Post on 02-Apr-2018
transcript
Design of new injection
wells for injecting
surplus desalinated
water into the aquifer
Dr. Joseph GuttmanDr. Ido Negev
Hydrology departmentMekorot
Water Quality WorkshopAlgarve, Portugal June 25-26, 2015
Sea Desalination in Israel
Weekly desalinated surplus
Yearly Sea desalination
Source: Water Authority
Goal• New concept of injection well was designed to inject
surplus desalinated water into the aquifer.
• Most of the old injection wells suffered from clogging
problems and are abundant.
• Until now, the new concept of injection wells was
implemented in two sites.
• The new concept includes: different wells for pumping and
for artificial recharge. New well construction and
establishing of a monitoring system.
• Pilot on the air clogging is running in parallel.
Artificial Recharge via wells (Mekorot experiences during
the 70’s-80’s)
• The water source was the Sea of Galilee that contained high concentration of
organic matters.
• The well design wasn’t uniform (different kind of perforations).
• The main clogging was by bacteria and fine sand.
• Injection rate in sand aquifer vary between 50-200 m3/h.
• Injection rate in karst aquifer vary between 300- 2400 m3/h.
• During the injection the well yield reduced (in comparison to the initial
conditions) by 30-60% in sand aquifer and by 10-20% in karst aquifer.
• Long re-pumping after the recharge period return the well yield close to its
previous values. At the beginning of the re-development the water contained
an excessive bacteria count.
Construction of old Injection wells in the coastal aquifer
basket
Perforated steel pipe 1.5 mm X 7 cmwith baskets
Screen from steel pipe 0.5 mm (slot 20)
Guidelines in designing new artificial recharge wells
The motivation: to recharge surplus desalinated water
• The design should take in consideration the clogging problem and the necessity
of doing routine maintenance to reduce the clogging potential.
• The desalinated water is without suspended solid and organic matters and
contain low chloride concentration.
• The main clogging problem is from air entrainment.
• The best construction is larger outside diameter (26”-30”) and casing + screen of
14-16” diameter. Using Johnson stainless steel screen or GRP.
• Drilling with water or biodegradable mud.
• To have several piezometers to measure the changes in the water level during the
recharge (for clogging rate and operational protocol).
• The water level should be at a level that will prevent any air entrainment.
• The injection pipe should be without air (full with water).
• The injection water should be clean from turbidity (NTU ~ 0.1).
Layout of artificial recharge site-Sharon Zefoni 113, 213
Recharge well
Pumping well
Obs. 1
Obs. 2
Pumping wellRecharge well
GRP types for the new injection wells
Mekorot consider to use
GRP pipe or Johnson
stainless steel in the new
injection wells.
According to the literature,
the development of
biofouling and biological
clogging on GRP is lower
than on other pipe type.
The problem is the low
percentage of the open
space in comparison to
Johnson stainless steel
screen. Larger open space is essential in
injection well.
Clogging and maintenance
• Clogging in the recharge well is the main problem in maintaining the
recharge capacity of the well.
The right rehabilitation method should be determine for each well
according to the clogging source and to the rate of the clogging
phenomena.
The desalinated water in Israel have very low suspended solid and
organic matters. The clogging may come from air bubbles during the
injection (air entrainment clogging).
Periodic backwashing (re-pumping) of the recharge wells at specific
times of volumes recharged. The frequency may determine after
running a pilot.
We found only one hydraulic instrument that enable to inject and to
pump from the same instrument (Baski flow control valve- FCV).
Mekorot is running a pilot to study the air clogging problem and to
design her own pumping/ injection system.
Conclusion
• The major goal in Israel is to increase the overall artificial recharge capability and to inject surplus desalinated seawater into the coastal sandy aquifer.
• The new injection wells have new design, based on lessons from the past and the new drilling innovations.
• The design should be in such a way that it will reduce (as much as possible) the clogging phenomena and to do routine maintenance.
• The main clogging problem in injecting of desalinated water is air entrainment clogging.
• Mekorot is running a pilot that his final outcome will be an injection protocol to minimize the air entrainment clogging and for periodic backwashing.
• Proper monitoring and maintenance is the key factor in long term operating of the artificial recharge well.