Surface water resource, such as river, is constantly contaminated by domestic and industrial pollutants. In order to properly manage the water resource, a composite index for water quality assessment, such as water quality index (WQI), has been designed to monitor and evaluate the properties of surface water. However, this index is quite subjective in terms of determination of relative weights. A principal component analysis (PCA) can be used to reduce the dimension and subjectivity of water quality variables. The purpose of this study was to implement the use of hybrid PCA and WQI methods to assess and monitor the water quality of the Bengawan Solo River, which is located in Java Island, Indonesia. The result suggested that COD, BOD, TSS, TDS, nitrate, nitrite, and ammonia were the main factors that determine water quality of the Bengawan Solo River. Furthermore, it was revealed that most samples from the river showed water quality status as slightly polluted. In addition to this, the seasonal variation of the PCWI values indicated a significant increase of water pollution in the Bengawan Solo River per year.
Phytoplankton has an important role in aquatic ecosystem as the primary natural feed for another aquatic biota. However, the density of phytoplankton must be controlled at desirable level in order to prevent eutrophication. Because eutrophication can damage the ecosystem and as the consequence will led to mass mortalities of fish. There are several factors that affecting phytoplankton density such as light availability, temperature, pH, and nutrient content. Nutrient content is composed by nitrate and phosphate. The relationship between nutrient content and phytoplankton density commonly performed by using simple linear regression. But, this method cannot give an overall description of the data since it is worked at conditional mean. Moreover, simple linear regression has several limitation like highly influence by outlier and need the fulfillment of classical assumption. Thus, the aims of this research are to offer an alternative method namely Bayesian quantile regression and provide its performance compared to simple linear regression under various data condition. Also to apply such model to the relationship between nutrients content and phytoplankton density in Sutami Reservoir. The results indicate that Bayesian quantile regression performs better than simple linear regression when the outlier exists. Unfortunately, the data of phytoplankton density and nutrients content in Sutami Reservoir contains outlier according to Cook's distance criteria. It means that Bayesian quantile regression should be used. The obtained model showed that the parameter values of regression model between nutrients content and phytoplankton density vary, which are depended on the analyzed quantile
This study aims to analyze the lipid, carbohydrate and protein content of Chlorella pyrenoidosa after being treated with the tofu wastewater. The method used in this study was an experimental method with 4 treatments and 3 replications. The treatment was performed by administering different concentrations of the tofu wastewater to the C. pyrenoidosa. The concentrations used were 10%, 15% and 20%. Determination of these concentrations was based on the preliminary test. The main parameters observed were the lipid, carbohydrate and protein content of C. pyrenoidosa and the supporting parameters were the growth rate, doubling time and characteristics of the tofu wastewater. The study was conducted for 8 days using the batch culture method. In the exponential phase, the microalgae were harvested and then their contents were analyzed. The data obtained were analyzed using MS Office Excel 2016. The highest content of lipid, carbohydrate and protein of C. pyrenoidosa was in the treatment of 20% tofu wastewater, reaching 1.56%; 28.92%; and 28.92%, respectively. Meanwhile, the highest growth rate and the smallest doubling time in the treatment of 20% tofu wastewater accounted for 0.8264 day -1 and 0.0349 hours -1 . Moreover, the rates of BOD and TSS of the tofu wastewater at the end of the study decreased. It can be concluded that administering different concentrations of the tofu wastewater can affect the lipid, carbohydrate and protein content of C. pyrenoidosa. It was suggested that further research is needed to conduct semi-continuous cultivation of C. pyrenoidosa using a higher density so that the results obtained can be optimized.
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