Integrated Anaerobic Biological Treatment of Industrial Wastewater In Pakistan the major threat to the livelihood of the people is water pollution. A large amount of the municipal and industrial wastes are thrown everyday in to the environment. Current study aimed to characterize, treat the industrial effluent of HIE Hattar and also assessed the impacts of selected metals and volatile compounds on anaerobic digestion. Effluent samples were collected from five drains carrying the combined effluent of industries and characterized for various physicochemical parameters. All wastewater samples had values above the National Environmental Quality (NEQ) standards. Hattar industrial wastewater was treated by the Anaerobic Bio-Reactor (ABR). The ABR average RE of 11.9% was observed for the Total Dissolved Solids (TDS) with the concentration of 10~15.7 mg/L. Its maximum removal efficiency (RE) of 90% and 77% was noted for NO3-N and NH4-N respectively with the highest RE of 69-85% for the Mn and minimum of 17-22% for Pb. It was noticed that the ABR remained unsuccessful in meeting the NEQ standards for COD, NO3-N, NH4-N, PO4 and most of the metals like Cd, Ni, Pb, Cu, Cr and Hg. As a post treatment stage for the ABR effluent, monoculture Constructed Wetland (CW) of Arundo donax (AR), Pistia sp. or Water Lettuce (WL) and Eichhornia crassipes (Water Hyacinth (WH) or their mixed cultures were investigated. It was evident that AR was the leading plant in treating most of the wastewater pollutants (TDS, COD, NO3-N, NH4-N, PO4, Pb, Cd and Hg). WH was able to reduce turbidity, TDS, COD and BOD within NEQ standards. It was shown from this study that the combination of AR and WH for treating real wastewater within the NEQ standards. The toxicity of various Volatile Fatty Acids (VFAs) as AD intermediates was investigated at pH 7. Indicator organism Photobacterium phosphoreum T3S was used to assess the toxicity. Binary, ternary and mixtures of VFA were also evaluated through equitoxic mixing ratio method. The half inhibitory concentration (IC50) values of acetic acid, propionic acid, butyric acid and ethanol were 9.812, 7.76, 6.717 and 17.33 g/L, respectively, displaying toxicity order of: butyric acid > propionic acid > acetic acid > ethanol. The binary and ternary mixtures were additive in nature, while the four combined had synergistic effect. The acute toxicities of heavy metals to P. phosphoreumT3S were studied with the 15-min IC50 at pH 5.5 – 6. A linear corealtion x was found between the toxicity of metals Cd, Cu and Pb to P. phosphoreum and their concentrations. The values of 15- min IC50 for Cd, Cu and Pb were 0.537, 1.89 and 1.23 mg/L respectively and the toxicity order was Cd> Pb> Cu. The equivalent concentration mixing method was used to determine the combined effects of Cd, Cu and Pb. The combined effects of Cd+Cu, Cd+Pb, Cu+Pb, were found to be antagonistic and Cd+Cu+Pb were partly additive. The VFAs and heavy metals combined effect showed that mixtures of single metals with VFAs Cd+ [VFAs], Cu+[VFAs] and Pb+[VFAs] partly additive. While the combination of two heavy metals with VFAs i.e. Cd+ Cu+[VFAs] and Cu+ Pb+[VFAs] had synergistic effect. The combination of all three heavy metals with VFAs Cd+Cu+Pb+[VFAs] was synergistic. The toxicity results of P. phosphoreum would be helpful in the optimization and stable performance of the bioreactors and information about the heavy metals toxicity at different concentration gradients would also be very useful to the environmental engineers for administering the timely corrective measures.