract

The increase in using antibiotics, especially Azithromycin have increased steadily since the beginning of COVID19 pandemic. This increase has led to its presence in water systems which consequently led to its presence upon using this water for irrigation. The aim of the present work is to study the impact of irrigation using Azithromycin containing water on soil microbial community and its catabolic activity in the presence of phenolic wastes as compost. Wild berry, red grapes, pomegranate, and spent tea waste were added to soil and the degradation was monitored after 5 and 7 days at ambient and high temperatures. The results obtained show that at 30 °C, soil microbial community collectively was able to degrade Azithromycin, while at 40 °C, addition of spent tea as compost was needed to reach higher degradation. To ensure that the degradation was biotic and depended on degradation by indigenous microflora, a 25 kGy irradiation dose was used to kill the microorganisms in the soil and this was used as negative control. The residual antibiotic was assayed using UV spectroscopy and High Performance Liquid Chromatography (HPLC). Indication of Azithromycin presence was studied using Fourier Transform Infrared Spectroscopy (FTIR) peaks and the same pattern was obtained using the 3 used detection methods, the ability to assign the peaks even in the presence of soil and not to have any overlaps, gives the chance to study this result in depth to prepare IR based sensor for quick sensing of antibiotic in environmental samples.