  |
|
|
|
|
| Title | The Cause(s) of Continued Hypolimnetic Anoxia in Long Lake, Washington, Following Advances Wastewater Treatment by the City of Spokane. | |||
| Month-Year Published | August 1982 | |||
| Online Availability |
5175 kilobytes, requires version 4.0 or later of Adobe Acrobat Reader Software get Acrobat Reader
| |||
| Short Description |
The purpose of this study was to determine the cause(s) of continued hypolimnetic anoxia in Long Lake with advanced wastewater treatment in operation. Biochemical oxygen demand, chemical oxyen demand, and sediment oxygen demand were determined. (Also see abstract below) | |||
| Publication Number | 82-31 | |||
| Author(s) | Wagstaff, W., and R. Soltero | |||
| Print Availability |
Not maintained in stock. Copy must be made from archive version. Request will be referred to the source program.
| |||
| Number of pages | 71 pp. | |||
| Keywords | algae, anoxia, chemical, chemical oxygen demand, chlorophyll, dissolved oxygen, investigation, lake, phosphorus, Reservoir, river, secchi disk, sediment, Spokane River, stream, study, waste, wastewater treatment plant, water | |||
| Subject Waterbodies |
| |||
| Abstract | Long Description |
Long Lake is an impoundment of the Spokane River downstream from Spokane, WA. Prior to 1978, the reservoir was characterized by excessive summer algae growth, limited water clarity, and extensive hypolimnetic anoxia. Advanced wastewater treatment (AWT) by Spokane's sewage treatment plant began in the fall of 1977. Advanced treatment included at least 85 percent biochemical oxygen demand (BOD) removal, 90 percent suspended solids removal, and 85 percent phosphorus removal. Investigations during post-AWT years (1978-1981) have shown significant reductions in phosphorus loading with corresponding declines in chlorophyll a, phytoplankton biovolume, primary productivity, and increased water clarity. However, anoxia has continued to exist although the degree of anoxia has been considerably less. The purpose of this study was to determine the cause(s) of continued hypolimnetic anoxia in Long Lake with AWT in operation. Biochemical oxygen demand, chemical oxyen demand (COD) and sediment oxygen demand (SOD) were determined. Sediment oxygen demand was measured under stationary and dynamic conditions with a Gilson Differential Respirometer. In addition, the areal hypolimnetic oxygen demand (AHOD) for all study years (1972-1981) was determined. Chlorophyll a concentrations, phytoplankton biovolume, primary productivity, and Secchi disk visibility were used as measures of phytoplankton standing crop. The AHOD calculated for 1981 was less than those calculated for previous study years. Post-AWT mean AHOD was significantly less than pre-AWT mean AHOD. Chlorophyll a, phytoplankton biovolume, and primary productivity were correlated with AHOD on a volume and areal basis. Reservoir and hypolimnetic BOD and COD were considerably greater than influent BOD and COD. Correlations were found between chlorophyll a, phytoplankton biovolume, and primary productivity versus BOD and SOD. The phytoplankton standing crop in Long Lake does affect oxygen demand both within the water column and at the sediment-water interface, and is a primary factor in the seasonal decline of dissolved oxygen levels in Long Lake. |
||
Copyright © Washington State Department of Ecology. See http://www.ecy.wa.gov/copyright.html.
