Decontamination process for reducing heavy metal pollution

A decontamination treatment of process water is disclosed herein originating from electroplating/metal finishing and etching operations wherein the process water is loaded with heavy metal ions. The inventive process combines predetermined quantities of alkali/acid solutions together with a quantity of Sodium Humate so as to produce a disposable sludge which is environmentally safe and poses the least risk for leeching of harmful metals from the resultant sludge.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a process or treatment for decontaminating 
process water, and more particularly relates to a novel process for 
removing metal pollution from electroplating and etching process water, 
such as the removal of metal ions commonly used in metal plating, etching 
and anodizing operations. 
2. Brief Description of the Prior Art 
As the requirement for environmental control has expanded with the increase 
in technological advancement and with the widening demand for improved 
processes and apparatus capable of handling waste products therefrom, the 
need for improved and safer decontamination treatments of liquids as a 
waste product has become of increasing importance. A concomitant of this 
trend is the need for effectively lowering the amounts of metal ions to 
acceptable standards of regulatory agencies which, while providing the 
requisite degree of safety, provides a convenient and manageable form of 
solid product rendered to a state of least environmental risk for storage 
or disposal. Under the thrust of this expanding requirement, it has become 
an economic necessity to provide an innovative process and apparatus which 
both minimizes the possibility of error in the decontamination procedures 
and reduces overall system complexity. 
Particularly, in the field of electroplating and etching procedures, the 
accumulation of metal ions in the process water has accelerated into a 
critical problem for contamination and disposal. Treatment technology for 
removal of metal ions associated with metal plating, electroplating and 
etching operations is essentially linked to the use of hydroxide or 
sulfide precipitations. However, under actual operating field conditions, 
complete removal of metal ions is rarely achieved. Thus, a substantial 
amount of metal ions remain in the process water, some of which are 
carcinogenic and/or are toxic to human life, which the regulatory 
authorities find objectionable. There have been several new and emerging 
technologies to lower the levels of metal ions in the process water; 
however, such prior attempts have not satisfied or reached acceptable 
decontamination levels and questions of storage and disposal are still in 
existence. 
Therefore, there is a growing concern, as well as a real need to improve 
the technology that effectively removes metal ions from the process water. 
An equally important concern is the fate or ultimate disposal of the 
resultant sludge or final sludge product. 
SUMMARY OF THE INVENTION 
Accordingly, the above problems and difficulties are obviated by the 
present invention which provides a novel process for decontamination of 
heavy metal pollution from metal plating and etching process water, as an 
example. The process permits such a treatment to be accomplished during 
the routine processing of wastewaters generated in metal plating, 
anodizing and etching operations. 
In one form of the invention, the process comprises the main steps of 
adjusting the pH with alkali (Sodium Hydroxide) to approximately 7 or 8 so 
that the quantities of alkali required to neutralize and precipitate the 
metal ions are minimized. Next, the novel process involves addition of 
chemical moiety (Sodium Humate, whose amount depends on the level of metal 
ions and variety of metal ions in the process water). A typical amount of 
Sodium Humate is between 0.5 g to 1.0 g for every liter of wastewater. 
This step involves thorough mechanical mixing or agitation providing a 
residence time of up to 30 or 60 minutes depending upon the local 
conditions. A final step in the process consists of allowing the liquid 
containing metal ions, alkali and Sodium Humate to settle in a settling 
tank for approximately 60 to 90 minutes, followed by demoisturizing the 
resultant sludge into disposable cakes or product. 
Therefore, a primary object of the present invention is to provide a novel 
decontamination process for heavy metal polluted process water which 
provides a process additive that effectively lowers the amount of metal 
ions to acceptable standards prescribed by regulatory agencies. 
Another object of the present invention is to provide a novel process that 
renders the resultant slude from process water to a state of least 
environmental risk in a manner that ultimately the sludge product may be 
safely disposed of in a municipal landfill. 
Still, another object of the present invention is to provide a novel 
process for effecting the removal of metal ions from the process water so 
that the ultimate disposal of the resultant sludge or final sludge product 
may be stored in a manner meeting regulatory agency requirements. 
Another object of the present invention is to provide a novel process for 
removal of metal ions from polluted process water wherein the process 
allows such a treatment to be achieved during the routine processing of 
wastewaters generated in metal plating, anodizing and etching operations. 
Yet another object of the present invention is to provide an inventive 
process wherein the additive chemical moiety is totally compatible with 
the existing treatment facilities making the invention economical and 
effective. 
