Storm flow

Siace the mid-1980s, contaminated storm mnoff has become an object of increasing concern within iadustrial complexes. Storm flow is intermittent and unpredictable ia aature, and tittle data has been collected to typify its characteristics. The level of flow and degree of contamination not only varies within an iastallation it has its own geometric characteristics, which influence patterns of surface mnoff. 

Provisions should be included for infiltration in the case of separate sewers as well as storm flows in the case of combined sewers. 

Because of large equipment and land requirements, capital costs for wastewater-treatment plants are high. A collection system that conveys both sanitary and storm flows must be designed to deal with high peak flows at the treatment plant detention basins are usually provided in order to smooth the flow into the plant and reduce the sudden peak flow. In the absence of such precautions, it may be necessary to by-pass a portion of the flow. 

Zeta potentials of floe produeed in the plant may also be measured as a means of eontrol. The zeta potential value for optimum eoagulation must be determined for a given wastewater by aetual correlation with jar tests or with plant performance. The control point is generally in the range of 0 to 10 millivolts. If good correlations can be obtained between some zeta potential values and optimum plant performance, then it is possible to make rapid measurements of particle charge to compensate for major variations in wastewater composition due to storm flows or other causes. 

Determine, in collaboration with the biological and hydrological scientific communities, tolerances of stream ecosystems to perturbation. This includes tolerance to physical perturbations, such as increased storm flow volumes, which may destroy habitat architecture, and tolerances, or thresholds, of stream biota to higher amplitude fluctuations in temperature, oxygen, and nutrient levels. 

Figure 9 Storm flow samples from the Mattole River, California, have and 5D values that do not plot along the mixing line (solid line) between the two supposed sources new rain and pre-storm base flow. Therefore, there must be another source of water, possibly soil water derived from a previous storm, contributing significant amounts of water to storm flow. The stream samples plot along a mixing line (dashed line) between the composition of average new rain and the composition of previous rain (after Kennedy et aL, 1986).

Figure 15 versus 5 0 values of nitrate during storm flow and base flow conditions from Waller and Shoal... 

On crude oil units the problem may be aggravated if the blowdown from the imit discharges into the branch sewer. The quantity of fire water will depend on the number of hoses and turret nozzles that would be drained to a given area. For branch sewers from units, the flow specified by various refiners range from 1,000 gpm to 2,500 gpm plus normal process water flows. Storm flows will depend on the geographical area in which the refinery is located. 

Neary, D.G., P.B. Bush, and J.E. Douglass. Off-Site Movement of Hexazinone in Storm-flow and Baseflow from Forest Watersheds, Weed Sci., 31 543-551 (1983). 

Figure 10. Aluminium and pH along the Svartberget stream during base flow and storm flow (from Townsend et al, 1990).

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