Fresh Human Faeces Research Articles

Dynamic nature of viral and bacterial communities in human faeces

Bacteriophages are a major component of the gut microbiome and are believed to play a role in establishment and stabilization of microbial communities by influencing taxonomic and functional diversity. We show that the activity of lytic and temperate phages can also significantly affect bacterial community structure in a model of extended colonic retention. Intact fresh human feces were incubated anaerobically at 37°C without homogenization and subjected to metagenomic sequencing. We observed subject-specific blooms and collapses of selected bacteriophage and bacterial populations within some individuals. Most notable were striking collapses of Prevotella populations accompanied by increases in specific bacteriophages. In a number of cases, we even observed a shift from one bacterial "enterotype" to another within 48 h. These results confirm that intact feces represents a highly dynamic ecological system and suggests that colonic retention time could have a profound effect on microbiome composition, including a significant impact by bacteriophages.

Experimental evaluation of fresh human feces biogas and compost potential: Evidence for circular economy from waste streams in Ethiopia

Biogas toilets are one of the most resource-efficient sanitation technologies. The technology has dual purposes of generating energy and stabilizing waste-producing biofertilizers. In Ethiopia, knowledge of human feces' energy potential is limited to optimize the development of biogas toilet facilities. Therefore, this study was aimed to evaluate the biogas and biofertilizer potential of human feces in Jimma City, Ethiopia, which may contribute to the development of sustainable sanitation technologies. The study was lab-based experimental design. In the lab-scale batch experiment, fresh human excreta samples were collected using a urine diversion raised toilet. Using ultimate and proximate laboratory analyses, the theoretical yield of biogas was predicted. Then a series of anaerobic digestion batch experiments were conducted to determine the practical energy yield. The bio-fertilizer potential of human feces was determined by analyzing the nutrient contents of human feces. The findings of this study showed that the bio-methane yield from the experimental results has a mean of 0.393 m3 kg−1, which is 14.16 MJ kg−1. The bio-methane meter cube per capita per head per year were 28.71 (28.03–29.27) from the experimental result and 45.26 for the theoretical yield of methane. In this study, the bio-fertilizer potential of human feces was evaluated using nutrient analysis, specifically the NPK (nitrogen, phosphorus, and potassium). Accordingly, human feces contain potassium (2.29 mg kg−1), phosphorus (1.12 mg kg−1), and nitrogen (3.71 mg kg−1). This finding suggests the bio-methane potential of human feces can be used for energy recovery and alternative sanitation options, providing a positive remedy for the sanitation crisis in urban settings.

The Diversity of Scarabaeid Beetles (Scarabaeidae: Coleoptera) in The Lowland Rainforest Ecosystem of Sorong Nature Tourism Park, West Papua, Indonesia

Scarabaeid beetles have an essential role in forest ecosystems, such as nutrient recycling, seed dispersal, forest regeneration, controlling parasite, and reducing carbon emissions. Until now, there has been no publication on scarabaeid beetle diversity in the lowland rainforest ecosystem of Papua, Indonesia. This study aims to measure the diversity of scarabaeid beetles in the lowland rainforest ecosystem of Sorong Nature Tourisme Park (SNTP), West Papua, Indonesia. Determination of study sites used in this study was using the purposive sampling method in three habitat types i.e., rehabilitation zone, conservation zone, and protection zone using baited dung traps (type A, B, and C dung traps), light trap, and active sampling. The fresh cow and human feces baits were used for dung traps that was replaced every 24 hours (68 repetitions for 68 days) in each habitat. Results showed a total of 30 individuals belonging to 13 species of scarabaeid beetles were collected. Onthophagus has the highest species richness (5 species) and the low species richness were Aphodius sp., Anomala sp., and Adoretus sp. (1 species). The protection zone has the highest diversity index (H’=2.09), followed by the conservation zone (H’=2), and rehabilitation zone (H’=0.5). Based on trap type, dung trap collected the most beetle species (9 species), followed by light trap (6 species), and active sampling (2 species). Based on Pearson correlation, soil pH significantly correlated with beetle abundance. This study was the first report of scarabaeid beetles in the West Papua, Indonesia.

