Search Results (16)

Excessive phosphorus discharge from fertilizers and detergents has caused severe eutrophication in water bodies, necessitating the upgrading of efficient and cost-effective adsorbents for phosphorus removal. In this study, a novel lanthanum and extracellular polymeric substance (EPS) coprecipitation-modified ceramic (La-EPS-C-450) was developed to address the limitations of existing adsorbents. The ceramic filler served as a robust and scalable matrix for lanthanum loading, while EPS introduced functional groups and carbonate components that enhanced adsorption efficiency. The prepared adsorbent manifested a maximum phosphorus adsorption capacity of 83.5 mg P/g-La at 25 °C, with its performance well expressed by the Freundlich isotherm model, indicating that it was a multilayer adsorption process. The adsorption mechanism was driven by electrostatic attraction and ligand exchange between lanthanum and phosphate ions, forming inner-sphere complexes. The material demonstrated unfluctuating‌ performance across a pH range of 3–7 and retained high selectivity in the presence of competing anions. In practical applications, La-EPS-C-450 effectively removed phosphorus from actual river water, achieving a treatment capacity of 1800 bed volumes in a continuous-flow fixed column system. This work provides valuable insights into the progress of advanced ceramic-based adsorbents and demonstrates the potential of La-EPS-C-450 as a cost-efficient and effective material for phosphorus removal in water treatment applications. Full article

An ecological buffer zone system was designed using three different fillers (ceramsite, anthracite, and zeolite) and plants (Pennisetum hybridum, Canna, and Lythrum virgatum, 1:1:1) to explore the treatment efficiency and mechanisms for initial stormwater runoff. The effluent concentrations of COD, total nitrogen, ammonia nitrogen, and total phosphorus were tested. The removal efficiencies of various pollutants and an analysis of the microbial community on the surface of the fillers were used to determine the optimal combination of fillers and explore their influence mechanisms on the treatment of initial stormwater runoff by the ecological buffer zone. The results showed that when using the plant combination of Pennisetum hybridum, Canna, and Lythrum virgatum (1:1:1), zeolite and ceramsite performed better in nitrogen removal. The removal rates of total nitrogen and ammonium nitrogen using zeolite were 96.79% and 92.77%, respectively, while the removal rates for ceramsite were 93.76% and 91.49%. On the other hand, ceramsite was more effective in removing total phosphorus and COD, with removal rates of 83.64% and 71.67%, respectively. Based on the comprehensive research findings, the recommended filler combination for the ecological buffer zone was a mixture of zeolite and ceramsite. Full article

The pollution of urban landscape water bodies presents significant challenges. This study developed mass-produced nitrogen (N) and phosphorus (P) removal fillers for the integrated landscape water purification (ILWP) device, comprising an inlet, aeration, and N and P removal unit. The fillers were used to purify actual landscape water bodies. Indoor test results demonstrated that the substrates exhibited high and stable removal efficiencies for NO₃⁻-N (>60.5%), TN (>60.1%), and TP (>66.5%) under varying hydraulic retention times (HRT) (1~4 h), pH (5~9) and pollutant concentrations. After one year of operation in Meihu Lake, the ILWP device achieved NO₃⁻-N removal rates of 55.5–68.1% (average 61.3%), TN removal rates of 55.2–67.8% (average 60.9%) for, and TP removal rates of 37.7–66.3% (average 53.0%). Notably, N removal was higher in spring and summer, while P removal was more efficient in autumn and winter. The ILWP device successfully improved the N and P levels of the effluent of the landscape lake from below Class V to Class IV or Class III surface water standards. Additionally, the effluent showed reduced chlorophyll a content and significantly improved transparency. Microbial tests revealed that the fillers promoted the growth of key microorganisms like Pseudomonas and Acetoanaerium, supporting the long-term removal of pollutants. Full article

