Efficient disposal of waste in accordance with state waste and Ruhr Association laws
Waste balances contain information on the type, quantity and whereabouts of waste disposed of in the past. Waste management concepts, on the other hand, contain information on future disposal quantities and routes. Accordingly, the Ruhrverband must prepare an annual waste balance sheet and a waste management concept every five years.
The following types of waste to be disposed of by the Ruhrverband are produced in the association's plants: Sewage sludge, screenings, grit trap material, flotsam, aquatic plant cuttings, river sediments, waste from sewer operations.
The majority of the waste to be disposed of regularly is generated during the treatment of wastewater that is fed into the Ruhrverband's wastewater treatment plants. This includes, in particular, sewage sludge and, to a lesser extent, grit and screenings.
Sewage sludge is the targeted pollutant sink in wastewater treatment. Its removal therefore serves to protect water bodies. In order to reduce the pollutant load in sewage sludge, the Ruhrverband has been supporting industrial and commercial companies (indirect dischargers), particularly in the metalworking industry, for many years by providing extensive operational advice.
A reduction in volume is achieved through anaerobic or aerobic stabilisation. Over 96 percent of the raw sludge is stabilised anaerobically. This considerably reduces the amount of solids through digestion. At the same time, the digester gas is utilised, improving the energy efficiency of the wastewater treatment plant and the dewaterability of the sludge, as well as reducing its odour potential. Before disposal, the sludge is dewatered to sewage sludge. This reduces transport and creates more favourable conditions - especially for thermal disposal. The sewage sludge produced by the Ruhrverband, which amounts to around 135,000 to 140,000 tonnes per year, is disposed of exclusively thermally.
Grit trap material is a heterogeneous mixture of organic and mineral solids with different grain compositions. In principle, grit trap material cannot be avoided. At best, the organic content and thus the total mass can be reduced in a targeted manner using grit washing plants. After pre-treatment in grit washers, the washed grit is a low-organic material. The grit collected by the Ruhrverband, which amounts to around 3,500 tonnes per year, is exclusively recycled in soil treatment plants.
Screenings mainly consist of faeces, hygiene articles, plastics, household and kitchen waste as well as road waste. The composition is subject to seasonal fluctuations. Screenings cannot be avoided either. Screenings presses or screenings washing presses are used at the majority of the Ruhrverband's wastewater treatment plants, which lead to a reduction in water and organic matter and thus contribute to a considerable reduction in the mass of screenings. The 4,500 tonnes of screenings produced by the Ruhrverband each year are disposed of exclusively by thermal means.
Flotsam consists of coarse pieces of wood, plastic and glass as well as green waste. It accumulates at the weirs of the Ruhr reservoirs and dams depending on the water flow. Cuttings are produced during bank maintenance and mowing activities in the watercourse. The accumulation of mown and floating debris cannot be avoided.
With the takeover of sewer networks, the Ruhrverband is also responsible for the disposal and balancing of the unavoidable waste produced during operation. This amounts to a total of around 500 to 900 tonnes per year.
