A review of latrine front-end characteristics associated with microbial infection risk; reveals a lack of pathogen density data

Unsafe sanitation accounts for an estimated 898,000 global deaths annually. The faecal pathogen transmission pathway is complex with several possible routes. Latrine front-end characteristics and usage behaviours are one key transmission pathway for microbial pathogens, however, there has not yet been a synthesis of the available research. This review aims to compare the microbial infection risks with latrine front-end components including any quantified microbial densities within the household latrines. This review was conducted with no restriction on the geographical location of the research. Of 118 studies reviewed, only ten (8%) have quantified the microbial density inside the household latrines compared to 109 (92%) measuring the infection risks. The reported risks were most frequent for specific bacterial (n = 34), and helminths infections (n = 32) compared to diarrhoea (n = 23), combined (n = 15), protozoan (n = 4), and viral (n = 4) infections. The infections risk decreased for using latrines lying at a higher position on the sanitation ladder (for example flush latrines) compared to those lying lower (for example pit latrines). The trend was similar for using floor materials that were easier to clean and less favourable for pathogen survival inside the latrines (for example, concrete as opposed to earth). Faecal coliforms were reported highest on the surface of the squat pan (743 CFU/cm2) of pour-flush latrines and helminths on earth floors of pit latrines (1.5 eggs and larvae per gram of soil). Irrespective of latrine type and its position on the sanitation ladder, a dirty latrine, evidenced by a visible lack of cleanliness, significantly increased the risk for all infections. This study recommends that effective microbial infection risk reduction in latrines can be gained efficiently by ensuring washable surfaces and consistent cleaning practices. Future studies should include more rigorous measurements of microbial densities in various latrine types incorporating the different front-end components and usage behaviours.

Volatile fatty acid production from food waste: The effect of retention time and lipid content

The bioconversion of food waste to renewable products has an important role in alleviating the environmental burden of food wastage. This study evaluates the effect of solids retention time (1.5, 4, and 7 days) and lipid content (up to 30 % DS) on the solid's destruction efficiency and VFA yield from food waste fermentation. Although SRT below 4 days and lipid content beyond 20 % reduced the solids destruction efficiency (SRT -12 %, lipids -13 %), the VFA yield improved (SRT 0.36 to 0.48 g COD_VFA/TCOD_FED; lipids 0.17 to 0.39 g COD_VFA/TCOD_FED). This appeared to be a mechanism of improved acidification which doubled to 0.77 gCOD_VFA/g SCOD at 1.5-day SRT. The introduction of easily degradable organics in waste oils and methanogen inhibition by LCFAs were likely causes of process instability when lipids >20 %. Further research is needed considering the COD fractionation of the feed to maximize recoverable products on a commercial scale.

Unravelling the removal mechanisms of bacterial and viral surrogates in aerobic granular sludge systems

The aerobic granular sludge (AGS) process is an effective wastewater treatment technology for organic matter and nutrient removal that has been introduced in the market rapidly. Until now, limited information is available on AGS regarding the removal of bacterial and viral pathogenic organisms present in sewage. This study focussed on determining the relation between reactor operational conditions (plug flow feeding, turbulent aeration and settling) and physical and biological mechanisms on removing two faecal surrogates, Escherichia coli and MS2 bacteriophages. Two AGS laboratory-scale systems were separately fed with influent spiked with 1.0 × 10⁶ CFU/100 mL of E. coli and 1.3 × 10⁸ PFU/100 mL of MS2 bacteriophages and followed during the different operational phases. The reactors contained only granular sludge and no flocculent sludge. Both systems showed reductions in the liquid phase of 0.3 Log₁₀ during anaerobic feeding caused by a dilution factor and attachment of the organisms on the granules. Higher removal efficiencies were achieved during aeration, approximately 1 Log₁₀ for E. coli and 0.6 Log₁₀ for the MS2 bacteriophages caused mainly by predation. The 18S sequencing analysis revealed high operational taxonomic units (OTUs) of free-living protozoa genera Rhogostoma and Telotrochidium concerning the whole eukaryotic community. Attached ciliates propagated after the addition of the E. coli, an active contribution of the genera Epistylis, Vorticella, and Pseudovorticella was found when the reactor reached stability. In contrast, no significant growth of predators occurred when spiking the system with MS2 bacteriophages, indicating a low contribution of protozoa on the phage removal. Settling did not contribute to the removal of the studied bacterial and viral surrogates.

