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The minimization of sludge produced by municipal wastewater treatment plants (MWWTPs) is critical as its handling accounts for approximately 50% of the total operating cost. The challenges in predicting dewatering performance can be overcome by optimizing the sludge treatment process, especially conditioning and dewatering. This study aimed to investigate sludge dewaterability at four different MWWTPs, using a gravity drainage test unit and a bench-scale press. The effect of differently treated effluent used as a solvent to mix the flocculation polymers was observed during dewatering. The membrane bioreactor (MBR) treated effluent yielded the highest filtrate volume in the lowest amount of time, with the least polymer flocculant dosage. The Box Behnken Design model fitted the data and proved a relationship between polymer dosage, cake solids concentration, and cake height during the bench-scale press tests. Highlights The type of water used for polymer flocculant dissolution has, to an extent, a considerable impact on the gravity drainage of the sludge.; Increasing polymer flocculant dosing is not directly proportional to the cake height and cake dryness.; Significant correlation between sludge characteristics (e.g. feed solids) and the cake formed.;

Membrane technology has advanced substantially as a preferred choice for the exclusion of widespread pollutants for reclaiming water from various treatment effluent. Currently, little information is available about Ultrafiltration (UF)/Nanofiltration (NF)/Reverse Osmosis (RO) performance at a pilot scale as a practical engineering application. In this study, the effluent from a full-scale membrane bioreactor (MBR) municipal wastewater treatment works (MWWTWs) was treated with an RO pilot plant. The aim was to evaluate the effect of operating conditions in the removal of selected inorganics as a potential indirect water reuse application. The influent pH, flux, and membrane recovery were the operating conditions varied to measure its influence on the rejection rate. MBR/RO exhibited excellent removal rates (>90%) for all selected inorganics and met the standard requirements for reuse in cooling and irrigation system applications. The UF and NF reduction of inorganics was shown to be limited to meet water standards for some of the reuse applications due to the high Electron Conductivity (EC > 250 μS·cm−1) levels. The MBR/NF was irrigation and cooling system compliant, while for the MBR/UF, only the cooling system was compliant.

In the context of water scarcity, domestic secondary effluent reuse may be an option as a reliable source for alleviating acute water shortage. The increasing risks linked with the presence of natural steroid hormones and many emerging anthropogenic micropollutants (MPs) passing through municipal wastewater treatment works (MWWTWs) are of concern for their endocrine-disrupting activities. In this study, domestic wastewater treated by a full-scale membrane bioreactor (MBR) at an MWWTW in the Western Cape Province, South Africa, was used directly as the influent to a reverse osmosis (RO) pilot plant for the removal of selected natural steroid hormones 17β-estradiol (E2) and testosterone (T) as a potential indirect water recycling application. Estrogenicity and androgenicity were assessed using the enzyme-linked immunosorbent assays (ELISA) and the recombinant yeast estrogen receptor binding assays (YES). The influent pH and flux did not influence the rejection of E2 and T, which was most likely due to adsorption, size exclusion, and diffusion simultaneously. RO and nanofiltration (NF) exhibited excellent removal rates (>95%) for E2 and T. All the E2 effluent samples with MBR/ultrafiltration (UF), MBR/NF, and MBR/RO were lower than the US EPA and WHO trigger value of 0.7 ng/L, as well as the predicted no-effect concentration (PNEC) values for fish (1 ng E2/L).

We use a new set of data available to compute 21st century climate impacts on the hydrology of 221 catchments in high-mountain Central Asia. For each of these subcatchments, a parsimonious steady state stochastic soil moisture water balance model was set up and the partitioning of available water from precipitation into runoff and evaporation computed for different climate futures using the Budyko framework. Climate change sensitivity coefficients are analytically derived for the first time using the total differential method. Relative changes in discharge for three future periods 2011–2040, 2041–2070, and 2071–2100 were computed in relation to the baseline period from 1979–2011. For the baseline observation period, climate data from a global high-resolution climatology data set (CHELSA V21) were used to extract mean daily subcatchment-specific temperature and precipitation values. Data from the coupled model intercomparison project phase 6 (CMIP6) were used to compute catchment mean future climate data using 4 GCM models with 4 scenario runs each. CMIP6 data were bias corrected with CHELSA V21 observation data. For the spatial distribution of soil parameters, different global products were utilized. The robustness of the soil water balance model results was assessed using a comprehensive sensitivity analysis in relation to variations of these soil parameters over typically observed ranges for each subcatchment. The analysis of climate change suggests increasing precipitation over the three periods (+4.44 %, +5.89 %, and +8.51 % relative increases in median total precipitation averaged over subcatchment and scenarios). Median values of temperatures changes between periods relative to the baseline are +1.33 °C, +2.44 °C, and +3.55 °C. Results of the hydrological soil water balance model runs suggest a median increase of discharge of +4.71 %, +7.44 % and +10.87 % for the corresponding periods. This is a strong indication of a wetter and hotter future in Central Asia, relative to today's hydroclimate. Modelling results suggest that decreasing contributions from glacier melt over the course of the 21st century will be offset by increases in discharge consistently throughout the region, despite increasing potential evapotranspiration. Increases in relative discharge will be most pronounced in the Afghan Murghab-Harirud basin and in the Amu Darya. Changes in precipitation characteristics in terms of frequency and event depth also indicate possible impacts on hydrological extremes which remains a heavily under researched topic in Central Asia. [ABSTRACT FROM AUTHOR]