Acid Gases

Acid gases are the gaseous products of combustion (sulphur dioxide, nitrogen oxides), characterised by an acid reaction in the presence of water.

Activated Carbon

Activated carbon is a special type of finely powdered carbon that has an enormous number of fine pores that can adsorb liquid or gaseous pollutants.

Activated Sludge

The semi-liquid mass of micro-organisms that forms in a biological treatment plant is called activated sludge. This biomass is maintained in suspension by aeration and agitation systems that are installed in the treatment plant, and facilitates the degradation of the organic pollutants in the wastewater to be treated.

Air Sparging

Air sparging is an in situ remediation technique by which air is blown into the contaminated waterbed. The air blows through the contaminated site vertically and horizontally, volatising the contaminating pollutants and thus stripping them from the underground area. The contaminants are sent upward toward the zone that is not saturated, creating vapours that are then captured by soil vapour extraction. The air must be blown in at such a rate as to ensure close and direct contact between the underground water and the soil, in order to strip the pollutants. Adding oxygen to the underground waters and to the unsaturated area earth also enhances biodegradation of the contaminants present above and through the waterbed.


A colourless gas, ammonia's formula is NH3, and it is recognisable by its noxious odour. Air contains minimal traces of ammonia, as do volcanic fumes, and it forms during the process of putrefaction of organic substances. It is widely used in industry in various chemical processes as a base compound or chemical additive.


The aquifier is a geological unit that can store and transmit water.


Because of its insulating properties, asbestos was widely used in the past in construction insulation and in compound materials (for example, Eternit, a roofing insulation). Asbestos fibres and dust, however, are cancerous. Hence, today, asbestos is being removed from buildings and must be disposed of in accordance with very specific guidelines.


Bacteria And/or Micro-organisms

Bacteria are single-celled micro-organisms, visible only through a microscope. There are three characteristic bacterial shapes: rod-like (bacillus), spherical (coccus) and spiral (spirillum). They generally reproduce by fission and feed on soluble substances, the only type of nutrient that can penetrate the semi-permeable cell membrane enclosing them. Bacteria are very common in nature (air, water and soil) wherever there is water. The bacteria used in waste treatment plants can be aerobic or anaerobic, depending on whether there is oxygen in the waste to be treated.

Bag Filter

A bag filter is designed to clean gaseous effluents. It is composed of cloth bags open at one end. The gases pass through the bags and leave the particulate, including sub-micron particles, on the inner surfaces of the bags.

Biological Oxidation

This is the phase during which polluted waters are purified, by biological means, of organic contaminants. The organic substances are oxidized by aerobic bacteria that, in the presence of oxygen, transform them into carbon dioxide and water. The oxygen necessary to the process can be provided by one of two techniques: injected directly into the basin, in the form of air or pure oxygen, using special diffusers; supplied via direct exchange, again in the form of air or pure oxygen, through the use of turbine aerators that maintain a constant contact between a mass of moving water and the air or pure oxygen. In this case, the basins are covered and airtight.

Biological Oxygen Demand (Bod)

BOD refers to the content of biodegradable organic matter in wastewater, expressed as the quantity of oxygen needed by the micro-organisms that are carrying out the degradation process, in a five-day test. It is a measure of the degree to which the dissolved oxygen in the bodies of water receiving the wastewater would be reduced, thereby resulting in possible negative environmental impact.

Biological Percolation

This particular system of biological waste treatment is made up of a reactor filled with a filtering material upon which a layer of bacterial flora develops. The waste to be treated then "percolates" down through this layer.


Scrap produced by the agricultural or food industry that might be utilized as a renewable energy source.


This term refers to a bioremediation technique in which the contaminated soil is heaped into piles. Air, nutrients (nitrates, phosphates) and water are then fed into the pile, each through its own separate grid of pipes. The technique creates the kind of optimum aerobic conditions necessary for the development and activity of microbial flora that spark the biodegradation of pollutants.