An adaptable, low-cost, and easy-to-operate biological treatment system for pollutant abatement in aquaculture water at the field pond scale needs to be developed. In this study, the pollutant removal capacity of a stable bioreactor for aquaculture wastewater was assessed, and the related mechanism was elucidated via an analysis of the microbial community’s characteristics and functions. The average removal efficiencies of chemical oxygen demand, suspended solids, total nitrogen, and total phosphorus were 40%, 86.22%, 38.62%, and 53.74%, respectively. The effluent quality meets the Requirement for Water Discharge from Freshwater Aquaculture Pond, SC/T9101-2007. The results indicate that the fillers under anaerobic conditions could attract Denitratisoma and unclassified_Rhodocyclaceae, promoting the denitrification reaction. This aligns with the characteristic that total nitrogen in aquaculture sewage mainly exists in the form of nitrate nitrogen. An anaerobic atmosphere helps degrade organic contaminants at liquid interfaces and remove nitrogen in the solid phase. The fillers under anaerobic conditions could attract Bacteroidota and promote the production of polysaccharides to form biofilms, which may be associated with phosphorus removal. The results indicate that the anaerobic stage can promote the formation of biofilm on the fillers to remove pollutants, thus achieving higher aquaculture sewage treatment efficiency. Full article

Biological trickling filtration (BTF) has the advantages of simple operation, low energy consumption, and low sludge production, and its application in the treatment of domestic wastewater in rural areas has been widely discussed. In this study, ceramic granule (R1), zeolite (R2), and sponge (R3), three typical nitrogen and phosphorus removal fillers, were selected to investigate the differences in the removal performance of COD, nitrogen, and phosphorus in BTF, analyze the characteristics of the fillers and biofilm, and determine the performance of simultaneous nitrogen and phosphorus removal. The results show that among the three fillers, zeolite has the larger specific surface area and roughness and has the best treatment effect on the adhesion performance of sewage and biofilm. The richness and diversity of the microbial community are higher, and the system is more stable, with a COD removal rate of 77.10 ± 8.67% and an NH₄⁺-N removal rate of 75.20 ± 6.64%. The TP removal rate was 22.04 ± 10.27%. The surface of ceramic particles showed a regular cluster structure with a loose distribution. The removal rate of COD was 78.49 ± 6.92%, the concentration of NH₄⁺-N in the effluent was 27.95 ± 8.23 mg/L, and the removal rate of TP was 38.83 ± 12.14%. As a polymer composite material, the sponge has large internal pores and a smooth surface, which is not conducive to biofilm adhesion. Therefore, the removal rate of nitrogen and phosphorus in sewage is poor; the removal rate of COD is 75.94 ± 6.98%, NH₄⁺-N is 27.89 ± 21.06%, and the removal rate of TP is 14.07 ± 11.76%. Compared with the metabolic function of genes, zeolites have a more stable enzyme digestion ability than the other two fillers, and the genes related to the nitrification process (amo, hao, nxr, etc.) and functional genes encoding key enzymes related to the TCA cycle are relatively abundant. Full article

In order to investigate the enhancement mechanism of modified three-dimensional elastic filler (MTEF) on the nitrogen removal performance of the integrated fixed-film activated sludge (IFAS) process, and to clarify the interactions between competition and synergy between activated sludge and biofilm in the IFAS system, an IFAS reactor (T2) filled with MTEF was employed for the study, while a sequencing batch reactor activated sludge process (SBR) reactor (T1) was utilized for comparison. IFAS and SBR reactors were operated over an extended period at ambient temperature to assess the enhancement of pollutant removal performance with the addition of the filler to investigate the competitive dynamics between activated sludge and biofilm under varying influent water qualities (C/N, N/P, and organic loading), and to analyze the synergistic relationship between activated sludge and biofilm at the microbial level using high-throughput sequencing technology. The results demonstrate that throughout the entire operational phase, reactor T2 exhibited superior pollutant removal efficiency. Compared to reactor T1, reactor T2 achieved an average increase in the removal rates of COD, ammonia nitrogen, and total nitrogen by 13.07%, 12.26%, and 28.96%, respectively. The findings on the competitive dynamics between activated sludge and biofilm indicate that the nitrification volumetric load of the IFAS system is significantly higher than that of a pure activated sludge system, suggesting that the IFAS system possesses enhanced nitrification capabilities. Furthermore, when dealing with wastewater characterized by low C/N ratios and high phosphorus pollution, or under substantial organic loads, the biofilm holds a competitive edge and the IFAS system exhibits improved stability. High-throughput sequencing data reveal that the microbial community structures in activated sludge and biofilm can influence each other, thereby enabling the IFAS system to effectively enrich denitrification-related functional microbial populations. Additionally, the biofilm has a certain enhancing effect on the expression levels of nitrogen metabolism-related functional genes in the activated sludge phase microorganisms, indicating that, in addition to competitive interactions, there is also a synergistic effect between the biofilm and activated sludge. Full article

