A major U.S. waste management company provided a sample of wastewater generated by an underwater ship cleaning operation. The sample was to be tested in the KASELCO laboratory for removal of copper and zinc and for improvement of clarity (suspended solids removal). Customer is interested in treating 50GPM
The sample is seawater with granules of shell and contained copper at 0.366mg/l, zinc at 0.756mg/l, and iron at 0.107mg/l, and had a turbidity of 54FAU (Formazin Attenuation Units) after settling. The pH of the sample was 7.41 with a conductivity of 40,000μS (microsiemens).
CONCLUSION
This waste is a good match for the KASELCO process. The ease of treatment indicates that a 50gpm system with KASELCO Sur-Flo reactors could be used in this particular application. Reaction may be accomplished at low voltage and amperage settings or by an abbreviated reactor. Solids separation may be accomplished by DAF or agitation followed by settling. The final system must either include four hour settling equipment or
final filtration or both.
BENCH SCALE KASELCO ELECTROCOAGULATION TREATMENT
Test #1: Test as received:
The sample was processed in a type 011 reactor, chosen based on the high conductivity. The extremely high conductivity kept the voltage low, at 10-14, while the reactor drew the scale amperage at 4 amps.
The pH rose from 7.41 to 7.96 at mid-reactor (1A) and to 8.37 at the reactor exit (1B). The conductivity was not remarkably affected.
A second treatability test was not necessary.
Metals: Copper fell from 0.366mg/l to 0.079 at the reactor exit, while zinc was removed from 0.756 to less than detectable levels of 0.005mg/l at the same point. It appears possible that some of the copper is bound in an organic matrix.
Iron increased appreciably, since the reactor used iron plates with this high-chloride solution. Iron normally precipitates completely at pH’s above 8.1 unless high chlorides are present. The excess iron can be removed by filtration, and sometimes by processing the treated water by dissolved air flotation, as it typically oxidizes within minutes in the treated water.
Clarity was improved immediately following the reaction, then improved greatly with extended settling time. This could also be enhanced and the settling period shortened by filtration.
Sludge generation was 22.6 pounds of dry sludge per 1,000 gallons of wastewater after reaction. However, the reaction was essentially complete prior to mid-reactor and the extended processing simply added sludge from dissolution of the plates and the removal of unspecified contaminants. Installed treatment system would be adjusted to minimize post-treatment iron release. The sludge settling rate was somewhat slow, indicating the effluent may best be separated by dissolved air flotation. Additional testing is recommended.
LAB DATA
PROFILE: pH 7.41. Conductivity 40,000μS. Appearance is brown water. Run in # 11 steel reactor.
TEST # 1 (as is)
GLOSSARY and NOTES
• Profile: The characteristics of the waste being tested.
• Range Percent: Bench scale rectifier control setting.
• 1A: Equivalent of half a pass through a full-scale production reactor.
• 1B: Equivalent of one full pass through a full-scale production reactor.
• Type: KASELCO EC reactors come in three electrical configurations and is chosen based on the wastewater’s conductivity.
