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This study examines the economic benefits of food waste treatment projects in China and factors affecting them. National-level pilot projects for food waste treatment located in 29 cities were selected as samples. The economics of food waste recycling from the investors’ perspective, in terms of investment during the construction phase and cost and benefit during the operation phase, was assessed. Results indicate that the average tonnage investment of food waste treatment projects was RMB 700.0±188.9 thousand yuan, with a profit to cost ratio of 0.08±0.37. This ratio increased to 0.95±0.57 following the application of government subsidies. It highlights the limited economic benefits of food waste treatment facilities, which rely on government subsidies to maintain their operations in China. Further analysis using a multi-factor analysis model revealed that regional location, service population size, processing technique, and urban income exerted varying impacts on the economy of food waste treatment. Population size exerted the highest impact (P = 0.016) during the construction stage, and processing techniques notably influenced the project economy during the operation stage. The study highlights the need to prioritize service population size and processing techniques during economic decision-making and management of food waste recycling projects. The results of this study can serve as a valuable practical reference for guiding future policies regarding food waste treatment and related planning.

This study examined the environmental impacts and energy consumption of three solid digestate treatment scenarios to quantify their impacts on the entire food waste (FW)-based biogas system: (1) incineration; (2) composting, and; (3) landfill. The results showed that composting had the largest net energy consumption, but least total environmental impact of 57.3 kWh and 8.75 E-03, respectively, whereas landfill showed the opposite pattern. Moreover, there were significant differences (p 0.05) and relatively high contributions between the digestate treatment subunits among the three scenarios. The most significant contributions of digestate subunits in methods 1-3 to the 100-year global warming potential (GWP

Due to global warming, some regions of Earth may face frequent and severe droughts in the future, leading to the deterioration of surface water quality. In this study, we investigated the effects of drought-induced drawdown on the water quality of the Zhoucun Reservoir, Shandong Province, East China, during the fall overturn. Field surveys were conducted during stratification (April–November) over three standard years 2012, 2013, and 2014, and over the El Nino event of 2015. Temporal and vertical variations of the physical and chemical indexes were investigated during monitoring. Results show that after the formation of stratification, the hypolimnion rapidly shifted to anaerobic conditions, with the accumulation of pollutants such as manganese (Mn) and total phosphorous (TP). Due to the extreme El Nino event in 2015, both the upper and lower metalimnion limits moved down along with the water level in summer, which resulted in the transfer of hypolimnion water to the metalimnion. In summer 2015, large amounts of pollutants were measured in the metalimnion: a phenomenon that did not occur at the same period of the standard years. At the beginning of the overturn in 2015, the water quality of the whole reservoir deteriorated when the metalimnion water shifted to the epilimnion. Mn and TP concentrations in the epilimnion reached 0.202 mg/L and 0.086 mg/L, respectively, which are significantly higher than those in the standard years. Although the tributary rivers entered the epilimnion of the reservoir during the overturn, Mn and TP concentrations of the inflow were only of 0.049–0.072 mg/L and 0.033–0.047 mg/L, respectively, indicating that these rivers were not the source of the high TP and high Mn concentrations in the epilimnion. Hence, we conclude that more attention should be paid to the metalimnion position and the vertical distribution of pollutants when studying lakes and reservoirs experiencing droughts.

© 2016 Elsevier Ltd. Indigenous aerobic denitrifiers of a reservoir system were enhanced in situ by water lifting and aeration technology. Nitrogen removal characteristics and changes in the bacterial community were investigated. Results from a 30-day experiment showed that the TN in the enhanced water system decreased from 1.08-2.02 to 0.75-0.91 mg/L and that TN removal rates varied between 21.74% and 52.54% without nitrite accumulation, and TN removal rate of surface sediments reached 41.37 ± 1.55%. The densities of aerobic denitrifiers in the enhanced system increased. Furthermore, the enhanced system showed a clear inhibition of Fe, Mn, and P performances. Community analysis using Miseq showed that diversity was higher in the in situ oxygen enhanced system than in the control system. In addition, the microbial composition was significantly different between systems. It can be concluded that in situ enhancement of indigenous aerobic denitrifiers is very effective in removing nitrogen from water reservoir systems.

