WHERE RECLAIMED WATER
IS USED
Thousands of communities across the
United States are already using
reclaimed water in turf and landscape
irrigation applications rather than discharging that water into local natural
water sources. This has the dual effect
of protecting natural water ecosystems
that are sensitive to treated water discharge and reducing demand on the
increasingly strained potable water supply system. Beyond turf and landscaping, reclaimed water is also finding multiple other applications including
cooling tower water, toilet flushing, fire
suppression, dust control, agricultural
irrigation and ground injection for
recharging of natural aquifers. As a
prime example of extensive use, Israel is
deriving half its irrigation water from
reclaimed sources and is second only to
California in total usage. Potable water
is a finite resource that is declining in
some areas while facing growing
demand, so reclaimed water is an effective response.
Water
Collection
System
Increasing level of treatment
Primary
Treatment:
Sedimentation
Secondary Treatment:
Biological Oxidation,
Disinfection
• No uses
recommended
at this level
• Surface irrigation of
orchards and vineyards
• Non-food crop irrigation
• Restricted landscape
impoundments
• Groundwater recharge of
nonpotable aquifer**
Tertiary/Advanced Treatment:
Chemical Coagulation,
Filtration, Disinfection
• Landscape and golf course
irrigation
• Toilet flushing
• Vehicle washing
• Food crop irrigation
• Unrestricted recreational
impoundment
• Indirect potable reuse:
Groundwater recharge of
potable aquifer and surface
water reservoir augmentation**
Increasing level of human exposure
Suggested uses are based on Guidelines for Water Reuse, developed by U.S. EPA.
** Recommended level of treatment is site-specific.
SOURCE: U. S. ENVIRONMENTAL PROTECTION AGENCY
Table 1. Suggested Water Recycling Treatment and Uses*
HOW RECLAIMED WATER
AFFECTS VALVES
Using reclaimed water for irrigation
requires distribution and control systems that are completely and clearly
separated from the normal potable
water supply. This is because the
reclaimed water usually contains much
higher levels of disinfectant chemicals
required to control the level of microorganisms. These chemicals have become
the Achilles’ heel of reclaimed water
usage; valves traditionally used with
potable water for irrigation are now
subjected to new exposure issues. For
example, rubber compounds that used
to last for years in potable water can be
degraded in a matter of months with
reclaimed water, and stainless-steel formulations can see accelerated corrosion. Brasses and plastics, which have
been the mainstay of materials for irrigation valve components for years may
also be vulnerable under more extreme
conditions, such as shock treatment of
water using higher than usual concentrations of disinfectant chemicals.
Initially, the valve-damaging culprit
of reclaimed water was increased levels
of chlorine as a disinfectant; however,
more and more water treatment facili-
ties are using chloramines as a more
persistent chemical that does not break
down as rapidly. Chloramines can also
form in reclaimed water when chlorine
treatment combines with ammonia lev-
els still present in the wastewater. Other
treatment chemicals may include hydro-
gen peroxide, iodine and ozone. All take
their respective tolls on valve compo-
nents and can lead to failure. Because of
this, valves used in irrigation with
reclaimed water are making a transition
from more traditional industry materi-
als to more modern and application-spe-
cific formulations.
Elastomeric Components
The elastomeric valve components were
the first to experience issues with
reclaimed water, and they remain the
most vulnerable. Buna-N (Nitrile, NBR)
was especially susceptible and has been
replaced extensively by EPDM as the
material of choice for seals and
diaphragms in irrigation valves. Howev-
er, even EPDM needs the help of anti-
degradant additives to fight off the
attacks of chemicals used in reclaimed
water. These additives are highly pro-
tected as proprietary by elastomer pro-
ducers, so valve manufacturers are usu-
ally limited in getting the information
they need or they must do their own
endurance testing.
Stainless-Steel Parts
With higher concentrations of disinfectant chemicals, the stainless-steel components of irrigation valves also become
vulnerable. Shafts, springs, bolts,
screws, metering rods and solenoid components are all candidates for corrosion,
either through direct chemical reaction
or galvanic action when two different
metals are in contact with reclaimed
water acting as a salt bridge. This would
