Electrocoagulation Introduction and Overview
Government discharge standards have been established for water discharge to the environment. The discharge standards are established to meet political needs and seem to be lower end as technology has advanced detection limits. The government regulators may enforce the discharge limits by fines, public humiliation, or by shutting down the production facility. The required water testing, monitoring, reporting, and spot inspections by the regulators consume valuable time and resources. Water reuse on-site is the best way to save this most precious natural resource. The recycled water can be cleaned up and conditioned to meet the specific reuse need. Water recycling can eliminate water discharge. Without water discharge, the expense of testing, monitoring, reporting, and spot government inspections of the cost of water purchases and water disposal are reduced. Cleaning the water sufficiently to be reused can be accomplished in several ways including reverse osmosis, ion exchange, evaporation, chemical coagulation, and or electrocoagulation (EC). Each of the treatment methods, or a combination of the methods has advantages and disadvantages depending upon the type of water to be reclaimed and the intended use of the reclaimed water. Water recovery on-site allows the selection of the treatment based on the specifics of the water content to be recovered and the specific quality of water needed in the reclaimed water process. Reverse osmosis separates contaminants from the portion of the water that permeates the membrane and concentrates contaminates in the reject water that does not past through the membrane. The permeate water quality can be controlled by the type of membranes used. The reject water may be 30% of the total water stream. In addition to waste in the reject water, the disposal cost for the reject water may cost more than the reverse osmosis operating cost. The reverse osmosis process is not very effective in mixed streams containing oil, grease, bacteria, and silica, which cause membrane fouling. Ion exchange captures specific ions in the water. Ion exchange adds some type of ion to water as a second type of ion is removed. A common type of ion exchange adds two sodium ions to the water in the process of removing one calcium ion from the water. The cost of ion exchangers in regeneration is significant in terms of water loss. When regulated heavy metal ions like chrome are removed from the water, the regeneration liquid is high in acid and metal content creating a costly hazardous waste. Evaporation or distillation produces clean water. The solids separated during the distillation process can be concentrated in the bottoms. Energy consumption and capital cost are the main drawbacks. Coagulation caused by altering the charge on metal ions organics, and colloidal particles creates a large particle that can be settled or filtered out. Chemical coagulation typically uses a dissolved salt. Part of the salt will attach to the material in the water to be coagulated. The other part of the ion typically remains in the solution. Chemical coagulation creates a hydroxide sludge that attracts water. The hydrophilic sludge holds water, which increases the volume of sludge generated and increases the dewatering time. Electrocoagulation adds electrons to the solution by passing alternating current or direct current through the solution from the power grid or sustainable power source. This is where our NuEnergy's Power House Generator integrates with cavitations and the EC system being described here. The electrons destabilize the material in the water creating oxide sludge when sufficient activation energy is present. The oxide sludge repels water and filters well. The oxide sludge dewaters well, eliminating the bogging problem associated with polymer-treated sewage sludge in landfills, which will stica tractor for years. Heavy metal ions converted to metal oxides will pass the leachets making them nonhazardous. Metal oxides can be smelted to recover the metals in a usable form.
- 1.Renk (1989) Woytowich et al 1993: EPA 540R96502, 1998Google Scholar