Water quality of natural rivers and streams are becoming worst due to highly contaminated effluent in developing countries. In Pakistan, natural streams are presenting dramatic scenario along with deadly environmental conditions. Considering the water pollution issues and increasing demand of water, it is truly required to manage all these things on priority basis. In case of developing countries like Pakistan where there are severe financial constraints, it is necessary to formulate such tactics for water quality management which would maintain acceptable stream water standards. Considering the negative impacts on the environment due to dispose of untreated effluent, it is seriously required to plan environmental management for all natural rivers and streams. Environmental impacts of untreated effluent on “Ravi River” water quality have been taken up for investigation. Untreated effluents from the city of Lahore and it suburbs are seriously polluting “Ravi River”. The river section between “Ravi Syphon” and “Balloki” is presenting the most horrible scene, where industrial effluents from “Hudira” and “Deg Nallah” are also joining the river. In this segment the river water is being used for irrigation and livestock purposes. Considering the pollution scenario, more expansive effluent treatment systems will be required to maintain environmental standards of this river. It is concluded that due to high rate untreated effluent “Ravi River” is acting as a wastewater carrier. The study propagates different reasons for the surface water quality degradation in Pakistan. Mixing of untreated effluent in large quantity to “Ravi River” is a serious threat to the environment and public health. Surface water quality parameters like, Biological Oxyen Demand (BOD), Dissolve Oxygen (DO), Chemical Oxygen Demand (COD), Suspended Solids, Phosphorus, Chloride, Sodium, Total Kjeldahls,Nitrogen (TKN), Nitrate, Nitrites, Oil & Grease and Total Coliforms were measured on selected sampling stations for the period of three years. Laboratory results of collected samples are not satisfactory. To investigate the impacts of untreated effluent on microbial activities a biological survey was also carried out. Species of fish, oligochaetes, algae, stone fly, midge, and cadesfly were identified and discussed. It was investigated that during winter the river seems to be quite polluted. However conditions become better during summer VIAbstract months due to the increase in the flow rate. High concentration of wastewater microbes clearly explains that water quality of “Ravi River” is not satisfactory. Modeling of wastewater treatment process has gained much attention and a lot of research has been focused toward this area. Basic Activated Sludge Models (ASM) developed by International Water Association (IWA) task group are contributing considerably in wastewater treatment modeling. Different factors related to the model performance like model selection, model functions and model calibration are discussed in detail to support the effluent treatment process in Pakistan. The applications of ASM1, ASM2, ASM2d, ASM3, ASM3_2N, ASM3 bio-P model etc. are also studied. The white- box modeling techniques in this area are more significant. The importance of black-box models under special conditions where white-box models are not able to predict accurate results are also investigated. It was also found that use of hybrid, linearization and Artificial Intelligence (AI) techniques in wastewater treatment modeling can be more useful for process optimization and control. White-box modeling techniques in wastewater treatment modeling are most reliable for better understanding of the whole mechanism. Model purpose definition plays a vital role in model selection, data collection and calibration. Black-box modeling techniques can also be encouraged in this area to avoid wrong predicted results from white-box models under harsh environmental conditions like heavy rainfall or shock loading. It was also concluded during the investigation that hybrid modeling methodologies can be more supportive for process optimization and supervisory control. Low flow conditions in river along with high rate of contaminants are also damaging the ground water quality in the study area. During the study collected data from different departments, field sampling and field visits clearly narrate that hygienic conditions of “Ravi River” are becoming worst day by day. These conditions can only be improved by proper wastewater treatment plans, environmental management and powerful environmental legislation.