**2.1. Wastewater sampling**

In this chapter, the physicochemical characterization of six types of industrial wastewater and how to develop a treatment strategy for water recovery and how to add value to the byproducts formed are presented. The wastewater sampling protocol was followed as recommended by Mexican sampling standard (NMX-AA-003-1980). Residual water samples were taken from the nixtamalization industry (nejayote) that is dedicated to the manufacture of corn products and their derivatives. Another sample was collected from a candy factory that generates wastewater with a high content of dyes and suspended particles. The third case corresponds to a company dedicated to the recycling of cellulose and paper, which uses well water for its paper and cardboard manufacturing process. Another type of water sample was collected from the industry that is dedicated to the collection of hazardous waste that contains a greater proportion of oil and water. Finally, there is the sector dedicated to the metalworking industry and the semiconductor industry. Tested parameters were: total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), turbidity, color, particle size, electrical conductivity (EC), zeta potential (ζ), total phosphorous (TP), biological oxygen demand (BOD5 ), chemical oxygen demand (COD), total organic carbon (TOC) and total nitrogen (TN). Tests were carried out following the current Mexican standard procedures that are equivalent to those published by EPA (AWWA standard methods, respectively).
