Environmental pollution is becoming a serious and challenging problem all over the world because of high level of industrial development and growth. Various industries discharge toxic heavy metals and anions into the environment that considerably enhanced the humiliation of marine environment and significantly threats the ecosystem. These unwanted chemicals cause severe health problems, when they exceed the tolerance limit in water. For this reason, the removal of toxic pollutants is the greatest challenge. Biosorption method based on utilization of microorganisms has been given a significant attention due to efficient, rapid, easier, less expensive and environment friendly properties of biosorbent material for the removal of toxins from aqueous solution. Owing to the significance of biosorption technique, the projected work is based upon the biological preparation of environmental friendly fungal biomass Pleurotus eryngii (P. eryngii) and their exploitation for the removal of selected toxic metal ions (Pb, Cd, Hg) and anions (F-, NO3-) from aqueous system. Before and after sorption the biomass were characterized by FTIR, AFM, SEM and EDX techniques to verify surface functionality and morphology, whereas the surface chemistry charge studies (pHPZC) were carried out to measure the approx. pH at which biosorbent behave as cationic, anionic and neutral species. After optimization of experimental variables (concentration, time, temperature), isotherm (Langmuir, Freundlich, Temkin, D-R models), kinetic (Pseudo first, Pseudo second, Intra particle diffusion models) and thermodynamic (enthalpy, entropy, Gibbs free energy) parameters were calculated. The presence of interfering ions during biosorption and re-usability studies after appropriate desorption were carried out. Response Surface Methodology (RSM) was also employed in selected part of the studies to decrease the number of experiments, improved product yields and reduced treatment time and overall research cost. For the application of P. eryngii on real water samples; toxic pollutant (metals / anions) contaminated samples were collected from river, canal, lake and streams of Sindh, Pakistan. It was evaluated that under optimal conditions (at natural pH values) selected ions were removed effectively underneath the permissible limits of World Health Organization (WHO) drinking water standards. Briefly, for 30 mg L-1 Pb(II) ions 100% removal with sorption capacity of 2.971 mg g-1 was successfully achieved within 5 min at optimum pH 6.0 and 0.35 g sorbent dose. The results following the Langmuir isotherm, pseudo second order kinetic model and were thermodynamically feasible at temperature 30°C. Overall elution of Pb ions achieved from the biomass utilizing 0.1 N HCl solution. Field test results established effectiveness of P. eryngii biomass for the decontamination of Pb(II) ions from drinking water. Similarly, for Cd(II) ion removal 99.9% results were achieved at pH 5.0, dosage 0.2 g, concentration 20 mg L-1, time 10 min and temperature 50°C. A favorable biosorbent capacity of 1.51 mg g−1 was achieved that indicated a good capability of P. eryngii biomass. The sorption efficiency decreased from 99.99 to 56.89 % as the biomass was re-cycled up to 5 times. However, the efficiency of Cd(II) removal from real water samples still lies between 85 to 90%. Correspondingly, the sorption process was relatively fast and > 98% removal of Hg(II) was achieved within 5 min at pH 7.0 with 34.01 mg g-1 biosorption capacity. The Langmuir isotherm and pseudo-second order were the best applicable models to describe the sorption process. The sorption process was exothermic and spontaneous by increased randomness at the solid-solution interface. The adsorbed Hg(II) ions easily desorbed using 5 M HCl solution with higher effectiveness and can be reused up to five cycles. Different electronegative functionalities involve in the binding of Hg(II) metal ions on the surface as evident by various characterization techniques. The study revealed considerable potential of biosorbent for its exploitation in the treatment of industrial effluents containing Hg(II) ion contamination. In further study, toxic anions were selected for the biosorption by white - rot fungal biosorbent P. eryngii. More than 96% removal of F- was achieved at optimum conditions (pH: 2.0; biosorbent dose: 0.2 g; initial concentration: 5.0 mg L−1; temperature: 30°C; agitation: 100 rpm). Langmuir model with 66.6 mg g-1 biosorption capacity fitted the equilibrium data better and followed well pseudo-second order model; while intra particle diffusion was not by any means the only rate-controlling step. The biosorbent was multiple times reusable and showed slight decrease in sorption efficiency in presence of foreign impurities. The application of fungal biomass on F- removal showed satisfactory performance on water samples collected from a fluoride-endemic area. A three level, three factors Central Composite Design (CCD) was used to evaluate the effects and interactions of the process variables removal of NO3- ions from aqueous solution onto P. eryngii dried fungal biosorbent. ANOVA, Ftest, Student’s t-test and lack of fit test showed that NO3- ions biosorption is only slightly concentration dependent, but markedly increases with solution pH and biosorbent dose. The optimum pH (7.0), biosorbent dose (0.24 g) and initial concentration (700.0 mg L-1) were found by desirability function. Under these optimum combinations of process parameter conditions, maximum removal of 88.38% was obtained that assisting its use in larger scale. In final approach of this bio-analytical study, the fungal biomass packed in a mini glass column was used to remove one of the selected ion (Pb) from water. After studying the column performance parameters (initial concentration: 20 mg L-1, flow rate: 1 ml min-1, bed height: 3 cm) maximum Thomas model entrapping capacity of 3.30 mg g-1 at pH 7.0 was obtained. A laboratory column evaluation on real contaminated samples also evident the applicability of sorption column on commercial scale. Hence, the results indicated that P. eryngii is a good biosorbent for removal of heavy metals and anions from polluted water. In addition, the spent fungal biomass can be easily disposed of and can be used as an alternative raw material for large scale composting process.