Wastewater treatment with Zero Liquid Discharge: Optimizing the energy consumption
Siirtola, Panu (2019)
2019
Ympäristö- ja energiatekniikan DI-tutkinto-ohjelma
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2019-08-28
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-201908273026
https://urn.fi/URN:NBN:fi:tuni-201908273026
Tiivistelmä
Fresh water shortages and the increased regulations to protect water bodies and natural ecosystems have created a need to reduce the discharging of wastewater and to improve the water reuse. To achieve a closed water cycle which can recover majority of the used water and separate the solids from the wastewater feed can be achieved with a so called Zero liquid discharge (ZLD) treatment. This treatment usually combines different water treatment processes including membrane and thermal processes to achieve the solid separation.
The aim of this thesis was to find suitable unit processes which can be used to achieve a ZLD treatment and to optimize the process by considering the energy consumption and economics of the different technologies. The goal was to find an optimized process for a case study that could be economically viable and could be even installed to an industrial plant.
To achieve the goals, a consideration of different unit processes and the factors affecting the selection, such as characteristics of the wastewater, environmental regulations, energy factors and economics, were considered to create a technology selection process. This selection process was then used to choose a suitable ZLD treatment method for the case study. The selection contained high pressure reverse osmosis (HPRO) unit, mechanical vapor recompression (MVR) -evaporation and -crystallization units. The chosen ZLD process was optimized by minimizing the costs of calculated energy consumptions and equipment investments in different water recovery schemes. The optimized recovery rates for HPRO, MVR evaporation and distillation were 90%, 86% and 99%, respectively. The treatment of the incoming wastewater with the chosen recovery scheme was calculated to consume approximately 6.9 kWh/m3.
For the final investment of ZLD treatment, case specific accurate offers and additional technical consideration of possible fouling properties are required. However, the results enable making better early decisions concerning the technology selection and finding a suitable recovery rate for each of the components to reduce the total costs.
The aim of this thesis was to find suitable unit processes which can be used to achieve a ZLD treatment and to optimize the process by considering the energy consumption and economics of the different technologies. The goal was to find an optimized process for a case study that could be economically viable and could be even installed to an industrial plant.
To achieve the goals, a consideration of different unit processes and the factors affecting the selection, such as characteristics of the wastewater, environmental regulations, energy factors and economics, were considered to create a technology selection process. This selection process was then used to choose a suitable ZLD treatment method for the case study. The selection contained high pressure reverse osmosis (HPRO) unit, mechanical vapor recompression (MVR) -evaporation and -crystallization units. The chosen ZLD process was optimized by minimizing the costs of calculated energy consumptions and equipment investments in different water recovery schemes. The optimized recovery rates for HPRO, MVR evaporation and distillation were 90%, 86% and 99%, respectively. The treatment of the incoming wastewater with the chosen recovery scheme was calculated to consume approximately 6.9 kWh/m3.
For the final investment of ZLD treatment, case specific accurate offers and additional technical consideration of possible fouling properties are required. However, the results enable making better early decisions concerning the technology selection and finding a suitable recovery rate for each of the components to reduce the total costs.