Shivani Dhage

Numerical modeling for Thane creek

Abstract Water quality simulation of Thane creek has been carried out to determine the wastewater assimilative capacity of the creek using a two-dimensional numerical model considering organized wastewater discharges. Details of the results of calibration of the model against the observed water quality and hydrodynamic features have been presented. Creek water quality has been simulated for the projected flows and loads for the year 2015 to develop wastewater management strategy. On the basis of monitoring and simulation, it has been observed that with limited flushing capacity the multiple wastewater discharges have deteriorated water quality significantly. Extent of pollution is experienced more in the inner portion of the creek. The projected wastewater flows and loads for 2015 are above the assimilative capacity of the creek and therefore volumetric load in the creek need to be restricted.

Hydrodynamic assessment of sewage impact on water quality of Malad Creek, Mumbai, India

The rapid population growth and uncontrolled development in the coastal zone have led to major pollution impacts on creeks, estuarine, and coastal environment. Water quality models are valuable tools to understand the environmental processes for prediction of pollution impacts and evaluate future trends for management. Presently, the Malad creek in west coast of Mumbai receives wastewater and sewage from open drains and partially treated sewage from Malad and Versova treatment plants. The objective of the paper is to assess the environmental quality and estimate the extent of improvement in different parts of the creek by enhancing the collection efficiency and adequate treatment of sewage as well as disposal through ocean outfall. A hydrodynamic and water quality simulation has been carried out for the present condition in the creek and calibrated and validated with two different season data for better representation of the system. Calibrated model has been used to generate future scenarios based on various options. Among scenarios, option of treated effluent diverted to propose outfall and improvement in collection of unorganized flow through sewerage up to 40% and 60% are found most significant for biochemical oxygen demand reduction and increase in dissolved oxygen. Fecal coliform reduction is also found drastically but still very high against standard. To improve the environmental quality of the creek, still upper stretch requires more dilution and flushing due to narrow width and contribution of heavy pollution from open drains.

Evaluation of Marine Outfall at Mumbai for Domestic Waste Discharges Through Tracer Technique

Many coastal cities release liquid waste into marine water bodies through point and non-point discharges. Marine outfalls with multi-port diffusers are one of the modern systems adopted by mega cities along the coast for disposal of large volume of domestic wastewaters. Once the marine outfall is operational, it is cumbersome to find its functional and operational behavior in the coastal region. The evaluation of the extent of dilution achieved is complicated due to many reasons like variation in direction and buoyancy of upward flow, density, currents, tidal effects and also the submergence of the physical components of the diffuser. All these limitations create difficulty in establishing the fulfillment of the rationale behind outfall installation because accurate information on the compliance of the coastal water standards is not readily computable.