Evaporation is a high-yield technology, able to produce until to 95% of excellent physico-chemical quality treated water, against elevated investment costs, due to need of employ of building materials as stainless steel, metal alloys or silicon carbide, that guarantee a high resistance to corrosion caused from solutions. Minimization of pollutants volumes to dispose and reduction of energy consumption, thanks to application of under vacuum technology and multiple effects systems, allow nonetheless lowering of operating costs, that facilitate return on investment. In case of small or external spaces and temporary interventions, mobile units, easy to transport and handle, are the more convenient choice.


One of the more efficient system for water treatment is membrane filtration, that has different techniques, as ultrafiltration, nanofiltration, multimedia filtration and reverse osmosis. The need of maintenance and periodic replacement of membranes is the factor that weights mostly on operating costs. By application of innovative technologies, in any case, it is possible obtain a reduction of mineral scaling and a lowering of energy consumptions. In water scarcity situations, for water potabilization can be employed mobile reverse osmosis units, that through connection with a photovoltaic system are able to reach energy autonomy.


Ion exchange resins treatments are employed for water demineralization and softening. Demineralization generally occurs by passage of water throughout two beds of resins, anionic and cationic, that eliminate the salts dissolved in water by an exchange of ions. Sometimes the treatment can be made in the same plant with mixed bed resin. Pollutants remaining in eluates produced from resin regeneration are removable with an evaporation treatment. In the softening process, in particular, calcium and magnesium ions are replaced with sodium by a passage throughout cationic resins bed. These technologies are efficient for removal of boron from water of contaminated sites and of arsenic from groundwater destined to human consumption.


In many industrial fields it is possible a total recovery of working process water thanks to zero liquid discharge treatment systems, combining the action of different technologies. These plants, economically convenient as allow complete reuse of water in production cycle and sometimes also recovery of sub-products, are particularly suggested in case of effluents contaminated from noxious substances, that, even if in small quantity, can stay in water also after treatment processes.


Biological treatments of waters exploit the activity of aerobic and anaerobic bacteria for removal of organic compounds as BOD (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand), nitrogen and phosphorus. Between the more efficient biological plants there are the activated sludge ones, composed of an oxidation tank, where takes place aerobic digestion of carbon, and a final settling tank, in that clarified effluent is separated from sludge. In case of wastewater with a high nitrogen content, as digestate from agricultural biomass and zoo-technical sewage, continuous or discontinuous flow nitrification and denitrification processes are advisable. In this field, moreover, have developed innovative technologies allowing an optimization of spaces, as MBR (Membrane Bio Reactor), upgrading the output of biological process thanks to a combination of oxidation treatment with membrane reverse osmosis filtration, also inserted into biological tank, and MBBR (Moving Bed Biofilm Reactor), increasing activated sludge concentration thanks to input of plastic or metallic supports (carriers) with a high specific surface favouring biomass adhesion.


The separation of pollutants from water can be made thanks to application of physico-chemical treatments: between that, flotation, a technique provoking floating of aerophilic substances by insufflation of gas or other floating agents in the effluent, and clariflocculation, that, thanks to addition of coagulants, causes group and precipitation of pollutants. Water disinfection processes also make use of chemicals as chlorine and ozone.


Ultraviolet radiation are employed for disinfection of water destined to human use for their ability to destroy the DNA of pathogenic microorganisms, neutralizing their action. Their bactericidal power is enhanced from combination with filtration pretreatments. This technology is applied also for depuration of discharge water of some industrial fields, as textile and food ones.