Occurrence and Removal of Earthy-Musty Odorants in Two Waterworks in Kinmen Island, Taiwan

et al. 2021

IJERPH

Geosmin is a major concern in the management of water sources worldwide. Thus, we predicted concentration categories of geosmin at three different depths of lakes (i.e., surface, middle, and bottom), and analyzed relationships between geosmin concentration and factors such as phytoplankton abundance and environmental variables. Data were collected monthly from three major lakes (Uiam, Cheongpyeong, and Paldang lakes) in Korea from May 2014 to December 2015. Before predicting geosmin concentration, we categorized it into four groups based on the boxplot method, and multivariate adaptive regression splines, classification and regression trees, and random forest (RF) were applied to identify the most appropriate modelling to predict geosmin concentration. Overall, using environmental variables was more accurate than using phytoplankton abundance to predict the four categories of geosmin concentration based on AUC and accuracy in all three models as well as each layer. The RF model had the highest predictive power among the three SDMs. When predicting geosmin in the three water layers, the relative importance of environmental variables and phytoplankton abundance in the sensitivity analysis was different for each layer. Water temperature and abundance of Cyanophyceae were the most important factors for predicting geosmin concentration categories in the surface layer, whereas total abundance of phytoplankton exhibited relatively higher importance in the bottom layer.

Section: Introductionmentioning

confidence: 99%

Prediction of Geosmin at Different Depths of Lake Using Machine Learning Techniques

Kwon

Cho

et al. 2021

IJERPH

“…In that reservoir, when a musty-odor of 10 ng/L or more, which is the Japanese water quality standard (Drinking Water Quality Standards in Japan, Ordinance of Ministry of Health, Labor and Welfare No. 101, 2003) occurs, it is removed using activated carbon or ozone because it is partly used as a water supply [17][18] . An additional cost of about 10 million yen every year is required to remove the musty odor.…”

Section: Introductionmentioning

confidence: 99%

Effect of Rainfall and pH on Musty Odor Produced in the Sanbe Reservoir

Hayashi

Masuki

et al. 2021

Preprint

Harmful cyanobacterial blooms (HCBs) are continuously formed in water systems such as reservoirs and lakes around the world. In particular, geosmin and 2-methylisoborneol (2-MIB), which are made by cyanobacteria, have caused serious musty-odor problems in the drinking water of the Sanbe reservoir in Japan. To investigate the cause of this musty odor, we conducted field observations for five years (2015–2019). As a result, it was determined that the geosmin was caused by the cyanobacteria as Dolichospermum crassum and Dolichospermum planctonicum, and 2-MIB was caused by the cyanobacteria as Pseudanabaena sp and Aphanizomenon cf. flos-aquae. It was also determined that the occurrence of geosmin and 2-MIB are influenced by changes in water temperature and pH due to the inflow of rainfall. Especially, the geosmin and 2-MIB tended to occur in low rainfall conditions. When there is low rainfall, the reservoir changes to an alkaline state due to the consumption of CO2 by the photosynthesis of phytoplankton. In an alkaline reservoir, CO2 exists in the form of bicarbonate (HCO3-); thus, under these condition cyanobacteria will increase because it uses both CO2 and bicarbonate (HCO3-) for photosynthesis. Our study suggests that for solving the musty-odor problem in the reservoir, it is important to control the reservoir’s pH. Moreover, more focus should be place in managing the water quality problem of the Sanbe Reservoir, especially, during low rainfall years. The results of this study will help in addressing odor related water quality problem in other reservoirs.

“…101, 2003). Moreover, for removal of the geosmin and 2-MIB, activated carbon has been generally used [21,22]. In Sanbe Reservoir, partly used as a water supply, located in the mountainous area of Oda City, Shimane Prefecture (Figure 1), a musty odor due to geosmin and 2-MIB was produced in recent years.…”

Section: Introductionmentioning

confidence: 99%

Effect of Rainfall and pH on Musty Odor Produced in the Sanbe Reservoir

Hayashi

Masuki

et al. 2021

Water

Harmful cyanobacterial blooms are continuously formed in water systems such as reservoirs and lakes around the world. Geosmin and 2-methylisoborneol (2-MIB) produced by some species of cyanobacteria have caused odor problems in the drinking water of the Sanbe Reservoir in Japan. Field observations were conducted for four years (2015–2019) to investigate the cause of this musty odor. It was found that geosmin was produced by Dolichospermum crassum and Dolichospermum planctonicum (cyanobacteria), and 2-MIB was due to Pseudanabaena sp. and Aphanizomenon cf. flos-aquae (cyanobacteria). Changes in water temperature and pH caused by rainfall were correlated with changes in the concentration of geosmin and 2-MIB. In particular, geosmin and 2-MIB tended to occur under low rainfall conditions. When there was low rainfall, the reservoir changed to an alkaline state because the phytoplankton consumed CO2 for photosynthesis. In an alkaline reservoir, dissolved inorganic carbon mainly existed in the form of bicarbonate (HCO3−). Thus, the results suggest that under such conditions in reservoirs, cyanobacteria grew easily because they could use both CO2 and HCO3− for photosynthesis. Specifically, our study suggests that in order for the musty odor problem in the reservoir to be solved, it is important that the pH of the reservoir be controlled.