ENCON Evaporators
1368 Hooksett Road
Hooksett, NH 03106
Phone: (603) 624-5110
Fax: (603) 627-9520

ENCON Wastewater Evaporator vs. Chemical Treatment

Treatment of industrial wastewater using traditional chemical treatment and physical separation (chem/phys treatment) became popular as a method for gross contaminant removal in the 1950's.

Since enactment of the 1973 Federal Clean Water Act, the permittable discharge limits became increasingly strict, causing a drop in popularity and effectiveness of this treatment methodology.

encon Regardless of the waste stream, chemical treatment requires adherence to a multi-step procedure. For oily water applications, the procedure often referred to as chemical splitting, involves lowering the pH of the wastewater with acidic chemistry (H2SO4, HCl) to a range of 3-4, which causes the oil to separate from the water. The oil is then decanted from the water surface. After decanting, the pH is elevated to an acceptable range for discharge (typically 6.5-8.5). Prior to discharging to the sewer or tributary, an analysis of the treated wastewater must be completed to confirm compliance.

Evaporation Comparison

Evaporation entails feeding water to the evaporator, followed by heating to a boiling temperature. Upon heating, oily emulsions will break and a layer of free oil will separate from the water in the evaporator. This free oil can easily be decanted into a drum and evaporation of wastewater resumed.

There are also numerous non-oily wastewater applications that can be handled with evaporation. Waste streams with compliance issues related to metals in solution, total dissolved solids (TDS), total suspended solids (TSS), chemical oxygen demand (COD), and biological oxygen demand (BOD) can be handled much more effectively with evaporation compared to chemical treatment, which requires a series of steps generally referred to as flocculation and precipitation to only partially address these parameters. Notable advantages for evaporation compared to chemical treatment are:

Elimination of the hassle and expense of monitoring the discharge effluent.
Chemical treatment does not completely address emulsified oils, Chemical Oxygen Demand (COD), or dissolved solids.
Residue disposal volumes will be lower for evaporation because there is no generation of additional sludge as a result of chemical additions.
Evaporation can handle a wide range of waste water streams at the same time.
Evaporation is a simple technology that requires minimal manpower. Chemical treatment systems are typically more complex and require adherence to procedure.

It is important to note that chemistries used for flocculation and precipitation tend to be specific to constituents being targeted for treatment. If you are treating different waste streams, multiple chemistries and repetition of treatment steps may be required to effectively remove all the targeted contaminants.

Compared to chemical treatment, evaporation can effectively handle a wide range of different waste streams without having to add steps or modify and alter operation of the system.

In addition to the issues referenced above (i.e. chemical handling, chemical inventory, adherence to procedure, sludge generation, ongoing analysis for compliance), flocculation and precipitation can require numerous additional processes and capital equipment, including clarifiers for sludge thickening, sludge pumps, and filter presses.

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