Bioremediation is a system in which organic pollutants are degraded by the micro-organisms that are naturally present in the contaminated soil, and that under controlled conditions, can completely degrade the organic pollutants to CO2 and water.


Biosparging is the injection of low-pressure air and nutrients (nitrogen and sulphur) into the groundwater, to facilitate the biodegradation activity of the microbial flora present.


Bioventing is an in situ remediation technique that stimulates the biodegradation of the contaminating substances, providing oxygen to the micro-organisms normally present in the soil. Air is slowly blown into the unsaturated area of the soil, thereby supplying oxygen, which facilitates the degradation activity of the micro-organisms. This method is particularly appropriate for the degradation of petroleum-related hydrocarbons, non-chlorinated solvents, certain pesticides and other organic substances.


Carbon Dioxide (Co2)

Carbon dioxide is a colourless, odourless and tasteless gas that is heavier than air and forms in all processes of combustion, respiration and decomposition of organic material, through the complete oxidation of carbon. CO2 is essential to plant life (in the process of photosynthesis) and is practically inert. It is transparent to the sun's light but absorbs the infrared radiation from the earth's surface, thereby creating the so-called greenhouse effect. Various activities of man (combustion, deforestation) can alter the concentration of CO2 over time, and cause changes in the Earth's climate.

Carbon Monoxide (Co)

Carbon monoxide is produced by the incomplete combustion of motor fuels and fossil fuels. CO is a highly toxic gas that attacks the cerebral and respiratory systems. Gasoline-powered automobiles that are not equipped with catalytic converters are the leading source of carbon monoxide.

Chemical Oxygen Demand (Cod)

COD is a measure of the quantity of oxygen utilized to oxidize organic and inorganic substances in a water sample treated with powerful oxidants. This parameter, like BOD, is used primarily to estimate the organic content, and thus the potential level of pollution, in natural water and wastewater. A high COD level in wastewater means a reduction of the dissolved oxygen in the body of water that is to receive the wastewater and a reduction in the ability of that body of water to purify itself and sustain life forms.


Combustion is the reaction of organic matter with oxygen in the atmosphere. It produces carbon oxides, water vapour and thermal energy.

Combustion Residue/slag

This is the solid residue remaining after combustion made up of a material with a high inert content (incombustible fraction). Examples include the residue from coal combustion, also known as heavy ash, or from incineration of solid urban waste. Specifically, the residue from an urban-waste incineration process, made up of the incombustible fraction of the waste, represents approximately 30% of the weight and 10% of the original waste volume.


See pollutant



Degradation is the conversion of one organic compound into another that has a lower number of carbon atoms.

Dioxins (Pcdd-pcdf)

Dioxins are chlorinated organic compounds that include a family of 75 molecular types that are similar (co-genus) but have varying toxicity levels. The 2, 3, 7, 8 tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic. They are present in the environment in a colourless, insoluble crystal form that is extremely stable in the ecosystem. Thus, it easily enters the food chain, with the consequent bio-accumulation in higher life forms. They are thought to be cancer-causing in humans. Dioxins are present virtually at every level of the ecosystem, given the myriad sources that produce them, including: the iron metallurgy industry; combustion of fossil fuels; production of pesticides, pharmaceuticals, solvents, etc; incineration of municipal and industrial wastes; the paper industry (certain paper-whitening processes). The field of dioxins formation is between 300°C and 400°C. At temperatures higher than 800°C, in the presence of oxygen, dioxins can be completely destroyed.


Dryers are devices used to reduce the moisture in sludge to as little as 5% of its weight. The purpose of the drying treatment is to reduce the final volume of the sludge to be treated, stabilize it with a heat treatment, to achieve an almost total absence of water. At that point, the sludge can either be used in agriculture or incinerated in special plants that produce thermal or electrical energy. Essentially there are two types of dryers, direct and indirect. In direct systems, the heating fluid comes into direct contact with the sludge; in indirect systems, it does not.



