About the project
Production of sewage sludge waste stream
Sewage sludge is a residual material left from waste water treatment processes, provided from both the municipal source or numerous other industrial production lines. The management of these wastes mostly depends on the organic and inorganic solids contaminants, which can be toxic to the environment and human health. The physicochemical properties of these materials on the stage of their production. In this project, the valorisation is performed onsewage sludge from the first (physical and chemical) and secondary (biological) treatment stage of municipal sewage, carried out in the "GOŚ-ŁÓDŹ" Municipal Water Treatment Plant, which currently (2017) receives 51% of all waste water of the Łódzkie Voivodship.
Recommended by EU Directives (EU Sludge Directive 86/278/EC) and Polish law ("National Waste Management Plan 2014", Act no. 217 of the Council of Ministers of 24 December 2010, Journal of Acts no. 101, item 1183) method of disposal of sewage sludge is incineration. It has been estimated that more than 1,7 million tonnes of fly ash and slag from the sludge disposal process are produced annually through the process of their thermal treatment. The sewage sludge itself is produced in an amount of approximately 17 million tonnes per year (combined data from the USA and the EU). It is also foreseen that these numbers will increase.
Taking into account the above mentioned legislative regulations, sewage sludge from "GOŚ-ŁÓDŹ" is therefore stabilized in the Sludge Thermal Treatment Plant, which has been operating since 2009 and built on-site to address the problem of sediment and screenings management. The combustion process is carried out at 850ºC in two parallel fluidized bed furnaces with a combined capacity of 159 Mg/d. The pre-step of drying applied to already dehydrated sludge is implemented in disc dryers, yielding 30 - 32% S.M. In fluidized-bed furnace, sludge is then burned in the sand deposit, as well as the resulting exhaust gas is recycled to the process. Originated during incineration fly ash (19 01 14) (9,0 Mg/d) and dust from off-gas treatment (19 01 07) (0,5 Mg/d) are appropriately deposited at the "GOŚ-ŁODŹ" "Laguna" landfill site. Stabilized in this way sewage sludge (19 08 05) (223 Mg/d) is deposited on the main square of the facility as non-toxic waste.
By-products as mineral additions to Portland cement based binders
Mineral additions in cement production for their inclusion in concretes are very advantageous economically, as they produce less Portland clinker, hence saving energy. Technological benefits from this title are related to the manufacturing of Portland cement based binders products with higher initial values of mechanical strenght, workability and chemical durability of biulding structures. Ecological benefits are associated with reduced CO2 emissions, which indirectly contribute to the reduction of the greenhouse effect.
These mineral additions of Portland cement have been in use for four decades. In principle, two types of mineral additions are used for direct mixing with Portland clinker or cement: active, pozzolanic (natural and artificial pozzolans: thermally activated clays, fly ash, vocanic natural pozzolans, diatomite, silica fume) or hydraulically active additions (blast furnace slags), and non-active, crystalline fillers (siliceous or calcareous).
End-of-Waste technology for sewage sludge ash streams of "GOŚ-ŁÓDŹ"
A case study carried out within the project on one of the production lines of "GOŚ-ŁÓDŹ" plant is expected to allow the development of a new End-of-Waste technology for sewage sludge that is currently being incinerated, stabilized and deposited as non-toxic waste. Developing of criteria for transforming the produced waste into by-product that can be included as a mineral addition to clinker or cement will enable its introduction to the market. In order to increase its competitiveness in the building materials sector of primary and natural available resources, technical guidance will be developed to support the use of the new product.