In recent years, the phenomenon of black–odorous water has occurred frequently, and constructed wetlands have been widely used as an effective means of treating black–odorous water. In order to achieve the goal of low-carbon and high-efficiency long-term clean-up of black–odorous water, the modular constructed wetland system was optimized in this study. The optimized modular constructed wetland consisted of aeration, denitrification, and phosphorus removal, of which the denitrification module was a sulfur–iron autotrophic denitrification unit and the phosphorus removal module was a polyaluminum chloride composite filler phosphorus-removal unit. Experimental findings indicated that modular systems with layout ratios of 1:3:1 (A) and 1:2:2 (B) exhibit outstanding performance in remediating contaminants from black–odorous water. Notably, system B demonstrated superior treatment efficiency. Under conditions of high pollution loading, system B consistently achieved stable removal rates for COD (95.79%), TN (91.74%), NH₄⁺-N (95.17%), and TP (82.21%). The combination of along-track changes and high-throughput sequencing results showed that the synergies among the units did not produce negative effects during the purification process, and each unit realized its predefined function. Changes in the substrate and internal environment of the wetland units caused changes in the microbial populations, and the unique microbial community structure of the units ensured that they were effective in removing different pollutants. Full article

Ecological floating beds, with their compact footprint and mobility, offer a promising solution for sustainable surface water remediation in rural areas. However, low removal efficiency and instability still limit its application. In this study, iron–carbon-based fillers were integrated into ecological floating beds to investigate their impact and mechanisms in removing pollutants, including carbon, nitrogen, phosphorus, and heavy metals. Results indicate that all five fillers (activated carbon, iron–carbon fillers, sponge iron, activated carbon + iron–carbon fillers, and activated carbon + sponge iron) can completely remove orthophosphate, and the sponge iron filler system can completely remove nitrate. Then, fillers were applied to ecological floating beds, and the iron–carbon microelectrolysis (activated carbon + sponge iron filler)-enhanced ecological floating bed showed superior removal efficiency for pollutants. It achieved 95% removal of NH₄⁺-N, 85% removal of NO₃⁻-N, 75% removal of total phosphorus, 90% removal of chemical oxygen demand, and 90% removal of heavy metals. Typical nitrifying bacteria Nitrospira, denitrifying bacteria Denitratisoma, and a variety of bacterial genera with denitrification functions (e.g., Rhodobacter, Dechloromonas, Sediminibacterium, and Novosphingobium) coexisted in the system, ensuring efficient and robust nitrogen removal performance. These findings will provide support for the sustainable treatment of surface water in rural areas. Full article

It is crucial to develop an effective and easily recoverable phosphate absorbent for the control of eutrophication problems in polluted rivers. In this study, a stable particulate adsorbent with a diameter of 5 mm synthesized from lanthanum, activated carbon, and zeolite (La-CZ) was developed, characterized, and tested for the removal of phosphate from wastewater in a small-scale reactor, which was designed to easily recycle La-CZ with a basket. Batch studies showed that La-CZ could reach adsorption equilibrium within 2 h and the maximum phosphate sorption capacity was 18.2 mg g⁻¹. The experimental data showed good compliance with the Langmuir isotherm model and pseudo-second-order kinetic model, implying that chemisorption dominates the phosphate uptake process. La-CZ exhibited a stable adsorption capacity over a wide pH range (3–7), while the adsorption capacity decreased slightly under alkaline conditions. Although Nitrates (NO₃⁻) and Carbonate (CO₃²⁻) had some effects, normal coexisting ions such as Chloride (Cl⁻), Sulfate (SO₄²⁻), and Fluorine (F⁻) had no significant effects on the phosphate adsorption capacity of La-CZ. The main form of phosphate removed from the reaction system was HCl-P (77.68%), as determined through phosphorus fractionation. In particular, this study designed a replaceable filler-type reactor integrating a reflux and aeration system, 98.8% of phosphorus could be removed from actual wastewater, and La-CZ could be reclaimed easily. This work provides an excellent reference for particulate adsorbents that can efficiently remove phosphate in practical applications in the future. Full article

