Chapter 2 Integrated processes in Innovative and Integrated Technologies for the Treatment of Industrial Wastewater (original) (raw)

One of the major threats to water quality is chemical pollution from heavy metals, solvents, dyes, pesticides, etc. Chemicals enter the aquatic medium in several different ways, either dumped directly, such as industrial effluents, or from wastewater treatment plants (WWTP) that do not fulfil their obligations. They may also enter the water indirectly through the use of plant health products, such as biocides and fertilizers, in agriculture. In general, very water-soluble substances can be transported and distributed more easily in the water cycle. Discharge resulting from lax enforcement of the rules, illegal use and inappropriate application of substances may be considerable. In the past, the focus was on detecting the severe, direct effects of individual pollutants and the short-term negative impact on ecosystems. But as scientific understanding has advanced, and the more concentrated emissions have been lowered, environmental evaluation reveals a considerable number of chronic effects that can usually only be detected after a long period of time. Furthermore, larger and larger quantities of persistent substances are being found at long distances from their sources of discharge (Meyer and Wania, 2007). Evaluation also used to concentrate mostly on the effect of individual substances, whereas we are now beginning to study and understand interactions in mixtures of these substances (Hernando et al., 2005; Hildebrant et al., 2006). The main routes for destroying toxic compounds in natural water are biodegradation and photodegradation. Photodegradation may be by direct or indirect photolysis. In indirect photolysis, a photosensitizer (as nitrate or humic acids) absorbs the light and transfers the energy to the pollutants, which otherwise would not react, since they do not absorb light in the wavelength interval of the solar photons that arrive on the Earth's surface (i.e. .300 nm). Biological degradation of a chemical refers to the elimination of the pollutant by the metabolic activity of living organisms, usually microorganisms and in particular bacteria and fungi that live in natural water and soil. In this context, conventional biological processes do not always provide satisfactory results, especially for industrial wastewater treatment, since many of the organic substances produced by the chemical industry are toxic or resistant to. Conventional methods of water decontamination can address many of these problems. However, these treatment methods are often chemically, energetically and operationally intensive, focused on large systems, and thus require considerable infusion of capital, engineering expertise and infrastructure, all of which precludes their use in much of the world. Furthermore, intensive chemical treatments (such as those involving ammonia, chlorine compounds, hydrochloric acid, sodium hydroxide, permanganate, alum and ferric salts, coagulation and filtration aids, anti-scalants, corrosion control chemicals, and ion exchange resins and regenerants) and residuals resulting from treatment (sludge, brines, toxic waste) can add to the problems of contamination and salting of freshwater sources. Air stripping and adsorption, merely transferring toxic materials from one medium to another, is not a long-term solution. Incineration is