Wastewater Treatment Capacity Research Articles

Creating a new polyaniline@oak acorn biocomposite to remove chromium ions from wastewater effectively

A novel biocomposite material, polyaniline@oak acorn (PANI@OA), was synthesized through a straightforward in situ chemical polymerization process. The resulting adsorbent was subjected to a comprehensive analysis using various techniques, including Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), specific surface area measurement (BET), and X-ray photoelectron spectroscopy (XPS). This thorough characterization provided a detailed understanding of the material’s structure and properties. The effectiveness of synthesized material in removing Cr(VI) ions from water was investigated in a controlled batch adsorption setup. The findings highlighted a firm reliance on physicochemical properties during adsorption. The adsorption behavior of Cr(VI) onto PANI@OA fits best with the pseudo-second-order kinetic model and closely follows the Langmuir isothermal mode. The maximum adsorption capacity of this composite material was accurately measured at 249.09 mg.g−1. We also found that PANI@OA can be easily regenerated using a NaOH solution. Thus, allowing it to be used repeatedly to eliminate Cr(VI) from water. These outcomes strongly suggest the practical feasibility of employing PANI@OA as a versatile, low-cost, and environmentally friendly composite for environmental remediation due to its adequate adsorption capacity for wastewater treatment.

Pilot scale application of a hybrid process based on ozone and BAF process: Performance evaluation for livestock wastewater treatment in a real environment

Environmental pollution was generated continuously because of the slack standard of effluent from livestock wastewater treatment even though the specific treatment process was applied. Despite the continuous ecological pollution caused by livestock wastewater effluent, a comprehensive treatment process for livestock wastewater effluent has not been investigated. This study utilized an ozone-biological aerated filter (BAF) hybrid process at a pilot scale (1st ozone–BAF–2nd ozone), with a 1 m3/day capacity for real-livestock wastewater treatment. Compared with each process configuration, the single-ozone process showed effective performance in removing chromaticity, but the removal ratio of suspended solids, organic matter (OM), and trace-organic compounds (TrOCs) was insufficient, even at high ozone concentrations. The ozone–BAF hybrid process improved the removal ratios of suspended solids and biochemical oxygen demand (BOD) by 61.61 and 17.70 %, respectively, due to aeration and filtration by the BAF; however, TrOC removal ratios remained low, at <75 %. The removal ratios of TrOCs of the 1st ozone–2nd ozone hybrid process were better than those of the ozone–BAF hybrid process (by 28.2–77.9 %) owing to enhanced oxidation from increased ozone exposure to livestock wastewater. Nevertheless, the removal ratios of suspended solids and BOD were below 40 %. Owing to the complementarity between the BAF and 2nd ozone process, the removal ratios of chromaticity, suspended solids, and TrOCs reached 98, 95, and 92 %, respectively, by the optimized 1st ozone–BAF–2nd ozone hybrid process. Our results highlight the necessity of developing a new hybrid process based on ozone and BAF for treating livestock wastewater, and provide guidelines for livestock wastewater treatment.

Preparation of a novel lactose-lignin hydrogel catalyst with self-reduction capacity for nitrogenous wastewater treatment

Preparation of a novel lactose-lignin hydrogel catalyst with self-reduction capacity for nitrogenous wastewater treatment

Rising groundwater levels in Dare County, North Carolina: implications for onsite wastewater management for coastal communities

ABSTRACT Onsite wastewater treatment systems (OWTS) are a common wastewater treatment approach in coastal communities. Vertical separation distance (VSD) requirements between the drainfield and groundwater aim to ensure aerated soils for wastewater treatment. When the VSD declines, OWTS can fail. This study evaluated groundwater response to sea level rise (SLR) and the implications for OWTS. A groundwater monitoring network (13 wells) was used to evaluate groundwater depth in Dare County, North Carolina. Groundwater levels were measured with water level meters and pressure transducers. Trends in groundwater depth and SLR were analyzed to evaluate the influence of SLR on groundwater depth. From 1984–2022, mean groundwater levels have risen (∼7.6 mm/year) in response to SLR. Currently, sites at &amp;lt;2.7 m land elevation are most likely to have groundwater depths &amp;lt;1 m and inadequate VSD. Based on current precipitation and NOAA intermediate SLR projections, groundwater depth projections suggest that OWTS at lower elevations are more likely to experience groundwater inundation by 2040–2060. SLR has resulted in reduced VSD causing diminished wastewater treatment capacity in low-lying areas. OWTS VSD requirements are typically static due to regulatory constraints. Future management approaches should consider adapting to rising coastal groundwater levels because of increasing wastewater contamination risks.

