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Diffuser design for discharge to a stratified recipient
136
Reservoirs,
Lakes and Marine Waste Disposal
The thermal equilibrium conditions are illustrated by the long-term records which indicate that the most marked increases occur on the southern shore close to the discharge. In this part of the Blackwater the highest recorded mean temperature rise is never more than 1.5” C, whilst that for the main body of the water in the estuary is less than 1’ C.
BAADWELL POWER
i.pEE%q
~.
NUCLEAR STATION
__
HEASUREHENT TAKEN Al S"R.=ACE 1 16th NOVEMBER I%3
FIG. 3. Discharge of cooling water at outfall, measurement taken at surface, Bradwell Nuclear Power Station, 16 November 1963.
DiiTuserdesign for discharge to a stratified recipient. POUL HARREMOES, Denmark The background for this paper is an investigation of sewage disposal from the municipality of Halsingborg, which is situated on the Swedish coast of The Sound between Denmark and Sweden. Measuring techniques for the tracer investigations, which were performed during 1964 and 1965, were reported in the article “Tracer Studies of Jet Diffusion and Stratified Dispersion”, 3rd Int. Con. Wat. Pollut. Res. Vol. 3, p. 4. This article deals with the interpretation of obtained data and with the ultimate design of the outfall. The basic assumption for this design is, that a standard for acceptable E. coli-concentrations at neighbouring beaches has been decided upon, and that this standard is expressed statistically in order to account for the statistical nature of the parameters (currents, winds and stratifications), which determine the E. coli-pollution to be experiencedfrom a given outfall arrangement. The aim has been to determine the relationship between pollution and outfall arrangement in order to determine the most economical solution that satisfies the standard.
Reservoirs, Lakes and Marine Waste Disposal
137
Jet diffusion and trapping of the jet from a temporarily established outlet was measured for different density variations with depth. The measured results were compared with theoretical results obtained from jet diffusion theory, which was modified to account for a stratified recipient. Computer techniques were used in order to make the calculation of levels of submergence for all measured density profiles. Agreement between measured and theoretical results was found for all practical purposes. Measured dilution of submerged sewage fields was compared with the three-dimensional, anisetropic Fichian diffusion model and an empirical relation between density gradient and vertical and horizontal coefficients of dispersion (apparent coefficients of diffusion) was established. Comparison with a revised treatment of results from an American investigation proved vertical coefficients of dispersion in The Sound to be approximately one order of magnitude lower than that found at the Pacific coast of the U.S.A. The computer programme for jet diffusion was extended to include dilution of the established submerged sewage field. A statistical presentation of expected E. coil-concentrations at neighbouring beaches could then be calculated for any diffuser arrangement by applying the computer programme to density profiles, which frequently were measured during the bathing season of 1966. Through 41 runs on the computer it was possible to find the most economical combination of length of tube, outlet velocity, number of holes and degree of purification. Conventional design criteria for diffusers will be discussed in the paper. The design criteria, which were expressed with the well-known formula: q. S ~
Reservoirs,
Lakes and Marine Waste Disposal
The thermal equilibrium conditions are illustrated by the long-term records which indicate that the most marked increases occur on the southern shore close to the discharge. In this part of the Blackwater the highest recorded mean temperature rise is never more than 1.5” C, whilst that for the main body of the water in the estuary is less than 1’ C.
BAADWELL POWER
i.pEE%q
~.
NUCLEAR STATION
__
HEASUREHENT TAKEN Al S"R.=ACE 1 16th NOVEMBER I%3
FIG. 3. Discharge of cooling water at outfall, measurement taken at surface, Bradwell Nuclear Power Station, 16 November 1963.
DiiTuserdesign for discharge to a stratified recipient. POUL HARREMOES, Denmark The background for this paper is an investigation of sewage disposal from the municipality of Halsingborg, which is situated on the Swedish coast of The Sound between Denmark and Sweden. Measuring techniques for the tracer investigations, which were performed during 1964 and 1965, were reported in the article “Tracer Studies of Jet Diffusion and Stratified Dispersion”, 3rd Int. Con. Wat. Pollut. Res. Vol. 3, p. 4. This article deals with the interpretation of obtained data and with the ultimate design of the outfall. The basic assumption for this design is, that a standard for acceptable E. coli-concentrations at neighbouring beaches has been decided upon, and that this standard is expressed statistically in order to account for the statistical nature of the parameters (currents, winds and stratifications), which determine the E. coli-pollution to be experiencedfrom a given outfall arrangement. The aim has been to determine the relationship between pollution and outfall arrangement in order to determine the most economical solution that satisfies the standard.
Reservoirs, Lakes and Marine Waste Disposal
137
Jet diffusion and trapping of the jet from a temporarily established outlet was measured for different density variations with depth. The measured results were compared with theoretical results obtained from jet diffusion theory, which was modified to account for a stratified recipient. Computer techniques were used in order to make the calculation of levels of submergence for all measured density profiles. Agreement between measured and theoretical results was found for all practical purposes. Measured dilution of submerged sewage fields was compared with the three-dimensional, anisetropic Fichian diffusion model and an empirical relation between density gradient and vertical and horizontal coefficients of dispersion (apparent coefficients of diffusion) was established. Comparison with a revised treatment of results from an American investigation proved vertical coefficients of dispersion in The Sound to be approximately one order of magnitude lower than that found at the Pacific coast of the U.S.A. The computer programme for jet diffusion was extended to include dilution of the established submerged sewage field. A statistical presentation of expected E. coil-concentrations at neighbouring beaches could then be calculated for any diffuser arrangement by applying the computer programme to density profiles, which frequently were measured during the bathing season of 1966. Through 41 runs on the computer it was possible to find the most economical combination of length of tube, outlet velocity, number of holes and degree of purification. Conventional design criteria for diffusers will be discussed in the paper. The design criteria, which were expressed with the well-known formula: q. S ~