Category Archives: Metals

Find Information an how to remove metals from your waste stream.

Aluminum Anodizer Case Study

  By Integrated Engineers | May 11, 2010 - 8:38 am | Green Industrial Wastewater Treatment, Metals, New at I.E.
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Aluminum Anodizer Case Study 2

The facility treats their wastewater using an EQ Tank followed by a Mix tank and clarifier. The solids that settle are dewatered with a plate and frame press. The treatment process uses caustic to raise the pH from 4 to 9 and then a coagulant along with a metal precipitant as well as a flocculent to treat their wastewater. The clarified water is discharged to the local POTW and the sludge is hauled offsite for landfill disposal. The filtrate from the plate and frame press estimated at 600 gallons/day is returned for retreatment to the EQ Tank.

Aluminum Anodizer Wastewater Treatment Jar Test

Wastewater Sample

The sample of the wastewater was bench tested and according to the client, was the worst case scenario and at a pH of 1.3. The 1,000 ml sample was pH adjusted with 5.4 grams of caustic to a pH of 9.0. The Floccin 1105 was added at a dosage of 0.75 grams in the 1,000 ml (750 ppm or 6.3 lbs/1,000 gallons) and a good settled floc formed after mixing for 2 minutes. The solids settled in as shown in the photo (below) in 45 seconds.

Aluminum Anodizer Wastewater Treatment Dewaterd Sludge Cake

Sludge Cake

The settled sludge volume was 25% by volume (refer to the photo). It dewatered well in our simulation and generated a sludge weight of 7.2 grams from 1,000 ml of wastewater with a % solids of 30%. So this represents a sludge generation rate of 60lbs/1,000 gallons.

The treatment cost for the caustic is estimated at $15/1,000 gal (45 lbs./1,000 gallons) and the Floccin 1105 at $9.45/1,000 gallons.

Metal (total) Untreated Treated
Chromium 0.98 0.0018
Copper 2.0 0.050
Nickel 20 3.8
Zinc 4.7 0.054

Units in ppm or mg/L

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Floccin™ for Metals Removal Beats Hydroxide Precipitation Hands Down

  By Integrated Engineers | December 23, 2009 - 11:17 am | Green Industrial Wastewater Treatment, Metals, Sludge Dewatering
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The traditional approach for metals removal is Hydroxide Precipitation where the solubility for the metals changes to insoluble (precipitation) in the form of a metal Hydroxide as the pH increases.

The common pH range for this is between 10-11 pH depending on the metal.  Lime (calcium hydroxide or CAOH2), caustic (sodium hydroxide or NAOH) or magnesium hydroxide (MgOH2) are generally the chemicals of choice as the hydroxide ion source.  The process uses a rapid mix to add the hydroxide source and usually an anionic flocculant to help as a settling aid and sludge conditioner.

The problems with this technology are:

  • Large volumes of sludge production
  • Inability of the metal hydroxide to become sufficiently insoluble if chelating or surfactants are in the water
  • Unstable treated metal levels especially if the influent is highly variable.

The quantity of sludge is directly proportional to the amount of hydroxide source added.  This can range from 500 to 3,000 ppm by weight and yields 4 times this weight in sludge addition assuming a 25% dry sludge cake.

The dewatered sludge is then classified by its leachable metals following the EPA TCLP/STLC testing protocols where hydroxide sludge most often leach their heavy metals and are therefore classified as hazardous.

Additional problems are in the form of…click here to continue reading Floccin™ for Metals Removal Beats Hydroxide Precipitation Hands Down…

The traditional approach for metals removal is Hydroxide Precipitation where the solubility for the metals changes to insoluble (precipitation) in the form of a metal Hydroxide as the pH increases.

The common pH range for this is between 10-11 pH depending on the metal. Lime (calcium hydroxide or CAOH2), caustic (sodium hydroxide or NAOH) or magnesium hydroxide (MgOH2) are generally the chemicals of choice as the hydroxide ion source. The process uses a rapid mix to add the hydroxide source and usually an anionic flocculant to help as a settling aid and sludge conditioner.

The problems with this technology are:

  • Large volumes of sludge production
  • Inability of the metal hydroxide to become sufficiently insoluble if chelating or surfactants are in the water
  • Unstable treated metal levels especially if the influent is highly variable.

The quantity of sludge is directly proportional to the amount of hydroxide source added. This can range from 500 to 3,000 ppm by weight and yields 4 times this weight in sludge addition assuming a 25% dry sludge cake.

The dewatered sludge is then classified by its leachable metals following the EPA TCLP/STLC testing protocols where hydroxide sludge most often leach their heavy metals and are therefore classified as hazardous.

Additional problem are in the form of

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Copper and Nickel Removal

  By Integrated Engineers | March 5, 2009 - 10:21 am | Metals
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Circuit Board Manufacturer

A Circuit Board Manufacturer in southern California was not able to achieve the discharge levels of copper and nickel with their existing system of coagulant, anionic and cationic flocculants and metal precipitant treatment process followed by lamella plate clarification. The previous treatment process developed a settled sludge that had poor shear characteristics and required further coagulant addition to be able to dewater in the filter press. The facility processes 50,000 gal/day and recycles all but 2,500 gal/day, which is discharged to the Los Angeles County Sanitary Sewer system. Their target was 1.0 ppm and they were achieving 0.5 to 1.5 ppmin a sporadic manner.

Before and After Floccin

Before and After Floccin

Integrated Engineers treated the water with IE-061 (a metal precipitant) to a set point pH of 10.2 and flocked with Floccin D. Samples were analyzed using current EPA methods on an ICP.

Component

Untreated

Previous Treatment

Floccin
Treatment

Copper

156 ppm

0.5-1.5 ppm

0.3 ppm

Nickel

210 ppm

0.6-1.5 ppm

0.4 ppm

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Copper and Zinc Removal

  By Integrated Engineers | March 5, 2009 - 9:37 am | Metals
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Ammunitions Manufacturing

An ammunition manufacturing facility was having problems removing copper and zinc from their 900 gpm wastewater system. The process used lime to raise the pH from 1.5 to 10, sodium carbamate for a metal precipitant, and an anionic flocculant to increase the flock size and get the solids to settle in the clarifier. Current chemical costs are estimated at $225,000/year with a significant amount of sludge addition from the lime, thereby adding to the operational costs due to the sludge being a hazardous waste. Integrated Engineers, Inc. tested the wastewater and found that adding caustic to a pH of 10.0 and Floccin D worked as well as the current chemistry. The Floccin D dosage was 0.35 grams in 800 ml (280 ppm). The third sample shown below is with 160 ppm of IE-061. The test results are shown below:

Before and After Floccin

Before and After Floccin

In addition, by switching from lime to caustic the reduction in solids generation would be a significant cost reduction. At peak flow the amount of lime required (17.3 lbs./1,000 gallons) generates 7,450 pounds of 100% dry solids. In a normally dry cake the solids are 30%, therefore they were generating nearly 25,000 lbs. of sludge per day that was hazardous and expensive to dispose of in a landfill. Based on a disposal cost of $35/ton, the cost reduction due to the lime addition to the sludge would be $450 per day ($160,000/year).

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