Evaluation of acute toxicity of effluents of industrial wastewater treatment plants of industrial towns of Gorgan city using biomonitoring

Effective treatment of domestic sewage and industrial effluent to maintain the quality of the utmost importance. Quality wastewater treatment, usually with parameters such as PH, dissolved oxygen, chemical oxygen, biochemical oxygen demand, total organic carbon, total dissolved solids, total suspended solids, concentration of some special compounds and other parameters can be expressed. There are several methods for determining toxicity, including bioluminescence, respiration, nitrification, denitrification, molecular-based tests and sensors, and bioassay. Toxicity testing for aquatic life is a method in which the reactions of aquatic organisms are used to detect or measure the presence or effect of one or more toxic substances, wastewater, or environmental factors alone or in combination. This method has many deficiencies, including lack of recognition synchronized effects and toxicity index them. Even the most comprehensive physico-chemical properties wastewater effluent adverse effects on ecosystems will not show the effects of bio-waste only determined by bioassay tests. One of the standard methods for determining the toxicity of wastewater is the toxicity test or bioassay. Although all bioassay tests are very similar in principle, this study focuses more on bioassay with the help of microorganisms, because bioassays focus on microorganisms in addition to their specificity in controlling water pollution. There are many types for bioassay. The two most commonly used types are chronic and acute toxicity. Many organisms such as fish, algae, bacteria and freshwater and sea creatures are used in the bioassay. One of these indicators is a hard skin called Daphnia Magna. The results of research on a variety of laboratory organisms show that bioassay with Daphnia Magna compared to some organisms with high sensitivity, short reproduction, simplicity of testing and low laboratory costs and most importantly due to fertilization. They have a genetic similarity, which is one of the most important factors in the validity of the results of bio-experiments, in infants born of the same sex. It also has a special place in water pollution control measures. Today, the use of Daphnia Magna is accepted in different countries due to its high sensitivity and easier use to monitor the effluent and determine the efficiency of the treatment plant in reducing toxicity.The aim of this study was to evaluate the toxicity of effluent from wastewater treatment plants, industrial city of Gorgan in Golestan Province Using the biology test.

The accuracy of a biological test is limited to a number of reasons, which are due to natural differences between members of a species. Study with accidentally selected species does not provide accurate information about the toxicity of a compound compared to other species and life stages. Experiments with one species, provide an accurate estimate of toxicity only to other similar species in terms of size, age, and physiological conditions in water with similar characteristics and conditions. Daphnia Magna is the largest daphnia, measuring 5 mm in size. Many of them can be grown in a relatively small space. Daphnia Magna babies are 0.8 to 1 mm long and can be seen with the naked eye. Daphnia magna is very important in biological experiments at this stage of the life cycle. The female genus Daphnia magna can survive for up to 4 months at 20 ° C. They grow in natural waters and dechlorinated tap water. Their diet consists of bacteria, algae and yeasts along with soil extracts and organic matter. Daphnia magna is grown individually in small containers and in large aquariums. According to the sensitivity of Daphnia and the reports that Daphnia magna is the most sensitive invertebrate to various organic compounds; To determine the effectiveness of the processes used in this study, Daphnia Magna was used as a bioindicator of bioassay experiments. First, the test materials, diluent water, and toxic solutions are prepared, and the test and control solutions are introduced in 100 ml volumes into wide-mouthed glass or similar containers. Necessary tests such as pH, DO, TSS, temperature, BOD, COD, EC were performed on the effluent sample. After preparing the test solutions, 10 Daphnia infants were placed in each test container and control container; then observation is performed regularly. Observation is usually done after 1, 2, 4, 6, 12 hours and then daily for up to four days (96 hours). The number of moving animals in each test vessel should be recorded. Mortality in control samples should not be more than 10% and preferably more than 5%, which indicates a sick organism in the group of 10 to 20. Then using Daphnia magna Bioandicator acute toxicity unit and LC50 at 12, 24, 48, 72 and 96 hours with probit test in SPSS version 22 was used. Composite samples of raw sewage and industrial wastewater treatment plant of the city of Gorgan were refined. It should be noted that all toxicity tests determined in the Health college laboratory of Medical Sciences university was conducted. In this study, LC50 and toxicity unit (TU) were determined.

To determine the toxicity of raw and treated effluents during different treatment times by COP method with experimental method, the results related to Magna and LC50 mortality and toxicity unit (TU) are presented in Figures 1 to 7. BOD5 and COD parameters treated wastewater Industrial Town BandarGaz, respectively 44 ± 4 and 28 ± 2 mg with 0.8% and 47% by volume of input and output LC50-96h with the TU respectively 12773 and 214 for Agh Ghala Industrial Town COD 50 ±25 mg LC50-96h with the input and output, respectively 0.8% and 39.9%, respectively 12159 and 251 were measured by the TU.

The results showed that the removal of toxic wastewater treatment LC50-96h Aq Qala and Bandar Gaz respectively from 0.8% to 39.9% and from 0.8% to 47% by volume, respectively. The acute toxicity of waste water treatment plants Aqqala from 12159 to 251and acute toxicity of the wastewater treatment plant Bandargaz after 96 hours measure fell from 12 773 to 214. Considering that the toxicity of Aqqala water treatment plant effluent is approximately 1.1 times than Bandar-e-Gaz treatment plant, according to the classification of toxic compounds based on the toxicity unit, the effluent from both treatment plants is extremely toxic. Therefore, necessary measures to monitor and reduce toxicity, in addition to observing the parameters of the standard index of wastewater treatment plants are necessary.