An electrostatic precipitator removes particulate from gaseous emissions. The basic principles of electrostatic precipitation are: a high voltage current is induced to charge the particles in the gas to be treated; an electric field is created between the negative and positive electrodes, attracting the negatively charged particulate to the positively charged collector plates; the particulate is then removed by devices that either shake the plates or run water over them.


Emissions are discharges of any solid, liquid or gaseous substance into the ecosystem that, directly or indirectly, can have an impact on the environment.

Energy Recovery

This term refers to the use of thermal energy released in a waste incineration process. Normally, the energy is used to produce steam that is sold to others or used in a thermal cycle to generate electrical energy.

Environmental Impact

Environmental impact is defined as the overall effect that any given project (industrial plant, energy plant, road, etc.), has on the surrounding territory, causing alterations or disturbance in the individual constituents of the environment or of the total ecosystem.



During this coagulation phase, the individual colloidal particles that are dispersed in the sewage - having been destabilised with the addition of precipitants - thicken, coagulate and "flocculate", forming larger flakes that settle to the bottom more rapidly.


Flotation is the phase of water treatment that separates liquid and solid substances from the water. It utilizes a transport gas that stimulates the collection of these substances on the surface of the water. The transport gas, predominantly air, can either be dispersed in the running liquid to be treated with the use of dissolved air flotators or aspirated directly from the water through induced air flotators. This technique is used primarily to separate oil-based substances from the water and thicken the sludge produced by biological treatment.

Flue Gas Purification

This is a series of devices designed to remove, or rather, reduce the concentration of pollutants in the flue gas to be treated. Depending on the chemical-physical properties of the flue gas and the pollutants, the system can be composed of one or more stages. The decision on which of the systems below is most appropriate depends on the physical state of the pollutant present in the gaseous current, and its chemical properties. The options include: dry systems (for dust or drops) that can be either dynamic (ex. cyclones) or static (ex. bag filters); moist systems (for example for sulphur dioxide or chloride acid) such as scrubbing absorption towers; thermal and catalytic systems (for nitrogen oxides and polycyclical and/or polychlorinated organic compounds), such as combustors and catalytic reactors; aAbsorption systems (for organic compounds insoluble in water) such as activated carbon columns; biological systems such as biofilters.These stages are generally mixed and matched, for example, dry stages such as filtering with moist stages such as absorption units. It is also common to have a final catalytic or adsorption stage that ensures a last powerful reduction of particularly hazardous pollutants such as chlorinated organic compounds.


Essentially, a fluidised-bed kiln is made up of a vertical cylinder that contains an inert material (sand) held in suspension (fluidified) by high-velocity air injected through a grid at the base of the cylinder. The waste products are fed into and burned on the sand bed, which enhances the heat exchange process and supplies sufficient thermal inertia to the system to regulate the combustion process.

Free Floating Product Recovery

FPR refers to separate-phase systems for recovering pollutants that are free-floating in the waterbed. They include active systems (pumps) and passive systems (oil skimmers)



Underground water present in layers of porous or pervious rock, generally overlaying layers of impermeable rock. It is a critical natural resource that is in danger of being both polluted, by toxic substances filtering down through the earth, and impoverished, by, among other phenomena, the reduction in the infiltration rate caused by the increasing extension of impermeable surface. In other cases, changes in offtake and increased rainfall raise the level of the water in the earth's substrate.


Hazardous Waste

According to European directive 91/689/EEC and EU Decision 94/904Legislative Decree 22/97 lists those waste considered hazardous. This list takes into account the origin and composition of the waste. Hazardous wastes are defined as those that meet at least one of the 14 hazard characteristics set forth in European Community regulations with regard to risk to human health and the environment.

Heavy Metals

Metals with a specific gravity of more than 5 are classified as "heavy". Some heavy metals (lead, cadmium, mercury, antimony, selenium, nickel, vanadium and others) are released into the environment in the form of oxides or sulphides during the combustion of fuel oil, coal and/or waste that contains traces of them. They are also released by industrial plants. After they have been in the atmosphere for a certain time, these compounds find their way into the water-soil system and can thereby enter into the food chain. The result can be the dangerous bioaccumulation in living organisms.


