A novel process for removing sulfur from wastewater containing dissolved sulfide has been developed and implemented in a membrane bioreactor (MBR) process treating anaerobically pretreated industrial (pulp and paper) wastewater at the Gippsland Water Factory. Controlled oxygen addition to the first bioreactor zone (constituting 27.7% of the total bioreactor volume) to create oxygen-limiting conditions, followed by oxygen-sufficient conditions in the remaining zones of the bioreactor, provide the necessary conditions. Dissolved sulfide is oxidized to elemental sulfur in the first zone, and the accumulated sulfur is retained in the bioreactor mixed liquor suspended solids (MLSS) in the remaining zones. Accumulated sulfur is removed from the process in the waste activated sludge (WAS). Oxidation of dissolved sulfide to elemental sulfur reduces the associated process oxygen requirement by 75% compared to oxidation to sulfate. Microscopic examinations confirm that biological accumulation of elemental sulfur occurs. Process performance was analyzed during a nearly 2-year commissioning and optimization period. Addition of air in proportion to the process influent dissolved sulfide loading proved the most effective process control approach, followed by the maintenance of dissolved oxygen concentrations of 1.0 and 1.5 mg/L in the two downstream bioreactor zones. Sufficient oxygen is added for the stoichiometric conversion of dissolved sulfide to elemental sulfur. Enhanced biological phosphorus removal also occurred under these conditions, thereby simplifying supplemental phosphorus addition. These operating conditions also appear to lead to low and stable capillary suction time values for the MBR mixed liquor.

The Blue Plains Advanced Wastewater Treatment Facility is being upgraded to achieve low effluent nitrogen concentrations. Two modeling approaches were used to assess the plant at different times during the design. Steady state modeling and dynamic models were utilized. The configuration of the treatment process was very similar in each model and influent wastewater characteristics were identical. The steady state model was found to be very useful in examining the preliminary design and assessing effluent characteristics on a general basis. The dynamic model allowed assessment of shorter term parameters (aeration requirements) and allowed the evaluation of unit processes placed in series on a dynamic basis. The computing requirements associated with steady state modeling were substantially less than those required for dynamic modeling. This characteristic was reflected in run times and digital storage requirements. However, both approaches to modeling provide value to the understanding of the plant design.

In response to significant growth, the City of Calgary is currently building a third wastewater treatment facility, the Pine Creek Wastewater Treatment Plant (WWTP), to accommodate Calgary's immediate and long-term wastewater treatment needs. The first stage of this project will include a state-of-the-art 100 ML/day biological nutrient removal (BNR) wastewater treatment plant with tertiary filtration.Water is a "Newtonian" fluid, in which the pressure drop is proportional to the velocity and viscosity. However, most wastewater sludges exhibit non-Newtonian characteristics that are best modeled as Bingham plastics. The approach to modeling sludge flows described in this poster accounts for the much larger values of yield stress at low flow velocities.A Bingham plastic exhibits an initial resistance to flow, followed by a straight-line relationship between shear stress and flow. As the velocity approaches the transition to turbulent flow, it begins to show characteristics similar to Newtonian fluids. Each type of sludge resists movement with different intensity. Below the material's Yield Stress (Y s ), the Bingham plastic retains a solid-like matrix and no movement is observed. Above the Y s , the material will induce friction losses at a rate proportional to the shear stress as flow increases. In clean water, shear in proportion to shear stress is identified as the viscosity. For a Bingham plastic, the Coefficient of Rigidity (R c ) identifies this relationship.With municipal sludges, several factors affect the response of the sludge to shear stress. Solids content of the sludge is critical and is commonly used as a guide to selection of appropriate values for the yield stress and the coefficient of rigidity. The source of the sludge has also been demonstrated to have an impact on the selection of the rheological factors. Thickened waste activated sludge tends to have a higher yield stress and coefficient of rigidity than a thickened primary sludge of equivalent solids content.To gain a better understanding of the flow properties of the sludge at the Bonnybrook WWTP, the City of Calgary undertook sludge rheology testing to more accurately estimate pressure drop. Viscometer tests were performed to determine the viscosity of various sludge streams, at varying flow rates, to simulate both start-up and steady state conditions respectively.Because the Buckingham equation describes laminar flow, limits are placed on its use. A transition zone is defined by the upper critical velocity and lower critical velocity. The 3000 WEFTEC®.07

The Greater Vancouver Sewerage & Drainage District (GVS&DD) is a major regional wastewater agency serving Vancouver, British Columbia and surrounding municipalities. In the late 1980's it was mandated to upgrade its largest treatment plant from primary treatment to secondary treatment. From 1990 until the present the GVS&DD has engaged in Predesign, Design, Construction and Commissioning of the Annacis Island WWTP Secondary Upgrade. The size of the facility and the fact that no secondary treatment components were previously in place combined to make the upgrade a very large project valued at nearly $470 million CDN. This paper describes the major project components of the liquid stream process improvements. In addition to the major biological treatment components, other aspects of the project are described including, odour management, influent pumping, and primary treatment upgrades.

This paper describes the implementation of biological nutrient removal technology at the City of Calgary's wastewater treatment plants between 1989 and the present. Prior to 1989, the City met the effluent total phosphorus limits at its two wastewater treatment plants through in-plant alum addition. Two modules of the Bonnybrook WWTP, with a capacity of 400 ML/d, were sequentially retrofitted to biological phosphorus removal and nitrification. A separate new module, with a capacity of 100 ML/d and designed for optimal biological phosphorus and nitrogen removal, brought the total plant capacity up to 500 ML/d, making the Bonnybrook WWTP one of the largest BNR facilities in North America, and possibly the largest cold-weather BNR facility in the world. The resulting savings in chemical costs are estimated to be more than CDN$ 3.5 million (US$ 3.1 million) per year. Details are also provided of a new 100 ML/d state-of-the-art BNR facility that is currently under construction to serve the rapidly growing south and southeast areas of the City.