• Energy Research

To find an appropriate method for sulfate-rich wastewater containing ethanol and acetate with COD/sulfate ratio of 1, a UASB reactor was operated for more than 180 days. The influences of HRT (hydraulic retention time) and OLR (organic loading rate) on organics and sulfate removal, gas production, and electrons utilization were investigated. The sludge activity and microorganism composition were also determined. The results indicated that this system removed more than 80% of COD and 30% of sulfate with HRT above 6h and OLR below 12.3 gCOD/L d. Further HRT decrease caused volatile fatty acids accumulation and performance deterioration. Except at HRT of 2h, COD and electron flow were mostly utilized by methane-producing archaea (MPA), and methane yield remained in the range of 0.18-0.24 LCH4/gCOD. Methane was mainly generated by Methanosaeta concilii GP6 with acetate as substrate, whereas sulfate was mainly reduced by incomplete-oxidizing Desulfovibrio species with ethanol as substrate.

The characteristics of nitrogen (N) and phosphorus (P) removal were studied during the 2-year operation of a free water surface flow wetland of 900 m2 with hydraulic loading of 0.1 m/d to evaluate its potential to treat water from an urban stream polluted with municipal and industrial wastewater. Attention was focused on the removal of dissolved N and P by harvesting plants (local Phragmites australis and Typha orientalis) at the end of each growing season. According to findings, the removals of N and P increased from 47.1% and 17.6%, respectively, in the 1st year to 52.3% and 32.4%, respectively, in the 2nd year. Increments of N and P removal were largely attributable to plant biomass, which increased from an average dry weight of 1.77 kg/m2 in the 1st year to 3.41 kg/m2 in the 2nd year. The amount of nutrients assimilated by plants in the 2nd year was almost double that of the 1st year. Increasing biomass in the 2nd year also improved redox conditions in the substrate layer, which contributed to increasing the efficiency of N removal. Compared with T. orientalis, P. australis was more competitive and adapted to conditions in the wetland better; it regenerated more vigorously and contributed more to nutrient removal.

Three PAC-DMBRs were developed for wastewater treatment under different PAC dosages with biomass concentrations averaged at 2.5, 3.5 and 5.0g/L. The DMBRs could be continuously operated at 40-100L/m2h, while higher fluxes were obtained within the PAC-DMBRs with hydraulic retention times varying in 4-10h. A dose of 1g/L PAC brought about obvious improvement in the sludge particle size distribution, settling, flocculating and dewatering properties due to the formation of biological PAC, and the sludge properties were further improved at a higher PAC dose (3g/L). The addition of PAC notably shortened the DM formation time after air backwashing and enhanced pollutant removal. Moreover, under a long solid retention time (approximately 150d), the concentrations of both soluble and bound extracellular polymeric substances (EPS) decreased substantially because of the adsorption and biodegradation effects of the biological PAC. No obvious impact on biomass activity was observed with PAC addition.

Water eutrophication may be affected not only by nutrients but also the coexisting organic carbon. In order to reveal the effect of external carbon on algal growth, an experimental study was conducted using Chlorella vulgaris as the representative microalgae to investigate their growth under varied N and P levels with/without added glucose at TOC = 18 mg/L. The TOC consumption by microalgae growth depended much on N and P concentrations and N/P ratio especially when P was sufficient. This ultimately increased the specific growth rate and resulted in higher N and P accumulations but lower carbon fixation in algal biomass in contrast to non-TOC addition. The biomass dry weight became much lower with TOC addition, along with an apparent change of algal composition shown by the much lower chlorophyll contents in the microalgae cells, which might associate the extent of two carbon fixation pathways - anabolism vs catabolism.

Batch experiments were conducted using biochar (BC) to promote stable and efficient methane production from thermophilic co-digestion of food waste (FW) and waste activated sludge (WAS) at feedstock/seed sludge (F/S) ratios of 0.25, 0.75, 1.5, 2.25, and 3. The results showed that the presence of BC dramatically shortened the lag time of methane production and increased the methane production rate with increased organic loading. The higher buffer capacity and large specific surface area of BC promoted microorganism growth and adaption to VFAs accumulation. Additionally, the electron exchange in syntrophic oxidation of butyrate and acetate as intermediate products was significantly facilitated by BC possibly due to the selective succession of bacteria and methanogens which may have participated in direct interspecies electron transfer, in contrast with the control group with low-efficient electron ferried between syntrophic oxidizers and methanogens using hydrogen as the electron carrier.

