Osamu Yamanaka

Model based optimal control for SWRO process based on pilot plant data

Generally, operating values such as reverse osmosis (RO) recovery rates are adjusted to a desired power consumption cost during the initial stage of design. However, the power consumption is dependent on changes in membrane permeability associated with seasonal/daily variations of seawater conditions such as temperature, salinity and potential of Hydrogen (pH). These variations might be a vital contributing factor to the difference from desired cost. In order to solve this problem, it is desirable to develop optimal control which can minimize specific energy consumption (SEC) automatically. This paper proposes an optimal operational approach for tracking a minimum SEC under the variations of seawater conditions. In this approach, numerical simulations are carried out to estimate SEC and determine operating values. Several simulation results demonstrate the effectiveness of the proposed controller compared with the constant RO recovery rate.

A Monitoring Technique Using Multivariate Statistical Process Control Method for Performance Improvement with Application to Wastewater Treatment Plant Operation

Abstract This paper presents a new monitoring technique to improve the performance of plant operation based on multivariate statistical process control (MSPC). The proposed method combines with MSPC by principal component analysis (PCA-MSPC) and monitoring of a predefined performance index for efficient and stable plant operation. Fault detection and isolation (FDI) related to the performance index is selectively performed by monitoring the time series data of the index wherein the sample points violating the control limit of the Q statistic or that of the T 2 statistic in PCA-MSPC are indicated. Hidden patterns of probable cause to deteriorate the performance index are discovered from the FDI by observing the time series data of the isolated variables. Applications of the proposed method to real wastewater treatment process illustrate the effectiveness of the proposed method by showing possible improvement for energy-saving operation and stable plant operation.