KASELCO Electrocoagulation

Electrocoagulation provides immediate treatment of mixed wastes in wastewater without the addition of chemical reagents (except under special circumstances). A complete trip through a KASELCO Sur-Flow reactor is 14 seconds. That's all it takes (in all but the toughest waste streams). This is one of the amazing and most beneficial aspects of KASELCO Electrocoagulation: the process requires no segregation of treatable wastes. It can treat hexavalent chromium simultaneously with other heavy metals, emulsified oils, cyanide (low concentrations), suspended solids, bacteria, viruses, and many other contaminants. Electrocoagulation typically lowers the dissolved solids concentration, making the water more amenable to reuse. KASELCO Electrocoagulation is most often done without the use of any chemicals, even acids or bases for pH adjustment. It may be necessary to adjust the pH if the waste falls outside a pH range of 5.0 to 8.5 for "normal" wastewater or 2.0 to 8.5 for very dilute wastes.

Since KASELCO Electrocoagulation systems need only a couple basic tanks to simply manage water flow, the space required for electrocoagulation is usually much less than for chemical processes. Chemical treatment methods typically need multiple tanks for segregation of waste streams by type. Also, the tanks associated with KASELCO EC can be relatively small because the treatment is immediate.

Electrocoagulation is very effective in removing suspended particles that cause high chemical oxygen demand (COD), but less effective with dissolved COD. Chemical hazards to the operator are limited to the condition of the waste being treated.

Chemical

Chemical processes typically require that each type of waste be segregated and treated separately, as each uses its own chemical reagents and concentration requirements. Reagent chemical consumption can be very high in volume and in cost. The chemical processes add reagent chemicals which then often become precipitated solids, adding to the volume of sludge generated. The chemicals may also contribute additional dissolved solids, making the water less suitable for re-use. The need to segregate wastes by type adds to the physical space and cost of the systems. Because the processes are designed for specific concentrations of specific chemicals, more operator watchfulness and time is required. Solid separation for chemical or electrocoagulation are nearly the same, but the volume of solids from chemical systems is higher and requires larger equipment. Chemical processes are usually not effective in removing organic chemicals unless special "clays" are used. These "organo-clays" are among the most expensive chemical processes. Handling reagent chemicals can present hazards of injury to the operator.

Biological

Biological systems are very effective when properly applied and can reduce organic chemical contaminants better than electrocoagulation or chemical processes. However, many contaminants are poison to biological systems and must be removed prior to the process by electrocoagulation or chemical methods. There are different biological processes required for different contaminants. For example, anaerobic digestion is favored for high concentrations of nitrates, while it is not effective for non-nitrates such as organics and may require two subprocesses (anaerobic followed by aerobic digestion). Biological systems are slow in performance, with residence time required up to 30 days for some wastes and concentrations. Residence in very active systems such as for sewage requires days of retention. The physical size of the plant is determined by the length of time required for the biological degradation to be completed. Since retention of many days of waste flow are often required the plants must be very large. The solids separated following biological treatment include living organisms that add to the volume for disposal. The solids may be also contain heavy metals and other contaminants that make them unsuitable for land application. Disposal can be problematic. Sterilization of the discharged liquid is also necessary. The long retention time undergoing forced aeration of the aerobic systems is very effective in reducing COD, even though the systems are much less effective in removal of actual contaminants such as heavy metals. The biological processes have fewer chemical hazards than the chemical, but impose an infection hazard to operators.

Note on COD:

The Chemical Oxygen Demand (COD) value is often used to measure "pollutants" in developing countries. This parameter is appropriate for sewage and other household waste, but is not appropriate for industrial pollutants. As countries develop their environmental standards and waste treatment is applied to industry separately form sewage, specific parameters for the industries are usually developed and applied. The COD of wastewater from an industrial plant can be acceptable even when the plant is discharging toxic and harmful contaminants at a
concentration harmful to humans and the environment. Conversely, the COD from an industrial plant may be high simply from oxygen depletion caused by innocuous substances, even when there are no or few harmful contaminants present. China is beginning to recognize that the application of COD to an industrial stream is not appropriate and has begun developing more specific standards for industry.