Yet another object of the present invention is to provide an innovative 
process additive chemical moiety for decontamination of heavy metal 
pollution from electroplating, metal plating or etching process water that 
effectively lowers the level of metal ions in the process water from the 
metal plating, anodizing or etching operations to amounts that are 
acceptable to regulatory agencies.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawing, process or wastewater is produced from an etching 
or metal plating or anodizing source through normal operations wherein the 
process water is loaded with heavy metals such as copper, iron or the 
like. The process water is pumped into a reservoir or sump for temporary 
storage in an environmentally contained solution of approximately 100 to 
200 gallons in volume until processing is commenced. Next, the process or 
wastewater is routed either by pump pressure or gravity feed from the sump 
or storage tank to a mixing tank in quantities of approximately 80 
gallons. This latter tank will serve as a mixing tank where quantities of 
Sodium Humate and alkali are introduced for reaction with metal ions from 
the waste water. The Sodium Humate and alkali are provided in solution 
from a reservoir directly into the mixing tank wherein the solution 
represents a proportion of Sodium Humate and alkali effective to gain 
chemical reaction so as to control and balance the pH of the mix. The 
mixing tank employs a stirrer or other means of agitation to ensure 
complete mixing of the Sodium Humate and alkali with the resident metal 
ions contained within the process or wastewater. Mixing in the tank will 
typically take between 30 to 60 minutes. 
Next, a clarifier tank is employed and serves as a reservoir for the Sodium 
Humate and alkali solution with the metal ions. The substances will be 
dissolved in water and released into the mixing tank as required by the 
contents of the mixing tank. 
The wastewater, Sodium Humate and alkali mixture is then routed from the 
mixing tank and serves as an influent introduced to an 80 gallon clarifier 
tank, either by pump or gravity feed. As the water enters the tank, it is 
directed to the bottom of the tank by a plate A. As the clarifier tank 
fills and starts to empty through the exit opening at valve A, particulate 
matter (Humate-metal complexes as precipitates) are somewhat impeded from 
passing through the exit C by the diagonally disposed plates indicated by 
letter B. As the particulate matter rises, it contacts the diagonal plates 
and heavy materials fall to the bottom. This contact redirects some of the 
particulate matter away from the exit opening. This redirection allows 
more of the particulate matter to settle to the bottom of the clarifier 
tank. At the same time, clarified water (water that has had Humate-metal 
complexes deposited in the bottom of the clarifier tank) passes out of the 
clarifier tank into a sand filter. The Humate-precipitate known as sludge 
can be drawn out of the bottom of the clarifier tank through the valve A. 
Successful precipitation of sludge in this tank depends upon a minimal 
amount of liquid agitation. 
The clarified liquid from exit C enters the sand filter and this filter 
serves as a trap for any of the precipitate that may have escaped 
precipitation in the clarifier tank. The filter will require periodic 
recharging to ensure maximum filtering process. Once the water leaves the 
sand filter, it may be passed into a public sewer or reused in the plant 
as rinse water. 
The sludge from the bottom of the clarifier tank is drawn off via valve A 
and pumped by a sludge pump to a sludge press. Here the slurry-like sludge 
is compressed into sludge cakes by the removal of a substantial amount of 
the water. For example, a closure force of approximately 45,000 lbs. is 
sufficient to remove most of the moisture so that a relatively heavy, 
solid and sealed waste cake is produced. These cakes contain most of the 
metal ions originally found in the wastewater. The composition of the 
cakes is primarily that of Humate-metal complexes and the cakes can then 
be disposed of in a variety of appropriate manners. 
Therefore, it can be seen that the inventive process of the present 
invention provides a method and means for removing pollutant metal ions 
from process water through the use of a combined Sodium Humate and alkali 
solution and mixture which effectively seals and coats and otherwise 
breaks down the metal ions so that they are contained in a readily 
disposable sealed cake. The cake is non-ferrous and is environmentally 
risk-free for safe disposal in landfills. A typical example is for 
wastewater contaminated with 237 mg/l of copper to the copper reduced to 
0.78 mg/l and for wastewater contaminated with 1,620 mg/l of iron to have 
the iron reduced to 5.14 mg/l with the resultant sludge environmentally 
risk-free. 
While particular embodiments of the present invention have been shown and 
described, it will be obvious to those skilled in the art that changes and 
modifications may be made without departing from this invention in its 
broader aspects and, therefore, the aim in the appended claims is to cover 
all such changes and modifications as fall within the true spirit and 
scope of this invention.