In the present work, acute impact of heavy metals on activated sludge was investigated, specifically the release of biopolymers and nitrogenous soluble microbiological products (N-SMP) that significantly impact tertiary effluent quality. Based on the previously reported studies, Hg2+ and Ag+ were selected as representative “non-essential” heavy metals, while Cu2+ was selected as the “essential” heavy metal. Stress tests show that under the present experimental conditions, adding a higher concentration of heavy metals to the activated sludge increases the concentration of biopolymers and SMP in the supernatant; N-SMP increased more significantly than carbonaceous products, implying a greater risk of formation of toxic nitrogenous disinfection by-products or membrane fouling in relevant tertiary treatment processes. The severity of the release of SMP into the supernatant depended on the heavy metal, with an order of Hg2+ > Ag+ > Cu2+ (“non-essential” > “essential”) under identical molar concentrations. The mass balance of typical organics (e.g., biopolymers) in SMP and extracellular polymeric substances (EPS) in activated sludge was analyzed, and a negative correlation between the organics in the SMP and tightly bound EPS was observed, implying that a significant fraction of the SMP could be quickly released from the tightly bound EPS under heavy metal shock conditions and could be related to cell response or damage.

This study investigated the acute impact of heavy metals on activated sludge with respect to the amount properties of biopolymers and other solvable microbiological products (SMPs) released from the sludge. Ten heavy metals were selected for the evaluation. Under the experimental conditions, exposing activated sludge to different metals led to an increase in SMPs, with a more significant increase in nitrogenous organics than in carbonaceous ones, where Hg2+, Ag+, Cu2+, and Cr6+ led to the highest increase in SMP species, while Cd2+, Ni2+, Mn2+, Pb2+, and Co2+ caused limited increase in the middle and small SMP molecules, and Zn2+ and Cr3+ resulted in a decrease in SMP content. To probe the molecular impact of heavy metals and the association between cellular stress and SMP formation, the toxicity of heavy metals was evaluated using a toxicogenomics assay. Based on a correlation analysis between the increase in SMP and the molecular toxicity index-transcriptional effect level index (TELI) of different genes under corresponding stress conditions, eight genes demonstrated a strong correlation with SMP properties and were pre-assumed to have the most significant influence on the increment in SMPs. We further validated the correlation equation established to predict SMP production based on the molecular disturbance of the eight key biomarkers, using arsenic As3+ and vanadium V5+ as tests, and by quantifying the amount of SMPs released from the activated sludge under the influence of these metals using a TELI-derived equation. In addition, the heavy metals that generated greater amounts of reactive oxygen species also caused larger increases in SMPs.

Here, we studied seasonal variation of effluent organic matter (EfOM), based on molecular weight distribution and fluorescent components, during the traditional anaerobic/anoxic/oxic (A2O) wastewater treatment processes. Microbial community structure and effect of temperature on some isolated pure strains were analyzed to explain the related mechanism. Results showed that the anaerobic process played a key role in EfOM removal by removing building blocks, low molecular weight (LMW) neutrals, biopolymers, and protein-related substances (C4 and C5), thus determining the fate of EfOM during the A2O processes. On the other hand, humic substances, LMW neutrals, large molecular-sized hydrophobic humic-like compounds (C3), and aromatic proteins (C4) were generated during the anoxic process in summer and winter. Proteobacteria (Gamma-, Beta-, and Alpha-proteobacteria) and Bacteroidetes constituted over 50% of the sludge community. Temperature was found to be positively correlated with the generation of soluble microbial products (SMP) based on the performance of the mixture of isolated Herbaspirillum sp. (Beta-proteobacteria) and Pseudomonas sp. (Gamma-proteobacteria). Through comprehensive analysis of the co-action of Proteobacteria and temperature, we proposed the Synergetic Effect of Temperature and Proteobacteria as a possible mechanism of the seasonal variation of EfOM. These findings are important for understanding the fate of EfOM during the wastewater treatment processes and therefore be helpful for better EfOM control.

