Abstract
The aim of this study was to find out if the use of septic tank sludge, urine and compostedfaeces as fertilizer for barley and carrot crops would pose a health risk due to pathogentransfer,This study was accomplished as a greenhouse experiment in the premises of the TAM KUniversity of Applied Sciences, Tampere. The study concentrated on the qualitative detectionof Salmonella and a quantitative detection of coliform bacteria in the growing medium - andmore importantly, in the plant products. Methods used were based on instructions given onthe compact salmonella (SL) detection plates and the Compact coliform (CF) detection plateswith a modified method of standards SFS 3950 and SFS 4447. The results were comparedamong others to the European Commission regulation 2073/2005 on microbiological criteriafor foodstuffSalmonella was absent in the fertilizers, and thus its presence would be impossible in the plantproducts. Coliform bacteria were initially detected in the growing medium, but generally theamount decreased significantly within time. At the end of the experiment barley grains fromthe first urine duplicate and first composted faeces duplicate were totally free of coliformbacteria. Also, the amount of coliform bacteria in barley grains of other treatments wasacceptable in hygienic terms, being less than I cfu/g. The amount of coliform bacteria incarrots grown in commercial fertilizer and composted faeces treatments were within thesatisfactory limits. The small size of carrots from urine and septic tank sludge treatments didnot allow complete handling, nevertheless, the amount of colony forming units wasconsidered to be within the acceptable limit of 100-IO00 cfu/g. Results from this studyindicate that the use of composted excreta and source separated human urine as fertilizer isnot posing a health risk in terms of coliform bacteria. More thorough research, however, isneeded in order to define the risk of other disease causing microbes, like enterococci andviruses.
Highlights
On average, an adult person annually produces approximately 500 kg of urine and 50 kg of faeces
The substrate was a mixture of unfertilised horticultural peat (Biolan), lime and sand, Two parallel treatments of both barley and carrot were used: commercial Keviitviljan Y3 -fertilizer for barley and Puutarhan keviit -fertilizer for carrot; 2 treatments for separated urine; 2 for composted human faeces, collected from private households and 2 for STS, collected from private households in municipality of Kangasala, The amounts of fertilizers were determined based on the recommendations of the manufacturers of commercial fertilizers, The recommendation for Keviitviljan Y3 fertilizer was 50 kg/ha and for Puutarhan keviit -fertilizer 8 00 kg/ha
The results of this study indicate that human excreta compost could be used as fertilizer without it posing a significant pathogen risk for the users or consumers of the foodstuffs produced
Summary
An adult person annually produces approximately 500 kg of urine and 50 kg of faeces. There is a considerable difference between both the nutrient and pathogen content of different excreta. [2] In the past, human excreta was widely used as a fertilizer in fields due to its nutrient-rich content. [4] In most cases, the most significant health risks are a result of improper handling during the different phases - the excreta used is untreated, the crops are eaten raw and unwashed, and the levels of personal hygiene are low. [5] They used several indicator bacteria, among others Salmonella and Escherichia coli. Both types of pathogens were found in all the raw sludge samples taken from 22 different treatment plants. [5] In addition, Heinonen-Tanski et al studied the outdoor cucumber cultivation fertilized with separated urine. Commercial fertilizers were used as a control and the results showed that there were no coliforms present in the cucumbers, though the urine used had not been preserved before utilization. [6]
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