Recovery of phosphorus from municipal wastewater treatment sludge through bioleaching using Acidithiobacillus thiooxidans

Conventional wastewater treatment plants remove phosphorus, which is captured in sewage sludge. Increasing attention is paid to suitable process pathways that allow recovery and recycling of phosphorus. One of the processes under investigation is acid leaching and recovery of phosphorus, but this requires considerable chemical additives, which could be avoided by stimulating acidification via microbiological processes. This study investigated phosphorus leaching from sewage sludge by biogenic sulfuric acid, using Acidithiobacillus thiooxidans. Sulfur supplementation and solid to liquid ratio were varied to examine how these factors affected phosphorus leaching yield. Chemical leaching by sulfuric acid from sewage sludge and thermally-treated sludge was conducted to compare with bioleaching from sewage sludge. Sewage sludge samples were collected from wastewater treatment plants in Ghent, Belgium, and Delft, The Netherlands. Both bioleaching and chemical leaching were conducted at laboratory scale using shake flask technique, and highest phosphorus leaching yield and time was determined using one-way ANOVA statistical tests. Biogenic sulfuric acid produced by A. thiooxidans extracted phosphorus from both sludge samples. The highest phosphorus leaching yield observed was 48 ± 0% for 17 days from Ghent samples and 57 ± 4% for 27 days from Delft samples with 5.0% (w/v) sulfur supplementation and 1.0% (w/v) solid to liquid ratio. Chemical leaching took shorter than bioleaching, but the leaching yield was lower, i.e. 41 ± 1% for 4 h from Ghent samples, 44 ± 1% for 1 h from Delft samples, 48 ± 1% for 1 h from thermally-treated Ghent samples and 51 ± 2% for 4 h from thermally-treated Delft samples. During phosphorus bioleaching, pH increase was observed during the early stage which hampered the activity of A. thiooxidans and therefore increased phosphorus leaching time. This study suggests that creating conditions for A. thiooxidans to overcome acid neutralizing capacity of sewage sludge is needed to extract phosphorus effectively.

Inactivation of indicator organisms on different surfaces after urban floods

The high frequency and intensity of urban floods caused by climate change, urbanisation and infrastructure failures increase public health risks when the flood water contaminated from combined sewer overflows (CSOs) or other sources of faecal contamination remains on urban surfaces. This study contributes to a better understanding of the effects of urban and recreational surfaces on the occurrence of waterborne pathogens. The inactivation of selected indicator organisms was studied under controlled exposure to artificial sunlight for 6 h followed by 18 h in dark conditions. Concrete, asphalt, pavement blocks and glass as control were inoculated with artificial floodwater containing, as indicator organisms, Escherichia coli bacteria, which are common faecal indicator bacteria (FIB) for water quality assessment, Bacillus subtilis spores chosen as surrogates for Cryptosporidium parvum oocysts and Giardia cysts, and bacteriophages MS2 as indicators for viral contamination. On practically all the surfaces in this study, E. coli had the highest inactivation under light conditions followed by MS2 and B. subtilis, except asphalt where MS2 was inactivated faster. The highest inactivation under light conditions was seen with E. coli on a concrete surface (pH 9.6) with an inactivation rate of 1.85 h^-1. However, the pH of the surfaces (varying between 7.0 and 9.6) did not have any influence on inactivation rates under dark conditions. MS2 bacteriophage had the highest inactivation under light conditions on asphalt with a rate of 1.29 h^-1. No die-off of B. subtilis spores was observed on any of the surfaces during the experiment, neither in light nor in dark conditions. This study underpins the need to use different indicator organisms to test their inactivation after flooding. It also suggests that given the sunlight conditions, concentration of indicator organisms and type of surface, the fate of waterborne pathogens after a flood could be estimated.

