Starch degradation and intermediate dynamics in flocculated and dispersed microcosms.

A large fraction of the organic substrate in municipal wastewater is particulate. Prior to uptake, particles have to be degraded through potentially a range of intermediates. However, research on intermediate dynamics during particle hydrolysis is limited. In this paper, batch experiments on flocculated and dispersed biomass microcosms using starch as particulate substrate are reported. Overall hydrolysis rate was not significantly different between the two systems. Particle colonization, and increased particle porosity in combination with particle breakup, led to increased substrate availability over time. Particle breakup was more important for flocculated biomass, while increased particle porosity and particle colonization played a larger role for dispersed biomass. During particle degradation intermediates were formed; however, all intermediate polymer sizes were not formed to the same extent. This can be explained by non-random enzymatic degradation, where some products are preferred over others. Intermediates' dynamics also depend on the biomass structure, and in a floc-based system, diffusion limitations allow glucose to accumulate in the system.

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. Toilet paper is found to be a major inhibitor to settling of solids. While a lower overflow point results in better phase separation through displacement of liquid, a higher overflow point and frequent removal of solids may be more advantageous for the liquid quality.

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. Those who commonly use Urine Diversion Dehydration Toilets were far more receptive. The user-centred field trials were complemented by a controlled laboratory experiment, using synthetic urine, -faeces, and -menstrual blood, to systematically assess the efficiency of three swipe materials to clean the rotating bowl of the flush. A silicone rubber with oil-bleed-effect was found to be the best performing material for the swipe. Lubrication of the bowl prior to use further reduced fouling. A mechanical waterless flush that does not require consumables, like plastic wrappers, is a novelty and could - implemented in existing dry toilet systems - improve acceptance and thus the success of waterless sanitation.

Wastewater characterisation by combining size fractionation, chemical composition and biodegradability.

The potential for resource recovery from wastewater can be evaluated based on a detailed characterisation of wastewater. In this paper, results from fractionation and characterisation of two distinct wastewaters are reported. Using tangential flow filtration, the wastewater was fractionated into 10 size fractions ranging from 1 kDa to 1 mm, wherein the chemical composition and biodegradability were determined. Carbohydrates were dominant in particulate size fractions larger than 100 µm, indicating a potential of cellulose recovery from these fractions. While the particulate size fractions between 0.65 and 100 µm show a potential as a source for biofuel production due to an abundance of saturated C16 and C18 lipids. Both wastewaters were dominated by particulate (>0.65 µm), and oligo- and monomeric (<1 kDa) COD. Polymeric (1-1000 kDa) and colloidal (1000 kDa-0.65 µm) fractions had a low COD content, expected due to degradation in the sewer system upstream of the wastewater treatment plant. Biodegradation rates of particulate fractions increase with decreasing size. However, this was not seen in polymeric fractions where degradation rate was governed by chemical composition. Analytical validation of molecular weight and particle size distribution showed below filter cut-off retention of particles and polymers close to nominal cut-off, shifting the actual size distribution.

Menstrual Hygiene Management and Waste Disposal in Low and Middle Income Countries-A Review of the Literature.

Menstrual hygiene management (MHM) has gained some attention and several literature reviews have been published. However, both original papers and reviews tend to focus on absorbent access and use and not on the disposal of menstrual waste. This review aims to fill a gap in the water, sanitation and hygiene (WASH) sector by bringing a focus specifically on menstrual hygiene safe disposal in low- and middle-income countries (LMIC). We reviewed published literature since 2002 on menstrual hygiene with a focus on menstrual waste management and menstrual absorbent disposal in LMIC. Database searches were conducted of both peer reviewed literature and grey literature, in addition to hand searching of references of relevant earlier literature reviews. In total 152 articles and reports were identified and 75 met the inclusion criteria and was included in the final review. Existing polices on MHM was also reviewed with a focus on India and South Africa. The review showed that disposal of menstrual waste is often neglected MHM and sanitation value chains, leading to improper disposal and negative impacts on users, the sanitation systems and the environment. Findings call for further research to gain better understandings of MHM waste streams, disposal behaviors, absorbent materials and waste management technologies to deliver health, safety, mobility and dignity for women and girls.