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.

On the compressional rheology of fresh faeces: Evidence for improving community scale sanitation through localised dewatering.

Non-sewered sanitation is currently dependant upon pit latrine emptying, the safety of which is compromised by the high costs of faecal sludge transport to centralised treatment facilities. Transport in turn is hindered by the complex rheology of pit latrine sludge. This study therefore characterised the compressional rheology of fresh faeces and modelled the implications for passive (gravity) or mechanical (forced) solid/liquid separation.

Hydrolysis and Methanogenesis in UASB-AnMBR Treating Municipal Wastewater Under Psychrophilic Conditions: Importance of Reactor Configuration and Inoculum.

Three upflow anaerobic sludge blanket (UASB) pilot scale reactors with different configurations and inocula: flocculent biomass (F-UASB), flocculent biomass and membrane solids separation (F-AnMBR) and granular biomass and membrane solids separation (G-AnMBR) were operated to compare start-up, solids hydrolysis and effluent quality. The parallel operation of UASBs with these different configurations at low temperatures (9.7 ± 2.

Membrane distillation of concentrated blackwater: Effect of temperature, solids concentration and membrane pore size.

This study has elucidated the mechanisms governing water recovery from blackwater using membrane distillation, and has clarified the role of the organic particle fraction on membrane performance. Whilst fecal pathogen growth was initially observed at lower temperatures, pathogen inactivation was demonstrated over time, due to urea hydrolysis which liberated ammonia in excess of its toxic threshold. During the growth phase, membrane pore size <0.

Faeces - Urine separation via settling and displacement: Prototype tests for a novel non-sewered sanitation system.

The development of novel, non-sewered sanitation systems like the Nano Membrane Toilet requires thorough investigation of processes that may seem well-understood. For example, unlike the settling of primary sludge, the separation of solids from liquids in a small-volume container at the scale of a household toilet has not been studied before. In two sets of experiments, the settling of real faeces and toilet paper in settling columns and the settling of synthetic faeces in a conical tank are investigated to understand the factors affecting the liquid quality for downstream treatment processes.

Planning and communicating prototype tests for the Nano Membrane Toilet: A critical review and proposed strategy.

Urban sanitation in growing cities of the Global South presents particular challenges. This led to the Bill & Melinda Gates Foundation's Reinvent The Toilet Challenge, which sparked the development of various non-sewered sanitation technologies like the Nano Membrane Toilet. Complex disruptive technologies like this entail an extensive product development process, including various types of prototype tests.

Improving energy efficiency of electrochemical blackwater disinfection through sequential reduction of suspended solids and chemical oxygen demand.

Onsite reuse of blackwater requires removal of considerable amounts of suspended solids and organic material in addition to inactivation of pathogens. Previously, we showed that electrochemical treatment could be used for effective pathogen inactivation in blackwater, but was inadequate to remove solids and organics to emerging industry standards. Further, we found that as solids and organics accumulate with repeated recycling, electrochemical treatment becomes less energetically sustainable.

Field testing of a prototype mechanical dry toilet flush.

A prototype of a non-fluid based mechanical toilet flush was tested in a semi-public, institutional setting and in selected peri-urban households in eThekwini municipality, Republic of South Africa. The mechanism's functionality and users' perception of the flush were assessed. User perception varied depending on background: Users accustomed to porcelain water flush toilets were open to, yet reserved about the idea of using a waterless flush in their homes.

Membrane stripping enables effective electrochemical ammonia recovery from urine while retaining microorganisms and micropollutants.

Ammonia recovery from urine avoids the need for nitrogen removal through nitrification/denitrification and re-synthesis of ammonia (NH) via the Haber-Bosch process. Previously, we coupled an alkalifying electrochemical cell to a stripping column, and achieved competitive nitrogen removal and energy efficiencies using only electricity as input, compared to other technologies such as conventional column stripping with air. Direct liquid-liquid extraction with a hydrophobic gas membrane could be an alternative to increase nitrogen recovery from urine into the absorbent while minimizing energy requirements, as well as ensuring microbial and micropollutant retention.