Screening of skatole-degrading bacteria and control of human fecal odor by compound bacteria

PurposeThe biodegradation of skatole was used as a starting point in this study, and existing strains of degrading NH3 and H2S in the laboratory were combined to create a composite deodorant. The deodorization effect of the composite deodorant on human feces was investigated in order to provide a foundation for fecal odor gas treatment.MethodsSkatole-degrading bacteria were identified, degradation conditions were optimized, and skatole metabolites were identified using liquid chromatography-mass spectrometry (LC-MS). The skatole-degrading bacteria were combined with the existing strains of degrading NH3 and H2S in the laboratory to make a compound deodorizer, and the deodorizing effect of the compound deodorizer on fresh human feces and old human feces was compared. Liquid chromatography, specific sensors, and gas chromatography were used to determine the contents of skatole, NH3, H2S, and volatile organic compounds, and the microbial diversity was examined.ResultsMicrobial agents H and Y capable of utilizing skatole were screened out under aerobic and facultative anaerobic conditions, respectively. Within 48 h, the degradation rate of skatole by microbial agent Y was 88.52%. Following condition optimization, the optimum temperature for skatole degradation by microbial agent Y was 33 °C, and the optimum pH was 7. The main functional bacteria were Acinetobacter xiamenensis. The metabolites of skatole were determined by liquid chromatography-mass spectrometry (LC–MS), and six possible metabolites were found, including 3-aldehyde indole, 3-carboxyl indole, 1H-indole-2,3-dione, and 3-methyl indole pyruvate. The skatole-degrading bacteria Lactobacillus rhamnosus and Saccharomyces cerevisiae were then combined in proportion to form a composite deodorant. The 5-day degradation rate of skatole in the old manure group was 88.11%, while the 5-day degradation rate in the fresh manure group was 47.56%.ConclusionsThe compound microbial agent developed in this study has a solid deodorizing effect, particularly in the control of the odor of obsolete feces. The use of composite microbial agents can efficiently degrade skatole in human feces, providing a theoretical foundation for the use of microbial remediation in the actual world.Graphical

Effects of Polyphenols and Glucosinolates in Broccoli Extract on Human Gut Microorganisms Based on Simulation In Vitro.

Broccoli extract mainly contains polyphenols and glucosinolates (GSLs). GSLs can be hydrolyzed by gut microorganisms into isothiocyanates (ITCs) and other active substances. These substances have anticancer, anti-inflammatory, antimicrobial, and atherosclerosis-reducing functions. In this study, a high concentration (2000 μmol/L GSLs and 24 μmol/L polyphenols) and a low concentration (83 μmol/L GSLs and 1 μmol/L polyphenols) of broccoli extract were prepared. Gut microorganisms from fresh human feces were cultured to simulate the gut environment in vitro. The GSL content decreased and the types and content of ITCs increased with broccoli extract hydrolysis through cyclic condensation and gas chromatography-mass spectrometry (GC-MS) analyses. Broccoli extract significantly increased probiotics and inhibited harmful bacteria through 16S rDNA sequencing. Based on phylum level analysis, Firmicutes and Lachnospiraceae increased significantly (P < 0.05). At the genus level, both high- and low-concentration groups significantly inhibited Escherichia and increased Bilophila and Alistipes (P < 0.05). The high-concentration group significantly increased Bifidobacterium (P < 0.05). The broccoli extract improved the richness of gut microorganisms and regulated their structure. The GSL hydrolysis was significantly correlated with Bilophila, Lachnospiraceae, Alistipes, Bifidobacterium, Escherichia, and Streptococcus (P < 0.05). These study findings provide a theoretical foundation for further exploring a probiotic mechanism of broccoli extract in the intestine.