Simulation and Experimental Study of Circulatory Flash Evaporation System for High-Salt Wastewater Treatment

Treatment methods for high-salt wastewater mainly consist of physical methods, chemical methods and biological methods. However, there are some problems, such as slow treatment speed, high investment costs and low treatment efficiency. To address NaCl solutions, in this study, a circulatory flash system was designed based on gas–liquid equilibrium, mass conservation equation and energy conservation equation. A circulatory flash evaporation simulation and a static flash evaporation experiment were conducted on NaCl solutions under various operating conditions to investigate the effects of heating temperature, flash pressure and initial NaCl concentration on the circulatory flash evaporation system. The significance of each factor’s influence on the evaporation fraction and energy consumption was examined through static flash experiments. The simulation results demonstrated that increasing the heating temperature, decreasing the flash pressure and having a higher initial NaCl concentration could enhance the treatment capacity of high-salt wastewater. The flow rate of vapor outlets increased with higher heating temperature but decreased as the flash pressure rose. The experimental results demonstrated that flash evaporation pressure was the primary factor influencing both the evaporation fraction and the energy consumption per unit mass of vapor produced. It was observed that with an increase in heating temperature, the flash pressure decreased and there was a corresponding decrease in energy consumption per unit mass of vapor produced. The optimal experimental conditions were achieved at a heating temperature of 99 °C, a flash pressure of 15 kPa, and an initial NaCl concentration of 20%.

Biological nitrogen removal characteristics and mechanisms of a novel salt-tolerant strain Vibrio sp. LV-Q1 and its application capacity for high-salinity nitrogen-containing wastewater treatment

High concentration of salts in wastewater can adversely affects the metabolic activities and growth of microorganisms, resulting in reduced efficiency of biological nitrogen removal. Screening high-efficiency heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria with salt tolerance is important for the wastewater treatment. In this study, a novel salt-tolerant strain LV-Q1 capable of HN-AD was isolated and identified as Vibrio sp. This strain demonstrates a salinity tolerance range of 0–8 %. Notably, strain LV-Q1 exhibited exceptional nitrogen removal efficiencies (at initial concentrations of 100 mg/L), achieving 97.97 % for NH4+-N, 100 % for NO3--N, and approximately 100 % for mixed nitrogen (NH4+-N and NO3--N) at a salinity of 5 %. Optimal ammonium removal parameters for LV-Q1 were established. The nitrogen removal pathway of LV-Q1 primarily involves direct assimilation of ammonium and its conversion into N2 through HN-AD. Analysis of the salt tolerance mechanism revealed LV-Q1's ability to equilibrate osmotic pressure through the accumulation of amino acids and betaine, production of antioxidative enzymes or extracellular protein, and utilization of its quorum sensing (QS) properties to withstand high-salinity environments. The strain LV-Q1 exhibited strong resistance to salinity shock in bioaugmentation within a moving bed biofilm reactor (MBBR), markedly enhancing nitrogen and carbon removal performance with an improved removal efficiency of 26.74 % and 10.15 % averagely at the end of the reaction at a salinity of 5 %. Moreover, Vibrio sp. LV-Q1 successfully proliferated and dominated, and its relative abundance gradually increased to 59.81 %. This study contributes new insights and resources for the treatment of nitrogen in saline effluents.

