The food and beverage sector is by far the largest consumer of water resources. Close to 50% of regional water is used by the agricultural sector. Irrigation and animal husbandry are the leading users of water resources while the processing industry—food and beverage production—consumes less but produces wastewater with very high organic loads and often with strong seasonal variations. This type of discharge deserves great attention and appropriate studies because each plant has its own production strategy and different types of waste. Various materials can be recovered through the treatment of food and beverage wastewater, from fats to be used for bio-digestion to the production of biogas, electricity, from bio-metmethane and biodiesel to sludge reused as soil conditioners in agriculture or for the synthesis of bioplastics (PHA). Above all, purified water can be reused in secondary cycles within the plant. The use of certain technologies can lead to zero liquid discharge (ZLD).
Wastewater from the mechanical industry can contain various inorganic substances, some of which can be very dangerous for the environment. Depending on the production process, metals, acids, alkalis and solutions are used which can contain toxic substances like cadmium, mercury, ammoniacal molecules, chlorine, chromium, cyanides, fluorine, lead, copper, nickel, nitrites, sulphides, zinc, hydrocarbons and cobalt (in enamelling).
Many industrial processes use a number of heavy metals (mainly nickel, lead, cadmium and zinc), which can be a serious problem for humans and the environment; their concentration in wastewater is subject to very strict legal limits due to their high toxicity. There are now criminal sanctions for failure to respect limits. The characteristic of this type of wastewater is that it must undergo exclusively chemical treatment with specific processes for each element to be reduced or recovered. These are oxide-reduction, flocculation, precipitation, filtration and emulsion breakage processes. Precipitation sludge can sometimes be recovered and used as asphalt and pavement supplements..
Laundries and dyeworks use or generate large amounts of surfactants, detergents, softeners, suspended solids and coloured pigments, which are difficult to treat. This waste must be studied carefully because different interventions may be required depending on the quality of the discharged water. Biological treatment is often sufficient, but sometimes physical-chemical pre-treatment and post-treatment with strong oxidants is necessary. In most cases, the use of membranes makes it possible to obtain an effluent of sufficient quality to be reused in the process.
Condominiums, resorts and campgrounds are small communities that are required to comply with discharge regulations. This type of wastewater can be easily treated and purified because of its high biodegradability but poses major environmental problems due to acoustic and olfactory impacts, and the disposal of various types of waste from screened sludge.
Biological and treatment is the most appropriate and membrane treatment is strongly recommended not only for the quality of the discharge, but because small community plants are often built with static sedimentation chambers and sludge recirculated through airlift or even worse with natural recirculation with serious hydraulic decompensation and sludge discharged with effluent. The membrane process allows water stored in suitable tanks to be reused for irrigation or secondary washing circuits.
The water we drink is essential for our health. The quality of the water in our homes and in public environments is of fundamental importance in our daily lives. Water sources are not always of perfect quality, so quality improvements are sometimes required to protect consumers. There are technical solutions for every chemical, physical or bacteriological problem that can be proposed to protect human health and to protect water systems and extend their life.