Die-off of E. coli as fecal indicator organism on different surfaces after urban floods

A better understanding of the effects of different urban and recreational surfaces on the die-off of water-borne pathogens that can cause infections after urban floods if released from surcharged combined sewers and other sources of fecal contamination is needed. The die-off of fecal indicator Escherichia coli was studied under controlled exposure to simulated sunlight on a range of different surfaces found in urban environments: gravel, sand, asphalt, pavement blocks, concrete, playground rubber tiles and grass, using glass as control. The surfaces were inoculated with artificial flooding water containing 10⁵ colony forming units (CFU) of E. coli per mL and sampled periodically using the sterile cotton swab technique, after lowering the water level. The results show that dark inactivation was not statistically significant for any surface, suggesting that chemical composition and pH (varying between 6.5 ± 0.8 and 9.2 ± 0.4) did not affect the die-off rates. The highest light-induced die-off rates for E. coli after the floodwater recession, observed on rubber (>3.46 h^-1) and asphalt (2.7 h^-1), were attributed to temperature stress and loss of surface moisture.

Photo-oxygenation for nitritation and the effect of dissolved oxygen concentrations on anaerobic ammonium oxidation

Removal of nitrogen from wastewater without using electricity consuming aerators was previously observed in photo-bioreactors with a mixed algal-bacterial biomass. Algammox is the particular process based on algae, ammonium oxidizing organisms and anammox bacteria. In this research the activity of anammox bacteria in such an oxygen-producing environment was tested, as well as the effect of short-duration increase in dissolved oxygen (DO) to values potentially inhibiting anammox activity. Sequencing batch photo-bioreactors were fed with settled domestic wastewater enriched with ammonium (200mgNH₄⁺-N/L) and exposed to light within the photosynthetic active range with intensity of about 500μmol/m²·s. Each cycle consisted of 12h illumination and 12h darkness. A well-settling biomass (10days solids retention time) developed that carried out nitritation, nitrification and anammox. Ammonium removal rate during the light period was 4.5mgN-NH₄⁺/L·h, equal to 858mgN-NH₄⁺/m²·h or 477mgN-NH₄⁺/(mol photons). When the reactors were aerated for 3h to temporarily increase the DO, anammox was inhibited at bulk DO values larger than 0.4-1.0mg/L. For almost oxygen saturated conditions, recovery time was about 9days. Algammox photo-bioreactors are therefore able to overcome short periods of oxygen stress, provided they occur only occasionally.

Two-step bioleaching of copper and gold from discarded printed circuit boards (PCB)

An effective strategy for environmentally sound biological recovery of copper and gold from discarded printed circuit boards (PCB) in a two-step bioleaching process was experimented. In the first step, chemolithotrophic acidophilic Acidithiobacillus ferrivorans and Acidithiobacillus thiooxidans were used. In the second step, cyanide-producing heterotrophic Pseudomonas fluorescens and Pseudomonas putida were used. Results showed that at a 1% pulp density (10g/L PCB concentration), 98.4% of the copper was bioleached by a mixture of A. ferrivorans and A. thiooxidans at pH 1.0-1.6 and ambient temperature (23±2°C) in 7days. A pure culture of P. putida (strain WCS361) produced 21.5 (±1.5)mg/L cyanide with 10g/L glycine as the substrate. This gold complexing agent was used in the subsequent bioleaching step using the Cu-leached (by A. ferrivorans and A. thiooxidans) PCB material, 44.0% of the gold was mobilized in alkaline conditions at pH 7.3-8.6, and 30°C in 2days. This study provided a proof-of-concept of a two-step approach in metal bioleaching from PCB, by bacterially produced lixiviants.

