جستجوی مقالات مرتبط با کلیدواژه « turbidity » در نشریات گروه « محیط زیست »

Aquaculture includes the propagation and husbandry of aquatic plants, animals, and other organisms for various purposes, including commercial, recreational, and scientific use, which has gained significant attention in recent times. However, its uncontrolled development like any other production activity, can have adverse environmental effects, Thus, the removal of water pollutants is crucial. This study aimed to investigate the impact of a mechanized water disinfection device that uses ultraviolet (UV) radiation at different doses to reduce microorganisms in the effluent of rainbow trout farms.  Also, the efficiency of the device in deactivating pathogens was investigated in different flow rates and water turbidity levels.

The study was conducted in a rainbow trout farm with a 30-ton capacity, located in Kiyar County, approximately 30 kilometers from the center of Chaharmahal and Bakhtiari province. The UV device, at various doses (60, 120, 180, and 240 mW/cm2 = joule), was applied to the farm's effluent, considering different levels of turbidity and flow rates (ranging from 2.5 to 25 liters per second). Water samples were collected both before and after the installation of the UV disinfection device. Subsequently, the average counts of total coliforms, fecal coliforms, fungi, and yeast were calculated with three replications. Probit regression was utilized within the SPSS software environment, with a statistical significance level of 0.001, to examine changes in the removal percentage of microorganisms at different UV doses. Graphs were created using Microsoft Excel 2016 software.

The findings indicated that increased water flow rates and water turbidity reduced the efficiency of removing the targeted microorganisms. The findings indicated that increased water flow rates and water turbidity reduced the efficiency of removing the targeted microorganisms. Moreover, higher UV doses led to a higher removal percentage of total coliforms, fecal coliforms, fungi, and yeast. For instance, at a dose of 56 mJ/cm2, the total counts of total coliforms, fecal coliforms, fungi, and yeast decreased by 1.7, 3.2, 0.7, and 0.86 logs, respectively. However, complete removal of yeasts required significantly higher UV doses, depending on water flow rates and turbidity (up to a maximum of 240 mJ/cm2). Additionally, the results of the probit regression indicated that at doses of 40.50 mJ/cm2, 20.22 mJ/cm2, 30.31 mJ/cm2, and 14.36 mJ/cm2, approximately fifty percent of the yeast population (P<0.001), fungi (Z=13.5, P<0.001), fecal coliform (Z=22.77, P<0.001), and total coliform (Z=6.8, P<0.001) would be removed.

In summary, this research demonstrated that at a dose of 20 mJ/cm2, the gradual elimination of microorganisms begins, but at doses higher than 120 mJ/cm2, the intensity of elimination decreases. Therefore, adjusting the doses of ultraviolet radiation based on the water quality of fish farms can help maintain system health and subsequently increase productivity. The insights obtained from this study can be valuable for commercial water treatment systems and recirculating aquaculture systems. More studies are needed for the efficiency of removing viruses in water by UV rays. It is recommended to construct a sediment pond and employ various water filtration methods, including sand filters, before utilizing ultraviolet rays. This approach aims to decrease the presence of suspended particles in the water and enhance the efficiency of the disinfection system.

Using herbal and natural substances for treatment of drinkable water has been common in many developing countries. The present study aimed to investigate the efficiency of pistachio green hull coagulant on water and wastewater treatment processes. All experiments related to coagulation were done by Jar Test set. The water was contaminated artificially and kaolinite was used to create turbidity. In the present study, the effect of parameters such as pH, concentration of coagulant and primary turbidity on coagulation process and sedimentation of pistachio green hull was investigated. Results indicated that this coagulant, with the concentration of 50 mg/l, can reduce water turbidity most efficiently in pH=5 and primary turbidity of 300 NTU. Pistachio green hull has the best performance in coagulation process with 88% efficiency in the optimal condition. It has been suggested that pistachio green hull can be used as a natural coagulant-aid along with other chemical coagulants to reduce water/wastewater turbidity and also costs accordingly.                 Keywords:

