ENT
TUI UNIVERSITY
Timothy N. Tarrant
Module 3:
BHE 314
Environmental Health and Safety
Dr. Rania Sabty-Daily
14 August 2008
Abstract
The purpose of this case study is to compare and contrast the
secondary water treatment method to the tertiary water treatment (also
known as advanced or final water treatment) method, in the context of the
wastewater treatment process and to discuss the appropriate uses of
reclaimed water. In addition, I will explain whether I would recommend
secondary treatment or tertiary treatment for the groundwater recharge, if
it were to be used for drinking purposes.
Reclaimed water is wastewater that is treated. Wastewater includes
domestic sewage and industrial waste. It is treated to remove harmful or
unwanted items in an effort to improve the quality of the wastewater. It
is accomplished for a variety of reasons and has a multitude of uses. For
example, it is done to keep nature from becoming polluted, to conserve
needed potable water for human consumption, power generation, irrigation,
fire protection, and even for the conservation of marine life. The
treatment process will reduce the amount of suspended solids, biodegradable
organics (BODs), pathogenic bacteria, and nutrients.
The treatment process involves three stages that can be used
individually or in conjunction with one another for a cleaner water end
product. The stages are: primary or physical, secondary or biological,
and tertiary or chemical. During the physical treatment the removal of
large floating solid materials from raw sewage occurs. This primary
process is often referred to as “mechanical treatment” because it uses
screens and traps, along with gravity, to remove up to 60% of solid
materials.In addition, it also is able to remove up to 30% of the BOD of
the wastewater.
The secondary and tertiary treatment processes have both gone through
primary treatment. The main difference between the two is that secondary
treatment is designed for the removal of biodegradable organic matter and
the removal of additional suspended solids and the tertiary treatment
involves chemical disinfection. The activated sludge treatment process is
the secondary process that is most often used because of its versatility
and relative low cost. The tertiary treatment process removes suspended,
colloidal, and dissolves any remaining constituents after secondary
treatment. The tertiary treatment is able to remove more than 99% of all
impurities from sewage. This produces a water quality that almost meets
the standards to drink.In an article from the World Health Organization
website, it was discussed that groundwater recharge might be used in the
future as a potable source. The article goes on to say, ” Inasmuch as
recharged groundwater may be an eventual source of potable water supply,
groundwater recharge with recycled municipal wastewater may often involve
treatment beyond the conventional secondary wastewater treatment level. In
the past, several apparently successful
groundwater recharge projects were developed and operated using primary and
secondary effluents in spreading basins. However, because of the increasing
concerns about protozoan cysts, enteric viruses, and trace organics in
drinking-water, groundwater recharge with recycled wastewater in
industrialized countries now generally entails further treatment after
conventional secondary treatment. For example, surface spreading operations
practiced in the USA to reclaim wastewater commonly include primary and
secondary wastewater treatment, tertiary granular-medium filtration and,
finally, chlorine disinfection.” It is with this in mind that I would
choose to use the tertiary treatment process vs. secondary for groundwater
recharge if it were to be used by the public for drinking.
Drinking water is a precious commodity with limited resource.
Reclaimed water is being viewed as a valuable resource for the
agricultural, industrial and municipal because it is readily available. In
an effort to manage our drinking water supplies, we must turn to ideas like
reclaimed water to provide a reliable source of water for non-potable uses.
In 2006 the Southwest Florida Water Management District has used reclaimed
water to power six local power plants, irrigate 9,000 acres of crops,
irrigate 83,000 residential areas, and irrigate over 160 area golf courses.
(SW Florida, 2008) Clearwater Florida is an excellent example of using
water reclamation to benefit their society. In an article called “My
Clearwater/Reclaimed”, it says, “The use of reclaimed water (RCW) helps us
preserve high quality drinking water, by providing a reliable and
economical alternative source of irrigation water. It is in coastal areas
like ours that ground water supplies are most limited. The use of
reclaimed water for irrigation helps us manage our drinking water supplies
and costs because we postpone the day when we’ll have to acquire new
drinking water supplies. Drinking water is a precious, limited resource,
while reclaimed water is readily available.” (Clearwater, 2006) As a
nation, we have a responsibility to ensure the continued preservation of
our environment and its resources. Treating and reclaiming water is one
way that we can accomplish this.
References
Environmental Services Department, City of San Jose. South Bay Water
Recycling: Treatment Process. Retrieved on August 11, 2008 from
http://www.sanjoseca.gov/sbwr/treatmentprocess.htm
My Clearwater/Reclaimed (2006). Public Utilities: Reclaimed Water.
Retrieved August 11, 2008 from http://www.clearwater-
fl.com/gov/depts/pwa/public_utils/divisions/reclaimed/index.asp
Southwest Florida Water Management (2008) Water Conservation: Reclaimed
Water. Retrieved August 11, 2008 from
http://www.swfwmd.state.fl.us/conservation/reclaimed/
World Health Organization (ND). Groundwater recharge with recycled
municipal wastewater: health and regulatory considerations. Retrieved
August 11, 2008 from
http://www.who.int/water_sanitation_health/wastewater/wsh0308chap6.pdf