In Situ Biodegradation

In situ remediation technologies are those in which the pollutants are bioremediated (biodegraded) by the micro-organisms naturally present in the soil, without moving the contaminated soil (in situ), under controlled conditions.

In Situ/ex Situ

Environmental remediation of sites is considered either in-situ or ex-situ. In-situ projects are executed within the contaminated area, without moving the affected soil. Ex-situ projects involve excavating and moving the contaminated materials off site to a treatment centre.


Incineration is the process of high-temperature combustion (between 850°C and 1200°C) in the presence of oxygen. Incineration is utilized to destroy waste and the hazardous constituents thereof. Combustion of waste facilitates: Conversion of waste into energy: 1 kg of municipal waste produces 600 Wh Reduction of the volume of waste (by 90% of the initial volume). Incineration allows the complete destruction of hazardous organic substances (ex. PCBs, dioxins, halogenated organic compounds, solvents, etc.). Combustion exhaust gases are then treated and purified in a special section of the kiln itself (See also: flue gas purification).

Industrial Waste

Legislative Decree 22/97 defines industrial waste as: a) waste from agricultural and agro-industrial activities; b) waste generated by demolition and construction activities as well as hazardous waste from quarrying activities; c) waste produced by industrial operations; d) waste produced by artisan operations; e) waste produced by commercial operations;f) waste produced by the service industry; g) waste generated by waste recovery and disposal activities, sludge produced by water treatment plants (including plants that produce drinking-quality water), and sludge produced by waste water treatment plants and flue-gas treatment systems; h) waste from hospitals, clinics, etc; i) damaged and obsolete machinery and equipment; j) out-of-use motor vehicles, trailers, etc., and parts thereof.



Landfarming is an ex-situ bioremediation technology in which the contaminated soil is excavated and positioned in 20-50 cm thick layers, on surfaces insulated with impermeable liners to control leaching of contaminants. The soil is periodically turned over or tilled to aerate the waste and optimise the rate of contaminant degradation. Soil conditions are often controlled; the soil is irrigated and aerated; sometimes other amendments are added.


Landfills are areas designed to contain waste. The specifications by which a landfill is built will vary based on the type of waste it is authorized to accept, and in accordance with the law. In the wake of Resolution 27.7.84 of the Interministerial Commission, three categories of landfills were created for Italy. The first category includes landfills designed to accept municipal and similar waste. The second includes landfills for industrial waste, and is divided into industrial waste landfills (2B) with limitations of the content of hazardous substances, and landfills for hazardous waste (2C). The third category including waste that has particularly hazardous characteristics, that cannot be disposed of in Category 2 landfills. Clearly, the methods used to build these landfills and isolate them from the surrounding environment become more and more stringent the higher the numerical category.


Material Recovery/recycling

Material recovery operations provide for the exploitation and reutilisation of industrial and consumer scrap (plastic, glass, paper, metals, etc.) in the form of "secondary raw materials". Definitions include: a) Reutilisation: the use of scrap (waste) in the same industrial or consumer cycle that produced the scrap; b) Recycling: the use of scrap (waste) in a different industrial or consumer cycle from the one that produced the scrap.


These are pollutants present at modest levels (µg/m3; 1µg = 1 millionth of a gram) in combustion exhaust. Despite the low levels, they can pose a risk to the environment because of their toxicity and longevity. Micro-pollutants are divided into two categories: inorganic, essentially selected heavy metals, and organic, which includes the dioxins.

Municipal Waste

Legislative Decree 22/97 defines urban waste as: a) domestic-type waste, including unwieldy items, produced by residential housing units; b) non-hazardous waste, similar in nature to urban waste as defined by the aforementioned decree, produced by units other than those included in paragraph a); c) waste generated by street-cleaning operations; d) waste of any nature or origin that is found on public streets or in public areas, or on private streets and areas that are subject to public use, or on the seacoasts, lake shores or river banks; e) plant-related waste from parks, gardens and cemeteries; f) waste from exhumations and disinterment


Natural Attenuation

The term natural attenuation refers to the combination of all natural degradation processes that take place in soil and groundwater, such as biodegradation, adsorption, dilution and chemical reactions with the soil itself. Over time, these natural processes reduce the concentration of contaminants to acceptable levels, in other words, levels that pose no risk for human health and for the health of the ecosystem. Free-floating, or mobile, pollutants can spread in liquid or vapour form and are thus easily captured by degradation processes. On the other hand, organic compounds that have a high molecular weight and many inorganic substances become trapped in the soil, which impedes their diffusion.

