To understand the characteristics of bacterial viability and diversity in landscape waters replenished with reclaimed water, the typical landscape lake using reclaimed water was investigated in this study. Samples were collected from a reclaimed water inlet (P1), a reclaimed water distribution outlet (P2), and a landscape lake replenished by reclaimed water (P3). By means of measuring adenosine triphosphate (ATP), flow cytometry (FCM), and 16S rRNA gene high-throughput sequencing, the bacterial viability and diversity in reclaimed water distribution system and landscape lake were illustrated. The bacterial ATP contents at P1, P2, and P3 were 3.55 ± 1.79 ng/L, 3.31 ± 1.43 ng/L, and 18.97 ± 6.39 μg/L, and the intact bacterial cell concentrations were 5.91 ± 0.52 × 10⁴ cells/mL, 7.95 ± 2.58 × 10⁴ cells/mL, and 5.65 ± 2.10 × 10⁶ cells/mL, respectively. These results indicated a significant increase of bacterial viability in the landscape lake. The Shannon diversity index of 6.535, 7.05, and 6.886 at P1, P2, and P3, respectively, demonstrated no notable change of bacterial diversity from reclaimed water distribution system to landscape lake. However, the relative abundance of Pseudomonas sp. at P3 was significantly higher than that at P1. These findings indicated that viable but non-culturable (VBNC) bacteria could be revived in the landscape lake. The bacterial viability during reclaimed water reuse should deserve special attention.

In this paper, three different designs of a hybrid PV/T double-pass finned plate solar air heater (DPFPSAH) are investigated. The PV module is used to produce electricity needed to run the pump and blow the air into the solar collector. In the first design, the PV module is placed on the absorber plate of the air heater. In the second design, the PV module is placed beside the glass cover of the air heater; while, in the third one, the PV module is completely separated from the solar collector. The effects of mass flow rate of air, flow, and fan pumping powers are studied. The top losses of the third design are found to be higher than that of the first and the second designs by average values of 7.5% and 29%, respectively. The third design of the hybrid systems has the highest overall performance. The daily thermal efficiencies of the first, second, and third designs of the hybrid systems are obtained as 53%, 27%, and 64%, respectively, at mass flow rate of 0.02 kg/s.

The present study evaluated the sequential biodiesel-bioethanol production from seaweeds. A total of 22 macroalgal species were collected at different seasons and screened based on lipid and carbohydrate contents as well as biomass production. The promising species was selected, based on the relative increase in energy compounds (REEC, %), for further energy conversion. Seasonal and annual biomass yields of the studied species showed significant variations. The rhodophyte Amphiroa compressa and the chlorophyte Ulva intestinalis showed the highest annual biomass yield of 75.2 and 61.5 g m⁻² year⁻¹, respectively. However, the highest annual carbohydrate productivity (ACP) and annual lipid productivity (ALP) were recorded for Ulva fasciata and Ulva intestinalis (17.0 and 3.0 g m⁻² year⁻¹, respectively). The later was selected for further studies because it showed 14.8% higher REEC value than Ulva fasciata. Saturated fatty acids (SAFs) showed 73.4%, with palmitic acid as a dominant fatty acid (43.8%). Therefore, biodiesel showed high saturation degree, with average degree of unsaturation (ADU) of 0.508. All the measured biodiesel characteristics complied the international standards. The first route of biodiesel production (R1) from Ulva intestinalis showed biodiesel recovery of 32.3 mg g⁻¹ dw. The hydrolysate obtained after saccharification of the whole biomass (R2) and lipid-free biomass (R3) contained 1.22 and 1.15 g L⁻¹, respectively, reducing sugars. However, bioethanol yield from R3 was 0.081 g g⁻¹ dw, which represented 14.1% higher than that of R2. Therefore, application of sequential biofuel production using R3 resulted in gross energy output of 3.44 GJ ton⁻¹ dw, which was 170.9% and 82.0% higher than R1 and R2, respectively. The present study recommended the naturally-grown Ulva intestinalis as a potential feedstock for enhanced energy recovery through sequential biodiesel-bioethanol production.