Integrating in-bed gas looping and CO2 capture in the FeD-Latrine

Sanitation equity and climate actions are world concerns stated by the United Nations in the Sustainable Development Goals. A significant source of greenhouse gas emissions is inputted by human wastes, either in developing countries through wastewater treatment plants, or in the underdeveloped world, through anaerobic digestion of fecal sludge in pit latrines. For the first time, an integrated process for CO2 reduction and capture is implemented in a thermally sustainable, latrine-like device that destroys fresh human feces using smoldering combustion, the FeD-Latrine. A gas looping oxidizes combustible gases and creates favorable conditions to capture CO2 in bed. CH4 and H2 molar fractions are decreased around 90 % and 30 %, respectively. CaO used as a sorbent captures up to 8 mmol of CO2 per gram, forming a stable CaCO3. Compared to kinetic-dominant processes for CO2 capture, we obtain an efficiency of around 52 %. Our findings show that using the FeD-Latrine to replace typical pit latrines reduces 60 % of the CO2-eq emissions.

The effects of dehydration and local soil on parasite recovery: A preliminary paleoparasitological evaluation on experimental coprolites

Experimental paleoparasitological approaches have been used in order to optimize the methodology previously to the application in archeological samples. In this study we evaluated the action of dehydration and local soil (Central Argentina) on the loss of parasite eggs in experimental coprolites, using two parasitological techniques: spontaneous sedimentation and sucrose-flotation. Experimental coprolites comprised fresh human feces, positive for Hymenolepis nana, Ascaris sp., and Enterobius vermicularis, submitted to controlled artificial dehydration. Experimental coprolites with soil addition were prepared by mixing archeological sediment with equal mass of fresh feces. Helminth eggs were counted and eggs per gram were estimated in each subsample. Statistical analyses were applied to compare subsamples before and after desiccation and with and without addition of soil sediment. The performance of parasitological methods statistically differed, the sucrose flotation technique being the less effective when fresh feces and experimental coprolites were analyzed. Partial deformation of eggs was observed via both techniques only in subsamples containing H. nana eggs. However, this was not seen in Ascaris sp. subsamples, possibly due to eggshell composition. We found that sample desiccation significantly decreased the number of eggs in the experimental coprolites. Mixing archeological sediment with the fecal material also resulted in significantly fewer eggs surviving, independent of desiccation. This shows that climate and soil in which archeological fecal samples are found can strongly influence the survival of parasite eggs from past populations. The small amount of parasite evidence often found in paleoparasitological analyses, including Central Argentina, could be attributed to the action of taphonomic processes rather than to the real absence of infection in these ancient populations. Importantly, the study highlights the role of local soil, confirmed for the first time by empirical data. The research provides valuable insights into the understanding of the paleoparasitological results of the region and of general paleoparasitology.

Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems

In order to obviate the economic issues associated with pit latrine emptying and transport such as high water additions and rheologically difficult sludge properties, the implications of prompt solid/liquid separation were investigated. This was achieved through rheological characterisation of fresh human faeces and synthetic faeces, and comparison with aged faecal sludges. Shear yield stress, thixotropy and post-shear structural recovery were characterised for a total solids (TS) concentration range of 5–35% total solids (TS) and stickiness yield stress was determined for concentrations up to 100% TS. Fresh faeces rheology proved to be favourable when compared to aged matrices, evidenced by a lower shear yield stress and higher gel point solids concentration, suggesting that aging could alter the physico-chemical properties of faecal sludge. Fresh and synthetic faeces exhibited similar shear thinning, thixotropic behaviour with the majority of structural breakdown occurring at a low shear rate of 10 s−1, and the extent increasing with higher solids concentrations. At 32% TS, fresh faeces shear yield stress was permanently reduced by 80%, suggesting that low shear pumping could reduce the energy demand required for faeces transport. The sticky phase, which represents the region to avoid faecal transport and mechanical drying processes, was identified to range from 30 to 50% TS, with 25% TS as ideal to commence dewatering processes. This also coincides with the average solids concentration of faeces, which is achievable by source separation. This study has identified that handling of fresh faeces as opposed to aged faecal sludges would result in economic and environmental benefits, with energy, water and labour savings.

