Effects of Algal Blooms on Water Quality
199
PROBLEMS ASSOCIATED WITH RECHARGE OF KINNERET WATER INTO AQUIFER
More than 100 million cubic meters of Lake Kinneret water are recharged annually in
central and southern parts of the country in order to enrich groundwater resources. Most
of the recharge operation is done through wells, either special recharge wells or
dual-purpose wells in sandy aquifers. In both methods the presence of Peridinium caused
severe interference in the recharge operation and utilization of the recharged water.
In special recharge wells the main problem is clogging by suspended matter, most of it
Peridinium cells. As a result of this clogging there is a gradual reduction in recharge
capacity of such a well, in many cases up to 60% (Degani, 1971).
In dual-purpose wells the recharge capacity is partly restored by redevelopment. Here
the main problem is accumulation of organic matter in the well. During the pause
between recharge and pumping this material enables development of large bacterial
population, among them many coliforms (Eren and Goldshmid, 1970). High coliform
counts together with turbidity and taste and odor make it necessary to drain to waste up
to 5% of the recharged water.
DISCUSSION
During the first years of the INWS, the main problem was the high salinity of Lake
Kinneret water. Due to diversion of saline springs there has been a gradual reduction in
salinity of the lake water since 1967 and now algal blooms in Kinneret are the major
factor affecting water supply from the lake.
The Mekoroth Water Company considered several ways to prevent entrance of
Peridinium into the network, or at least to reduce its undesirable effects there.
Total removal of algae at the intake of INWS can be achieved by microstraining. This
method is used successfully in many waterworks to get rid of algal cells. However to use
microstrainers with a capacity of straining 1 million cubic meters per day will require
heavy initial investment and high maintenance costs.
It was suggested that there should be adjustment of the pumping schedule of the INWS
according to the vertical migration of Peridinium in the lake and thus possibly to reduce
the quantity of algal material pumped from the lake. Currently this possibility is being
investigated.
As an alternative way to reduce the amount of algae reaching the distribution part of
the network, it was proposed to settle Peridinium in one of the northern reservoirs.
During 1966 and 1967 copper sulfate was tested and gave good algicidal results. But it
caused lysis of benthic blue-green algae and release of their odorous metabolites. For this
reason use of CuS0 4 was abandoned. Chlorination (2 mg C1 2 /liter) caused partial
immobilization and settling of Peridinium, without the undesirable side effects of CuS0 4 .
Chlorination was used during the last three Peridinium seasons and there is evidence that
it reduced accumulation of algal material beyond the open part of the INWS.
The quality of the water in the INWS is determined by the quality of water in Lake
Kinneret. The conditions prevailing on the lake have therefore an influence on the water
supply throughout the entire country. For the past years these physical, chemical and
biological conditions supported blooms of the dinoflagellate Peridinium. But recently
there are indications that there are changes in the lake. It is being enriched by nutrients,
and especially nitrogen compounds from its watershed. It may be expected that blooms
199
PROBLEMS ASSOCIATED WITH RECHARGE OF KINNERET WATER INTO AQUIFER
More than 100 million cubic meters of Lake Kinneret water are recharged annually in
central and southern parts of the country in order to enrich groundwater resources. Most
of the recharge operation is done through wells, either special recharge wells or
dual-purpose wells in sandy aquifers. In both methods the presence of Peridinium caused
severe interference in the recharge operation and utilization of the recharged water.
In special recharge wells the main problem is clogging by suspended matter, most of it
Peridinium cells. As a result of this clogging there is a gradual reduction in recharge
capacity of such a well, in many cases up to 60% (Degani, 1971).
In dual-purpose wells the recharge capacity is partly restored by redevelopment. Here
the main problem is accumulation of organic matter in the well. During the pause
between recharge and pumping this material enables development of large bacterial
population, among them many coliforms (Eren and Goldshmid, 1970). High coliform
counts together with turbidity and taste and odor make it necessary to drain to waste up
to 5% of the recharged water.
DISCUSSION
During the first years of the INWS, the main problem was the high salinity of Lake
Kinneret water. Due to diversion of saline springs there has been a gradual reduction in
salinity of the lake water since 1967 and now algal blooms in Kinneret are the major
factor affecting water supply from the lake.
The Mekoroth Water Company considered several ways to prevent entrance of
Peridinium into the network, or at least to reduce its undesirable effects there.
Total removal of algae at the intake of INWS can be achieved by microstraining. This
method is used successfully in many waterworks to get rid of algal cells. However to use
microstrainers with a capacity of straining 1 million cubic meters per day will require
heavy initial investment and high maintenance costs.
It was suggested that there should be adjustment of the pumping schedule of the INWS
according to the vertical migration of Peridinium in the lake and thus possibly to reduce
the quantity of algal material pumped from the lake. Currently this possibility is being
investigated.
As an alternative way to reduce the amount of algae reaching the distribution part of
the network, it was proposed to settle Peridinium in one of the northern reservoirs.
During 1966 and 1967 copper sulfate was tested and gave good algicidal results. But it
caused lysis of benthic blue-green algae and release of their odorous metabolites. For this
reason use of CuS0 4 was abandoned. Chlorination (2 mg C1 2 /liter) caused partial
immobilization and settling of Peridinium, without the undesirable side effects of CuS0 4 .
Chlorination was used during the last three Peridinium seasons and there is evidence that
it reduced accumulation of algal material beyond the open part of the INWS.
The quality of the water in the INWS is determined by the quality of water in Lake
Kinneret. The conditions prevailing on the lake have therefore an influence on the water
supply throughout the entire country. For the past years these physical, chemical and
biological conditions supported blooms of the dinoflagellate Peridinium. But recently
there are indications that there are changes in the lake. It is being enriched by nutrients,
and especially nitrogen compounds from its watershed. It may be expected that blooms