Microspheres as surrogate helminth eggs

Re-use of water containing helminth eggs during irrigation for agricultural purposes poses health risks, and likewise during research, due to the potential of spreading on contact. Therefore, polystyrene latex microspheres could be used as surrogates for chemical or biological species during colloidal transport. The aim here is to compare the settling velocities of microspheres having varied surface coatings - that is, proteins A, G and A/G; with that of real helminth eggs obtained from literature. The settling velocities of the microspheres were experimentally determined in tap- and wastewater, as well as theoretically in tap water; which was found to be within the range of mean values for those experimentally determined. There were no differences amongst the microspheres types used for settling in wastewater (i.e., A = 0.072 $\pm$ 0.02; G = 0.060 $\pm$ 0.03; A/G = 0.053 $\pm$ 0.01 mm/s). The same applied for settling in tap water (i.e., A = 0.068 $\pm$ 0.02; G = 0.047 $\pm$ 0.004; A/G = 0.095 $\pm$ 0.02 mm/s), except for microsphere G being different from microsphere A/G. All three types of microspheres settled at velocities lower than that of the wastewater particles (=0.118 $\pm$ 0.03). T-test analyses of settling velocities of microspheres in both tap- and wastewater, versus that from literature (i.e., $\it Ascaris$, $\it Trichuris$ and $\it Oesophagostomum$), showed that microsphere A and A/G may surrogate for $\it Ascaris$ in tap water, the same as A/G for $\it Oesophagostomum$. In wastewater however, both microspheres A and G are a good fit for $\it Trichuris$

Slow sand filtration of raw wastewater using biochar as an alternative filtration media

The efficiency of anaerobic biofilters (AnBF) as low-cost wastewater treatment systems was investigated. $\it Miscanthus$-biochar was used as filtration media and compared with sand as a common reference material. Raw sewage from a municipal wastewater treatment plant was stored in a sedimentation tank for two days to allow pre-settlement of wastewater particles. Subsequently, wastewater was treated by AnBFs at 22 °C room temperature at a hydraulic loading rate of 0.05 m∙h$^{−1}$ with an empty bed contact time of 14.4 h and a mean organic loading rate of 509 $\pm$ 173 gCOD∙m$^{−3}$∙d$^{−1}$. Mean removal of chemical oxygen demand (COD) of biochar filters was with 74 $\pm$ 18% significantly higher than of sand filters (61 $\pm$ 12%). In contrast to sand filters with a mean reduction of 1.18 $\pm$ 0.31 log-units, $\textit {E. coli}$ removal through biochar was with 1.35 $\pm$ 0.27 log-units significantly higher and increased with experimental time. Main removal took place within the $\it schmutzdecke$, a biologically active dirt layer that develops simultaneously on the surface of filter beds. Since the $\textit {E. coli}$ contamination of both filter materials was equal, the higher removal efficiency of biochar filters is probably a result of an improved biodegradation within deeper zones of the filter bed. Overall, performance of biochar filters was better or equal compared to sand and have thus demonstrated the suitability of $\it Miscanthus$-biochar as filter media for wastewater treatment