Isothermal drying characteristics and kinetics of human faecal sludges.

Background: Drying is an important step for the thermochemical conversion of solid fuels, but it is energy-intensive for treating highly moist materials. Methods: To inform the thermal treatment of faecal sludge (FS), this study investigated the drying characteristics and kinetics of various faecal wastes using thermogravimetric analysis and isothermal heating conditions. Results: The findings show that FS from the anaerobic baffled reactor (ABR) and ventilated improved pit latrines (VIP) exhibit similar drying characteristics, with maximum drying rates at 0.04 mg/min during a constant rate period that is followed by a distinct falling rate period. On the contrary, fresh human faeces (HF) and FS from urine diversion dry toilets (UDDT) exhibited a falling rate period regime with no prior or intermittent constant rate periods. The absence of a constant rate period in these samples suggested limited amounts of unbound water that can be removed by dewatering and vice versa for VIP and ABR faecal sludges. The activation energies and effective moisture diffusivity for the sludges varied from 28 to 36 kJ/mol and 1.7·10 -7 to 10·10 -7 m 2/s at 55°C and sludge thickness of 3mm. The Page model was consistent in modelling the different sludges across all temperatures. Conclusions: These results presented in this study can inform the design and development of innovative drying methods for FS treatment.

Isothermal drying characteristics and kinetics of human faecal sludges

Background: Drying is an important step for the thermochemical conversion of solid fuels, but it is energy-intensive for treating highly moist materials. Methods: To inform the thermal treatment of faecal sludge (FS), this study investigated the drying characteristics and kinetics of various faecal wastes using thermogravimetric analysis and isothermal heating conditions. Results: The findings show that FS from the anaerobic baffled reactor (ABR) and ventilated improved pit latrines (VIP) exhibit similar drying characteristics, with maximum drying rates at 0.04 mg/min during a constant rate period that is followed by a distinct falling rate period. On the contrary, fresh human faeces (HF) and FS from urine diversion dry toilets (UDDT) exhibited a falling rate period regime with no prior or intermittent constant rate periods. The absence of a constant rate period in these samples suggested limited amounts of unbound water that can be removed by dewatering and vice versa for VIP and ABR faecal sludges. The activation energies and effective moisture diffusivity for the sludges varied from 28 to 36 kJ/mol and 1.7·10 -7 to 10·10 -7 m 2/s at 55°C and sludge thickness of 3mm. The Page model was consistent in modelling the different sludges across all temperatures. Conclusions: These results presented in this study can inform the design and development of innovative drying methods for FS treatment.

Isothermal drying characteristics and kinetics of human faecal sludges

Background: Drying is an important step for the thermochemical conversion of solid fuels, but it is energy-intensive for treating highly moist materials. Methods: To inform the thermal treatment of faecal sludge (FS), this study investigated the drying characteristics and kinetics of various faecal wastes using thermogravimetric analysis and isothermal heating conditions. Results: The findings show that FS from anaerobic baffled reactor (ABR) and ventilated improved pit (VIP) latrines exhibit similar drying characteristics, with maximum drying rates at 0.04 mg/min during a constant rate period that is followed by a distinct falling rate period. On the contrary, fresh human faeces (HF) and FS from urine-diverting dry toilets (UDDT) exhibited a falling rate period regime with no prior or intermittent constant rate periods. The absence of constant rate period in these samples suggested limited amounts of unbound water that can be removed by dewatering and vice versa for VIP and ABR faecal sludges. The activation energies and effective moisture diffusivity for the sludges varied from 20 to 30 kJ/mol and 3∙10-7 to 1∙10-5 m2/s at 55°C and sludge thickness of 3mm. The Page model was consistent in modelling the different sludges across all temperatures. Conclusions: These results presented in this study can inform the design and development of innovative drying methods for FS treatment.