The discharge of wastewater from aquaculture ponds causes a certain degree of damage to the environment. It is necessary to continuously improve the treatment efficiency of wastewater treatment devices. The purpose of this study is to obtain an optimal ratio of wastewater circulation devices in order to obtain the best operating parameters and to reduce the discharge of polluted water. We constructed an experimental wastewater circulation device consisting of three units. The primary unit contained modified attapulgite (Al@TCAP-N), volcanic stone, and activated carbon for precipitation. The secondary and tertiary units used biological methods to enhance removal rates of nitrogen and phosphorus. Water quality indicators of total phosphorus (TP), total nitrogen (TN), ammonia (NH₃-N), permanganate (COD_Mn), and total suspended solids (TSS) were detected. Water quality was tested under different matching ratios for three units of different hydraulic retention time (HRT) and load Results showed that the removal rate of TP, TN, NH₃-N, and TSS reached 20–60%, 20%, 30–70%, and 10–80%, respectively. The average reduction efficiencies of secondary module chlorella and filler on TP, TN, NH₃-N, COD_Mn, and TSS were 56.88%, 30.09%, 0.43%, 46.15%, and 53.70%, respectively. The best removal rate can be achieved when the matching ratio of each unit becomes 2:1:1 and the hydraulic retention time is maintained within 2 h in the high-concentration load. Finally, the average removal rates of TP, TN, NH₃-N, and TSS reached 58.87%, 15.96%, 33.99%, and 28.89%, respectively. The second unit obtained the enhanced removal effect in this wastewater treatment system when adding microorganisms and activated sludge. Full article

Integrated sewage treatment equipment has been widely used, but the commonly used fillers for wastewater treatment are not suitable in rural areas due to their price and performance issues. In this study, an integrated magic filter filled with waste fillers was proposed and established for wastewater treatment. The filter was composed of functional modules and an equipment room, and the fillers in each module can be taken out separately and changed arbitrarily according to the needs of specific treatment conditions. The fillers used include waste plastic shavings, loofah, and waste iron shavings, generated during the processing of plastic, crop, and steel. At the same time, a 91 d experiment was performed for real wastewater treatment, and a satisfactory removal performance was obtained, with average removal rates of COD, TP, NH₄⁺-N, TN, and SS being 83.3%, 89.6%, 93.8%, 74.7%, and 94.0%, respectively. Through microscope observation, a large number of microorganisms were attached to the surface of the fillers, which was conducive to the simultaneous removal of nitrogen and phosphorus. The micro-electrolysis of waste iron shavings can produce Fe²⁺ and Fe³⁺, which would combine with PO₄³⁻ to form Fe₃(PO₄)₂ and FePO₄ precipitates, enhancing the removal of phosphorus. In addition, the filled fillers have an excellent physical filtering effect, which can reduce the effluent SS. The magic filter achieves both the recycling of wastes and the treatment of wastewater. Full article

