With rapid industrialization all over the world, pollution is on the increase, and Pakistan is no exception. One of the modes through which pollutants enter the biosphere is that of industrial effluents. Bioremediation is a low cost method available for reclaiming the soils which have been polluted. The present study was carried out in order to determine the effects caused by textile effluent on soil, as well as upon the macro and micro flora present in its environment, and to develop an indigenous remediation technology for cleaning up heavy metal ions and organic pollutants associated with textile industry effluent.
The study was carried out on the effluent and its surrounding soil of Koh-i-Noor Textile Mills Limited, located near the thickly populated peri-urban suburbs of Rawalpindi, Pakistan. Initial recording of data comprised of electrical conductivity, pH and temperature of effluent and soil. The collected samples were processed for further physio-chemical analysis, which included soil field capacity, total soluble salts, organic matter, organic carbon, sulphates, nitrates, phosphorus, potassium and exchangeable cations. The soil and effluent samples were processed for heavy metal analysis using an atomic absorption spectrophotometer. Similarly, plant material was also digested and analyzed for heavy metals. The metals analyzed were Zn, Cu, Cr, Ni, Cd, Fe, Pb, and Mn. Selected fungal strains were studied for Zn detoxification and degradation of 4-aminobenzene sulphonic acid (4ABS), using shake flask transformation studies.
Effluent samples were alkaline, highly coloured, foul smelling, having temperature more than 51°C, with high COD and BOD values. At the reservoir (site 6), all heavy metal ions assessed were above the NEQS. Soil sample analysis showed that soil was alkaline with low field capacity and organic matter. Fe, Cd, and Zn concentrations were very high in soil samples.
Macroflora of various sites, within the factory area, comprised of Zea mays, BromllS sativa, Canabus sativa, Ricinus communis, Xanthrin stromarium and Dichanthillm annulaticllm. Effluent samples showed high bacterial load (CFU/mL) and 65 bacterial strains were isolated, identified and characterized from these samples. Micrococcus and Listeria were predominant genera found in all effluent samples. On the other hand, in soil samples 49 bacterial strains were isolated, identified and characterized. Among soil isolates, high incidence of Bacillus and Micrococcus genera was found. Aspergillus and an unidentified white mycelial mass were prevalent fungal strains found among the 16 strains isolated from the effluent samples. In the soil samples, 22 fungal isolates were identified, having Aspergillus. Rhizopus and an unidentified white mycelial mass as the major fungal population. V AM colonization with the macroflora was assessed alongwith the incidence of infective propogules. Glomus was the most abundant V AM genus found, having 3 morphotypes. All the plant roots were externally colonized by hyphae with abundance of vesicles.
Both fungal and bacterial strains showed not only a tolerance against heavy metals (Zn2+, Cd2+, Cu2+, Ni2+, Mn2+, Pb2+, Fe3"', Cr3+ and Cr6+), but also against organic pollutants (aniline, 4-ABS and pentachlorophenol). Multiple metal and organic pollutant resistances were found among the isolates. Among the Zn tolerant fungal strains, two strains, Aspergillus fumigatus RHOS and Aspergillus flavus RH07, due to their high tolerance (7000 mgfL) were further studied for Zn detoxification. Optimum pH and temperature were found to be 5.0 and 28°C, respectively, for the growth of both strains.
Zn removal of 24.002:0.088% by Aspergillus fumigatus RH05 and 11.632:0.035% by Aspergillus flavus RH07 was observed at a concentration of 4000 mgfL Zn, pH 5.0 and 28°C. For optimal Zn biosorption, temperature was 28°C and pH was 4.0. However, non-living biomass of Aspergillus fumigatus RHOS and Aspergillus flavus RH07 was more efficient as biosorbent for Zn removal. pH 6.0 and pH 5.0 were optimum pH for Zn adsorption in case of Aspergillus fumigatus RH05 and Aspergillus flavus RH07, respectively, at the optimal temperature of 34°C. Dead biomass of Aspergillus flavus RH07 showed better adsorption, as compared to Aspergillus fumigatus RH05.
Non-growing biomass of both Aspergillus fumigatus RH05 and Aspergillus flavus RH07 at pH 4.0 and 28°C, showed maximum Zn removal in 100 mgIL Zn, 59.722:0.454% by Aspergillus fumigatus RHOS and 40.89::!:O.67S% by Aspergillus flavus RH07. Growing and non-growing pellets of Aspergillus fumigatus RHOS showed a better removal of Zn, as compared to Aspergillus flavus RH07.
Among 4-ABS tolerant fungal strains, Aspergillus spp. RH 19 showed best degradation of 4-ABS. For optimal growth, pH for Aspergillus spp. RH 19 was 5.0, and temperature 34°C. 4-ABS degradation was also maximum at 34°C and pH 5.0. In shaking conditions, degradation of 4-ABS by Aspergillus spp. RH 19 took place at a higher rate, as compared to static conditions. Degradation of 4-ABS occurred in the presence, as well as absence, of glucose. Adsorption of 4-ABS by Aspergillus spp. RH 19 was also studied where 4-ABS was adsorbed to the inoculum soon after addition of spores. Both induced, as well as non-induced, non-growing pellets of Aspergillus spp. RH 19, showed degradation of 4-ABS in the presence of glucose.
Textile effluent not only alters the surrounding soil chemistry, but also affects the micro and macroflora existing in such environments. On the other hand, bacteria and fungi, due to exposure to high load of metals and other contaminants, develop high resistance. Aspergillus fumigatus RHOS and Aspergillus flavus RH07 are two strains which are not only Zn tolerant, but, also removed Zn at a very high concentration. Aspergillus spp. RH19, another fungal strain, degraded 4-ABS, an intermediate of azo dye degradation, under various conditions. These strains have the potential to remediate not only textile effluent, but, can be used for bioremediation of other waste waters as well.