Rainfall-induced nutrient fluctuations in surface water affect phytoplankton communities and cause algal blooms. To examine this influence in the Zhoucun Reservoir, China, field surveys were performed weekly or biweekly from February 2013 (a wet year) to December 2014 (a dry year). Physical conditions, nutrient levels, and phytoplankton functional groups were investigated during monitoring. Nutrient levels increased in the summer of 2013 (TN: 0.85–2.66 mg/L; TP: 0.037–0.138 mg/L), while nitrogen deficiency occurred in the summer of 2014 (TN: 0.38–0.73 mg/L, TP: 0.044–0.079 mg/L). A cyanobacteria bloom that appeared in the summer of 2013 had the dominant phytoplankton functional groups M and Tc. In the summer of 2014, algal cell density and biomass were much lower than those during the corresponding period in 2013, and the co-dominant phytoplankton groups were F, L0, Tc, and S2. Non-N-fixing cyanobacteria were not abundant in summer 2013 probably because of the low ratio of NO3− to NH4+, although nitrogen ...

Denitrification is a major biological process that reduces nitrate to nitrogen gas (N2 or N2O). In shallow eutrophic reservoirs, this process can remove the largest portion of fixed nitrogen and play an important role in the self-purification of this ecosystem. To understand the structure of denitrifying communities in a shallow eutrophic reservoir, NirS-Type and NirK-Type denitrifier communities were explored using a MiSeq high-throughput sequencing technique. NirK and NirS are two functional marker genes for denitrification that encode copper- and cytochrome cd1-containing nitrite reductases, respectively, which catalyze the reduction of nitrite to nitric oxide. MiSeq sequencing revealed a total of 13 102 and 3490 OTUs with 97% similarity for NirS-Type and NirK-Type denitrifiers, which contained 4 and 5 phyla, and 22 and 21 genera for NirS-Type and NirK-Type denitrifiers, respectively. The ACE, Chao diversity, and Shannon richness estimates for NirS-Type denitrifiers were higher than those for NirK-Type denitrifiers. However, the Simpson richness exhibited the opposite trend. The denitrification community structure exhibited significantly seasonal variations during the whole experiment period based on the PCA, Hcluster analysis, OTUs distributions, community composition, and heat map analysis. Meanwhile, the RDA indicated that the total sediment nitrogen, aerobic denitrifiers, functional genes, denitrification rates, and temperature were critical environmental factors influencing the seasonal variation in the bacterial denitrification community.

Sulfides and volatile organic sulfur compounds (VOSc) in water are not only malodorous but also toxic to humans and aquatic organisms. They cause serious deterioration in the ecological environment and pollute drinking water sources. In the present study, a source water reservoir--Zhoucun Reservoir in East China--was selected as the study site. Through a combination of field monitoring and in situ release experiments of sulfides, the characteristics of seasonal variation and distribution of sulfides and VOSc in the reservoir were studied, and the cause of the sulfide pollution was explained. The results show that sulfide pollution was quite severe in August and September 2014 in the Zhoucun Reservoir, with up to 1.59 mg·L(-1) of sulfides in the lower layer water. The main source of sulfides is endogenous pollution. VOSc concentration correlates very well with that of sulfides during the summer, with a peak VOSc concentration of 44.37 μg·L(-1). An installed water-lifting aeration system was shown to directly oxygenate the lower layer water, as well as mix water from the lower and the upper layers. Finally, the principle and results of controlling sulfides and VOSc in reservoirs using water-lifting aerators are clarified. Information about sulfides and VOSc fluctuation and control gained in this study may be applicable to similar reservoirs, and useful in practical water quality improvement and pollution prevention.