Refine
Document Type
- Doctoral thesis (1)
Has Fulltext
- yes (1)
Is part of the Bibliography
- no (1)
Year of publication
- 2016 (1) (remove)
Language
- English (1)
Keywords
- Biogasgewinnung (1)
- Composting (1)
- Contaminated biowaste (1)
- Enteropathogens (1)
- Enterophatogene Mikroorganismen (1)
- Hygenisierung (1)
- Hygienisierung (1)
- Kompostierung (1)
- Kontamination (1)
- Kontaminierter organischer Abfall (1)
Institute
In this study, the aims were to investigate the die-off levels of pathogens attainable under conventional biotreatments, introduce alternative hygienization options and study their performance at eliminating pathogens from biowaste. In addition, the study investigated feasibility of biotreatment of potato peels waste (PPW) as management option for the peels waste generated in Dar es Salaam city. Pathogens inactivation studies using simulated biowaste (moisture ˃77%w/w) composed of PPW spiked with Escherichia coli and Salmonella senftenbergensis at laboratory-scale resulted into low temperature-time patterns of the aerobic In-vessel composting system and turned the process anaerobic thus demonstrated inefficiency at eliminating the spiked bacteria. Likewise, two-phase anaerobic digestion at continuous stirred tank reactor confirmed incapable at effecting complete inactivation of the bacteria unless substrate residence is prolonged above 72hrs. These distasteful confirmations inevitably advocate the importance of applying either pre- and/or post-biotreatment hygienization processes on biowaste for safer biotreatments. Existing hygienization options including acid/lime conditioning and batch pasteurization were applied, their hygienization efficacy investigated and the latter validated. Acetic acid treatment of biowaste at pH value 4 for 5days or lime treatment at pH value 11-12 for 1day brought complete die-off in E. coli and S. senftenbergensis. Temperature-time combination at 65°C for 30min was sufficient at effecting ˃1log cycle die-off of the spiked enteropathogens with z-Value of 11˚C for S. senftenbergensis hence validates the temperature-time regime of 70˚C for 30min and 70˚C for 60min set by U.S-EPA/625/R-92/013 and Regulations (EC) No. 208/2006 respectively. In addition, alternative hygienization options namely UV radiation and passive solar heating (PSH) were proposed, applied and evaluated. Modes of application and achievable bacteria die-off for all hygienization options are given in Chapter 2 to 6 of this document. Owing to its small investment capital (mostly do yourself construction), independence from fuel supplies and low running costs, the study highly recommend PSH as environmental friendly and economic viable pre- and post- biotreatment hygienization option especially for tropical climates and developing countries with adequate sunshine. In vessel co-composting of PPW with yard-waste at 6:1 ratio gave microbiologically safe and good quality compost. Endowed with higher CO2 removal, mesophilic/thermophilic two-phase anaerobic processing of PPW showed comparable results to biogasification from other biowaste. Biogas productivity from PPW was 2.3lNbiogas/l.day with an average CH4 yield of 0.13-0.35m3/kgoTS input having 58% CH4. The digestion resulted into H2S removal from above LoQ to less than 230ppm with 81% VS removal at substrate OLR of 2.4kgoTS/m3.day input without sign of inhibition. It is estimated that 1.0m3biogas with 5hrs burning potential and equivalent to 3.5kg firewood can be produced from 10.2kg of PPW anaerobic digested. The resulting biogas production would complement household energy need thus conserve forest resources which are subjected to high deforestation rate estimated at 4.1kilotons of wood per day as fuelwood. Digestate resulting from the anaerobic reactors would make valuable fertilizer to urban agriculture thus enhance soil fertility and productivity.