Drinking water supply with proper quality is one of the main goals of water treatment plants. Filtration is a process which has the largest share of quality making in water treatment plants and about 20% of the cost is allocated to this process. The main indicator used for filters efficiency is water turbidity at outlet.
In this research, the effect of various heights (20-50-70-90 cm), effective sizes (0.75-1) and uniform coefficients (1-1.5) sand filter’s packing on turbidity removal and coliforms has been studied for four months from May 2010. Sampling was performed according to standard procedures and the samples were analyzed immediately in Tehran Islamic Azad University of Science Research laboratories and water treatment plant laboratory.
Finding: Results of coarse packing filter show the maximum efficiency of turbidity reduction was 83.58% for turbidity of 5 NTU and packing height of 90cm. The minimum turbidity reduction was 29.25% for turbidity of 10 NTU and packing height of 20cm. The maximum coliform reduction was about 87.92% for turbidity of 2 NTU and packing height of 90cm and the minimum coliform reduction was about 38% for turbidity of 10 NTU and packing height of 20cm. The effective height which causes maximum turbidity and coliform reduction is 90cm. The longest operation time in the context of a coarse bed was 35 hours in turbidity of 2 NTU and the shortest operation time in the context of a coarse strainer was 23 hours in turbidity of 10 NTU.
Results of fine packing filter show the maximumefficiency of turbidity reduction which was 93% for turbidity of 2 NTU and packing height of 90cm. The minimum turbidity reduction was 54.9% for turbidity of 7 NTU and packing height of 50cm. The maximum coliform reduction was about 91.92% for turbidity of 2 NTU and packing height of 90cm and the minimum coliform reduction was about 45% for turbidity of 10 NTU and packing height of 20cm. The effective height which causes maximum turbidity and coliform reduction is 90cm. According to the results, efficiency of the fine bed and coarse bed filter directly depends on outlet turbidity and operation of previous unit (sedimentation). The maximum and minimum operation times in fine bed were about 28 hours (NTU=2) and 14 hours (NTU=10) respectively.

In the present study, trophic state of Valasht Lake was investigated monthly at 3 stations, from December 2008 to December 2009. The purpose of this study is investigating the trophic state of the lake and introducing the basic solutions to maintain this valuable ecological resource.
Trophic state index (TSI) was used in this study. Also, the effective parameters on primary production and trophic state determined in this study include: total phosphorus (TP), total nitrogen (TN), a-chlorophyll, Secchi depth (SD), and TN/TP ratio.The results from all mentioned parameters were compared with different trophic levels of fresh water lakes published by U.S Environmental Protection Agency and Organization for Economic Cooperation and Development.
According to trophic state index and based on nutrient levels (phosphor and nitrogen), Valasht lake is classified in Mesotrophic to Eutrophic state and based on the other mentioned parameters, it is classified in mesotrophic state.
Mean rate of trophic state index reveals the mesotrophic state in this lake. According to the results of Red Field ratio and TSI, nitrogen and turbidity, especially in wet (rainy) seasons, are the main determinative parameters in primary production in Valasht Lake.

Paper mill’s wastewater is the most pollutant industrial wastewaters. The effluent causes production sludge، scum formation and loss of aesthetic beauty in the environment. They also increase the amount of toxic substances in the water which causes death to the zooplankton and fish. The present research investigated the effect of coagulant of PACL for reduction of the pollutants in paper mill wastewater. For reduction of the pollutants the quantity and quality of wastewater investigated. This study showed that this wastewater has chemical oxygen demand (COD) 3523 mg/l and turbidity= 872. In this test، parameters of turbidity، COD، total solid (TS)، optimum pH and dosage of coagulant determined. According to data obtained from studies optimum pH and dosage of PACL were obtained to be 7، 785 mg/l، respectively. The results of the present study revealed that coagulant of PACL could reduce 90% of TS، 88% of COD and 93% of turbidity in paper mill wastewater