Application of QUAL2EU Model for the Simulation of Dissolved Oxygen Concentration in Pawtuxet River

Lee, Young-Soo

Environmental Engineering Research 1998;3(3): 157-165.

Young-Soo Lee^†

Department of Environmental Engineering, College of Engineering, Kwangwoon University

Corresponding Author: Young-Soo Lee ,

Received: June 11, 1998; Accepted: August 11, 1998.

ABSTRACT

A small scale river flows through heavily urbanized areas, receives effluents from 3 municipal wastewater treatment facilities (WWTFs) and one industrial WWTF. The river has summer dissolved oxygen (DO) concentrations well below 5 mg/L standard for most of its path. The QUAL2EU model was used to allocate the waste loads into the river. Biochemical oxygen demand (BOD) decay and nitrification rates were calculated by measuring instream concentrations. The hydrologic and water quality data incorporated into the model were very close to the ₇Q₁₀ flow and served as a basis for a DO/BOD waste load allocation (WLA). The WLA results were used to develop permit limits for the 3 municipal WWTFs along the river. The WLA indicated that discharge permit limits of BOD 10 mg/L, ammonia (NH₃) 2 mg/L are required to attain the instream DO criteria of 5 mg/L. When simulating an advanced treatment, effluent DO concentrations were set to 6 mg/L and instream BOD decay rates were decreased from the validated rate of 0.35 to 0.23 day^-1. BOD decay rates were decreased to correspond to the lower effluent concentrations which would leave only refractory' materials that are difficult to degrade. Flow augmentation was not found to be an acceptable alternative to advanced treatment

Keywords: Dissolved Oxygen | Waste Load Allocation | Numerical Model | Advanced Treatment