Pathogens and pharmaceuticals in source-separated urine in eThekwini, South Africa

In eThekwini, South Africa, the production of agricultural fertilizers from human urine collected from urine-diverting dry toilets is being evaluated at a municipality scale as a way to help finance a decentralized, dry sanitation system. The present study aimed to assess a range of human and environmental health hazards in source-separated urine, which was presumed to be contaminated with feces, by evaluating the presence of human pathogens, pharmaceuticals, and an antibiotic resistance gene. Composite urine samples from households enrolled in a urine collection trial were obtained from urine storage tanks installed in three regions of eThekwini. Polymerase chain reaction (PCR) assays targeted 9 viral and 10 bacterial human pathogens transmitted by the fecal-oral route. The most frequently detected viral pathogens were JC polyomavirus, rotavirus, and human adenovirus in 100%, 34% and 31% of samples, respectively. Aeromonas spp. and Shigella spp. were frequently detected gram negative bacteria, in 94% and 61% of samples, respectively. The gram positive bacterium, Clostridium perfringens, which is known to survive for extended times in urine, was found in 72% of samples. A screening of 41 trace organic compounds in the urine facilitated selection of 12 priority pharmaceuticals for further evaluation. The antibiotics sulfamethoxazole and trimethoprim, which are frequently prescribed as prophylaxis for HIV-positive patients, were detected in 95% and 85% of samples, reaching maximum concentrations of 6800 µg/L and 1280 µg/L, respectively. The antiretroviral drug emtricitabine was also detected in 40% of urine samples. A sulfonamide antibiotic resistance gene (sul1) was detected in 100% of urine samples. By coupling analysis of pathogens and pharmaceuticals in geographically dispersed samples in eThekwini, this study reveals a range of human and environmental health hazards in urine intended for fertilizer production. Collection of urine offers the benefit of sequestering contaminants from environmental release and allows for targeted treatment of potential health hazards prior to agricultural application. The efficacy of pathogen and pharmaceutical inactivation, transformation or removal during urine nutrient recovery processes is thus briefly reviewed.

Towards sustainable sanitation: Identifying and mitigating microbial health risks in the production of urine-derived fertilizers

Timothy R. Julian, Tamar Kohn, Simon Schindelholz

Sanitation systems that systematically recover and reuse waste can promote social enterprise, reduce discharge of harmful nutrients, pathogens and other contaminants to the environment, replace synthetic fertilizer sources, and increase access to sanitation for improved human health. However, one significant obstacle towards successfully modernizing sanitation practices is the need to assure human health safety in the production and application of waste-derived products. This is especially important in resource-poor settings, where an added challenge to safe waste reuse is limited financial capacity for technology implementation. This project seeks to identify and reduce human and environmental health risks in the collection of urine and its processing into a fertilizer (struvite) in a large decentralized sanitation system in Durban, South Africa, where a network of over 80,000 urine-diverting dry toilets (UDDTs) is in place. A screening of fecal pathogens in source-separated urine was conducted to assess microbial health hazards. Rotavirus, Adenovirus and Shigella spp. were identified as the most frequently occurring pathogens. Occupational exposure to Rotavirus in urine via surface-to-hand followed by hand-to-mouth transfer was then evaluated to quantify the relative microbial health risks associated with urine collection and fertilizer production. The microlevel activity time series (MLATS) method was selected for the exposure assessment. First person videography of urine collection and processing was coded into high-resolution data yielding the frequency, duration, and chronology of contacts between each study participant hand and each surface. Additionally, a tracer exposure study was conducted to measure the volume of urine contacted by study participants. A model was constructed using this data to simulate the concentrations expected of pathogens on worker hands and potential dose of pathogens ingested from intermittent hand-to-mouth contacts. Study participants contacted visibly wet, presumably urine-contaminated surfaces more frequently during the production of struvite than during the collection of urine (e.g., 10 vs. 3 wet-surface contacts/hr). The tracer study revealed that during the production of struvite, study participant gloves contacted 0.04 – 50 ml urine per batch of struvite produced. Nevertheless, the probability of Rotavirus infection associated with single dose events from presumed hand-to-mouth contacts was somewhat low during struvite production (e.g., median P(response) [ 95% CI] = 1.5×10-4 [1.4×10-5 , 5.4×10-4] per dose for 10K simulations). This exposure may be unacceptable if urine collection and fertilizer production system is conducted at scale or if multiple hand-to-mouth contacts occur during urine handling. In the context of resource reuse, source-separated urine is often falsely considered “sterile” or nearly so. Urine treatment via storage can reduce pathogen concentrations in struvite reactor influent to reduce exposure. Fertilizer production techniques that reduce human contact with urine during processing such as automated reactors should be favored. This study is unique in its approach to accurately model the time-dependent concentration of pathogens on hands due to urine contamination and to quantify the consequent exposure potential using videography, fecal contamination analysis in urine and on surfaces and a tracer study. Quantitatively identifying risks in this way is an important strategy for identifying and overcoming barriers to safe and sustainable sanitation.

2017

Towards sustainable sanitation: Identifying and mitigating microbial health risks in the production of urine-derived fertilizers

Timothy R. Julian, Tamar Kohn, Simon Schindelholz

2017