Drying and incineration unit in Jurmala (Sloka) WWTP
Jurmala WWTP is designed for a working capacity of 35 400 PE and treats municipal wastewater via biological phosphorus and nitrogen removal in a circular basin without primary settling tank, no industrial wastewater is accepted. Sludge treatment consists of a two-chamber sludge storage tank, a drum thickener and two decanter centrifuges. Currently approximately 10 tons of dewatered sludge are landfilled daily. Within the framework of IWAMA project Jurmala WWTP is piloting a drying and incineration unit (hereafter, unit).
The unit is designed to reduce the amount of surplus sludge from the wastewater treatment process using vapor of thermal decomposition of volatile products and non-condensable gases as fuel. It shall be integrated into the existing technological chain of WWTP. Sludge shall be fed to the drying part of the unit via surplus sludge feed screw, where it shall be dried by gas and steam flow. Additional heating source may be used at this stage. After drying, sludge will be fed to the incineration part of the unit where a gasification reaction shall occur in the magnetron generated microwave field. The external power consumption of the unit must not differ significantly from conventional drying-incineration setups.
It is expected that as a result of this pilot project a decrease of landfilled sludge by at least 70% is achieved, thus significantly reducing the sludge biomass accumulation in the environment.
The gas from the process may potentially be burned in a heat exchanger to obtain hot water for heating or to generate electricity for the premises of WWTP. Although these processes are not in the scope of this project, the supplied unit must ensure that they are possible, prompting energy efficiency issues. It is also possible to study the potential use of sludge ash in the production of building materials, excluding landfilling in general.
Reduced sludge removal rate also means reducing air pollution from used transport equipment.
Overall, as a result of this particular pilot project, an innovative approach shall be implemented towards solving the problem of small WWTP surplus sludge utilization, which is very topical in the water sector and aims to protect the environment.