Wastewater reuse in liquid sodium silicate manufacturing in Alexandria, Egypt

ABSTRACT

Soluble sodium silicates [watergiass] are liquids containing dissolved glass which have some water like properties. They are widely used in industry as sealants, binders, deflocculants, emulsifiers and buffers. Their most common applications in Egypt are in the pulp and paper industry [where they improve the brightness and efficiency of peroxide bleaching] and the detergent industry, in which they improve the action of the detergent and lower the viscosity of liquid soaps. The survey results showed that the production was carried out batch-wise, in an autoclave [dissolver]. Sodium silicate in the state of crushed glass was charged in an autoclave [dissolver] with sodium hydroxide and water. The product is filtered through a press. The left over sludge [mud and silicates impurities] is emptied into the local sewer system. Also, sludge [silica gel] was discharged from the neutralization process of the generated alkaline wastewater and consequently clogging the sewerage system. So this study was carried out to modify the current wastewater management system which eliminates sludge formation, the discharge of higher pH wastewater to the sewer system, and to assess its environmental and economic benefits. To assess the characteristics of wastewater to be reused, physico-chemical parameters of 12 samples were tested using standard methods. The survey results showed that a total capacity of the selected enterprise was 540 tons of liquid sodium silicates monthly. The total amount of wastewater being discharged was 335 m[3]/month. Reusing of wastewater as feed autoclave water reduced water consumption of 32.1% and reduced wastewater discharge/month that constitutes 89.6% as well as saving in final product of 6 ton/month. It was concluded that reusing. of wastewater generated from liquid sodium silicate manufacturing process resulted in cheaper and environmental-friendly product