The discussers wish to thank the authors of the original paper for investigating the comparing accuracy of artificial intelligence techniques trained to predict chlorophyll-a in US lakes. In the original paper (Luo et al., Environ Sci Pollut Res 26: 30524–30532, 2019), four data-driven models were established to estimate the chlorophyll-a (CHLA) values in natural and man-made lakes. Three of these models are adaptive neuro-fuzzy inference system (ANFIS)-based, while one is (artificial neural network) ANN-based. The authors used total phosphorus (TP), total nitrogen (TN), turbidity (TB), and the Secchi depth (SD) as independent variables in order to predict CHLA. They stated that ANFIS with subtractive clustering method (ANFIS_SC) models and multilayer perceptron neural network (MLPNN) models gives higher accuracy in the prediction of CHLA values for natural lakes and man-made lakes, respectively. In this letter, some of the missing points in the original publication, which is important for the estimation and comparison of CHLA values in two different lake sets that differ according to the type of formation, are highlighted. In addition, several points are mentioned in order to make these points more clarified for potential readers.

In the Chinese high-level radioactive waste geological disposal program, Gaomiaozi (GMZ) bentonite has been selected as the potential buffer/backfill material. After the closure of the repository, the Ca-OH-type alkaline solution (evolved cement water) released by cement degradation may last for more than 100,000 years. The bentonite will undergo the corrosion of evolved cement water (ECW) for a long period. This work focuses on the sorption property of GMZ bentonite altered by ECW. Firstly, the corrosion experiments on compacted GMZ specimens with the dry density of 1.70 Mg/m³ were carried out under constant volume conditions at two temperatures. Then, the sorption of europium (Eu (III)) onto the corroded GMZ bentonite was studied by batch experiments. The results of batch sorption tests indicate that the altered GMZ bentonite keeps an effective removal property with the uptake of Eu (III) more than 99%. The effect of high-temperature conditions of the repository on the sorption property of bentonite is not significant. The results also suggest that the evolved cement water presents no detrimental effect on the long-term adsorption performance of bentonite even under higher temperature conditions.

Both ultrafine particle and toxicity emissions originating from diesel engine gain an increasing concern. In this study, size distribution and toxicity of particles from a turbocharged common rail engine fueled with clean fuels—dimethyl ether (DME) and biodiesel blends—were investigated. Effects of different DME–biodiesel blends (B0, B5, B10, and B15) and different engine loads were considered. The results demonstrate that particles emitted from DME–biodiesel engine are mainly in form of nucleation mode. Engine running at intermediate load exhausts the maximum number of accumulation mode particles owing to local hypoxia and not high enough combustion temperature. The addition of biodiesel slightly increases the total particle number, peak of particle number concentration, and particle size corresponding to the peak. Effect of biodiesel proportion on particle size distribution gets weaker with the increase of engine load. Engine fueled with B5, B10, and B15 mainly exhausts low molecular weight polycyclic aromatic hydrocarbons (PAHs) (ring number ≤ 4) which are closely related to unburned fuel, and the total PAH emissions are linear versus the fuel consumption. Toxicity equivalent (TE) of particles at low load is lower than that at intermediate load. DME–biodiesel blends with biodiesel mass proportion ≤ 15% can release the DME engine from abrasion and leakage, but no obvious increase in both particle emissions and the risk of particle toxicity.

Recently, the recycling of kerf loss silicon waste has trigged much attention due to the rapid growth of PV market. In this study, 3-aminopropylethoxysilane (APTES)-functionalized nanoporous silicon (NPSi) hybrid materials were prepared by nanosilver-assisted chemical etching (Ag-ACE) of kerf loss silicon waste derived from diamond-wire saw cutting silicon ingot process. The resulting APTES-NPSi indicated high-effective adsorption ability of Cr(VI) from aqueous solution, which was highly pH dependent, and the maximum adsorption capacity reached up to 103.75 mg/g after 60 min at room temperature. The adsorption kinetics and adsorption isotherms were in good agreement with pseudo-second-order model and Langmuir isotherm. Additionally, the Cr(VI) up-take mechanism was carefully investigated and ascribed to the Cr(VI) adsorption on the protonated anime groups by chemical chelating reaction in which the Cr(VI) was reduced to Cr(III). It was worth mentioning that the APTES-NPSi maintained excellent adsorption capacity after five successive regenerated cycles. Therefore, the work would pave the way for recycling of silicon cutting waste and the potential of Cr(VI) removal from aqueous solution based on the modified NPSi.