Effect of storage time on the properties of faeces

Background: This short-term study was carried out in 2013 at the Pollution Research Group at the University of KwaZulu-Natal (Durban, South Africa) as an asisgnemnt of a final year Chemical engineering student project. It focussed on the effect of storage time on the properties of fresh human faeces, more particularly moisture content, thermal conductivity, volatile solids and chemical oxygen demand (COD). These properties are important as they are often used in the design of drying or thermal treatment technologies for faeces. A storage period of one week was hypothesised at room ambient temperature. Methods: The samples were tested for chemical properties using standard operational procedures developed at the Pollution Research Group with parameters such as totals solids, moisture content, suspended solids, volatile solids, COD and thermal conductivity. Results: The thermal conductivity on average was 0.44 W/m.K. The moisture content was observed to decrease by 16%, from 77% to 61%. Thermal conductivity was plotted over the range of moisture contents to observe any trends, varying from 0.074 W/m.K to 0.61 W/m.K for dry faeces and water respectively. The use of a composition weighted average model fitted the data well and was found to be within 95% of the confidence interval of the best fit line. Conclusions: The effect of storage time was found to be negligible on COD and thermal conductivity however moisture content decreased as days progressed and the volatile solids increased with an increase in storage time. Examining the relationship between thermal conductivity and moisture content, it was found that thermal conductivity increase with an increase in moisture content.

C-Terminal Part of Glutamate-Ammonia-Ligase Adenyltransferase Gene Identified by RAPD-HRM with 3H Primer for E. Coli Screening

A single random oligonucleotide 3H primer has been previously applied in random-amplified- polymorphic-DNA (RAPD)-PCR to distinguish stocked bacteria E. coli within a cocktail mixture also containing Enterococcus faecalis, Bifidobacterium longum and Ruminococcus gnavus. In this study, we demonstrate that a 702 base pair (bp) gene fragment can be amplified as a unique pattern by RAPD-PCR using a 3H primer in human faeces containing E. coli. This unique 702 bp amplicon contained a 687 bp gene fragment identified as the C-terminal region of the glutamate-ammonia-ligase adenyltransferase (glnE) gene of E. coli. By high-resolution melt (HRM) analysis, a mean melt-curve temperature of this 702 bp amplicon was determined to be approximately 88.1 ± 0.22 degrees Celsius (°C). A combination of RAPD with HRM in one single reaction based on this amplicon can achieve semi-quantitative detection of up to 102 CFU/ml of E. coli. To increase the signal intensity of HRM, a primer pair capable of screening E. coli directly from fresh human faeces was re-designed from the 687 bp gene segment, giving a mean peak melt-curve temperature at 88.35 ± 0.11 °C. Finally, single-nucleotide polymorphisms of this 687 bp gene segment were analysed for pathogenic E. coli strains, including UMN026, O83:H1, O104:H4, O157:H7 and O169:H41. We conclude that this 687 bp segment of the glnE gene has a high potential for screening of human faecal E. coli, including pathogenic strains, in contaminated food and water.

Effects of Elevated Tetracycline Concentrations on Aerobic Composting of Human Feces: Composting Behavior and Microbial Community Succession.

