Abstract

Water-borne sanitation of toilet waste is not a viable option for the estimated 2.6 billion people that lack improved sanitation throughout the world. In Environmental Systems Analysis, source separating sewage systems have proven to be of interest, since both energy and nutrients are saved compared with conventional systems. As the urine and faecal matter contribute with the majority of nutrients to wastewater but constitute a small part of the volume, these fractions are suitable for nutrient recycling to agriculture. The potential content of pathogenic (disease causing) microorganisms makes it a necessity to sanitise the material before use as a fertiliser, especially as many pathogens are zoonotic, infecting both man and animal. The main objective of this study was to evaluate ammonia based sanitation technology for source separated urine and faeces aiming for production of safe fertilisers. To achieve this objective, the inactivation kinetics of several groups of organisms was investigated in relation to concentration of free ammonia, NH3, temperature and dry matter content. Inactivation of Ascaris suum eggs, Salmonella spp. Enterococcus spp., S. Typhimurium phage 28B, an fspecific RNA phage MS2 and a coliphage ΦX 174 was monitored in spiked human urine and faeces. Storage of urine diluted 1:0, 1:1 and 1:3 with water was studied at 4, 14, 24, and 34°C. Faecal material, source separated dry, was treated with urea at concentrations ranging from 0.5% to 2% at 14, 24, and 34°C. Faecal material with ash amendments was studied at 24 and 34°C, separately and with supplementary addition of 1% urea. Temperature was found to be a key factor for the efficiency of the ammonia based sanitation, both through synergy and by affecting transformation of ammonia into NH3. At 34°C the NH3 concentrations in urine and faecal material resulted in short decimal reduction (D) values for microorganism concentrations, except for the bacteriophage 28B, which showed little inactivation in stored faecal material. At 24°C, treatments of both urine and faeces with NH3 concentrations of 50 mM and above gave significant reductions whereas at lower concentrations (urine 1:3 and storage of faecal matter) little inactivation of bacteriophage 28B and ascaris eggs was observed. This means that urine must be collected as concentrated as possible in order to contain sufficient ammonia to reduce pathogens by storage. Treatment with urea, a 2% addition resulted in stable pH and NH3 concentrations that resulted in fast Salmonella spp. inactivation even at 4°C and 14°C, and inactivation of ascaris and the bacteriophage at temperature 24°C and above. Coverage with ash and lime during collection can give an enhanced pathogen inactivation when later treated in closed containers. Accompanying urea treatment of faeces collected with ash is possible but with a high pH (>10) in the material urea will not be degraded and thus not contribute to inactivation. 

Keywords

lic.-avh; ammonia; ascaris suum; bacteriophages; disinfection; temperature; faeces; urine; nutrients; recycling; pathogens; salmonella; enterococcus; zoonoses

Published in

Licentiate thesis (Swedish University of Agricultural Sciences, Department of Biometry and Engineering)
2007, number: 6
Publisher: Department of Biometry and Engineering, Swedish University of Agricultural Sciences

SLU Authors

• Nordin, Annika

  • Department of Biometry and Engineering, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Other Environmental Engineering


Permanent link to this page (URI)

https://res.slu.se/id/publ/15861