Effectiveness of UV-C light irradiation on disinfection of an eSOS(®) smart toilet evaluated in a temporary settlement in the Philippines

Ultraviolet germicidal (short wavelength UV-C) light was studied as surface disinfectant in an Emergency Sanitation Operation System(®) smart toilet to aid to the work of manual cleaning. The UV-C light was installed and regulated as a self-cleaning feature of the toilet, which automatically irradiate after each toilet use. Two experimental phases were conducted i.e. preparatory phase consists of tests under laboratory conditions and field testing phase. The laboratory UV test indicated that irradiation for 10 min with medium-low intensity of 0.15-0.4 W/m(2) could achieve 6.5 log removal of Escherichia coli. Field testing of the toilet under real usage found that UV-C irradiation was capable to inactivate total coliform at toilet surfaces within 167-cm distance from the UV-C lamp (UV-C dose between 1.88 and 2.74 mW). UV-C irradiation is most effective with the support of effective manual cleaning. Application of UV-C for surface disinfection in emergency toilets could potentially reduce public health risks.

Lactic Acid Fermentation, Urea and Lime Addition: Promising Faecal Sludge Sanitizing Methods for Emergency Sanitation

In this research, three faecal sludge sanitizing methods—lactic acid fermentation, urea treatment and lime treatment—were studied for application in emergency situations. These methods were investigated by undertaking small scale field trials with pit latrine sludge in Blantyre, Malawi. Hydrated lime was able to reduce the E. coli count in the sludge to below the detectable limit within 1 h applying a pH > 11 (using a dosage from 7% to 17% w/w, depending faecal sludge alkalinity), urea treatment required about 4 days using 2.5% wet weight urea addition, and lactic acid fermentation needed approximately 1 week after being dosed with 10% wet weight molasses (2 g (glucose/fructose)/kg) and 10% wet weight pre-culture (99.8% pasteurised whole milk and 0.02% fermented milk drink containing Lactobacillus casei Shirota). Based on Malawian prices, the cost of sanitizing 1 m³ of faecal sludge was estimated to be €32 for lactic acid fermentation, €20 for urea treatment and €12 for hydrated lime treatment.

The metagenome of the marine anammox bacterium 'Candidatus Scalindua profunda' illustrates the versatility of this globally important nitrogen cycle bacterium

Anaerobic ammonium-oxidizing (anammox) bacteria are responsible for a significant portion of the loss of fixed nitrogen from the oceans, making them important players in the global nitrogen cycle. To date, marine anammox bacteria found in marine water columns and sediments worldwide belong almost exclusively to the 'Candidatus Scalindua' species, but the molecular basis of their metabolism and competitive fitness is presently unknown. We applied community sequencing of a marine anammox enrichment culture dominated by 'Candidatus Scalindua profunda' to construct a genome assembly, which was subsequently used to analyse the most abundant gene transcripts and proteins. In the S. profunda assembly, 4756 genes were annotated, and only about half of them showed the highest identity to the only other anammox bacterium of which a metagenome assembly had been constructed so far, the freshwater 'Candidatus Kuenenia stuttgartiensis'. In total, 2016 genes of S. profunda could not be matched to the K. stuttgartiensis metagenome assembly at all, and a similar number of genes in K.stuttgartiensis could not be found in S. profunda. Most of these genes did not have a known function but 98 expressed genes could be attributed to oligopeptide transport, amino acid metabolism, use of organic acids and electron transport. On the basis of the S. profunda metagenome, and environmental metagenome data, we observed pronounced differences in the gene organization and expression of important anammox enzymes, such as hydrazine synthase (HzsAB), nitrite reductase (NirS) and inorganic nitrogen transport proteins. Adaptations of Scalindua to the substrate limitation of the ocean may include highly expressed ammonium, nitrite and oligopeptide transport systems and pathways for the transport, oxidation, and assimilation of small organic compounds that may allow a more versatile lifestyle contributing to the competitive fitness of Scalindua in the marine realm.

A multi-proxy study of anaerobic ammonium oxidation in marine sediments of the Gullmar Fjord, Sweden