The effects of antibiotics on aerobic composting are investigated by dosing of tetracycline (TC) in fresh human feces with sawdust as biomass carrier. Variability in process parameters such as temperature, pH, water-soluble carbon, germination index (GI) and dehydrogenase activity (DHA) are evaluated at TC dosages of 0, 100, 250 and 500mg/kg in a 21-day composting. Moreover, microbial community succession is examined by high-throughput 16S rRNA gene sequencing. Findings indicate significant impacts to the process parameters with the increase of TC concentration such as inhibition of temperature increases during aerobic composting, lowering of pH, increasing of water-soluble carbon residue, a decrease of GI, and hindering of DHA. Furthermore, elevated TC concentrations significantly alter the microbial community succession and reduce the community diversity and abundance. Therefore, interference in microbial community structures and a hindrance to biological activity are believed to be the main adverse effects of TC on the composting process and maturity of the composting products.

Impact of nutrient addition on diversity and fate of fecal bacteria

Understanding the variations in the microorganisms associated with human fecal pollution in different types of water is necessary to manage water quality and predict human health risks. Using an Illumina sequencing method, we investigated variations in the fecal bacteria originating from fresh human feces and their decay trends in nutrient-supplemented water and natural river water. Nutrient addition contributed to the growth of heterotrophic bacteria like Comamonadaceae, Cytophagaceae, and Sphingobacteriaceae, but led to lower concentrations for Bacteroidaceae, Lachnospiraceae, and Ruminococcaceae. This result suggests that the utilization of nutrients by high-activity bacteria may suppress other bacteria via depletion of the available nutrient resources. As we did not observe proliferation of Bacteroidales, Lactobacillales, Clostridiales, or Ruminococcaceae in either supplemented or river water, we consider these groups suitable for use as indicators to determine the level of fecal pollution. Moreover, we tested the persistence of Bacteroidales markers, including general-Bacteroidales marker GenBac and human-specific Bacteroidales marker qHS601, by quantitative PCR. We observed similar trends in the decay of the Bacteroidales markers GenBac and qHS601 in the nutrient-supplemented water and natural river water, and the high R2 values of the GenBac (R2nutrient-supplemented = 0.93, R2natural river = 0.81) and qHS601 (R2nutrient-supplemented = 0.93, R2natural river = 0.91) suggests they are a good fit for the first-order decay model. We also found stronger correlations between the markers and potential pathogenic anaerobes in the different types of water, demonstrating the validity of the use of GenBac and qHS601 from Bacteroidales for the identification of human-associated pollution sources.

Differential decomposition of bacterial and viral fecal indicators in common human pollution types

Understanding the decomposition of microorganisms associated with different human fecal pollution types is necessary for proper implementation of many water quality management practices, as well as predicting associated public health risks. Here, the decomposition of select cultivated and molecular indicators of fecal pollution originating from fresh human feces, septage, and primary effluent sewage in a subtropical marine environment was assessed over a six day period with an emphasis on the influence of ambient sunlight and indigenous microbiota. Ambient water mixed with each fecal pollution type was placed in dialysis bags and incubated in situ in a submersible aquatic mesocosm. Genetic and cultivated fecal indicators including fecal indicator bacteria (enterococci, E. coli, and Bacteroidales), coliphage (somatic and F+), Bacteroides fragilis phage (GB-124), and human-associated genetic indicators (HF183/BacR287 and HumM2) were measured in each sample. Simple linear regression assessing treatment trends in each pollution type over time showed significant decay (p ≤ 0.05) in most treatments for feces and sewage (27/28 and 32/40, respectively), compared to septage (6/26). A two-way analysis of variance of log10 reduction values for sewage and feces experiments indicated that treatments differentially impact survival of cultivated bacteria, cultivated phage, and genetic indicators. Findings suggest that sunlight is critical for phage decay, and indigenous microbiota play a lesser role. For bacterial cultivated and genetic indicators, the influence of indigenous microbiota varied by pollution type. This study offers new insights on the decomposition of common human fecal pollution types in a subtropical marine environment with important implications for water quality management applications.

