Kwang-Hun Jang, “정수처리공정에서 여과지 역세척 최적제어,” 아주대학교 공학석사 학위 논문, 2014. > Paper

Demands and concerns for higher water quality from customers have been continuously increased due to the gradual improvement

of quality of citizen’s life. Water treatment process, therefore, has evolved from the conventional to advanced treatment processes.

Filtration process (including subsequent backwashing), however, is the essential unit process both the conventional and advanced

treatment processes. Since the filtration process is the final polishing process, only optimal backwash of filters will guarantee the

supply of crystal clear water without any turbidity, pathogens, taste, or odor. On the other hand, the non-optimized filter backwashing

process requires the frequent operation of auxiliary facilities such as backwash pumps and air scouring blowers, thus, requiring

increased energy consumption. In this thesis, the optimum filter backwash strategy is proposed by selecting optimized steps

(or modes) for HMI(Human Machine Interface) based on seasonal changes or water quality fluctuations. To verify the optimizing

strategy, a water treatment plant which is in operation is selected, and conditions of filters and their auxiliary facilities and long-term

operation data and patterns are analysed. Based on those data, the optimized backwash control logic is formulated by steps and

steps and are divided into several groups to upload into the filter control programmable logic controller (PLC). The operation of the

filter backwash process is evaluated in terms of water qualities and energy efficiency. In conclusion, the step control (PI control) of a

backwash valve opening (throttling) results in higher efficiency in terms of turbidity removal and filter media loss in comparison to

the ON/OFF control of the backwash valve. The step control strategy can, thus, resolve many such problems caused by the

conventional ON/OFF control. Moreover, the step control strategy of backwash valve throttling (or backwash pump speed) based on

Backwash Time Chart can save energy consumption, not only because of the increased backwash efficiency, but also because of

lesser operation frequency of auxiliary facilities. It is expected that the step control strategy can effectively the optimize filter

backwash operation by formulating several steps based on the seasonal variation of turbidity, water temperature, characteristics of

backwash equipments and application of the logics during commissioning and plant start-up phase.