Anaerobic ammonium oxidation (anammox) is an important process for nitrogen removal in marine pelagic and benthic environments and represents a major sink in the global nitrogen cycle. We applied a suite of complementary methods for the detection and enumeration of anammox activity and anammox bacteria in marine sediments of the Gullmar Fjord, and compared the results obtained with each technique. (15) N labelling experiments showed that nitrogen removal through N2 production was essentially limited to the upper 2 cm of the sediment, where anammox contributed 23-47% of the total production. The presence of marine anammox bacteria belonging to the genus 'Candidatus Scalindua' was shown by 16S rRNA gene sequence comparison. FISH counts of anammox bacteria correlated well with anammox activity, while quantitative PCR may have underestimated the number of anammox bacterial 16S rRNA gene copies at this site. Potential nitrogen conversion by anammox ranged from 0.6 to 4.8 fmol N cell(-1) day(-1) , in agreement with previous measurements in the marine environment and in bioreactors. Finally, intact ladderane glycerophospholipid concentrations better reflected anammox activity and abundance than ladderane core lipid concentrations, most likely because the core lipid fraction contained a substantial fossil component, especially deeper in the sediment.

Impact of temperature on ladderane lipid distribution in anammox bacteria

Anaerobic ammonium-oxidizing (anammox) bacteria have the unique ability to synthesize fatty acids containing linearly concatenated cyclobutane rings, termed "ladderane lipids." In this study we investigated the effect of temperature on the ladderane lipid composition and distribution in anammox enrichment cultures, marine particulate organic matter, and surface sediments. Under controlled laboratory conditions we observed an increase in the amount of C(20) [5]-ladderane fatty acids compared with the amount of C(18) [5]-ladderane fatty acids with increasing temperature and also an increase in the amount of C(18) [5]-ladderane fatty acids compared with the amount of C(20) [5]-ladderane fatty acids with decreasing temperature. Combining these data with results from the natural environment showed a significant (R(2) = 0.85, P = <0.0001, n = 121) positive sigmoidal relationship between the amounts of C(18) and C(20) [5]-ladderane fatty acids and the in situ temperature; i.e., there is an increase in the relative abundance of C(18) [5]-ladderane fatty acids at lower temperatures and vice versa, particularly at temperatures between 12 degrees C and 20 degrees C. Novel shorter (C(16)) and longer (C(22) to C(24)) ladderane fatty acids were also identified, but their relative amounts were small and did not change with temperature. The adaptation of ladderane fatty acid chain length to temperature changes is similar to the regulation of common fatty acid composition in other bacteria and may be the result of maintaining constant membrane fluidity under different temperature regimens (homeoviscous adaptation). Our results can potentially be used to discriminate between the origins of ladderane lipids in marine sediments, i.e., to determine if ladderanes are produced in situ in relatively cold surface sediments or if they are fossil remnants originating from the warmer upper water column.

Physiological and phylogenetic study of an ammonium-oxidizing culture at high nitrite concentrations

Oxidation of high-strength ammonium wastewater can lead to exceptionally high nitrite concentrations; therefore, the effect of high nitrite concentration (> 400 mM) was studied using an ammonium-oxidizing enrichment culture in a batch reactor. Ammonium was fed to the reactor in portions of 40-150 mM until ammonium oxidation rates decreased and finally stopped. Activity was restored by replacing half of the medium, while biomass was retained by a membrane. The ammonium-oxidizing population obtained was able to oxidize ammonium at nitrite concentrations of up to 500 mM. The maximum specific oxidation activity of the culture in batch test was about 0.040 mmol O(2)g(-1)proteinmin(-1) and the K(s) value was 1.5 mM ammonium. In these tests, half of the maximum oxidation activity was still present at a concentration of 600 mM nitrite and approximately 10% residual activity could still be measured at 1200 mM nitrite (pH 7.4), or as a free nitrous acid (FNA) concentration of 6.6 mg l(-1). Additional experiments showed that the inhibition was caused by nitrite and not by the high sodium chloride concentration of the medium. The added ammonium was mainly converted into nitrite and no nitrite oxidation was observed. In addition, gaseous nitrogen compounds were detected and mass balance calculations revealed a nitrogen loss of approximately 20% using this system. Phylogenetic analyses of 16S rRNA and ammonium monooxygenase (amoA) genes of the obtained enrichment culture showed that ammonium-oxidizing bacteria of the Nitrosomonas europaea/Nitrosococcus mobilis cluster dominated the two clone libraries. Approximately 25% of the 16S rRNA clones showed a similarity of 92% to Deinococcus-like organisms. Specific fluorescence in situ hybridization (FISH) probes confirmed that these microbes comprised 10-20% of the microbial community in the enrichment. The Deinococcus-like organisms were located around the Nitrosomonas clusters, but their role in the community is currently unresolved.