Insights into the occurrence, spatial distribution, and ecological implications of organophosphate triesters in surface sediments from polluted urban rivers across China

Organophosphate triesters (tri-OPEs) are a kind of widespread contaminants in the world, particularly in China, which is a major producer and user of tri-OPEs. However, tri-OPE pollution in urban river sediments in China remains unclear. In current work, we carried out the first nationwide investigation to comprehensively monitor 10 conventional and five emerging tri-OPEs in sediments of 173 black-odorous urban rivers throughout China. Concentrations of 10 conventional and five emerging tri-OPEs were 3.8–1240 ng/g dw (mean: 253 ng/g dw) and 0.21–1107 ng/g dw (68 ng/g dw), respectively, and significantly differed among the cities sampled but generally decreased from Northeast and East China to Central and West China. These spatial patterns suggest that tri-OPE pollution was mainly from local sources and was controlled by the industrial and economic development levels in these four areas, as indicated by the significant correlations between tri-OPE concentrations and gross domestic production, gross industrial output, and daily wastewater treatment capacity. Although the tri-OPE composition varied spatially at different sites, which indicated different tri-OPE input patterns, it was commonly dominated by tris(2-chloroethyl) phosphate, tris(2-ethylhexyl) phosphate, and tris(1-chloro-2-propyl) phosphate (conventional tri-OPEs) and bisphenol A-bis(diphenyl phosphate) and isodecyl diphenyl phosphate (emerging tri-OPEs). A risk assessment indicated that tri-OPEs in most sampling sediments had a low to moderate risk to aquatic organisms.

The effectiveness of using coconut husk powder as an adsorbent to enhance the wastewater quality of the cepuk textile industry in Nusa Penida, Bali, Indonesia

Introduction: Tenun Cepuk (traditional woven) from Nusa Penida holds great potential as a traditional textile art form, cherished for its intricate patterns and cultural significance. However, the textile industry's wastewater, with its dye-related pollution, presents a significant environmental challenge that needs sustainable solutions. Coconut husk powder exhibits promising potential as an adsorbent for treating dye wastewater from the textile industry. Investigating the interplay between varying thicknesses and contact durations is crucial to maximizing coconut husk powder's adsorption capacity and efficiency for dye wastewater treatment. Method: This study, following an Experimental research design with a Posttest Only Control Group Design, aims to assess the impact of an intervention on the experimental group compared to the control group. Coconut fibers, sourced from Nusa Penida agriculture, serve as the adsorbent. Coconut powder is added to these tanks at thicknesses of 5 cm, 10 cm, and 15 cm. Subsequently, wastewater samples from the Cepuk weaving process are introduced into each experimental tank, along with a control group. The process is left for 24 and 72 hours as varying contact times. The adsorption results are subjected to analysis for parameters, including total suspended solids (TSS), total dissolved solids (TDS), five-day biochemical oxygen demand (BOD5), and chemical oxygen demand (COD) at the Panureksa Denpasar Laboratory. Results: The use of coconut husk powder as an adsorbent effectively lowers TDS, TSS, BOD5, and COD in Cepuk textile dye wastewater. The reduction depends on adsorbent thickness and contact time. Thicker adsorbents notably reduce TDS, TSS, BOD5, and COD, enhancing wastewater quality and environmental safety. A 15 cm-thick adsorbent effectively reduces TDS to permissible levels. Prolonged contact times also significantly lower levels. Conclusion: Coconut husk powder can be utilized to decrease TDS, TSS, BOD5, and COD levels in textile dye wastewater. Thickness and contact time significantly impact the enhancement of wastewater quality.

Constructing mesoporous biochar derived from waste carton: Improving multi-site adsorption of dye wastewater and investigating mechanism

The development of cost-efficient biochar adsorbent with a simple preparation method is essential to constructing efficient wastewater treatment system. Here, a low-cost waste carton biochar (WCB) prepared by a simple two-step carbonization was applied in efficiently removing Rhodamine B (RhB) in aqueous environment. The maximum ability of WCB for RhB adsorption was 222 mg/g, 6 and 10 times higher than both of rice straw biochar (RSB) and broadbean shell biochar (BSB), respectively. It was mainly ascribed to the mesopore structure (3.0–20.4 nm) of WCB possessing more spatial sites compared to RSB (2.2 nm) and BSB (2.4 nm) for RhB (1.4 nm✕1.1 nm✕0.6 nm) adsorption. Furthermore, external mass transfer (EMT) controlled mass transfer resistance (MTR) of the RhB sorption process by WCB which was fitted with the Langmuir model well. Meanwhile, the adsorption process was dominated by physisorption through van der Waals forces and π-π interactions. A mixture of three dyes in river water was well removed by using WCB. This work provides a straightforward method of preparing mesoporous biochar derived from waste carton with high-adsorption capacity for dye wastewater treatment.

