ABSTRACT

Calcium and magnesium ions are the major components of scaling in different water sources, especially seawater. Calcium and magnesium scale causes problems in various industrial operations such as reverse osmosis unit, heating unit of multi-stage flash distillation, concentration operation of copper-molybdenum mining industry, cooling water system of power generation industry, and water injection operation of oil and gas production. In general terms, scaling affects the operation performance that leads to increased production, as well as maintenance costs. The pH control, scale inhibitors, and nanofiltration membrane have been implemented by industrial operations to control scale. However, the drawbacks of these technologies may force to seek alternative technologies which could be potential alternatives for scale control. This paper discusses the problems of calcium and magnesium scale affecting various industrial operations when seawater is used. It presents current technologies for scale control such as pH control, scale inhibitors, and nanofiltration. Moreover, the technology assessment (TA) was made to evaluate existing and emerging scale control approaches in the case of reverse osmosis (RO) process. The identification of the emerging technologies of scale control has been performed using bibliometric analysis. The comparison of the technologies was made using House of Quality (HOQ) matrix. The identified emerging technologies are: bioelectrochemical system, biomineralization, biosorbent, microbial desalination cells, step by step deposition and extraction technique, carbon dioxide as a precipitator, gas hydrate, ultrasonic crystallization, and capacitive deionization. The comparison of the technologies has shown that nanofiltration, as a common technology, could be an appropriate approach to ensure feasibility and efficiency of RO process, while emerging technology, microbial desalination cells, could become a potential alternative in the future.

Introduction

Water is a key element for agriculture, urban, and industrial development sector. However, many places in the world are facing water shortages and lack fresh water. Some of the major causes are climate change, rapid population growth, limited natural resources, and unsustainable development (Mahmoud and Obada, 2014). As less than 3% of the world’s water is fresh while the rest is seawater (Fry and Martin, 2005), the oceans and seas have become potential sources of water supply for industrial, urban, and agriculture sectors in semi-arid, arid, and hyperarid regions. For the industrial sector, quality of water is essential for its operations to achieve expected performance and desired specification of final products. Seawater quality is not suitable because it contains more dissolved ions of all types than fresh water. Nevertheless, it is used in several industrial operations, including reverse osmosis (RO) units, heating units in multi-stage flash distillation (MSF) (Khayet, 2016), cooling water systems in power generation industry (Pugh et al., 2005), water injection in oil and gas production industry (Bader, 2007), and concentration operation in copper-molybdenum mining industry (Jeldres et al., 2017). Industrial operations, in which seawater is used face problems of corrosion, biofouling, and scaling (Demadis et al., 2007). The latter occurs when soluble minerals precipitate from seawater and deposit on surfaces that affect the performance of industrial operations. Scale deposition increases the costs of production linked with maintenance costs that cause losses billions of dollars (Gilron, 2013). Calcium and magnesium are the main ions that cause scaling problem and their scale deposits are calcium sulphate (CaSO4,), calcium carbonate (CaCO3), calcium fluoride (CaF2), calcium phosphate (Ca3(PO4)2), magnesium hydroxide (Mg(OH)2), and magnesium carbonate (MgCO3) (MacAdam and Jarvis, 2015).