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Historical Articles



November, 1949

Since the close of the last war, there has been a growing tendency to limit or prohibit tile discharge of wastes into streams and sewers. As such legislation spreads, and as its enforcement becomes more stringent, many plating companies will find themselves faced with restrictions on their disposal of rinse waters and spent solutions.

In plants which have so far escaped the attention of pollution control authorities, farsighted executives and plating foremen are starting to plan for future regulation of their wastewater disposal. This paper will indicate the type of information needed for such planning, and will show how the data can be acquired for each individual plant.

Research Project No. 10 of the American Electroplaters Society is concerned with testing the various processes which can be used to treat plating-room wastes. In order to carry out this work with the greatest benefit to all platers, the Project Director should have as much information as possible on actual plant conditions, such as are provided by these surveys. Accordingly, the sharing of such survey information with the Project Director or Committee will guide the work of the Project to the advantage of the cooperating plants.

The plant chemical engineer or chemist is probably capable of supervising the collection of this information, although it might be desirable for a waste disposal engineer to be consulted to ensure the reliability and significance of the data acquired. This survey should extend over a period of at least one month, and becomes more valuable as this time period is made longer.


Keep a detailed record during the survey period of all disposal of concentrated baths or portions of such baths. This record should include: name or number of bath, date and exact time of dumping, time required to empty tank, volume of solution dumped, analysis or estimated analysis at time of dumping, treatment given at time of dumping, and place where dumped. The record should cover all plating baths, cleaners, acid dips, bright dips, and other solutions which are discharged at full strength or high concentration.


Keep a record of wash-water volume, including a daily total and occasional spot checks to determine the maximum and minimum rates. The daily total can frequently be estimated from the water meter which shows total water consumption by the plant. A breakdown of the above data for each rinse tank is desirable, but may not be possible in some plants.

Keep a record of wash-water analysis, including a daily composite sample and occasional spot samples which will show variations during the day. The daily composite is best obtained from an automatic sampling device which proportions the sample volume to the flow rate; if this is not available, samples should be taken regularly at least every hour and combined to make the daily composite. In the latter procedure, it is desirable to make the volume of each sample proportional to the flow rate at that time; if this is not possible, the samples should be made equal. Spot samples should be taken both for rate of flow and for analysis perhaps ten times within one operating day; this should be done two or three days each month, not always on the same day of the week. The analysis should cover each of the harmful components present in the waste, although if plant operation is uniform, it may be possible to shorten this procedure somewhat.


Include in the survey a record of all plating baths and other solutions operated during the survey period. This record should list the name or number of each bath, its operating volume, the composition as shown by regular analyses, and the average life of the solution. The last refers primarily to bright dips, cleaners, zincate dips, and other solutions which become spent or contaminated and which are dumped at more or less regular intervals.


If any method of treatment of the wastes is used, this should be described. If any treatment has been used in the past and subsequently abandoned, a record of this should be included, noting especially the reasons for discontinuing the process.


During the period of this survey, it is desirable to maintain an accurate record of the chemicals added to the plating baths and other solutions. If possible, this should be checked by means of solution analyses and stockroom inventories before and after the period. The weight of anodes dissolved during the survey period is also desirable information, provided it call be obtained without excessive trouble.

A record of tile electrical power consumed during this period might also be useful. This should be tabulated as kilowatt-hours per day, and possibly also as ampere-hours per day for each tank.

If the quantity of work plated can be measured, a daily record of output should be kept. This might be specified as number of parts plated, number of racks or barrels plated, or weigh! of small uniform parts plated. This information will be useful in considering changes in plant production and their effect on the quantity and nature of tile wastes.

The abovementioned data, acquired over a period of a few months, can be very helpful in the planning of a waste-disposal system for the plant. If a treatment process is needed, tile engineer responsible for its design will require this information to plan a suitable unit. Since the acquisition of the data requires some time, a survey of this type should be started in each plating plant at the earliest opportunity. It is quite probable that such data will be valuable to an observant plant manager in many ways not connected with waste disposal, even though that is the purpose for which the outline is presented here.

As has already been stated, data of this sort will also be helpful in the guidance 9f tile American Electroplaters’ Societys Research Project on waste disposal. The cooperation of plating firms in this way will be appreciated by the Project Committee, and will make tile work of the Project produce a maximum benefit to all platers.

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