MATHEMATICAL MODEL FOR THE PREDICTION
OF DISSOLVED OXYGEN LEVELS IN THE
ALEXANDER STREAM (ISRAEL)
ISRAELI MINISTRY OF HEALTH (CENTRAL DISTRICT)
Laboratories of Environmental Engineering at the Technion,
Israel Institute of Technology, Haifa, Israel
INTRODUCTION
Pollution of the Alexander Stream
The Alexander Stream is considered as the only stream in Israel which is still suitable
for recreational purposes. In the last five years, pollution of this stream has been
increased by sewage effluents from the city of Natanya and by other rural and industrial
wastes from settlements in the Regional Council Emek Hefer, resulting in a collapse of
the ecological balance of the stream, fish-kills, foul odours and nuisance, an unsightly
appearance and a pronounced oxygen deficit at night throughout the year.
Stream Dissolved Oxygen Equations
During the last fifty years various authors have developed the original Streeter-Phelps
(1) oxygen-sag curve equations, in order to include various stream conditions which were
not accommodated by the original equations. The one proposed by O'Connell-Thomas
(2) was found to be suitable for the Alexander Stream.
Symons et al. (3) proposed a three-probe method for the determination of the
parameters in the equation of O'Connell-Thomas. The aim of this research work was to
verify the validity of Symons' method for the specific case and conditions of the
Alexander Stream in Israel.
Hydrography of the A lexander Stream
A previous field survey (4) was carried out in order to understand the special
topographical structure of the stream. A pronounced depression in the bottom of the
stream, immediately after the discharge point of the sewage of Natanya into the stream
gave place to heavy depositions of sludge with strong oxygen-demand rates.
In order to account for the oxygen balance at the Alexander Stream, the combined
effects of BOD loading, benthal oxygen-demand, algal respiration, self-purification due to
algal photosynthesis, and atmospheric reaeration should be taken into account. Therefore
a modification of the Symons method was made by adding a fourth D.O. probe in order
to determine the parameter of the benthic oxygen demand.
Accuracy of Measurements
The application of the Symons method which made use of a computer program for the
simultaneous solution of the O'Connell-Thomas equations, required extremely accurate
measurements of D.O. concentrations.
In fact, errors greater than 0.01 mg/1, when measuring D.O., caused gross discrepancies
in using the Symons method by increasing the divergence during the mathematical
analysis of the data. Therefore a second tnodification was introduced in the Symons
method combining laboratory BOD determinations with D.O. measurements and
mathematical analysis in order to determine the six oxygen-balance parameters of the
271
OF DISSOLVED OXYGEN LEVELS IN THE
ALEXANDER STREAM (ISRAEL)
ISRAELI MINISTRY OF HEALTH (CENTRAL DISTRICT)
Laboratories of Environmental Engineering at the Technion,
Israel Institute of Technology, Haifa, Israel
INTRODUCTION
Pollution of the Alexander Stream
The Alexander Stream is considered as the only stream in Israel which is still suitable
for recreational purposes. In the last five years, pollution of this stream has been
increased by sewage effluents from the city of Natanya and by other rural and industrial
wastes from settlements in the Regional Council Emek Hefer, resulting in a collapse of
the ecological balance of the stream, fish-kills, foul odours and nuisance, an unsightly
appearance and a pronounced oxygen deficit at night throughout the year.
Stream Dissolved Oxygen Equations
During the last fifty years various authors have developed the original Streeter-Phelps
(1) oxygen-sag curve equations, in order to include various stream conditions which were
not accommodated by the original equations. The one proposed by O'Connell-Thomas
(2) was found to be suitable for the Alexander Stream.
Symons et al. (3) proposed a three-probe method for the determination of the
parameters in the equation of O'Connell-Thomas. The aim of this research work was to
verify the validity of Symons' method for the specific case and conditions of the
Alexander Stream in Israel.
Hydrography of the A lexander Stream
A previous field survey (4) was carried out in order to understand the special
topographical structure of the stream. A pronounced depression in the bottom of the
stream, immediately after the discharge point of the sewage of Natanya into the stream
gave place to heavy depositions of sludge with strong oxygen-demand rates.
In order to account for the oxygen balance at the Alexander Stream, the combined
effects of BOD loading, benthal oxygen-demand, algal respiration, self-purification due to
algal photosynthesis, and atmospheric reaeration should be taken into account. Therefore
a modification of the Symons method was made by adding a fourth D.O. probe in order
to determine the parameter of the benthic oxygen demand.
Accuracy of Measurements
The application of the Symons method which made use of a computer program for the
simultaneous solution of the O'Connell-Thomas equations, required extremely accurate
measurements of D.O. concentrations.
In fact, errors greater than 0.01 mg/1, when measuring D.O., caused gross discrepancies
in using the Symons method by increasing the divergence during the mathematical
analysis of the data. Therefore a second tnodification was introduced in the Symons
method combining laboratory BOD determinations with D.O. measurements and
mathematical analysis in order to determine the six oxygen-balance parameters of the
271