Anaerobic ammonium-oxidizing bacteria in marine environments: widespread occurrence but low diversity

Laboratory and field studies have indicated that anaerobic ammonium oxidation (anammox) is an important process in the marine nitrogen cycle. In this study 11 additional anoxic marine sediment and water column samples were studied to substantiate this claim. In a combined approach using the molecular methods, polymerase chain reaction (PCR), qualitative and quantitative fluorescence in situ hybridization (FISH), as well as (15)N stable isotope activity measurements, it was shown that anammox bacteria were present and active in all samples investigated. The anammox activity measured in the sediment samples ranged from 0.08 fmol cell(-1) day(-1) N(2) in the Golfo Dulce (Pacific Ocean, Costa Rica) sediment to 0.98 fmol cell(-1) day(-1) N(2) in the Gullmarsfjorden (North Sea, Sweden) sediment. The percentage of anammox cell of the total population (stained with DAPI) as assessed by quantitative FISH was highest in the Barents Sea (9% +/- 4%) and in most of the samples well over 2%. Fluorescence in situ hybridization and phylogenetic analysis of the PCR products derived from the marine samples indicated the exclusive presence of members of the Candidatus'Scalindua' genus. This study showed the ubiquitous presence of anammox bacteria in anoxic marine ecosystems, supporting previous observations on the importance of anammox for N cycling in marine environments.

Candidatus “Anammoxoglobus propionicus” a new propionate oxidizing species of anaerobic ammonium oxidizing bacteria

The bacteria that mediate the anaerobic oxidation of ammonium (anammox) are detected worldwide in natural and man-made ecosystems, and contribute up to 50% to the loss of inorganic nitrogen in the oceans. Two different anammox species rarely live in a single habitat, suggesting that each species has a defined but yet unknown niche. Here we describe a new anaerobic ammonium oxidizing bacterium with a defined niche: the co-oxidation of propionate and ammonium. The new anammox species was enriched in a laboratory scale bioreactor in the presence of ammonium and propionate. Interestingly, this particular anammox species could out-compete other anammox bacteria and heterotrophic denitrifiers for the oxidation of propionate in the presence of ammonium, nitrite and nitrate. We provisionally named the new species Candidatus "Anammoxoglobus propionicus".

Ladderane phospholipids in anammox bacteria comprise phosphocholine and phosphoethanolamine headgroups

Anammox bacteria present in wastewater treatment systems and marine environments are capable of anaerobically oxidizing ammonium to dinitrogen gas. This anammox metabolism takes place in the anammoxosome which membrane is composed of lipids with peculiar staircase-like 'ladderane' hydrocarbon chains that comprise three or four linearly concatenated cyclobutane structures. Here, we applied high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to elucidate the full identity of these ladderane lipids. This revealed a wide variety of ladderane lipid species with either a phosphocholine or phosphoethanolamine polar headgroup attached to the glycerol backbone. In addition, in silico analysis of genome data gained insight into the machinery for the biosynthesis of the phosphocholine and phosphoethanolamine phospholipids in anammox bacteria.

Deciphering the evolution and metabolism of an anammox bacterium from a community genome

Anaerobic ammonium oxidation (anammox) has become a main focus in oceanography and wastewater treatment. It is also the nitrogen cycle's major remaining biochemical enigma. Among its features, the occurrence of hydrazine as a free intermediate of catabolism, the biosynthesis of ladderane lipids and the role of cytoplasm differentiation are unique in biology. Here we use environmental genomics--the reconstruction of genomic data directly from the environment--to assemble the genome of the uncultured anammox bacterium Kuenenia stuttgartiensis from a complex bioreactor community. The genome data illuminate the evolutionary history of the Planctomycetes and allow us to expose the genetic blueprint of the organism's special properties. Most significantly, we identified candidate genes responsible for ladderane biosynthesis and biological hydrazine metabolism, and discovered unexpected metabolic versatility.