Assessment of different methods of water treatment on decreasing pathogenic bacteria in shrimp hatcheries

The project of "Assessment of different methods of water treatment on decreasing pathogenic bacteria in shrimp hatcheries" achieved by mean of reviewing the effectiveness of various methods on the water treatment to reduce bacterial load of sea water. The project performed in Bandargah region of Bushehr province in order to checking the effect of different methods on the sea water and bacterial population. This project has been done over a year. In this study a total of 138 samples was collected during seven times and was evaluated as well as 7 treatments. In this study, the comparison of the effect of each factors (sand filter, chlorine, ultra violet ray, chlorine combined with ultra violet ray) was analyzed on the sea water by means of disinfection. During this study, other environmental factors such as water temperature, dissolved oxygen, pH and salinity was measured till we can ensure that they don’t have any negative impact on the treatments. Results showed that the density of total bacteria in sea water (Control) was averagely 5187 CFU/ml, this was done while the total density of bacteria in the sea water, reservation pool sample, sand filter water, water that irradiated with ultraviolet rays, chlorinated water and the water that was influenced by both chlorine and ultra violet ray was respectively 5187 2137, 4449 2042, 2782 1335, 1164 692, 143 104, 87 76 CFU/ml. Therefore, reservation pool, sand filter, ultra violet ray, chlorine, chlorine-ultra violet ray each of them was reduce respectively 14, 46, 77, 97, 98 percent of the density of total bacteria or in other words they reduced 0.06, 0.27, 0.65, 1.56, 1.77 log of the total population of bacteria in water. Moreover, the results from the total count of vibrios showed that reservation pool, sand filter, ultra violet ray, chlorine, chlorine-ultra violet ray each of them was reduce respectively 17, 47, 74, 98, 99 percent of the density of total vibrios or in other words they reduced respectively 0.08, 0.27, 0.59, 1.66, and 1.95 log of the total population of vibrios in sea water. Also the bacteria that isolated from each treatment were identified with the use of biochemical methods that totally were includes a wide range of bacteria, the identified vibrios were: Vibrio alginolyticus, V. costicola, V. fischeri, V. fluvialis I, V. fluvialis II, V. harveyi, V. natriegens, V. nigripulchritudo, V. parahaemolyticus, V. plagius I, V. vulnificus, V. anguilarum I, V. campbellii, V. nereis, V. proteolyticus, V. splendidus, and Unknown V. spp. Other identified bacteria belonging to the following genus: Acinetobacter, Aeromonas, Alcaligenes, Bacillus, Borkholderia, Eschricia, Enteroacter, Flavobacterium, Micococcus, Proteus, Pseudomonas, Serratia, Staphaphylococcus, Streptococcus, and Unknown Bacteria spp. By comparing the results, we concluded that the best result was related to treatment that the sea water had been disinfected after the combined effects of chlorine and ultraviolet ray. It was determined that this process in compared with other treatments, had been reduced the total number of bacteria, the total number of Vibrios, the number of sucrose fermentative vibrios, and the number of non-sucrose fermentative vibrios respectively 98, 99, 98, 99 percent. In other words, the number of bacteria was reduced respectively 1.77, 1.94, 1.82, 2.23 log. So in this study, the applied method was introduced as the most effective way of disinfecting sea water. Meanwhile, none of pathogenic bacteria for shrimp including Vibrio harveyi was isolated by using this treatment. Comparing the results showed that the combined effects of chlorine and ultraviolet radiation is the most effective applied method for disinfecting sea water.

Iranian Fisheries Science Research Institute

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