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Report, 2005

Hygienisering av klosettvatten för säker växtnäringsåterförsel till livsmedelsproduktionen

Vinnerås, Björn


To fulfil the government goal of sustainable food production, the nutrients taken from the fields as food has to be recycled. Today, the net loss of nutrients is compensated by addition of fossil plant nutrients, which are non renewable resources. At the same time, the wastewater nutrients cause eutrophication in the water recipients. The main contribution of plant nutrients to the wastewater is the toiletwater. By sorting the toiletwater it is possible to recycle clean nutrients to agriculture. In this project, the possibility to inactivate pathogens during storage of toiletwater was investigated. To improve the inactivation of pathogens different concentrations of urea and lime were added to the toiletwater. Additionally, the reduction in the surface layer and the bottom layer were compared. The trials were performed in a half filled 600 m3 liquid manure tank, where ten two litre bottles with different additions of chemicals were used (Table S1). Table S1. The different trials presented together with the addition of urea and lime in wet weight percentage Trial Urea Lime Placement in tank U0K0Y 0 0 Surface U0K0B 0 0 Bottom U0,1K0Y 0,1 0 Surface U0,025K0Y 0,025 0 Surface U0,1K0B 0,1 0 Bottom U0K0,05B 0 0.05 Bottom U0,05K0B 0,05 0 Bottom U0,025K0B 0,025 0 Bottom U0,025K0,025B 0,025 0,025 Bottom U0,0125K0,0125B 0,0125 0,0125 Bottom To the different bottles Salmonella, Enterococcus fekalie and E coli O157 corresponding to 7-8 log10ml-1 were added. To a few ot the trials was also Ascaris suum added. The number of organisms was counted at three ocations; at day 28, day 68 and day 102 after the start at June 2, 2004. After 68 days, no viable bacteria was found in U0,1K0B. These two trials were the ones with the highest addition of urea (0.1%) and lime (0.05%), respectively. Ten weeks of treatment is thereby enough for finding no viable pathogenic bacteria. The survival of A suum was high, after 102 days of treatment were still 40% of the eggs viable in the highest addition of urea (0.1%). In the other trials where A suum was added did the viability stay at 60%. Entercoccus was the type of bacteria that survived the longest in the investigated material. Enterococcus is normally excreted in the faecal matter. Therefore, Enterococcus can be used as indicator for the treatment efficiency, regarding the reduction of pathogenic bacteria in the toiletwater. The cost of treatment for the used chemicals is low as the used chemicals are nog consumed during the treatment. The treatment is actually increasing the fertilising value of the treated material at the same time as a hygenically safe fertiliser is produced

Published in

Rapport. Miljö, teknik och lantbruk
2005, number: 4
Publisher: SLU, Institutionen för biometri och teknik

Authors' information

Swedish University of Agricultural Sciences, Department of Energy and Technology

UKÄ Subject classification

Agricultural Science
Environmental Sciences related to Agriculture and Land-use

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