Water treatment process

Details Water treatment process Water treatment process

2001-06-18

2003-06-10

Pak, John (Department: 1616)

Plant protecting and regulating compositions

Plant growth regulating compositions

Aquatic plant regulator

C504S151000, C424S630000, C424S632000, C424S633000, C424S634000, C424S635000, C424S637000, C424S638000, C424S646000, C424S647000, C424S648000, C424S682000, C424S698000, C514S499000, C514S500000, C514S502000, C210S705000, C210S723000, C210S724000, C210S728000, C210S732000, C210S735000, C210S749000, C210S753000, C210S764000

Reexamination Certificate

active

06576594

ABSTRACT:

This invention is a process for treating raw water and producing potable water meeting accepted purity standards.
BACKGROUND OF THE INVENTION
Surface water from rivers, lakes or reservoirs is treated in a water plant to convert the surface water into water for human consumption meeting accepted purity standards. The processes used have been honed over the years to produce high quality potable water. Surface water which has not been chemically treated is referred to by the industry as raw water and is referenced as same herein.
The process for treating water includes passing raw water through the municipal water plant while treating the raw water as it passes through the water plant. Primary treatment to the raw water in a water plant occurs in a clarifier or a basin (also referred to as a settling basin) after a flocculant has been added to raw water. The flocculant causes particles suspended in the water to coagulate, subsequently growing in size and weight. A water plant clarifier is a large sized, usually round structure whereas a basin is usually rectangular. The flocculant is generally added to the raw water in a small mixing chamber referred to as the rapid mix or flash mixer, to facilitate thorough, uniform mixing with the raw water. Depending on the design of the water plant, this chamber may be placed or positioned in various locations. In particular, the mixing chamber may be provided within the clarifier such as in a centerwell clarifier or adjacent to a basin. In other water plant designs, the mixing chamber may be provided upstream of the clarifier or the basin. The clarifier or the basin is generally sized to provide sufficient residence time for the majority of the solids to drop out of suspension. When necessary, the flocculant may be added to the water being treated in the water plant anywhere along the transfer pipe which delivers raw water from the river, lake or reservoir to the water plant to increase the total reaction time for the flocculant. Water is then passed through sand filters, perhaps treated with activated carbon, chlorinated and possibly fluoridated before being delivered to water supply mains which transport the treated water to residences, businesses and industries.
One of the recurrent problems in water treatment plant operations is the growth of algae in the clarifier or in the basin and sand filters. Algae come in many types including filamentous algae, such as Cladaphora and Spirogyra, planktonic algae such as Microcystis and Anabaena, branched algae such as
Chara vulgaris
and Nitellam, swimming pool algae commonly referred to as black, brown and red algae and algae found in ponds such as Dictyosphaerium, Spirogyra, Oedogonium, Chlorococcum, Pithophora, Hyudrodictyon and Lyngbya. It is not uncommon to see a municipal water plant clarifier or basin with a beard of algae around its peripheral walls and filamentous algae growths several feet long.
As used herein, the term municipal water plant is intended to mean a water plant used in treating raw water and converting it to potable water for human consumption, regardless of whether the entity doing so is public or private.
Algae blooms have been noted to appear literally overnight under the right temperature and sunlight conditions and, if left untreated, will cause taste and odor problems in the finished waters. The problems caused by algae in municipal water plants are handled in a variety of ways by current treatment methods. The taste and odor problems which typically recur during periods of high summer temperatures and long daylight hours occur from detritus thrown off by algae in the clarifier or basin. Not all of this detritus is removed by sand filters. A portion of the detritus passing through the sand filters is converted in the final chlorination process to a family of chloro-organic compounds which contribute to the objectionable taste and smell that consumers complain about.
The standard treatment for controlling algae in municipal water plants is to scatter crystals of cupric sulfate pentahydrate, CuSO
4
.5H
2
O, which is also known by its common name blue vitriol, into the water. Blue vitriol is commercially available in 50 pound bags having crystals ranging in size from fine (⅛″) to large (1″). Scattering is done with a shovel, a scoop, or by hand. Ideally, the crystals dissolve in the water so the copper ion is present in the water. The soluble or active copper (II) ion kills algae because of its effect on chlorophyll which is a large porphyrin structure occurring either as blue-green chlorophyll-a or yellow-green chlorophyll-b. Both molecules have four centrally placed nitrogen atoms which complex a single magnesium atom. The magnesium removes carbon dioxide from the water and delivers it to the algae thus allowing photosynthetic growth. The soluble copper (II) ion replaces the magnesium by forming a stronger porphyrin complex, which does not bond with carbon dioxide. The algae die by virtue of its growth mechanism being squelched by a lack of carbon dioxide, in a process analogous to the chemical poisoning of hemoglobin in mammals. One of the inherent advantages of copper algicides is that algae cannot mutate or evolve to avoid its effect. No amount of evolution can prevent copper from displacing magnesium in the chlorophyll and no amount of evolution can cause the copper porphyrin to absorb carbon dioxide.
Disclosures of some interest are found in U.S. Pat. Nos. 3,844,760; 4,012,221; 4,505,734 and 5,541,150.
SUMMARY OF THE INVENTION
The above description of the prior art is an idealized situation but which has a number of practical problems and disadvantages, some subtle and some not so subtle. A substantial part of the blue vitriol does not dissolve because it is difficult to dissolve in water which is not acidic. Plainly put, blue vitriol crystals do not dissolve very well in pH 7, or more alkaline water. Since the incoming raw water most often has a pH of 7 or above, this causes the crystals to acquire a coating of copper hydroxide that inhibits dissolution of the blue vitriol crystals into the water. Thus, much of the copper sulfate is wasted and ends up in the settled sludge in its undissolved form. Consequently, only a small portion is consumed, as intended, by intimate bonding to the algae chlorophyll. In addition, scattering blue vitriol crystals does not produce uniform dosages of copper sulfate in the water. Instead, very high dosages will be found immediately down current from the crystals and little copper sulfate will be found elsewhere.
In this invention, a water soluble copper salt is dissolved in an aqueous acidified solution such as an acidic flocculant because many water soluble copper salts, and the preferred copper sulfate, are much more soluble in low pH water than in neutral to high pH water. The resultant algicide-flocculant solution in accordance with the present method can be delivered in a tank truck or by a tank rail car and off loaded into storage tanks.
In the manner previously described, the treating of raw water in accordance with the present invention includes the standard steps of passing raw water through the municipal water plant while treating the raw water as it passes through the municipal water plant. In this regard, it should be appreciated that water continually flows through the various parts of the water plant such as the clarifier and/or basin as it is being treated in the water plant. In accordance with the present invention, the algicide-flocculant solution as described in further detail below is metered into the raw water being treated at an injection point which allows thorough mixing of the algicide-flocculant solution with the raw water as it continually flows through the water plant and is treated therein. In this regard, the solution may be metered into the raw water as it passes through the clarifier via a mixing chamber in the centerwell, or as it passes through the basin via a mixing chamber adjacent to the basin. In other applications, the algicide-flocculant solution may be metered into the raw

Affiliated with

Also associated with

Rating

Water treatment process does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Water treatment process, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Water treatment process will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3150492