Presence of Perch! orates and Chlorates --In some cases plants and fac- 

 tories discharge chlorates and perchlorates into receiving waters, e.g., 

 NH4CIO3 or NH4CIO4. Recently a group of bacteria have been discovered 

 which quickly reduce this compound under natural conditions (Romanenko, 

 oX al., 1976). It also has been established that in the bottom sediments 

 of the majority of waters, the processes of reduction of perchlorates are 

 either slow or absent, but in the waters containing wastes of a given in- 

 dustry, the number of the specific groups of bacteria greatly increases. 



The activity of these bacteria can be assayed using chlorine labeled 

 perchlorate (NH4 260104). Nutrient medium is prepared as described else- 

 where (Romanenko, eX al., 1976). The media consists of salts, microele- 

 ments, vitamine B]2, acetate, meat-peptone broth and perchlorate, 100 mg/1. 



The medium is poured into bottles with ground stoppers 60-70 ml in 

 volume. To this is added 5 ml of test water, or 100 mg of sediment, and 1 

 ml of a sterile solution of labeled perchlorate with activity of 0.1 x 10° 

 imp/mi n. After 3-5 days the contents of the bottle are filtered through a 

 filter paper made slight acidic with nitric acid. A one percent solution 

 of silver nitrate is introduced which precipitates the chlorides. If the 

 natural content of chlorides in the medium is not great, 2-3 mg of sodium 

 chloride should be added to precipitate the labeled 36ci ions. The pre- 

 cipitated chlorides should be filtered through a membrane filter washed 

 with distilled water (10 ml), dried; and the radioactivity of the pre- 

 cipitate Ag 36ci measured. Accounting for the initial amount of perchlo- 

 rate added to the medium, one may estimate the amount which was converted 

 to chlorides. If the values are close to zero, the given bacteria may be 

 considered to be absent, and the process of reduction lacking. If reduc- 

 tion occurs, perchlorates may be reduced to the extent of 50-100 percent 

 of the added substance. Control experiments with the samples fixed by 

 formalin should always be conducted. 



Presence of Chromates and Bichromates in Water --Chromates and 

 bichromates enter the waters from residues of electroplating shops, auto- 

 mobile factories, or chemical plants. Chromium is heavy metal toxic to 

 many organisms. In 1973 bacteria were isolated which decompose chromates 

 and bichromates under anaerobic conditions to chromium hydroxide using 

 these compounds as oxygen donors (Romanenko and Korenkov, 1975). These 

 bacteria may be used for purification of industrial wastes from chromates 

 and perchlorates (see above), as well as indicators of chromium oxides in 

 wastes. 



In the places of permanent discharge of chromates, the water in the 

 near-bottom layers and the surface layer of sediments are rich in chromium 

 reducing bacteria which can be detected by a special inoculating (Romanenko 

 and Korenkov, 1975). The medium is prepared in flasks, sterilized and ad- 

 justed to circum neutral pH. It is then decanted into stoppered test- 

 tubes. After inoculations, with the test water, the cultures are incubated 

 for 7-10 days. The presence of the chromium reducing bacteria is indicated 

 by the medium turning from yellow (hexavalent chromium) to colorless (tri- 

 valent chromium). Changes in color may be accurately measured on a spec- 

 trophotometer. 



64 



