Experimental Study on the Influence of Flexible Control on Key Parameters in Reverse Osmosis Desalination

Abstract

Variable-frequency drive (VFD) has been widely used in reverse osmosis desalination. Our purpose is to study how the VFD and pressure regulating valve affect the key parameters of reverse osmosis desalination and their action principle through experiments. Firstly, the power frequency is controlled by VFD, and the operating pressure is controlled by pressure regulating valve (needle valve) in the experiment. The feed water passes through the multimedia filter, precision filter and permeable membrane channel in turn, and permeate water and brine enter the fresh water tank and the brine tank respectively. Secondly, through experiments on seawater and brackish water respectively, the water flow rate, product water quality, energy consumption and recovery rate under different operating pressures are obtained when the power frequency is 25, 30, 35, 40, 45, and 50 respectively. Finally, combined with the working principle and mathematical model of VFD and high-pressure pump motor, the reason for the experimental results caused by the operation change is explained theoretically. The experimental results verify that for a certain recovery rate, the specific energy consumption required for water production decreases with decreasing power frequency. This provides desalination energy savings but at the expense of permeate production speed.

Challenges and Solutions for Global Water Scarcity

“…The energy consumption for SWRO desalination ranges between 3.5–4.5 kWh/m 3 [ 87 ], with the membrane separation process accounting for 71% of the total energy consumption [ 88 ]. Various approaches have been implemented to alleviate the energy consumption and costs of RO desalination.…”

Fuzzy State-Dependent Riccati Equation (FSDRE) Control of the Reverse Osmosis Desalination System With Photovoltaic Power Supply

“…These two assumptions imply the existence of a general state-dependent parameterization for 𝑓(𝑥). Therefore, the nonlinear differential equation ( 19) can be written as (21): 𝑥̇= 𝐴(𝑥)𝑥 + 𝐵(𝑥)𝑢(𝑥), 𝑥(0) = 𝑥 0 , 𝑓(𝑥) = 𝐴(𝑥)𝑥 Also, some more assumptions are made as follows: Assumption 3: 𝐴(0), 𝐵(0), 𝑄(0), and 𝑅(0) are matrix rated functions 𝐶 1 (𝑅 𝑛 ). Assumption 4: The pairs {𝐴(𝑥), 𝐵(𝑥)} and {𝐴(𝑥), 𝑄 1 2( 𝑥)} are point stabilized, and observable parameterizations of the nonlinear system (19) for all values of 𝑥.…”

“…In [20], a controller based on a nonlinear model has been designed and implemented on the reverse osmosis desalination laboratory system which used geometric control methods. The influence of the variable frequency drive (VFD) and the pressure regulating valve on the reverse osmosis desalination system were experimentally studied in [21]. The combined photovoltaic-reverse osmosis (PV-RO) system was studied in [22], but only the maximum power point tracking of the photovoltaic system was considered.…”

Effectivity Of Multi Tray Aerator As Pretreatment Process For Reverse Osmosis Membrane To Utilized As Raw Water At Sungai Itik Village

“…The complete RO desalination process includes 4 stages, that are water intake, pretreatment, reverse osmosis treatment and posttreatment. Reverse osmosis process accounts for about 71% of consumption the overall energy of the process, followed by water intake (maybe some differences in energy consumption due to the influence of water source location) [3].…”

“…This aeration process is included in the pretreatment stage which functions to remove polluting elements such as Fe, Mn and organic compounds, so that larger sized particles do not enter the RO membrane. The pretreatment process functions to avoid major damage that occurs in reverse osmosis [3]. This also aims to ensure that the RO (Reverse Osmosis) performance in the process of processing raw water into drinking water does not work too hard, more efficient, the membrane does not get damaged quickly and can last longer.…”