El flujo se distribuye a través del canal de entrada en treinta filtros de gravedad de doble capa que estarán aislados individualmente por compuertas. Cada filtro proporciona una superficie de 108 m2 para la filtración, con una capacidad total diseñada para tratar el agua de alimentación con dos filtros en retrolavado. Se instala antracita y arena de alta calidad como medios de filtración (con un coeficiente de uniformidad inferior a 1,5). La capa superior de antracita tiene una profundidad de 1,4 m y la capa inferior de arena tiene una profundidad de 0,7 m. Los filtros se controlan para mantener un nivel constante. El aumento de la pérdida de carga del lecho se compensa abriendo la válvula reguladora de la salida del agua filtrada, de acuerdo con el lazo de control principal. La turbidez a la salida de cada filtro se controla con un medidor de turbidez para cada línea de filtrado (3 en total), así como el SDI en la salida común después del bombeo intermedio. Sistema de drenaje inferior El lecho filtrante se apoya en el sistema de subdrenaje. El sistema de subdrenaje está diseñado para que las cámaras de alimentación y de compensación estén en el mismo bloque. El bloque incluye una cámara primaria (de alimentación de retrolavado) conectada a través de una serie de orificios con la de compensación (secundaria). Los orificios están situados en cuatro niveles diferentes y colocados para garantizar una distribución uniforme del agua y aire. PRE-TREATMENT The pre-treatment stage consists of dual media gravity filters to remove solids before the water enters the RO trains. Dual media filters (DMF) Raw water for the RO plant is sent to the dual media filter inlet channel by means of two DN1800 GRP pipes. The flow is chemically dosed in the 2 static mixers. Provision has been made for the injection of sodium hypochlorite for biofouling control, ferric chloride for coagulation and sulphuric acid for pH adjustment for coagulation purposes. The flow is distributed through the inlet channel into 30 dual media gravity filters, which are individually isolated by sluice gates. Each filter has a filter surface area of 108 m2, and a total capacity designed to treat the feed water when two filters are out of service due to backwashing requirements. High quality anthracite and sand are implemented as filter media (with a uniformity coefficient of less than 1.5). The upper anthracite layer has a depth of 1.4m and the lower sand layer has a depth of 0.7m. The filters are controlled tomaintain a constant level. Increases in filter-bed head loss are offset by opening the filtered water regulating valve, in accordance with the main control loop. Turbidity at the outlet of each filter line is monitored by a turbidity meter (3 turbidity meters in total), and the SDI is monitored at the common outlet after intermediate pumping. Underdrain system The filter bed is supported by the underdrain system, which is designed so that the feed and compensation chambers are in the same block. The block includes a primary chamber (backwash feeding chamber) connected through a series of orifices to the compensation (secondary) chamber. The orifices are located at four different levels and placed to ensure a uniform distribution of water and air. The secondary chamber guarantees the uniform distribution of pressure and flow from top to bottom. The media retention plate is located on the upper part of the blocks. This design provides both media support and suitable www.futurenviro.es | Junio-Julio June-July 2022 39 Desaladora Shuqaiq 3 (Arabia Saudí) | Shuqaiq 3 Desalination Plant (Saudi Arabia)
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