A novel fluidization backwash method by the air-water bubbly flow with air bubbles of various sizes has been proposed for rapid filters. The backwash efficiency is closely related to the bubble wake motion. Bubble coalescence, bed contraction and jet generation caused by the motion of air bubble wakes strikingly enhance the discharge of retained sludge. The effect of the bubble wakes on the backwash efficiency is ensured by controlling the fluidizing condition which is easily identified visually. The size of air bubbles should be controlled properly, and the air bubble size at the dense bed surface must be within several centimeters to prevent the loss of filter media particles from filter beds. The backwash efficiency of the filter bed achieved 94% in average by optimizing the air bubble size in the air-water bubbly flow. The air-water bubbly flow backwash method was also applied to a self-backwash filter where the backwash flow rate depends on an elevated water tank, and the backwash efficiency was as high as that for the constant flow rate backwash method.

The preparation of a copper aluminum/biochar composite and its application for the adsorption of procion red dye was studied. The composite materials were prepared by a co-precipitation method and characterised by X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy, and thermogravimetry. The results of the adsorption study show that adsorption on the copper aluminum/biochar composite follows pseudo-second-order kinetics, and the adsorption isotherm of procion red conforms to the Langmuir isotherm model. The Langmuir fitting result for the maximum adsorption quantity of procion red on copper aluminum/biochar composite is 175.439 mg/g, which is higher than copper aluminum layered double hydroxide. The thermodynamic analysis suggests that procion red adsorption is spontaneous (standard free energy < 0) and endothermic and involves a random solid–liquid phase interface. The composite materials exhibited good recycling performance.

In Japan, data on the reproduction sensitivity of Daphnia magna, which is a widely used organism in laboratory toxicity tests, to nickel are key to determination of water quality target values for nickel, which are used to set values for the environmental quality standards for conservation of the living environment. However, the use of data on the sensitivity of more than one species, including native species, will provide more relevant values. In this study, sensitivity of reproduction to nickel was investigated for five Daphnia species, D. magna, D. similis, D. pulex, D. galeata and D. ambigua, four of which are native to Japan. The no observed effect concentration and the 10% effect concentration (EC₁₀) values of dissolved nickel for reproduction were below the lowest test concentration and 7.9 µg/L for D. magna, 4.6 and 11.2 µg/L for D. similis, 26 and 25.8 µg/L for D. pulex, 23 and 41.0 µg/L for D. galeata, and 62 and 63.8 µg/L for D. ambigua, respectively. Our results indicate that use of ecotoxicity data for native, ecologically relevant Daphnia species can strongly influence the determination of the water quality target values for nickel.

This study aims to assess the performance of five municipal wastewater treatment plants (MWWTPs) from different locations in Morocco using chemical analyses and bioassays. The toxicity assessments were based on the chronic algal growth inhibition using the green microalgae Pseudokirchneriella subcapitata and acute immobilization using the crustacean Daphnia magna. The physicochemical results show that the effluents were mainly polluted with organic and nitrogenous compounds as indicated by higher values of chemical oxygen demand (COD), biochemical oxygen demand (BOD), as well as total nitrogen (TN). The promotion of algal growth was detected in all raw samples, except MWWTP₂, MWWTP₃, and MWWTP₄ influents, in which, the half maximal effective concentration after 72 hours (EC₅₀-72 h) were 61.83% v/v, 53.4% v/v and 87.46% v/v, respectively. Meanwhile, all treated effluents stimulate the algal growth, except MWWTP₂ effluent (EC₅₀-72 h: 55.1% v/v). Furthermore, the untreated samples display immobilizations towards Daphnia magna. The EC₅₀-48 h values were ranked from 7.30% v/v to 79.76% v/v. However, only two effluents from MWWTP₁ and MWWTP₂ exhibit acute toxicities (the EC₅₀-48 h were 45.80% v/v and 41% v/v, respectively). The Spearman correlation coefficients indicate strong positive correspondences between EC₅₀-48 h and COD (r = 0.840, p < 0.05), TN (r = 0.731, p < 0.05), total phosphorus (TP) (r = 0.730, p < 0.05), and PO₄^3- (r = 0.792, p < 0.05).

The major recreational hot springs of Sikkim which are famous tourist destinations were selected for the current study. Physicochemical and microbial quality of all the seven hot spring water samples were examined to assess the seasonal variation for three months. Polok hot spring was the hottest among all, whose temperature reached up to 75°C. In all the other hot springs, temperature ranged from 40°C to 50°C. Piper diagram, durov plot and schoeller plot categorized these hot springs as calcium chloride type. Elemental analysis showed similar pattern of composition in all the hot springs. Various other parameters such as total hardness of water, total alkalinity, phenolic compounds, biochemical oxygen demand, chemical oxygen demand were analyzed and they were found to be within the permissible limits of American Public Health Association and Bureau of Indian Standards. There was no growth in any differential and selection media used for the detection of coli-aerogenes, enteric bacterial pathogens belonging to Enterobacteriaceae, Salmonella-Shigella sp., Vibrio sp. and Pseudomonas sp. Hence, the hot springs of Sikkim are safe for recreational purposes.

This study aims to clarify the function of different porous media layers during accumulated organic matter degradation with enhanced sewer self-purification by porous sponge media. To do so, intermittent flow and low continuous flow were applied to channels containing sponge media while maintaining similar volumetric flow rates per channel. Accumulated organic matter, in the form of margarine, was placed underneath the sponge media. Aerobic activity related to organic matter degradation was monitored for 32 days followed by test sponge oxygen consumption and biomass density evaluation. Porous sponge media of different pore cell radii and thicknesses were tested under the described conditions. Findings for intermittent flow showed that although the top layers did not have direct contact to accumulated organic matter, they contributed 33–70% to the total aerobic activity related to organic matter degradation. A lower contribution of 12–42% was found for the top layers for channels subjected to low continuous flow. For all channels, higher biomass density was found for the bottom layer directly in contact with accumulated organic matter. Findings show that while the bottom layer may have higher contribution to organic matter degradation, the upper media layer contributes significantly to aerobic activity during enhanced sewer self-purification.