Neutralization (Ph Adjustment)

The chemical action through which an acid or basic solution is rendered neutral (neither acid or basic). In general, neutralisation refers to the process utilised to render a toxic chemical agent harmless.

Nitrogen Oxides (Nox)

Nitrogen oxides are oxygenated nitrogen compounds in a gaseous state. Nitric oxide (NO) is the result of a secondary reaction in all high-temperature combustion in the presence of oxygen. Through the process of oxidation, it is then transformed into NO (the most aggressive oxide) and N2O5, which, when absorbed by moisture in the air, becomes nitric acid. When combined with other gases that have similar affects, nitrogen oxides can affect the respiratory tract. They also act as "precursors" in the formation of photochemical oxidants (ozone, organic peroxides). Second only to sulphur dioxide, they are the most widespread and aggressive atmospheric pollutants. When combined with sulphur dioxide, they give rise to the phenomenon known as "acid rain".

Non-catalytic Nox Reduction System

This technology reduces nitrogen oxides in gaseous emissions by injecting additives (ammonia or urea) into the combustion chamber. The reaction takes place only within a certain temperature range (900°C-1000°C).



Oleum is sulphuric acid in which sulphur dioxide has been dissolved. This allows the creation of an acid rating in excess of 100% because the addition of water to the oleum, reacting with the SO3, produces more sulphuric acid.

On-site Treatment Of Contaminated Water

In this type of treatment, the water is extracted and transported to treatment systems that are generally made up of activated carbons, bio-reagents and stripping towers.



This is a measure of the acidity of a water-based solution. The pH of water, for example, is 7. Values lower than 7 indicate an acid solution, value higher than 7 indicate an alkaline solution.

Polichlorobiphenyls (Pcb)

PCBs are aromatic organic compounds that contain chlorine. Most are utilised as liquid insulation in electrical transformers. They are highly toxic and difficult to degrade.

Poli-cyclic Aromatic Hydrocarbons (Pah)

These are aromatic hydrocarbons with numerous benzenic rings, some of which are classified as cancerous to humans.

Pollutant And/or Contaminant

Any substance that when introduced into the environment can alter the chemical, physical or biological characteristics of that environment, posing a potential risk to human health and the ecosystem is called a pollutant.

Primary/secondary Sedimentation

Sedimentation takes place in tanks that are round or rectangular basins, made of concrete or iron, with a bottom that slopes slightly toward an area where sludge is directed by means of special sludge collectors. Sedimentation can take place at various phases of the wastewater treatment process. Normally, sedimentation takes place first at the beginning of the treatment process to remove solids with screens and sand traps (primary sedimentation). After the biological stages of the process, sedimentation separates the activated sludge (secondary sedimentation). Finally, after the coagulation and flocculation stages, sedimentation is used to separate the precipitated chemical substances.

Pyrolysis (Thermal Cracking)

Pyrolysis is the decomposition of a chemical molecule, generated by high temperatures. For example, at high temperature (approximately 1000°C) sulphuric acid decomposes and produces sulphur dioxide.



A quench process rapidly cools combustion exhaust with showers of water. This technique eliminates most of the particulate present in the exhaust fumes.


