Activated carbon treatment

Both batch and continuous processes employ excess sulfur and operate at 85—110°C. Trace amounts of polysulftdes produce a yellow color which iadicates that all the ammonium sulfite has been consumed. Ammonium bisulfite is added to convert the last polysulfide to thiosulfate and the excess ammonia to ammonium sulfite. Concentrations of at least 70% (NH 2S2 3 obtained without evaporation. Excess sulfur is removed by filtration and color is improved with activated carbon treatment or sodium siUcate (66). Upon cooling the aqueous concentrated solution, ammonium thiosulfate crystallines. 

Nickel plating solutions may contain excess iron and unknown organic contaminants. Iron is removed by peroxide oxidation, precipitation at a pH of about 5, then filtered out. The more complex, less water-soluble organic contaminants along with some trace metals are removed with activated carbon treatments in separate treatment tanks. About 5 g/L of plating-grade activated carbon is mixed in the plating solution for at least 1—2 hours, usually at warmer temperatures. 

The tray aeration method is a simple, low-maintenance method of aeration that does not use forced air.19 Water is allowed to cascade through several layers of slat trays to increase the exposed surface area for contact with air (Figure 18.9). Tray aeration is capable of removing 10 to 90% of some VOCs, with a usual efficiency of between 40 and 60%.53 This method cannot be used where low effluent concentrations are required, but could be a cost-effective method for reducing a certain amount of VOC concentration prior to activated carbon treatment. 

Carbo-Flo An integrated process for treating small volumes of effluent containing agrochemicals or other waste organic materials. Flocculation by proprietary chemicals is used, followed by sand filtration, and activated carbon treatment. Developed by ICI in the mid-... 

PACT [Powdered activated carbon treatment] A wastewater treatment process which combines activated carbon treatment with biological treatment, providing a single-stage treatment of toxic liquid wastes. Developed by DuPont in the 1970s at its Chambers Works, Deepwater, NJ, and now licensed by U.S. Filter/Zimpro. More than 50 units were operating in 1990. 

Reverse osmosis can remove dissolved metals to very low levels. It can also remove a variety of pollutants such as cyanide and residual organics from refinery wastewater. However, because it is an expensive process, it would be competitive only if removal of total dissolved solids is also required. It also requires extensive pretreatment to prevent membrane fouling and deterioration [52]. The pretreatment processes may include filtration to remove suspended solids, pH adjustment, softening, and activated carbon treatment to remove organics and chlorine. A major drawback of the RO process is the handling and disposal of the reject stream, which can amount to 20-30% of the influent flow. 

Thibault, G.T. Tracy, K.D. Wilkinson, J.B. Evaluation of powdered activated carbon treatment for improving activated sludge performance. API Refining Department, 42nd Midyear Meeting, Chicago, IL, May 11, 1977. 

T0826 U.S. Filter/Zimpro Products, Powdered Activated Carbon Treatment (PACT)... 

T0826 U.S. Filter/Zimpro Products, Powdered Activated Carbon Treatment (PACT) T0833 Ultraviolet Oxidation (UV/Oxidation)—General T0853 UV Technologies, Inc., UV-CATOX Technology... 

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