Thermodynamic analysis of a gamma type Stirling engine in an energy recovery system.

The demand for better hygiene has increased the need for developing more effective sanitation systems and facilities for the safe disposal of human urine and faeces. Non-Sewered Sanitary systems are considered to be one of the promising alternative solutions to the existing flush toilet system. An example of these systems is the Nano Membrane Toilet (NMT) system being developed at Cranfield University, which targets the safe disposal of human waste while generating power and recovering water.

Conceptual environmental impact assessment of a novel self-sustained sanitation system incorporating a quantitative microbial risk assessment approach.

In many developing countries, including South Africa, water scarcity has resulted in poor sanitation practices. The majority of the sanitation infrastructures in those regions fail to meet basic hygienic standards. This along with the lack of proper sewage/wastewater infrastructure creates significant environmental and public health concerns.

Design and commissioning of a multi-mode prototype for thermochemical conversion of human faeces.

This article describes the design and commissioning of a micro-combustor for energy recovery from human faeces, which can operate both in updraft and downdraft modes. Energy recovery from faecal matter via thermochemical conversion has recently been identified as a feasible solution for sanitation problems in low income countries and locations of high income countries where access to sewage infrastructures is difficult or not possible. This technology can be applied to waterless toilets with the additional outcome of generating heat and power that can be used to pre-treat the faeces before their combustion and to ensure that the entire system is self-sustaining.

Probabilistic performance assessment of complex energy process systems - The case of a self-sustained sanitation system.

A probabilistic modelling approach was developed and applied to investigate the energy and environmental performance of an innovative sanitation system, the "Nano-membrane Toilet" (NMT). The system treats human excreta via an advanced energy and water recovery island with the aim of addressing current and future sanitation demands. Due to the complex design and inherent characteristics of the system's input material, there are a number of stochastic variables which may significantly affect the system's performance.

Faecal-wood biomass co-combustion and ash composition analysis.

Fuel blending is a widely used approach in biomass combustion, particularly for feedstocks with low calorific value and high moisture content. In on-site sanitation technologies, fuel blending is proposed as a pre-treatment requirement to reduce moisture levels and improve the physiochemical properties of raw faeces prior to drying. This study investigates the co-combustion performance of wood dust: raw human faeces blends at varying air-to-fuel ratios in a bench-scale combustor test rig.

Quantifying the performance of a hybrid anion exchanger/adsorbent for phosphorus removal using mass spectrometry coupled with batch kinetic trials.

Increasingly stricter phosphorus discharge limits represent a significant challenge for the wastewater industry. Hybrid media comprising anionic exchange resins with dispersions of hydrated ferric oxide nanoparticles have been shown to selectively remove phosphorus from wastewaters, and display greater capacity and operational capability than both conventional treatment techniques and other ferric-based adsorbent materials. Spectrographic analyses of the internal surfaces of a hybrid media during kinetic experiments show that the adsorption of phosphorus is very rapid, utilising 54% of the total capacity of the media within the first 15 min and 95% within the first 60 min.

An experimental investigation of the combustion performance of human faeces.

Poor sanitation is one of the major hindrances to the global sustainable development goals. The Reinvent the Toilet Challenge of the Bill and Melinda Gates Foundation is set to develop affordable, next-generation sanitary systems that can ensure safe treatment and wide accessibility without compromise on sustainable use of natural resources and the environment. Energy recovery from human excreta is likely to be a cornerstone of future sustainable sanitary systems.

Conceptual energy and water recovery system for self-sustained nano membrane toilet.

With about 2.4 billion people worldwide without access to improved sanitation facilities, there is a strong incentive for development of novel sanitation systems to improve the quality of life and reduce mortality. The Nano Membrane Toilet is expected to provide a unique household-scale system that would produce electricity and recover water from human excrement and urine.

Biogas upgrading by chemical absorption using ammonia rich absorbents derived from wastewater.

