Determination of sediment oxygen demand in Shing-mun River

Abstract The importance of removing the small amounts of residual organics is increasing as the sources of clean surface water decrease. Knowledge of the nature of these soluble residual organics will be needed in order to assess the type of treatment required for their removal. Residual organics in three different biological treatment plants were analyzed and compared. An attempt was made to characterize these organics by a molecular size distribution on a Sephadex column monitored by differential ultraviolet and refractive index detectors. The organic carbon and chemical oxygen demand of the fractions collected from the column was also determined. An investigation of some of the problems inherent in the monitoring systems was conducted.

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Considering the impact of intermittent discharges when modelling overflows

Water Science & Technology ◽

10.2166/wst.1998.0370 ◽

1998 ◽

Vol 38 (10) ◽

pp. 23-30

Author(s):

Sarah Jubb ◽

Philip Hulme ◽

Ian Guymer ◽

John Martin

Keyword(s):

Water Quality ◽

Dissolved Oxygen ◽

Preliminary Investigation ◽

Oxygen Demand ◽

Sediment Oxygen Demand ◽

Combined Sewer Overflows ◽

River Hydraulics ◽

Combined Sewer ◽

The Impact ◽

Curve Equation

This paper describes a preliminary investigation that identified factors important in the prediction of river water quality, especially regarding dissolved oxygen (DO) concentration. Intermittent discharges from combined sewer overflows (CSOs) within the sewerage, and overflows at water reclamation works (WRW) cause dynamic conditions with respect to both river hydraulics and water quality. The impact of such discharges has been investigated under both wet and dry weather flow conditions. Data collected from the River Maun, UK, has shown that an immediate, transient oxygen demand exists downstream of an outfall during storm conditions. The presence of a delayed oxygen demand has also been identified. With regard to modelling, initial investigations used a simplified channel and the Streeter-Phelps (1925) dissolved oxygen sag curve equation. Later, a model taking into account hydrodynamic, transport and dispersion processes was used. This suggested that processes other than water phase degradation of organic matter significantly affect the dissolved oxygen concentration downstream of the location of an intermittent discharge. It is proposed that the dynamic rate of reaeration and the sediment oxygen demand should be the focus of further investigation.

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