Dynamic-chance-constrained-based Fuzzy Programming Approach for Optimizing Wastewater Facultative Ponds for Multi-period Case

In this article, a novel optimization model that was specifically designed as a dynamic-chance-constrained fuzzy uncertain programming framework is introduced. This model serves the purpose of optimizing the efficiency of facultative ponds utilized in domestic wastewater treatment. The primary focus of this study was maximizing the amount of the wastewater treated in the facility subject to quality requirements via the assessment of wastewater quality through the measurement of Biological Oxygen Demand (BOD). The model's development was grounded in a real-world scenario, where decision-makers encountered uncertainties in various parameters, such as the rate of BOD degradation and the incoming wastewater load, both characterized by fuzzy membership functions. In light of this uncertainty, the decision-maker aimed to maximize the wastewater treatment capacity while maintaining a suitable safety margin for both objective and constraint functions, employing policies founded on probability and chance. A case study was carried out at the Bantul domestic wastewater treatment plant, situated in Yogyakarta, Indonesia. The study successfully identified optimal decisions regarding wastewater flow rates and processing times. As a result, it can be concluded that the proposed model effectively resolved the problem at hand, making it a valuable tool for decision-makers in similar contexts.

Sustainable agricultural management: How to achieve carbon neutrality in agriculture – evidence from China agricultural sustainable development plan

AbstractAgricultural sustainable development is of significant importance for achieving food security, environmental protection, climate change adaptation, natural resource conservation, and economic development. We conducted a study using the 2015 China Agricultural Sustainable Development Plan (ASDP) as a natural experiment and employed the Difference‐in‐Differences (DID) model to estimate the impact of ASDP on agricultural carbon neutrality. Path analysis and heterogeneity analysis were also performed. The results of this study are as follows: First, ASDP promotes agricultural carbon neutrality. Second, increasing per capita agricultural machinery usage, agricultural labor efficiency, livestock manure management, wastewater and waste treatment capacity, toilet coverage rate, greening efforts, and reducing pesticide usage are potential pathways of ASDP. Third, the analysis of carbon emission types indicates that current ASDP mainly focuses on carbon emissions from traditional agricultural practices, with limited impact on carbon emissions associated with modern agricultural activities, such as diesel fuel and pesticides. Lastly, the heterogeneity analysis of agricultural regions demonstrates that ASDP has a more positive impact on grain, oil, fruit and vegetable low‐producing areas, cotton high‐producing areas, and poultry, meat, eggs and milk aquaculture high‐producing areas. This study estimates the carbon reduction effect of ASDP and provides new policy recommendations and reform directions for agricultural sustainable development in China and other developing countries.

A pilot study of situ sludge fermentation-driven multiple biological nitrogen removal pathways (SFBNR): Revealing microbial synergy mechanism based on co-occurrence network analysis

The sludge fermentation-driven biological nitrogen removal (SFBNR) has garnered increasing attention due to its efficient carbon resource utilization from waste activated sludge (WAS). This study successfully extended the application of this technique to a 38 m3 reactor, facilitating a daily ultra-low carbon to nitrogen ratio (<1) wastewater treatment capacity of 16 tons and a WAS capacity of 500 L. After 185-days operation, the system demonstrated commendable performance with a denitrification efficiency (DNE) of 93.22 % and a sludge reduction efficiency (SRE) of 72.07 %. To better understand the potential mechanisms, various functional bacteria interactions were revealed by co-occurrence network analysis. The results unveiled module hubs (e.g., Anaerolineaceae, Denitratisoma, and Candidatus Brocadia) and connectors (e.g., Tuaera and Candidatus Alysiosphaera) in the network exhibited synergistic relationships facilitated by carbon metabolism and nitrogen cycling. Furthermore, the interaction between biofilm sludge (BS) and suspended sludge (SS) contributed to the in-situ enrichment of anaerobic ammonium oxidizing bacteria (AnAOB), whose abundance in BS reached 1.8 % (200-times higher than in SS) after six months, and the suspend-biofilm interface served as a hotspot for anammox activity.

