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Bacterial Status and Pollution Level in the Water of Gulshan Lake, Dhaka

Md. Abdul Karim
Laboratory of Microbiology, Department of Botany, University of Dhaka, Dhaka-1000, Bangladesh.

Nazneen Akhter
Laboratory of Microbiology, Department of Botany, University of Dhaka, Dhaka-1000, Bangladesh.

Sirajul Hoque
Department of Soil, Water and Environment, University of Dhaka, Dhaka- 1000, Bangladesh.

Abstract/ Executive Summary:

Water samples were collected from four selected sites of the Gulshan lake during four different seasons. Four different media were used to study the aerobic heterotrophic, enteric and related bacterial abundance. Aerobic heterotrophic bacterial abundance ranged between 1×10⁶ and 9×10⁶ cfu/10⁰ ml, while enteric and related bacterial abundance in SS agar, MacConkey agar and Cetrimide agar media ranged between 1×10³ and 3×10⁵ cfu/10⁰ ml, between 1×10⁴ and 1×10⁷, and between 1×10⁰ and 1.4×10³ cfu/10⁰ ml, respectively. Among 40 bacterial isolates 14 were selected out of which seven were Gram-positive and seven were Gramnegative. Among Gram-positive isolates, six were rod-shaped spore former belonging to Bacillus and Lactobacillus, while another one was coccoid in shape and under the genus Planococcus. Out of seven Gram-negative isolates, two were the members of Pseudomonas, remaining five were Morganella, Neisseria, Escherichia, Aeromonas and Enterobacter. Inorganic nutrients like NH₄+-N, NO₃-N, NO₂-N and PO₄- values were found to be satisfactory from pollution point of view. The presence of different bacterial isolates indicate that the Gulshan lake water was polluted with chemical and bacterial pollutants.

Keywords: Aerobic heterotrophic bacteria, Enteric bacteria, Chemical properties, Lake water

Location: Gulshan lake, Dhaka, Bangladesh.

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Contamination

Objectives:

To determine aerobic heterotrophic, enteric and related bacteria.
To the context of biological pollution level along with physicochemical properties.
To reveal an overall status of pollution of the Gulshan lake water.

Methodology:

Water samples were collected in clean carbon polypropylene containers from four different sites (viz. GL-1, GL-2, GL-3 and GL- 4) of the lake. The lakeside, where floating people used to take their bath, swim and wash clothes in the lake water, were selected as the sampling sites. Nutrient agar (NA) medium was used for the enumeration and isolation of aerobic heterotrophic bacteria. MacConkey agar (Difco), SS agar (Diagnostic Pasteur) and Cetrimide agar (Difco) (for enteric bacteria) media were used for the determination and isolation of enteric bacteria. The pH of the isolation media was adjusted to 7.2 before sterilization, since the pH values of most of the samples were within the range of 6.4 to 7.6. Three different techniques, viz. serial dilution plate, spread plate and membrane filtration techniques were used for the enumeration and isolation of bacteria. Inoculated bacterial plates were inverted and incubated at 37°C for 24 hours. Bacterial colony counting was made with the help of a digital colony counter (OSK 10086, DC-3, Kayagaki, Japan). Discrete bacterial colonies were isolated immediately after counting. In case of MacConkey agar medium, pink or brick red colonies were considered as lactose fermenter and colorless colonies as nonlactose fermenter. Temperature of water samples was measured at the time of water sampling with the help of a mercury thermometer. The pH of collected water samples was measured by using a digital pH meter immediately after collecting the samples. For chemical analysis, water samples were passed through filter paper to eliminate suspended solid particles. Nitritenitrogen present in the water samples was determined by the modified Griess- IIosvay method. The nitrate-nitrogen of the water samples was determined calorimetrically. Soluble reactive phosphorous was determined by ascorbic acid blue color method. To determine ammonium nitrogen, the water samples were distilled under alkaline condition in a Micro-Kjeldahl apparatus. Important physiological and biochemical characteristics were studied for the identification of the selected isolates. Different biochemical tests, viz. catalase, oxidase, carbohydrate fermentation, deep glucose agar, tyrosine degradation, egg-yolk lecithinase, arginine hydrolysis, casein hydrolysis, starch hydrolysis, gelatin hydrolysis, protease, urease, Kligler’s iron agar (KIA), Levan, methyl red, nitrate reduction, indole production, phenylalanine deamination, citrate utilization, utilization of propionate, Voges-Proskauer (V.P) test etc. were carried out.

Source of Information: Bangladesh J. Zool. 40(2): 165-173, 2012 (December)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In Summer, the water temperature ranged between 22 and 24°C, while in Rainy season that was 25°C. In winter, the temperature ranged between 11 and 12°C and in late Autumn, it was found between 28.1 and 29.9°C. The results indicate a favourable temperature for bacterial growth except in Winter. The pH of the water samples ranged between 7.26 and 7.5 in Summer, 7.34 and 7.61 in Rainy season, 8.27 and 8.37 in Winter and 6.41 and 7.55 in late Autumn. In the present study, the values of NH₄+ were much lower than NO₃- and NO₂- that was a trend to nitrification process during both Winter and late Autumn. The value of the total amount of nitrogen (NH₄, NO₃- and NO₂-) and phosphorus were found to be satisfactory from the pollution point of view with the guidelines recommended by USPH. Among Gram-positive isolates, six were rod-shaped spore former belonging to Bacillus and Lactobacillus, while another one was coccoid in shape and under the genus Planococcus. Out of seven Gram-negative isolates, two were the members of Pseudomonas, remaining five were Morganella, Neisseria, Escherichia, Aeromonas and Enterobacter. Inorganic nutrients like NH₄+-N, NO₃-N, NO₂-N and PO₄- values were found to be satisfactory from pollution point of view. The presence of different bacterial isolates indicate that the Gulshan lake water was polluted with chemical and bacterial pollutants.

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