Abstract
The seasonal occurrence of algae blooms in surface waters remains a common problem, such as taste and odor (T&Os), the risk of disinfection by-products (DBPs), and disturbance to water treatment systems. The coagulation efficiency of plant-mineral composite (PMC) coagulant followed by UV-based advanced oxidation processes (UV-AOPs; UV/H2O2 and UV/Cl2) was evaluated for removal of algae, turbidity, dissolved organic matters, and taste and odor compounds in lab-scale and pilot-scale tests. In the lab-scale test, coagulation process with 20 mg/L of PMC shows high removal efficiency of turbidity (94%) and algae (99%) and moderate removal efficiency of UV254 (51%) and geosmin (46%). The pilot test results also show good removal efficiency of turbidity (64%), chlorophyll-a (96%). After PMC coagulation process, the major water factors, which affected the performance of UV-AOPs (i.e., UV transmittance (85–94%), and scavenging factor (64,998–28,516 s−1)), were notably improved, and further degradation of geosmin and 2-methylisoborneol (2-MIB) was achieved in both lab-and pilot-scale tests of the UV-AOPs. The UV/H2O2 process shows higher removal efficiency of geosmin and 2-MIB than the UV/Cl2 process because of the pH effect. The results confirmed that the PMC-based coagulation followed by UV/H2O2 process could be an effective process for the removal of algae, geosmin, and 2-MIB.
Highlights
Harmful algae bloom problems are becoming more serious with increasing frequency and quantity in the aquatic environment [1]
This study investigated two different UV based advanced oxidation processes (AOPs), i.e., UV/H2 O2 and UV/Cl2 processes, to enhance the geosmin and 2-MIB removal efficiencies after the plant-mineral composite (PMC)-based coagulation process
The level of residual taste and odor (T&O) compound was above the threshold
Summary
Harmful algae bloom problems are becoming more serious with increasing frequency and quantity in the aquatic environment [1]. In drinking water sources in Korea, the problem is significant because of the impact of the harmful algal on the water treatment performance [2]. An algal bloom event results in the release of geosmin, 2-methylisoborneol (2-MIB) and taste and odor (T&O). Sci. 2018, 8, 1502 compounds from the algal cells during and after bloom events. The toxic and/or odorous metabolites produced by these blooms impact the drinking water quality. Odors of organic compounds produced by algae are characterized as earthy and musty/camphorous. Odors of such compounds can be sensed by the human nose even at extremely low concentrations, e.g., concentrations as low as 4.0 and
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