Spatial distribution, conversion, and ecological risk assessment of hexabromocyclododecanes in the sediments of black-odorous urban rivers nationwide in China

Hexabromocyclododecanes (HBCDs) have become a global pollution problem, particularly in China—a major producer and user of HBCDs. However, little is known about the HBCD pollution status in urban rivers nationwide in China. In this study, we comprehensively investigated the pollution characteristics of HBCDs in 173 sediment samples from black-odorous urban rivers across China. Total HBCD concentrations ranged from not-detected to 848 ng/g dw, showing significant differences among the various sampling cities, but generally increasing from west to east China. This distribution pattern of HBCDs was strongly associated with the local industrial output, gross domestic product, and daily wastewater treatment capacity. α-HBCD was the predominant diastereoisomer in most sediments, with an average proportion of 63.8 ± 18.8 %, followed by γ-HBCD (23.8 ± 19.5 %) and β-HBCD (12.4 ± 6.49 %), showing a significant increase of the α-HBCD proportions relative to those in HBCD commercial mixtures and an opposite trend for that of γ-HBCD. These results suggested that HBCDs might undergo isomerization from γ- to α-HBCD and biotic/abiotic degradation with preference for γ-HBCD. Of these conversions, the microbial degradation of HBCDs was further verified by the preferential transformation of (−)-α-, (+)-β-, and (−)-γ-HBCDs and the detection of HBCD-degrading bacteria, including Dehalococcoides, Bacillus, Sphingobium, and Pseudomonas. A risk assessment indicated that HBCDs pose low to moderate risks to aquatic organisms in most black-odorous urban river sediments.

Study on H2SO4-modified corn straw biochar as substrate material of constructed wetland.

The high value resource utilization of corn straw is a long-term problem at present and in the future. Biochar preparation is an important utilization way of corn straw. The research on city tail water treated by constructed wetland (CW) with biochar was carried out to further increase the wastewater treatment capacity of the CW. Surface characterization, structural characteristics, and adsorption of straw biochar modified by different acids were measured. The study found that the ability of H2SO4 to remove ash from biochar was stronger than other acids and H2SO4-biochar was easy to be cleaned without H2SO4 residue. The performance of biochar modified by H2SO4 was obviously better than other acids, and the biochar adsorption was enhanced. The modification of biochar substrate modified by H2SO4 in CW reduced the change of electrical conductivity (EC) and promoted denitrification. H2SO4-modified biochar promoted the absorption of N and P by Iris pseudacorus L. The compound modification effect of straw biochar was obvious. The results revealed the acid modification characteristics of straw biochar, which were beneficial for increasing the wastewater treatment rate by CW. This study will promote the sustainable development of CW.

Strengthen high-loading operation of wastewater treatment plants by composite micron powder carrier: Microscale control of carbon, nitrogen, and sulfur metabolic pathways

The concentration of activated sludge is a crucial factor influencing the capacity and efficiency of sewage wastewater treatment plants (WWTPs). However, high sludge concentrations can lead to sludge loss in the secondary sedimentation tank, resulting in reduced processing capacity, particularly during low-temperature stages and sludge bulking. This study investigated the impact of adding composite micron powder carriers (CMPC) in high-concentration powder carrier biofluidized bed (HPB) technology to the biochemical units of WWTPs on sludge concentration and settling performance. For the traditional activated sludge method (ASM), its hydraulic retention time (HRT) was 8 h, with an average effluent total nitrogen (TN) of 15.14 mg/L. Sludge bulking was prone to occur in low-temperature environments, resulting in a high average sludge volume index (SVI) of 560 mL/g. Conversely, with a CMPC dosage of 4 g/L, the HRT of HPB technology was 4.8 h, and the average effluent TN was 11.40 mg/L, with a removal efficiency of 67.43 %. During operation of HPB technology under high sludge concentration conditions (8 g/L), the average SVI remained at 85 mL/g, indicating excellent settling characteristics. Moreover, in the sequencing batch reactor (SBR), the SVI value of bulking sludge decreased from the original 695 to 111 mL/g by the 9th day of operation with the CMPC dosage of 2 g/L. At the same time, the filamentous bacteria almost disappeared, suggesting that CMPC inhibit the growth of filamentous bacteria. Metagenomic analysis demonstrated that CPMC enhance the utilization of small molecular fatty acids in activated sludge and promote electron transfer between nitrate and nitrite, thereby improving wastewater treatment capacity. Additionally, CMPC enhanced the relative abundance of Saprospiraceae in sludge, which accelerate the degradation of polysaccharides in extracellular polymeric substances, weaken sludge's hydrophilic properties, and improve sludge's settling performance. Overall, these findings suggested that CMPC effectively strengthen the high-loading operation of WWTPs by improving sludge concentration and sedimentation performance.