Refuse-derived Fuel (Rdf)

RDF is secondary fuel derived from the dry constituents (paper, plastics, textile fibres, etc) in municipal solid waste, after treatment to separate and remove substances such as glass, metals and inert materials. On average, CDR has the following composition: 44% paper, 23% plastic, 12% textile residue, 4.5% timber scraps, 14% organic degradable waste and 2.5% inert materials. Its low heating value averages 15,000 kJ/kg (about 3,600 kcal/kg.). Currently this fuel can be used in two ways: 1) in industrial plants (cement and steel factories, thermal power plants, etc.), or 2) in bubbling or circulating fluidised-bed furnaces for the production of electrical energy. The characteristics and method of RDF use were defined in Ministerial Decree 5/2/98.


This term refers to the series of measures necessary to eliminate sources of pollution and the pollutants themselves, or reduce the concentrations of polluting substances in soil, surface waters or underground waters to the levels authorised under the law (Ministerial Decree 471/99). Remediation techniques can be chemical, physical or biological.

Renewable Energy Sources

Energy sources that are generated spontaneously in nature are considered renewable. Solar, hydroelectric wind and geothermal energy are considered renewable sources. Waste products are also considered renewable energy sources.

Risk Analysis

Risk analysis is used on a site-by-site basis to evaluate the effects that the contamination might have on the human health and the surrounding environment. It helps identify, on the basis of the extent of the contamination, the quantities of pollutants that could reach the various constituents of the environment (for example, underground waters).

Rotary Kiln

The rotary kiln is a refractory-lined, slightly inclined (1-3% slope) cylinder that rotates to facilitate the constant advancement of the waste being fed in. The waste is fed into the upper extreme of the kiln, and the combustion residue is deposited from the opposite (lower) end.


Scrubbing Tower

This is the tower in which combustion flue gasses are brought into contact with currents of liquid (water or water and soda) that absorb the acid pollutants (HCI, HF, SOX)

Soil Vapour Extraction

This technique captures organic vapours present in the unsaturated zones of the terrain utilised in remediation. It includes a system to treat the gases captured.

Soil Washing

Soil washing is a water-based chemical-physical process for scrubbing soils ex situ to remove contaminants. The process removes contaminants from soils by dissolving or suspending them in the wash solution (which can contain agents that facilitate the removal of organic substances and metals).

Solidification/stabilisation (S/s)

To eliminate contaminants, either they are physically bound or enclosed within a stabilized mass (solidification), or chemical reactions are induced between the stabilizing agent and contaminants to reduce their mobility (stabilisation). Stabilisation implies a radical transformation of the chemical and physical properties of a waste. Solidification, on the other hand, acts purely on the physical properties of the material. This treatment system is particularly useful for trapping or immobilising metals contaminants within their "host" medium. Silicates and other materials that chemically react with water to form a solid cementious matrix are used to form solid, insoluble and thermo-dynamically stable masses that encapsulate the heavy metals, prohibiting them from leaching out over time. (See also Stabilisation).

Solvent Extraction

This chemical extraction system is utilized in remediation to facilitate the separation of the pollutants from the contaminated soil, sludge and sediment. This technique uses specific chemical substances to extract contaminants such as acids, in the case of soil contaminated by metals, and organic solvents, in the case of contamination by organic substances (petroleum products, paint, pesticides, etc). Solvent extraction is generally teamed with other remediation techniques such as soil washing (which extract solvents with the use of additive-enriched water or water-based solutions) or solidification/stabilisation.


The stabilisation process is designed to reduce the mobility of contaminants, for example their solubility in water. This minimises the chances that the pollutants will escape into the environment.

Static Chamber

The static chamber furnace is the simplest type of incineration system, and is appropriate exclusively for liquid waste. Essentially it is a combustion chamber with no moving parts, into which the waste to be incinerated is fed.

Sulphur Dioxide (SO2)

Sulphur dioxide is a gas present in emissions from combustion of oil and coal. Most oil refinery processes are designed to reduce the sulphur content in fuels. High concentrations of SO2 in the atmosphere can cause the phenomenon known as acid rain, which provokes deforestation, particularly in areas with vulnerable terrains such as those found in central and northern Europe.