The use of ammonia (NH3) rich wastewaters as an ecological chemical absorption solvent for the selective extraction of carbon dioxide (CO2) during biogas upgrading to 'biomethane' has been studied. Aqueous ammonia absorbents of up to 10,000 gNH3 m(-3) demonstrated CO2 absorption rates higher than recorded in the literature for packed columns using 20,000-80,000 g NH3 m(-3) which can be ascribed to the process intensification provided by the hollow fibre membrane contactor used in this study to support absorption. Centrifuge return liquors (2325 g m(-3) ionised ammonium, NH4(+)) and a regenerant (477 gNH4(+) m(-3)) produced from a cationic ion exchanger used to harvest NH4(+) from crude wastewater were also tested.

Obtaining process mass balances of pharmaceuticals and triclosan to determine their fate during wastewater treatment.

To better understand pharmaceutical fate during wastewater treatment, analysis in both aqueous and particulate phases is needed. Reported herein is a multi-residue method for the determination of ten pharmaceutical drugs and the personal care product triclosan in wastewater matrices. Method quantitation limits ranged from 7.

Diagnostic investigation of steroid estrogen removal by activated sludge at varying solids retention time.

The impact of solids retention time (SRT) on estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2) removal in an activated sludge plant (ASP) was examined using a pilot plant to closely control operation. Exsitu analytical methods were simultaneously used to enable discrimination of the dominant mechanisms governing estrogen removal following transitions in SRT from short (3d) to medium (10d) and long (27d) SRTs which broadly represent those encountered at full-scale. Total estrogen (∑EST, i.

Assessing potential modifications to the activated sludge process to improve simultaneous removal of a diverse range of micropollutants.

It is proposed that wastewater treatment facilities meet legislated discharge limits for a range of micropollutants. However, the heterogeneity of these micropollutants in wastewaters make removal difficult to predict since their chemistry is so diverse. In this study, a range of organic and inorganic micropollutants known to be preferentially removed via different mechanisms were selected to challenge the activated sludge process (ASP) and determine its potential to achieve simultaneous micropollutant removal.

Quantifying the loss of methane through secondary gas mass transport (or 'slip') from a micro-porous membrane contactor applied to biogas upgrading.

Secondary gas transport during the separation of a binary gas with a micro-porous hollow fibre membrane contactor (HMFC) has been studied for biogas upgrading. In this application, the loss or 'slip' of the secondary gas (methane) during separation is a known concern, specifically since methane possesses the intrinsic calorific value. Deionised (DI) water was initially used as the physical solvent.

The determination of nonylphenol and its precursors in a trickling filter wastewater treatment process.

An ultra performance liquid chromatography method coupled to a triple quadrupole mass spectrometer was developed to determine nonylphenol and 15 of its possible precursors (nonylphenol ethoxylates and nonylphenol carboxylates) in aqueous and particulate wastewater matrices. Final effluent method detection limits for all compounds ranged from 1.4 to 17.

Fate of alkylphenolic compounds during activated sludge treatment: impact of loading and organic composition.

The impact of loading and organic composition on the fate of alkylphenolic compounds in the activated sludge plant (ASP) has been studied. Three ASP designs comprising carbonaceous, carbonaceous/nitrification, and carbonaceous/nitrification/denitrification treatment were examined to demonstrate the impact of increasing levels of process complexity and to incorporate a spectrum of loading conditions. Based on mass balance, overall biodegradation efficiencies for nonylphenol ethoxylates (NPEOs), short chain carboxylates (NP(1-3)EC) and nonylphenol (NP) were 37%, 59%, and 27% for the carbonaceous, carbonaceous/nitrification, and carbonaceous/nitrification/denitrification ASP, respectively.

Removal of steroid estrogens in carbonaceous and nitrifying activated sludge processes.

A carbonaceous (heterotrophic) activated sludge process (ASP), nitrifying ASP and a nitrifying/denitrifying ASP have been studied to examine the role of process type in steroid estrogen removal. Biodegradation efficiencies for total steroid estrogens (Sigma(EST)) of 80 and 91% were recorded for the nitrifying/denitrifying ASP and nitrifying ASP respectively. Total estrogen biodegradation (Sigma(EST)) was only 51% at the carbonaceous ASP, however, the extent of biodegradation in the absence of nitrification clearly indicates the important role of heterotrophs in steroid estrogen removal.