Intensive greenhouse vegetable production (GVP) has increased the pollution risk of potentially toxic elements (PTEs) in soils. This study examined the accumulation, sources, and potential ecological risk of six PTEs (Cu, Zn, As, Ni, Pb, and Cr) in soil under two GVP (solar greenhouse (SG) and round-arched plastic greenhouse (RAPG)) systems by portable X-ray fluorescence spectroscopy (pXRF) and conventional laboratory analysis. The results indicated that all PTE concentrations were lower than their corresponding thresholds in GVP soils, presenting a low potential ecological risk in both GVP soils according to risk indices (RI ≤ 40.67). As, Ni, Pb, and Cr were not significantly accumulated in both GVP soils. Although Cu and Zn accumulated in both GVP soils, their accumulation extents in SG soil were both greater than that in RAPG soil. Cu and Zn were mainly originated from anthropogenic activities based on multivariate statistical analysis, which were greatly associated with excessive manure application. Overall, pXRF can identify the accumulation difference of PTEs between the two GVP soils, which is generally consistent with conventional laboratory analysis. Hence, pXRF can be a promising alternative to conventional laboratory analysis for rapid assessment of PTEs accumulation, sources, and the potential ecological risk in the two GVP soils. Although PTEs had a low ecological risk, Cu and Zn accumulation in SG soil was increased with the planting years. Therefore, rational application of livestock manure containing high levels of Cu and Zn should inspire strategies to mitigate the environmental risk in GVP soils, especially in SG soil.

Aquaponics or the integration of aquaculture and hydroponic farming, is a sustainable food production system that is currently popular more as a hobby rather than on commercial scales. Recent increase in scientific and public interest in aquaponics and its environmental benefits supports research that addresses technical, economic, and legislative barriers to wider adoption of these systems. A successful combination of hydroponics with an aquaculture system requires high levels of knowledge and skill that are not necessarily available to all aquaponic practitioners. In this short communication, we analyzed the results of a worldwide survey of commercial aquaponic growers’ statements about their own knowledge base. Most respondents (59%) had some relevant prior knowledge. Surprisingly, many respondents (41%) claimed to have insufficient knowledge of both fish and plants in their first year of operating a commercial aquaponics system. We interpret this as a rough indication that about a third of the new aquaponic businesses are started by entrepreneurs who are not farmers and have no prior training or experience in growing fish or plants. If aquaponics is to become a more widespread commercially viable enterprise and be capable of delivering its environmental benefits, its promotion must consider the importance of prior knowledge held by entrepreneurs entering aquaponics.

Microbial quality of irrigation waters is a substantial food safety factor. Escherichia coli (E. coli) and Enterococci are used as the fecal indicator bacteria (FIB) to assess microbial water quality. Analysis of temporally stable patterns of FIB can facilitate effective monitoring of microbial water quality. The objectives of this study were (1) to investigate the spatiotemporal variation of E. coli and Enterococci concentrations in a large creek traversing diverse land use areas and (2) to explore the presence of temporally stable FIB concentration patterns along the creek. Concentrations of both FIB were measured weekly at five water monitoring locations along the 20-km long creek reach in Pennsylvania at baseflow for three years. The temporal stability was assessed using mean relative deviations of logarithms of FIB concentration from the average across the reach measured at the same time. The Spearman rank correlation coefficients between logarithms of FIB concentrations on consecutive sampling times was another metric used to assess the temporal stability of FIB concentration patterns. Logarithms of FIB concentrations had sinusoidal dependence on time and significantly correlated with temperature at all locations Both FIB exhibited temporal stability of concentrations. The two most downstream locations in urbanized areas tended to have logarithms of concentrations higher than the average along the observation reach. The location in the upstream forested area had mostly lower concentrations (log E. coli 1.59, log Enterococci 1.69) than average (log E. coli 2.07, log Enterococci 2.20). concentrations in colony-forming units (CFU) (100 mL)⁻¹. Two locations in the agricultural and sparsely urbanized area had these logarithm values close to the average. The temporal stability was more pronounced in cold seasons than in warm seasons. No significant difference was found between pattern determined for each of three observation years and for the entire three-year observation period. The Spearman rank correlations between observations on consecutive dates showed moderate to very strong relationships in most cases. Existence of the temporal stability of FIB concentrations in the creek indicates locations that inform about the average logarithm of concentrations or the geometric mean concentrations along the entire observation reach.