Sulphur Oxides (SOx)

Sulphur oxide emissions, consisting mostly of sulphur dioxide, are generated primarily by the combustion of solid and liquid fuels and are correlated to the sulphur content of the fuel. Sulphur oxides are pollutants common to urban and industrial areas where they accumulate easily because of the high density of the buildings, especially under unfavourable weather conditions. The most serious cases occur in winter when residential heating is added to the other sources of emissions. Sulphur oxides give rise to the phenomenon known as "acid rain".

Suspended Solids

Suspended solid (or fine particulate) consists of particles of matter that are so small (much less than a thousandth of a millimetre) that they can remain suspended in the atmosphere for lengthy periods before falling to the ground. The composition of particulate is quite varied, ranging from hydrocarbons generated by diesel motors when combustion is incomplete, partially oxidised heavy hydrocarbons, heavy metals produced by combustion plants, volcanic ash, dust, etc. The degree to which a particulate is hazardous to human health depends on the harmful substances it contains and the average size of the particles. If smaller than 10 microns (1 micron = one thousandth of a millimetre), the particles can pass through the respiratory system and lodge in the lungs.


Thermal Capacity

This term refers to the maximum potential of a furnace, expressed in terms of calories/hour of waste fed into the furnace.

Thermal Desorption

Thermal desorption is a physical separation process that does not involve the thermo-destruction of organic compounds but rather their volatilisation from the contaminated materials (soil, sludge, sediment). The contaminated terrain is heat-treated, at temperatures of between 200°C and 600°C, to convert the water and the organic pollutants it contains into gaseous form. Subsequently, the now-airborne contaminants are then transported to a special treatment section with the application of either a gas or a vacuum system.


Throughput is the maximum potential of a furnace, expressed as tons/hour of waste fed into the furnace.

Tkn (Total Kieldhal Nitrogen)

TKN is a measure of the total amount of nitrogen contained in the wastewater or liquid waste that the treatment plant can process. (See also chemical, physical and biological treatment).

Total Suspended Solids

TSS are any type of matter in a suspended state in water. If the suspended solids exceed certain limits, they alter the normal transparency of water.



Urea is an organic compound (chemical formula N2H4CO) and is water-soluble. It is one of the natural products of biological metabolism, where it forms as a result of the degradation of proteins. In industry, urea is used as a fertilizer or as a reagent in certain chemical processes.



This high-temperature (1300°C-1500°C) combustion process is able to melt and convert non-combustible inorganic residue.



The definition of Waste in Italy is governed by Legislative Decree 22/97 that adopts European Directives 91/156 and 91/689. Waste is defined as any substance or object of which the holder disposes or has the intention to dispose or is obliged to dispose. Whether a substance qualifies as waste depends essentially on the comportment of the producer and thus depends on whether the producer wants, intends or is obliged to dispose of the substance. The terms "to dispose of" in the Italian law refers to the destination of a material to disposal or treatment operations (ex. recovery), The definition of a substance as waste emerges, essentially, from the fact that it is sent to a recovery or disposal operation included in Annexes B and C of Legislative Decree 22/97.

Waste Disposal

Legislative Decree 22/97 defined waste disposal as: storage on or in the ground; treatment in terrain (ex. Biodegradation of liquid waste or sludge in the soil); depth injection; lagoonage; dumping in landfills; disposal of solid waste in bodies of water except for immersion; immersion, including interment under the sea bed; incineration on land or sea; permanent storage (for example in a mine); other biological treatments; other chemical-physical treatments (ex. evaporation, drying, calcination, etc.); assembly, storage or preliminary reconditioning before one of the aforementioned operations.

Waste Storage

Temporary or permanent storing of waste, authorised by the relative governmental authorities.


This is wastewater generated by industry or by house. Wastewater, collected in specifically designed sewerage pipes, can only be discharged into the environment if it meets the specifications set forth by law (Leg. Decree 152/99). If not, it must first undergo appropriate purification treatment.

Wastewater Equalisation

When wastewater is delivered to the treatment plant, it is accumulated for a period of time in order to equalize or balance the temporary variations, if any, in the concentration of pollutants. This process is known as equalisation.