Author(s): Robert L. Donekera; Adithya S. Ramachandranb; Frank Opilac
Linked Author(s):
Keywords: Regulatory mixing zone; Multiport diffuser design; Cormix; Corhyd; Water quality modeling; Dilution study
Abstract: Wastewater disposal systems are generally designed to meet minimum dilution requirements within a regulatory mixing zone, a limited region around the discharge structure where the initial dilution of the effluent occurs. We present a case study to site and design a multiport diffuser for a 0.7 m3/s (16 MGD) pulp mill discharge into a river. The field study includes a site bathymetry and velocity survey to determine optimal diffuser location. CORMIX mixing zone modeling software was used to design the diffuser for near-field mixing and regulatory compliance. In an iterative design process, CORMIX evaluated line source design dilution values within the regulatory mixing zone; the CorHyd model was then used to i) calculate port and pipe velocity, ii) verify uniform discharge distribution from the ports, and, iii) determine the diffuser head requirements. A fanned, unidirectional multiport diffuser design is proposed. It consists of risers with duckbill valves and three diffuser main pipe sections, each with successively smaller diameters to minimize the potential for sedimentation in the diffuser main and to maintain uniform flow distribution for the various ports. The design is optimized for dilutions at the mixing zone with port exit velocity and spacing that allows individual plumes to merge by the end of the near-field and minimizes the potential for scouring the river bed. Methods and techniques for riverine data acquisition, reduction, analysis, and mixing zone model application are presented in this paper.
Year: 2016