Assessment of hybrid fixed and moving bed biofilm applications for wastewater treatment capacity increase – In situ tests in El-Gouna WWTP, Egypt

This paper provides a procedure for comparing the performance of different biofilm carrier medias and their surrounding suspended biomass through oxygen uptake rate (OUR) tests. For in situ (oxygen uptake rate (OUR) measurements, three identical lab scale biofilm reactors were set up at the El Gouna wastewater treatment plant (WWTP). In this setup, two options of media for moving-bed biofilm reactors (MBBR) and one media for fixed-bed biofilm reactors (FBBR) were compared. The WWTP also used the same carrier in a real scale hybrid application to analyze how the interactions between the carrier type and the suspended biomass influences the overall performance. The in situ OUR approach is recommended to measure the contribution of the biofilm fixed biomass under site specific conditions. Specifically, settleability and diffusion limitations are the two opposite poles that cannot be predicted adequately for mild climate conditions based on the literature. A biofilm carrier application can add but actually can also reduce the capacity in a hybrid activated sludge system: The added MBBR-media was able to grind down the sludge flocs forming a poorly settleable suspended biomass. The added FBBR-media can lead to extracellular polymeric substances (EPS) rich biofilms that contribute very little as substrate and oxygen are unavailable for the microorganisms present in the biofilm. In this application of the comparison procedure, Kaldnes K1 like MBBR media was compared with a recycling MBBR carrier option (poly propylene bottle caps) and Jäger Envirotech “BioCurlz™” FBBR media. The study showed higher average rates for the MBBR but decreased settleability. The FBBR showed higher peak rates when flushed to break up the biofilm and well settleable sludge. The determination of OUR per g of volatile solids (SOUR) showed comparable results for all the carriers and in warm conditions, only the capacity to accommodate biomass determines the contribution of the carrier.

China’s Outward Foreign Direct Investment and the Environmental Performance of the “Belt and Road Initiative” Countries

Since the launch of the “Belt and Road Initiative” (BRI) in 2013, China’s outward foreign direct investment (OFDI) has grown rapidly. Moreover, the environmental protection issues introduced by these investment behaviors to BRI countries have attracted widespread attention from the international community. With the unbalanced panel data of 66 BRI countries from 2006 to 2020, this paper studied the impacts of China’s OFDI on the environmental performance of BRI countries from a systemic and partial perspective. We found that from a systemic perspective, China’s OFDI is conducive to the improvement of the comprehensive environmental performance of countries along the “Belt and Road”. From a partial perspective, the environmental performance influences of China’s OFDI in countries along the “Belt and Road” are threefold: (1) China’s OFDI can help mitigate climate change; (2) China’s OFDI improves wastewater treatment capacity; and (3) China’s OFDI has no significant impact on air quality. Therefore, China’s OFDI needs to continue its efforts to promote and improve the environmental performance of BRI countries to achieve their sustainable development goals. Some BRI developing countries should gradually change their extensive economic growth models; reduce their share of high energy-consuming, high-pollution, and inefficient industries in the national economy; and expand the proportion of their environmentally friendly industries while refraining from improving environmental performance by imposing high environmental pollution taxes.

