Treatment of cooling tower blowdown water containing silica, calcium and magnesium by electrocoagulation

Yeon

Environmental Engineering Research

2020

Reverse osmosis (RO) is the main process of current industrial desalination, and its performance is affected by the quality of water source. Natural water contains a certain level of silica, which is originated from metal silicate in the earth crust. Due to its complexity, silica fouling is difficult to control, which often causes less efficient design of RO system for safe operation. In the present work, we review the current state of silica treatment technology in RO desalination. Silica chemistry is investigated in standpoint of the scale formation mechanism among multiple forms of silica species and its synergistic interaction with other foulants such as organic matter. Then, pretreatment methods to remove silica in the RO feed water are outlined. They include softening/coagulation, seed precipitation/aggregation, tight ultrafiltration, ion exchange, adsorbents media, and electro coagulation. We finally highlight the mitigation of RO fouling under silica rich conditions, whose concept can be implemented in different ways of antiscalant dosing, high/low pH operation, and intermediate softening of the RO concentrate, respectively. This review will provide comprehensive information and insight about the optimal operation of industrial RO susceptible to silica fouling.

Section: Electro Coagulationmentioning

confidence: 99%

Silica treatment technologies in reverse osmosis for industrial desalination: A review

Yeon

Environmental Engineering Research

2020

“…The issue of dissolved silica in cooling towers has continued to receive attention since the project was started 1,2 . The approaches have included electrocoagulation and hybrid ion exchange resins.…”

Section: Figure 1 Proposed Ge Solution For the Use Of Impaired Watermentioning

confidence: 99%

Technology to Facilitate the Use of Impaired Waters in Cooling Towers

Colborn

2012

Executive Summary:The project goal was to develop an effective silica removal technology and couple that with existing electro-dialysis reversal (EDR) technology to achieve a cost effective treatment for impaired waters to allow for their use in the cooling towers of coal fired power plants. A quantitative target of the program was a 50% reduction in the fresh water withdrawal at a levelized cost of water of $3.90/Kgal.Over the course of the program, a new molybdenum-modified alumina was developed that significantly outperforms existing alumina materials in silica removal both kinetically and thermodynamically. The Langmuir capacity is 0.11g silica/g adsorbent. Moreover, a low cost recycle/regeneration process was discovered to allow for multiple recycles with minimal loss in activity. On the lab scale, five runs were carried out with no drop in performance between the second and fifth run in ability to absorb the silica from water. The Mo-modified alumina was successfully prepared on a multiple kilogram scale and a bench scale model column was used to remove 100 ppm of silica from 400 liters of simulated impaired water. Significant water savings would result from such a process and the regeneration process could be further optimized to reduce water requirements.Current barriers to implementation are the base cost of the adsorbent material and the fine powder form that would lead to back pressure on a large column. If mesoporous materials become more commonly used in other areas and the price drops from volume and process improvements, then our material would also lower in price because the amount of molybdenum needed is low and no additional processing is required. There may well be engineering solutions to the fine powder issue; in a simple concept experiment, we were able to pelletize our material with Boehmite, but lost performance due to a dramatic decrease in surface area.

“…Saha et al [10] evaluated the performance of electrochemical oxidation (EO) with a boron-doped diamond (BDD) anode to remove organic compounds (OCs) from CTB in the cooling tower. Liao et al [11] reported that the efficiency of hardness ion removal for the cooling tower blowdown in the cooling tower can be improved by the EC using Fe and Al electrodes, and the addition of coagulation aids.…”

Section: Introductionmentioning

confidence: 99%

Effects of Pulse Frequency on Performance of Electrochemical Cooling Water Treatment for Cooling Tower of Water-Cooled Chiller

Nhut¹,

Vietnan²,

Nhut³

2021

REPQJ

Due to the rapid economic development in recent years, water-chiller is being used more and more in hotels, restaurants, resorts, and industrial zones in Vietnam. The cooling tower’s cooling water quality is an important factor in determining the effect on electrical consumption and the coefficient of performance of a water-cooled chiller. Therefore, it is necessary to maintain the quality of cooling water during the operation time of the water-cooled chiller. The aim of this work is to investigate the effects of the pulse frequency and operational parameters such as current density, pulse duty cycle, and energy consumption on the performance of removing hardness ion of electrochemical cooling water treatment for the cooling tower of the water-cooled chiller. The results show that the highest efficiency of the total hardness removal corresponding to a pulse frequency of 1 kHz, a pulse duty cycle of 0.7, and a current density of 80A/m2.