20 Comparison of the Removal of Halogenated and Other Organic Compounds by Six Types of Carbon in Pilot Filters
Downloaded by CORNELL UNIV on May 18, 2017 | http://pubs.acs.org Publication Date: March 15, 1983 | doi: 10.1021/ba-1983-0202.ch020
J. J. ROOK Drinkwaterleiding Rotterdam, Galvanistraat 15, Postbus 6610, 3302 AP Rotterdam, The Netherlands Six types of granular activated carbon were subjected to comparative performance tests in water treatment. Total organic carbon and total organic halogens were determined, as were chlorine, bromine, and iodine levels. The adsorption capacity of the six carbons for trihalomethane was compared, as was chloroform adsorption. The general conclusion of this study was that activated carbon of different makes or origins provides a reliable water purification step for removal of nonvolatile halogenated organic compounds and of muta genicity. A massive development of planktonic fauna was observed, but the hygienic implication of this is not known.
T
HIS STUDY COMPARED the performance of six commercially available
types of granular activated carbon (GAC) used as terminal treatment in the Kralingen plant of Rotterdam. In this case study, the removal by GAC of halogenated organic compounds, especially the nonvolatile total organic halogens (TOX), that result from pretreatment with chlorine was the main objective. Since halogenated compounds often are associated with potential health hazards, the mutagenicity of the GAC effluents was investigated using the Ames test. The raw water for the plant is abstracted from the Meuse River and stored in open reservoirs with a residence time of 3 months. During storage, the quality is improved by self-purification, but TOX values as high as 10-14 μg/L have been measured. As a means of preservation against biological growth in the pipeline during the 10-14-h period of transportation to the treatment plant, the raw water is chlorinated during summer seasons; when the temperature exceeds 10°C, 0065-2393/83/0202-0455$07.25/0 © 1983 American Chemical Society
McGuire and Suffet; Treatment of Water by Granular Activated Carbon Advances in Chemistry; American Chemical Society: Washington, DC, 1983.
Downloaded by CORNELL UNIV on May 18, 2017 | http://pubs.acs.org Publication Date: March 15, 1983 | doi: 10.1021/ba-1983-0202.ch020
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T R E A T M E N T O F W A T E R BY G R A N U L A R A C T I V A T E D C A R B O N
1 mg/L chlorine is added. This dosage is below breakpoint (the chlorine demand may vary from 2 to 4 mg/L) so that, in the water arriving at the plant, the residual chlorine is in the combined form. Typical values for combined residual chlorine are 0.2-0.3 mg/L and for ammonium typical values are 0.05-0.2 mg/L. This practice limits total trihalomethane (THM) formation to 10 ^g/L. During the cold season when the transport chlorination is inter rupted, T H M concentrations remain lower than 1 μg/L. The treatment train comprises coagulation, sedimentation, ozonation (2-2.8 mg/L), and dual media filtration. Water from this stage was taken as the influent for the carbon filters. Table I gives a survey of some quality parameters of the influent water on the GAC. The high maximum value for chloroform was caused by an incidental overchlorination.
Experimental The six activated carbons tested were obtained from the manufacturers. The few properties available on the commercial data sheets are given in Table II, in which the six brands are coded 1-6. To obtain more information on their internal structure photomicrographs were made by scanning electron microscopy (Figures 1-6). Particular features are especially characteristic for anthracite-based carbon (1), petrol-coke-based carbon (4), and peat-based extruded product (6). The anthracite type (1) shows a graphite-like microstructure. The petrol coke based (4) typically shows an abundance of small pores. This carbon was especially developed for adsorption of micropollutants of small molecular size. In the micrograph of the peat-based carbon, which is composed of powdered carbon and a binder, the
Parameter T O C (mg/L) UV ext (cm) pH NH (mg/L) 0 (mg/L) CHCl (/ig/L) Total T H M (Mg/L) Turbidity (FTU) Cl-(mg/L) Br-( g/L) I-( g/L) 4
+
2
3
M
M
a
Table I. Quality of Influent Water (1979) Maximum Average Minimum 3.4 2.6 1.9 0.056 0.028 0.017 8.55 8.0 7.65 0.44 0.06
