Design and Validation of a Thermal Disinfection Unit for Wastewater using Biogas in Humanitarian Crisis Situations
Creators: name: Luz, Ludwig
Publisher: name: ETH Zurich
Year: 2022
Subjects: info:eu-repo/classification/ddc/620
Engineering &amp; allied operations

description: Adequate wastewater treatment, especially in humanitarian crisis situations is an unsolved challenge globally. The difficulty thereby is often related to the availability of treatment technologies itself but the availability or rather absence of resources to run these system such as e.g. fuels or electricity. If wastewater is discharged untreated, the spread of pathogens and thus diseases increases rapidly through cross contamination between e.g. faeces and food. This ultimately leads to a higher number of deaths due to diseases such as diarrhea or cholera.
To tackle this challenge, the large-scale social enterprise Sistema.bio in collab- oration with ETH Zu ̈rich and Opero is piloting a wastewater treatment system in Kisumu, Kenya. The key feature of the system is its operation independent of additional energy inputs. This is achieved through the production of biogas using latrine sludge and a biogas digester and subsequent combustion of the biogas in order to thermally disinfect the digester effluent.
This thesis is aimed at testing and validating a first prototype of such a system which was manufactured by Sistema.bio. Firstly, experiments in batch operation mode were conducted to confirm an appropriate temperature and contact time required to fully inactivate pathogens present in the effluent. Secondly, an ex- periment in continuous operation mode aimed at determining the thermal and treatment efficiency of the existing prototype was conducted. Both of the exper- iments were carried out in the field in Kisumu. Due to several inconsistencies in the results of the analyzed samples during the first experiment, no definite state- ment concerning a sufficient target temperature and contact time could be made. Nonetheless, based on the experiments and available literature, both of those pa- rameters were set and used for the continuous tests of the system, after which first statements on the thermal and treatment efficiency of the system could be made. The first version of the prototype was not able to meet the requirements set out at the beginning of the project, neither when it comes to thermal efficiency nor to treatment efficiency (which is dependent on chosen disinfection temperature and contact time). The system was not able to reach half of the required daily treatment capacity, based on projections about the biogas produced daily. 
The second part of the thesis consists of design proposals to improve the thermal efficiency of the system. No exact analytical calculation of the potential efficiency improvements was made as it would exceed the scope of this thesis. Nonetheless, all proposal were made on the basis of existing literature. The implementation of those proposals is is greatly dependent on the manufacturing capabilities in Kenya, where the pilot project is situated. Assuming the efficiency values which are reached by similar system in literature, the second improved ver- sion of the pasteurizer system should be able to meet the requirements, specifically the ability to treat 700 litres of digester effluent daily.