**4. Methodology**

To achieve the objective of this work, it is proposed to follow the following flow chart of the research methodology to be carried out (**Figure 2**). For this purpose, the use of water from the Luta River, feedwater to be treated in the reverse osmosis desalination plant, from which product water and brine are obtained, is considered.

**Figure 2.** *Methodology for the use of brine for the production of halophyte plants (proper elaboration).* *Use of Saline Waste from a Desalination Plant under the Principles of the Circular… DOI: http://dx.doi.org/10.5772/intechopen.105409*

The latter is the subject of this publication. For this, according to the existing brine disposal factors, it is proposed as an alternative to minimize the potential environmental impacts to apply the 3 principles and 11 strategies of circular economy [44] for the cultivation of halophyte plants (*A. nummularia*).

In addition, the methodology is based on mathematical calculations to obtain information on flow rate and brine concentration, feed flow, among others, according to formulas in item 2.5 calculation of brine concentrate, considering the factors that influence brine disposal [43].

### **4.1 Reverse osmosis plant location**

The reverse osmosis plant is located at the *"Plataforma Solar de Investigación y Entrenamiento: Tecnologías Solares para el Tratamiento de Agua"* at the Universidad de Tarapacá, city of Arica, in the region of Arica and Parinacota whose georeferencing is 18.4725111 latitude and 70.3127704 longitude [48]. Among the activities developed in this platform is the applied research in solar water treatment, where several technologies have been implemented to obtain water, among which is the reverse osmosis; however, as mentioned earlier, the problem with this technology is:What to do with the brine generated?

### **4.2 Feedwater quality**

The feedwater for the reverse osmosis plant was obtained from the Lluta River, which was transported by truck, in order to study real samples to generate information to support the rural communities that live in and use this water directly for their crops, limiting their diversification. The parameters used to determine the quality of the Lluta River feedwater were temperature, conductivity, pH, and total dissolved solids (TDSs). These were measured with a multiparameter apparatus (model HI 9828, HANNA Instruments, USA). The concentration of arsenic was also determined using the VARIAN FS 280 VGA 77 atomic absorption equipment with hydride generation and 950°C electrothermal blanket, which were analyzed according to international standards [49] at the Laboratorio de Investigación Ambiental de Zonas Áridas, LIMZA, of the Universidad de Tarapacá (Arica, Chile).

### **4.3 Soil quality in the lower Lluta River sector**

To evaluate the quality of the soil in the sector adjacent to the Lluta River, samples were taken to determine parameters such as, texture, organic matter, pH, electrical conductivity, arsenic, available phosphorus, and total nitrogen, which were analyzed according to international standards [49] and the recommended methods of analysis for Chilean soils of the Comisión de Normalización y Acreditación (CNA), 2004 [50] at the Laboratorio de Investigación Ambiental de Zonas Áridas, LIMZA, of the Universidad de Tarapacá (Arica, Chile).

### **4.4 Reverse osmosis desalination plant characteristics**

The pilot plant under study in this work corresponds to a reverse osmosis desalination plant, Wave Cyber Vessels, Model 300E 4" Side Port Housing, with 300 PSI (21 bar) maximum pressure, 49°C maximum temperature, 7°C minimum

### **Figure 3.**

*Reverse osmosis plant (proper elaboration).*

temperature, and dimensions of 328.2 cm in length. The product water yield is 360 L h<sup>1</sup> and the rejection factor is 50% brine [51].

The feedwater passes through a water pump first passing through sand and activated carbon filters, respectively. The 5-micron cartridge filter retains sediment (sand, sludge, and oxidation particles) to obtain clean water, and the granular carbon filter retains bacteria, chlorine, odors, and organic chemicals.

Subsequently, by reducing salts and compounds that can clog the membrane, it enters the osmosis system where arsenic and salts are reduced (**Figure 3**).

### **4.5 Application of the circular economy**

The use of brine as irrigation water for the cultivation of halophytes (*Atriplex munmularia*) will be evaluated, considering the 3 principles and the 11 strategies of circular economy, taking into account point 3.2.
