# Commission Implementing Decision (EU) 2018/1147 of 10 August 2018 establishing best available techniques (BAT) conclusions for waste treatment, under Directive 2010/75/EU of the European Parliament and of the Council (notified under document C(2018) 5070) (Text with EEA relevance), Division 6.3: Emissions to water Extent: E+W+S+N.I. Technique Typical pollutant(s) targeted Description Activated sludge process Biodegradable organic compounds The biological oxidation of dissolved organic pollutants with oxygen using the metabolism of microorganisms. In the presence of dissolved oxygen (injected as air or pure oxygen), the organic components are transformed into carbon dioxide, water or other metabolites and biomass (i.e. the activated sludge). The microorganisms are maintained in suspension in the waste water and the whole mixture is mechanically aerated. The activated sludge mixture is sent to a separation facility from where the sludge is recycled to the aeration tank. Adsorption Adsorbable dissolved non-biodegradable or inhibitory pollutants, e.g. hydrocarbons, mercury, AOX Separation method in which compounds (i.e. pollutants) in a fluid (i.e. waste water) are retained on a solid surface (typically activated carbon). Chemical oxidation Oxidisable dissolved non-biodegradable or inhibitory pollutants, e.g. nitrite, cyanide Organic compounds are oxidised to less harmful and more easily biodegradable compounds. Techniques include wet oxidation or oxidation with ozone or hydrogen peroxide, optionally supported by catalysts or UV radiation. Chemical oxidation is also used to degrade organic compounds causing odour, taste and colour and for disinfection purposes. Chemical reduction Reducible dissolved non-biodegradable or inhibitory pollutants, e.g. hexavalent chromium (Cr(VI)) Chemical reduction is the conversion of pollutants by chemical reducing agents into similar but less harmful or hazardous compounds. Coagulation and flocculation Suspended solids and particulate-bound metals Coagulation and flocculation are used to separate suspended solids from waste water and are often carried out in successive steps. Coagulation is carried out by adding coagulants with charges opposite to those of the suspended solids. Flocculation is carried out by adding polymers, so that collisions of microfloc particles cause them to bond to produce larger flocs. The flocs formed are subsequently separated by sedimentation, air flotation or filtration. Distillation/rectification Dissolved non-biodegradable or inhibitory pollutants that can be distilled, e.g. some solvents Distillation is a technique to separate compounds with different boiling points by partial evaporation and recondensation. Waste water distillation is the removal of low-boiling contaminants from waste water by transferring them into the vapour phase. Distillation is carried out in columns, equipped with plates or packing material, and a downstream condenser. Equalisation All pollutants Balancing of flows and pollutant loads by using tanks or other management techniques. Evaporation Soluble pollutants The use of distillation (see above) to concentrate aqueous solutions of high-boiling substances for further use, processing or disposal (e.g. waste water incineration) by transferring water to the vapour phase. It is typically carried out in multistage units with increasing vacuum, to reduce the energy demand. The water vapours are condensed, to be reused or discharged as waste water. Filtration Suspended solids and particulate-bound metals The separation of solids from waste water by passing them through a porous medium, e.g. sand filtration, microfiltration and ultrafiltration. Flotation The separation of solid or liquid particles from waste water by attaching them to fine gas bubbles, usually air. The buoyant particles accumulate at the water surface and are collected with skimmers. Ion exchange Ionic dissolved non-biodegradable or inhibitory pollutants, e.g. metals The retention of undesired or hazardous ionic constituents of waste water and their replacement by more acceptable ions using an ion exchange resin. The pollutants are temporarily retained and afterwards released into a regeneration or backwashing liquid. Membrane bioreactor Biodegradable organic compounds A combination of activated sludge treatment and membrane filtration. Two variants are used: a) an external recirculation loop between the activated sludge tank and the membrane module; and b) immersion of the membrane module in the aerated activated sludge tank, where the effluent is filtered through a hollow fibre membrane, the biomass remaining in the tank. Membrane filtration Suspended solids and particulate-bound metals Microfiltration (MF) and ultrafiltration (UF) are membrane filtration processes that retain and concentrate, on one side of the membrane, pollutants such as suspended particles and colloidal particles contained in waste waters. Neutralisation Acids, alkalis The adjustment of the pH of waste water to a neutral level (approximately 7) by the addition of chemicals. Sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH)2) may be used to increase the pH, whereas sulphuric acid (H2SO4), hydrochloric acid (HCl) or carbon dioxide (CO2) may be used to decrease the pH. The precipitation of some pollutants may occur during neutralisation. Nitrification/denitrification Total nitrogen, ammonia A two-step process that is typically incorporated into biological waste water treatment plants. The first step is aerobic nitrification where microorganisms oxidise ammonium (NH4 +) to the intermediate nitrite (NO2 -), which is then further oxidised to nitrate (NO3 -). In the subsequent anoxic denitrification step, microorganisms chemically reduce nitrate to nitrogen gas. Oil-water separation Oil/grease The separation of oil and water and subsequent oil removal by gravity separation of free oil, using separation equipment or emulsion breaking (using emulsion breaking chemicals such as metal salts, mineral acids, adsorbents and organic polymers). Sedimentation Suspended solids and particulate-bound metals The separation of suspended particles by gravitational settling. Precipitation Precipitable dissolved non-biodegradable or inhibitory pollutants, e.g. metals, phosphorus The conversion of dissolved pollutants into insoluble compounds by adding precipitants. The solid precipitates formed are subsequently separated by sedimentation, air flotation or filtration. Stripping Purgeable pollutants, e.g. hydrogen sulphide (H2S), ammonia (NH3), some adsorbable organically bound halogens (AOX), hydrocarbons The removal of purgeable pollutants from the aqueous phase by a gaseous phase (e.g. steam, nitrogen or air) that is passed through the liquid. They are subsequently recovered (e.g. by condensation) for further use or disposal. The removal efficiency may be enhanced by increasing the temperature or reducing the pressure. --- Source: https://www.legislation.gov.uk/eudn/2018/1147/annex/division/6/division/6.3 (the official version) Page: https://openlegislation.uk/eu-decision-2018-1147/annex/division-6/division-6.3 Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.