Influence of nitrogen sources on wastewater treatment performance by filamentous algae in constructed wetland system

Although filamentous algae have the characteristics of high nutrient assimilation ability, and adaptation to different conditions, studies on their role in water purification of constructed wetlands (CWs) are limited. In this study, the wastewater treatment capacity under different nitrogen sources was explored by constructing a filamentous algal CW (FACW) system. Results confirmed the fast and stable operation efficiency of the FACW system. Ammonia nitrogen was preferred in Cladophora sp. absorption and assimilation. The nutrient consumption rate (NCR) for total nitrogen (TN) of AG was 2.65 mg g−1 d−1, much higher than that of nitrate nitrogen (NG) (0.89 mg g−1 d−1). The symbiosis of bacteria and Cladophora sp. Contributed to pollutant removal. A stable and diverse community of microorganisms was found on Cladophora sp. Surface, which revealed different phylogenetic relationships and functional bacterial proportions with those attached on sediment surface. In addition, temperature and light intensity have great influence on the purification ability of plants, and low hydraulic retention time is beneficial to the cost-effective operation of the system. This study provides a method to expand the utilization of wetland plants and apply large filamentous algae to the purification of wetland water quality.

Design and operation insights concerning a pilot-scale S0-driven autotrophic denitrification packed-bed process

Elemental sulfur autotrophic denitrification (S0AD) is viewed as a promising alternative to conventional heterotrophic denitrification due to lower running costs, zero carbon dioxide emission, and minimum excess sludge production. However, its scale-up capability and robustness in treating real-life wastewater have not been convincedly demonstrated. In this study, a pilot-scale S0AD packed-bed with over 1000 m3/d of actual wastewater treatment capacity was operated for 197 days. The S0AD packed-bed could effectively remove nitrate to below 12 mg-NO3−-N/L that is 20% stricter than China’s national standard (15 mg-TN/L). The temperature effect coefficient Q10 was calculated as 1.01, illustrating that denitrification efficiency could be doubled when the temperature increased every 10 °C. Mass balance calculations indicated that 85% of removed nitrate was contributed by S0AD process, and the rest 15% was by heterotrophic and assimilative processes. A total of 2684 kg sulfur was consumed during the course of the experiment which was attributed to 16.1% DO oxidation and 83.9% denitrification. Nitrogen gas produced through denitrification, could be trapped in the S0 packed-bed that was the primary causality of clogging. Daily gas venting instead of conventional back washing, could effectively recover the packed-bed flux and promote denitrification efficiency. In addition, a weekly thorough back washing was deemed necessary to deeply clean the trapped SS and sloughed overgrowing biofilm. The predominant S0AD bacteria belonged to the genus Thiobacillus, was enriched throughout the packed-bed providing robust and stable denitrification. Overall, we provided some guidance to the design and operation of S0AD packed bed in practical engineering.

Electro-Fenton process with scalable modified carbonaceous electrode material processed by direct calcination for refractory organic pollutant degradation

Electro-Fenton (EF) regarded as a green substitution to traditional homogeneous Fenton, produces highly oxidizing OH through in-situ H2O2 electrosynthesis and electrochemical Fe2+ regeneration. One of obstacles that hinders translation of bench-scale EF performance to water treatment practices is the difficulty of scaling up catalyst/electrode preparation in low cost while producing high performance. Here we report scalable preparation of modified carbon catalysts for high-efficiency EF by directly calcinating commercial carbonaceous materials in air. The EF with modified carbon cathode shows high kinetics of 0.296–0.569 min−1 for levofloxacin removal in much wider pH range of 3.0–6.6 using less Fe dosage compared with homogeneous Fenton. This EF system can reduce chemical oxygen demand (COD) of coking wastewater from 312.0 to 99.5 mg L−1 to satisfy wastewater discharge standard in China while consuming low electricity of 1.8–4.9 kWh kg−1 COD−1. We demonstrated the scalability of this EF process by scaling up preparative throughput of catalyst (30 g that can be processed into electrodes with total working areas of 54000 cm2), enlarging electrode size (230 cm−2) and reactor volume with wastewater treatment capacity of 7.2 L/h. This scalability demonstration of EF technology shows the promising potential of achieving low-cost advanced wastewater treatment.