To tackle current water insecurity concerns, wastewater reclamation and reuse have appeared as a promising candidate to conserve the valuable fresh water sources while increasing the efficiency of material utilization. Climate change, nevertheless, poses both opportunities and threats to the wastewater reclamation industry. Whereas it elevates the social perception on water-related issues and fosters an emerging water-reuse market, climate change simultaneously presents adverse impacts on the water reclamation scheme, either directly or indirectly. These effects were studied fragmentally in separate realms. Hence, this paper aims to link these studies for providing a thorough understanding about the consequences of the climate change on the wastewater reclamation and reuse. It initially summarizes contemporary treatment processes and their reuse purposes before carrying out a systematic analysis of available findings.

There is little understanding of constructed wetlands (CWs) microbial community patterns in response to harvest management. Therefore, long-term impacts of harvesting Phragmites australis (Cav.) Trin. ex Steudel annually in November on the activity and community structure of microorganisms critical to the treatment efficiency of CW are elucidated. Findings show exponential increases in P. australis density and biomass with continuous harvesting, up to three times over unharvested CW. High-throughput pyrosequencing analysis demonstrates that plants harvesting improves the microbial community diversity and richness significantly, and more particularly, the relative abundance of Flavobacterium, Paenisporosarcina, and Povalibacter, which are extensively associated with CW performance. Consequently, increased plants biomass resulted in enhanced plants nutrients uptake in harvested (56.5 g N/m2, 5.5 g P/m2) than unharvested CWs (17.5 g N/m2, 1.8 g P/m2), whereas improved rhizosphere microclimates significantly enhanced nutrients removals in harvested CW (TN 109.9 g/m2 vs 67.4 g/m2, TP 18.0 g/m2 vs 13.0 g/m2).

Abstract In wastewater treatment plants (WWTPs), the majority of energy inputs is consumed by aeration systems to support both the biochemical oxidation of organics and transformation of ammonia-nitrogen into nitrate-nitrogen. Consequently, WWTPs energy efficiency evaluation only based on metrics derived from the organic constituents such as chemical oxygen demand (COD) or biological oxygen demand (BOD) may not reflect the true energy consumption of WWTPs with variable influent quality. Therefore, to overcome this limitation, total oxygen demand (TOD) is introduced in this article, and a novel index EO, namely the energy consumption for the removal of a unit mass of TOD is proposed for evaluating the energy efficiency in WWTPs. Furthermore, by considering the stoichiometric relations of oxygen consumption for the oxidation of both organics and ammonia-nitrogen, methods for calculating the EO are proposed. Using the novel EO index and the available annual operation data of 2022 WWTPs, the current status of energy consumption for wastewater treatment in China were analyzed. The findings show an average EO decrease from 5.2 kWh/kg to 1.2 kWh/kg as the WWTP loading rates increase from 20% to 100%. Also, EO decreased from 4.1 kWh/kg to 1.5 kWh/kg as the average TOD removal increased from 60% to over 90%. Moreover, EO decreased from 2.9 kWh/kg to 1.0 kWh/kg as the WWTP scale increased from less than 10,000 m3/d to over 5,00,000 m3/d. Thus, the energy efficiency of WWTPs increases with increasing loading rates, TOD removal, and scale. Also, the wastewater treatment technology applied influences the EO significantly, especially for small- and medium-size WWTPs with capacities less than 50,000 m3/d which account for circa 76% of all WWTPs in China. The WWTPs applying sequential batch tractors (SBR) tended to show lower average EO (

A feasible approach was developed for the co-production of 5-hydroxymethylfurfural (5-HMF) and furfural from corncob via a new porous polytriphenylamine-SO3H (SPTPA) solid acid catalyst in lactone solvents. XRD, SEM, XPS, N2 adsorption-desorption, elemental analysis, TG-DTA, acid-base titration and FTIR spectroscopy techniques were used to characterize the catalyst. This study demonstrates and optimizes the catalytic performance of SPTPA and solvent selection. SPTPA was found to exhibit superior catalytic ability in γ-valerolactone (GVL). Under the optimum reaction conditions, simultaneously encouraging yields of furfural (73.9%) and 5-HMF (32.3%) were achieved at 448K. The main advantages of this process include reasonable yields of both 5-HMF and furfural in the same reaction system, practical simplicity for the raw biomass utilization, and the use of a safe and environmentally benign solvent.