Energy recovery from human faeces via gasification: A thermodynamic equilibrium modelling approach

Non-sewered sanitary systems (NSS) are emerging as one of the solutions to poor sanitation because of the limitations of the conventional flush toilet. These new sanitary systems are expected to safely treat faecal waste and operate without external connections to a sewer, water supply or energy source. The Nano Membrane Toilet (NMT) is a unique domestic-scale sanitary solution currently being developed to treat human waste on-site. This toilet will employ a small-scale gasifier to convert human faeces into products of high energy value. This study investigated the suitability of human faeces as a feedstock for gasification. It quantified the recoverable exergy potential from human faeces and explored the optimal routes for thermal conversion, using a thermodynamic equilibrium model. Fresh human faeces were found to have approximately 70–82wt.% moisture and 3–6wt.% ash. Product gas resulting from a typical dry human faeces (0wt.% moisture) had LHV and exergy values of 17.2MJ/kg and 24MJ/kg respectively at optimum equivalence ratio of 0.31, values that are comparable to wood biomass. For suitable conversion of moist faecal samples, near combustion operating conditions are required, if an external energy source is not supplied. This is however at 5% loss in the exergy value of the gas, provided both thermal heat and energy of the gas are recovered. This study shows that the maximum recoverable exergy potential from an average adult moist human faeces can be up to 15MJ/kg, when the gasifier is operated at optimum equivalence ratio of 0.57, excluding heat losses, distribution or other losses that result from operational activities.

Acceptance of Human Feces-based Fertilizers in Fecophobic Ghana

Characterizations of Ghanaian societies as fecophobic suggest that the use of human feces, for example as an ingredient of organic fertilizer products, is not easily accepted by them. However, empirical evidence on this issue is lacking, despite extensive attention to the potential of feces for such purposes. This study examines perceptions of both human feces and fertilizers based thereon among fertilizer users around Accra. The findings show that although negative perceptions surround fresh human feces, dried or treated feces and their use as fertilizers are generally considered acceptable. Based on anthropological and other literature and empirical data, the study creates a framework for understanding human feces in this geographical context as symbols of personal moral badness. Seeing feces is intimidating; the more perceived feces resemble the beholder's own feces, the more they remind him of his own badness. Dried or treated feces no longer visually intimidate the beholder and are therefore more neutral. There is no contagion of negative connotations between these different forms of feces. Changing the appearance of feces is both a physical and symbolic way to take away its out-of-placeness, in Douglas' terms, and give it a new meaning as useful artifact instead of bodily secretion.

Human Parasites in Medieval Europe: Lifestyle, Sanitation and Medical Treatment.

Parasites have been infecting humans throughout our evolution. However, not all people suffered with the same species or to the same intensity throughout this time. Our changing way of life has altered the suitability of humans to infection by each type of parasite. This analysis focuses upon the evidence for parasites from archaeological excavations at medieval sites across Europe. Comparison between the patterns of infection in the medieval period allows us to see how changes in sanitation, herding animals, growing and fertilizing crops, the fishing industry, food preparation and migration all affected human susceptibility to different parasites. We go on to explore how ectoparasites may have spread infectious bacterial diseases, and also consider what medieval medical practitioners thought of parasites and how they tried to treat them. While modern research has shown the use of a toilet decreases the risk of contracting certain intestinal parasites, the evidence for past societies presented here suggests that the invention of latrines had no observable beneficial effects upon intestinal health. This may be because toilets were not sufficiently ubiquitous until the last century, or that the use of fresh human faeces for manuring crops still ensured those parasite species were easily able to reinfect the population.

Rheological modelling of fresh human faeces

An analysis of viscosity data from sets of raw data on the shear rheological properties of fresh human faeces was performed to generate model constants that can be used for the design of faecal treatment processes. The models selected are standard choices in computational fluid dynamics software for shear-thinning fluids. Initial screening for model selection was based on a literature review of similarly viscous materials. Results showed reasonable agreement with Power Law (PL). PL model parameters were proposed for fresh human faeces and correlated against sample properties. A PL model for shear stress as a function of moisture content was proposed.