WASTEWATER TREATMENT PROCESS
TO REMOVE METALS FROM
WASTEWATER
Because of certain characteristics, a number of metals are considered
highly toxic to be present in solutions discharged into the sewer
systems. Most such systems function in a way where the presence
of minute amount of dissolved heavy metals can interfere with
the operations of the sewage treatment facilities. Copper is recognized
as partically harmful. Solutions containing cadmium, chromium,
zinc, nickel, tin or lead are considered bad as well.
Traditional heavy metals wastewater treatment uses lime or caustic
soda to precipitate the metals as metal hydroxides, which have
a comparatively high solubility. Some of the hydroxides are amphoteric
which means, soluble in low or high pH. Generally the pH of treatment
solutions must be maintained between 6 and 10 to achieve maximum
metal hydroxide insolubility. Furthermore even after precipitation,
the resulting sludge may not pass the EPA toxicity test.
Therefore a need exists for a process for treating liquid waste,
which contains heavy metals, which process results in the production
of a non-hazardous sludge that can be disposed of in a landfill,
and a liquid with the heavy metals content having been reduced
to levels acceptable for discharge into the existing sewer systems.
This process provides a procedure wherein a substantial number
of metals may be effectively removed from solutions prior to discharge
into treatment facilities. This process has application to industries
such as precious metal plating and recovery, treatment of plating
bath and rinse solutions. Treatment of solutions from printed
circuit boards manufacture. Treatment of waste from paint manufacturing.
Treatment of oil solutions containing copper from automotive manufacture.
Treatment of organic dies utilized for anodizing operations, treatment
of waste in copper and nickel processing and treatment of petroleum
refining residues. In these various applications, the recovery
of metal salts may be employed for recycling where economically
feasible.
The process produces a non-hazardous sludge. The combination of
lower metals solubility and lack of amphoteric characters, provide
the necessary chemistry, which allows the production of a non-hazardous
sludge, where the sludge from wastes treated with lime, alkali
sulfate or sulfide to precipitate the heavy metals, is hazardous.
The process utilizes wastewater equipment usually exist in any
wastewater treatment plant. As a matter of fact the process utilizes
less equipment because it eliminates many stages and side streams
operations. This is usually a result of eliminating waste segregation,
which is required in the conventional hydroxide precipitation
to control the different pH zones. This process is unique because
metals are removed independent of the pH, which allows wide range
of metals precipitation to take place in one optimum pH. Elimination
of the different pH zones reduces chemical and energy consumption.
The chemicals are added in critical points to achieve optimum
results. Another factor, which contributes to the process success,
is the detention time. Detention time and point of application
are two critical components, which are disclosed in the detailed
description of the process. If followed precisely, the process
is not only successful in treating low concentration metal wastes
but also high concentration wastes such as dipping bath and spent
solutions.
In summary the benefits of the process are:
(a) Optimum metal removal
(b) Less solids production
(c) Non-hazardous sludge
(d) Fewer equipment and less energy consumption
(e) Minimum supervision needed
(f) System upsets are avoided
(g) Lower chemical usage
(h) Savings on charges accrued by sending concentrated liquid
wastes to be treated off site.
(i) Savings on sludge disposal costs because non-hazardous waste
cost less to dispose of in a landfill than RCRA approved sites.
(j) Compliance
(k) Profit
Fixed Phosphate Precipitation System
Order your copy of the process procedure today, please contact us at info@approvedce.com
or call 1-800-631-9747
