Copper
Copper can be found in many wastewater sources including, printed circuit board manufacturing, electronics plating, plating, wire drawing, copper polishing, paint manufacturing, wood preservatives and printing operations. Typical concentrations vary from several thousand ppm from plating bath waste to less than 1 ppm from copper cleaning operations.
Design Considerations
Copper can be removed from wastewater by precipitation as an insoluble hydroxide salt or by ion exchange. HydroFloTech designs and manufactures many types of metal precipitation systems including small and large batch type and a range of continuous flow treatment systems.
Precipitation of the insoluble cupric hydroxide salt is the most common form of treatment. This salt is formed by adjusting the pH of the water to about 9 to form the precipitate. The resulting precipitate can leave about 0.1 ppm of dissolved copper in solution if chelates are absent. If chelates are present, the final copper concentration can be much higher. When chelating agents are present, HydroFloTech can design a treatment system using special metal trapping chemistry.
Ion exchange can be used to remove copper from wastewater. HydroFloTech ion exchange systems are designed to treat plating rinse water with trace amounts of metals. The water is sent through cation and anion resin beds, along with activated carbon and/or media filtration to produce deionized water that can be returned to the process. The advantage offered by HydroFloTech ion exchange systems is that the resin is regenerated on-site, eliminating the need for bottle haul off. Since the regenerate waste will contain any copper and other metals removed during treatment, a vacuum distillation system can be used to concentrate the regenerate even further to reduce the amount of liquid waste hauled away. The purified water from the vacuum distillation system can also be returned to the process.
The equipment normally used for these processes is a batch treatment system for high copper concentrations (greater than 1,000 ppm), continuous precipitation if the copper concentrations are less than 1,000 ppm and the volume is greater than 5,000 gpd. Ion exchange is feasible if concentrations are less than 20 ppm and the desired effluent requires low copper concentrations, less than 20 ppb.
HydroFloTech has designed a fully modular system for copper removal:
Pre-Treatment Module: This module removes large solids and equalizes the water prior to any further treatment. The goal of this module to get the water provide the downstream treatment equipment with an equalized stream of water which if free from large solids.
Side Hill Screen / Grit Removal System: “Side hill” or “Grit Removal Systems” are used for the removal of large insoluble material from wastewater flows. These screens or systems are used on process and wastewater streams for particles that need to be removed to protect downstream systems. These screens can also be used for product recovery; large solids separation and mixed settleable solids for both municipal and industrial applications.
The HydroFloTech Side Hill Screen or Grit Removal System maximize solids removal in an easy to maintain unit. The screen is a barrier by which material larger than the gap or slot size may not pass, allowing the water to continue through.
Equalization Tank: HydroFloTech can work with an existing equalization “EQ” tank or provide one. Materials of construction can includes: Fiberglass (FRP), HDPE, steel (carbon steel or stainless steel), concrete, or even in-ground storage pits / ponds. The purpose of the equalization tank is to “equalize” and narrow any variances in water characteristics. The EQ tank also acts as a great buffer for two main purposes: First the EQ tank provides a buffer storage capacity in situations when there is a temporary surge in flowrate. This allows the system to be smaller than the peak surge flowrate. Secondly, the EQ tank also provides the ability to “narrow” any spikes in any contaminants.
Chemical Pre-Treatment and Solid Removal: This module chemically treats the water with pH adjustment (as necessary), coagulant and polymers to enhance the ability of HydroFloTech inclined plate clarifiers or dissolved air floatation systems (DAF) to effectively remove any Total Suspended Solids (TSS) or Fats, Oils and Grease (FOG).
ChemiSep Chemical Pre-Treatment System: The efficacy of any wastewater is as good as the pre-treatment of the wastewater prior to removal of any impurities. The HydroFloTech ChemiSep Pre-Treatment System provides great flexibility in treating various wastewater profiles:
- Stage 1 – Precipitation: pH is adjusted upward to a pH of 8-9.5 to the optimum hydroxide precipitation point. Often, a coagulant such as ferric sulfate is added to enhance metal co-precipitation and the formation of “pin floc”.
- Stage 2 – Flash-Mix: The wastewater with it’s precipitated pin floc is introduced to the flash mix zone where a polymer flocculent is added. This stage maximizes flocculent dispersion throughout the coagulated wastewater.
- Stage 3 – Flocculant: The wastewater is now introduced to the slow mix zone to agglomerate the pin floc into larger rapid settling particles.
Stinger Clarifer / ClariMax Clarifier: The flocculated wastewater is introduced into the clarifier where the settling particles accumulate in the sludge chamber. The clarified water then exits the clarifier and flows downstream to sewer or further treatment if necessary.
Sludge Management System: This module removes the precipitated solids from the water and converts those solids into dewatered “sludge” which may be eligible for re-use or landfill disposal.
Sludge Tank with Sludge Transfer Pump: The accumulated sludge is periodically removed from the clarifier and sent to a sludge holding tank where it further thickens for disposal or dewatering.
Sludge Dewatering: Sludge dewatering is typically handled by a HydroPress Filter Press or Screw Press. After processing a batch of “sludge” the filter press or screw press is emptied of “chrome cake” which is a semi solid of approximately 20-35 % solids. Chrome cake is high in chrome and sulfite and should be disposed of according to environmental regulations.
Re-Use Module: This module further reduces any remaining solids and biological / bacterial growth in the water to make it suitable for re-cycling or re-use.
RO System: The RO System removed any remaining dissolved solid (TDS) in the wastewater. The effluent coming out of the RO System is suitable for re-cycling / re-use.
UV Filter System: The UV Filter System finishing a final sanitizing of the water. The UV Filter System allows for the treated water to be used for most re-use / recycling purposes.