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

New design of an injection wellRecharge well

Profile of an observation well nearby the injection well and the

current layout

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.

The air entrainment pilot

Screen

Air Injection

Two kinds of injection pipe

The air entrainment pilot

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.

Thanks for your attention

We are opening to cooperation on air clogging and will be happy to submit a proposal to EU or other funding frame