This data set covers all relevant inputs and outputs from the treatment of incoming waste water from industrial processes. It contains mechanical, biological and chemical treatment steps for the waste water (including precipitation and neutralisation), and treatment steps for the sludge (thickening, dewatering, drying, conditioning). The outflow goes directly to the receiving water (natural surface water). The waste water composition to the plant represents an average outflow of a chemical industry commodity to the treatment plant with organic and inorganic substances or derivates from this average composition (see document "waste water composition"). The process steps are taking average elimination and transfer coefficients into account. The sewage passes through the bar screens for rag removal. In this section, automatic bar screen cleaners remove large solids (rags, plastics, etc.) from the raw sewage. Next, the sewage is transported to the grit tanks. These tanks reduce the velocity of the sewage so that heavy particles can settle to the bottom. In the separator suspended particles such as oils, fats are removed. The settlement tank can remove the larger suspended solids. FeSO4, and Ca(OH)2 are used as precipitant agents in the mixing tank to remove metals. Ca(OH)2 and H2SO4 to regulate the pH value. The primary clarifiers remove the suspended solids from the mixing tank prior to discharge to the aeration tanks. The aeration tanks provide a location where biological treatment of the sewage takes place. The activated sludge converts organic substances into oxidised products, which are settled out in the secondary clarifiers. Phosphoric acid is used as nutrient for micro-organisms. The cleared overflow in the secondary clarifiers goes to a natural surface water body (stream, river or bay). The settled solids, from the settlement tank, the primary clarifiers and secondary clarifiers, are pumped to the primary thickener where the solids are thickened (water content thickened sludge 96 %). The sludge is pumped to filter presses for dewatering, which use chemical flocculants to separate the water from the solids (water content dewatered sludge 65 %). Next, the sludge is getting dried with thermal energy (water content of dried sludge 25 %). The content from the screen and grit chamber can be mixed with the dried sludge and fed into an incinerator, which produces energy (electricity and thermal energy) for the wastewater treatment plant.
The composition of the sludge refers to the output of the municipal sewage plant modeled as described above.
The background system is addressed to average European conditions as follows:
As auxiliaries are used: precipitation agents, nutrients, neutralisation chemicals and conditioning agents. For these processes, cradle to gate data sets have been chosen for the following chemicals: Iron (II) sulphate, calcium hydroxide, sulphuric acid and phosphoric acid. When connecting the municipal sewage plant with waste incinerator the power and thermal energy resulting from the incineration process may either be looped back, neglected (worst case), credited completely (best case).
For the way of handling of these flows a standard procedure cannot be recommended. It must be decided dependent on the overall situation and the system considered. In this data set the power and thermal energy resulting from the incineration process is looped back.
Electricity, thermal energy: The electricity (and thermal energy as by-product) used is modelled according to the individual country-specific situation. The country-specific modelling is achieved on multiple levels. Firstly the individual power plants in service are modelled according to the current national grid. This includes net losses and imported electricity. Second, the national emission and efficiency standards of the power plants are modelled. Third, the country-specific fuel supply (share of resources used, by import and / or domestic supply) including the country-specific properties (e.g. element and energy contents) are accounted for. Fourth, the import, transport, mining and exploration processes for the energy carrier supply chain are modelled according to the specific situation of each power-producing country. The different mining and exploration techniques (emissions and efficiencies) in the different exploration countries are accounted for according to current engineering knowledge and information.
Steam: The steam supply is modelled according to the individual country-specific situation with regard to the technology efficiencies and energy carriers used. Efficiencies range from 84% to 94% in relation to the representative energy carrier (gas, oil, coal). Coal, crude oil and natural gas used for the generation of steam are modelled according to the specific import situation (see electricity).
Transports: All relevant and known transport processes used are included. Overseas transport including rail and truck transport to and from major ports for imported bulk resources are included. Furthermore all relevant and known pipeline and / or tanker transport of gases and oil imports are included.
Energy carriers: Coal, crude oil, natural gas and uranium are modelled according to the specific import situation (see electricity).
Refinery products: Diesel, gasoline, technical gases, fuel oils, basic oils and residues such as bitumen are modelled via a country-specific, refinery parameterized model. The refinery model represents the current national standard in refinery techniques (e.g. emission level, internal energy consumption,...) as well as the individual country-specific product output spectrum, which can be quite different from country to country. Hence the refinery products used show the individual country-specific use of resources. The supply of crude oil is modelled, again, according to the country-specific crude oil situation with the respective properties of the resources.