In rural toilets, black water still remains polluted by nitrogen and phosphorus after being pre-treated by septic tanks. This study uses aerated biofilters to purify black water, screen the biofilter filler, and determine its effect on nitrogen and phosphorus purification in rural black water. This study introduced the concept of the “shape factor” into the Langmuir and Freundlich equations and optimized the isotherm adsorption model to better fit the actual dynamics of nitrogen and purification in black water. Combined with the first-order kinetic equation, the double constant equation, and the Elovich equation, the adsorption performance of seven kinds of biofilter fillers (i.e., zeolite, volcanic rock, sepiolite, ceramsite, anthracite, vermiculite, and peat) was studied. Then, the biofilter was constructed using a combination of fillers with better adsorption properties, and its ability to purify rural black water was studied. Results showed that vermiculite and zeolite had little effect on nitrogen and a high saturated adsorption of 654.50 and 300.89 mg·kg⁻¹, respectively; peat and ceramsite had little effect on phosphorus and a high saturated adsorption of 282.41 mg·kg⁻¹ and 233.89 mg·kg⁻¹, respectively. The adsorption rate of nitrogen from fast to slow was vermiculite > peat > zeolite > volcanic rock > sepiolite > ceramsite > anthracite. The adsorption rate of phosphorus from fast to slow was peat > ceramsite > zeolite > sepiolite > vermiculite > volcanic rock > anthracite. Four combined biological filter fillers aided the removal of nitrogen and phosphorus from rural high-concentration black water. The combination of zeolite and ceramsite filler had a good nitrogen and phosphorus removal effect in high-concentration black water. After the system was stable, the nitrogen removal rate attained 71–73%, and the phosphorus removal rate attained 73–76% under the influent condition of total nitrogen and phosphorus concentrations of 150–162 and 10–14 mg·L⁻¹, respectively. This study provides technical support and reference for the purification and treatment of rural black water. Full article

The current study was aimed to investigate the filler layer structure in modified bioretention systems. Three different structural layers in bioretention were proposed to evaluate their hydrologic performance and pollutant removal efficiency under different rainfall intensities. These layers were as follows: all three layers (filter, transition, and drainage layers), without transition layer, and without drainage layer. Synthetic stormwater was used for experimental purpose in current work. Results revealed that compared with “all three layers”, runoff control rate of “without transition layer” and “without drainage layer” was reduced by 0 to 7.4%, 0 to 10.1%, and outflow start time was advanced by 6 to 8 min and 1.5 to 4.5 min, respectively. Moreover, COD_cr (chemical oxygen demand), NH₄⁺-N (ammonium nitrogen), TN (total nitrogen) and TP (total phosphorus) removal rates were 86.0%, 85.4%, 71.8%, and 68.0%, respectively. Particle size distribution of the fillers revealed that during operation, particle moved downward were mainly within 0.16–0.63 mm size. Findings showed that transition and drainage layer played an important role in runoff control, and total height of the filler layer should not be less than 800 mm. Filter layer effectively reduce runoff pollution but the thickness of the filter layer should not be less than 500 mm. Whereas, transition layer has the function of preventing the filler loss of the filter layer; therefore, proper measures must be taken into consideration during structural optimization. Full article

This study was aimed to explore the effect of elastic filler on pollutant removal in each compartment of anaerobic baffled reactor (ABR), ABR with elastic filler, and ABR without elastic filler were compared. The result showed that elastic filler increased the removal rate of chemical oxygen demand (COD) and suspended solid (SS) in the first compartment, decreased the removal rate of COD and SS in the second and third compartments, and had little effect on the removal rate of COD and SS in the fourth compartment. Elastic filler increased the increase rate of ammonia nitrogen in the first and second compartments, decreased the increase rate of ammonia nitrogen in the third and fourth compartments; elastic filler had little effect on the nitrate nitrogen, nitrite nitrogen, total nitrogen and total phosphorus in each compartment of ABR. In general, elastic filler could improve the removal rate of COD and SS of ABR but had little effect on the increase rate of ammonia nitrogen, the removal rate of nitrate nitrogen, nitrite nitrogen, total nitrogen and total phosphorus. Elastic filler slightly increased the concentration of formic acid, acetic acid, propionic acid, and butyric acid in the first compartment of ABR, and slightly decreased the sum of formic acid and acetic acid in the second, hird and fourth compartments. Elastic filler did not change the composition of dissolved organic matter (DOM)in each compartment of ABR, but changed the kinds and contents of aromatic proteins, soluble microbial products and humic acids in each compartment of ABR. Elastic filler had little effect on ABR in the removal of aromatic proteins, but they could improve the removal rate of soluble microbial products and humicacids. Elastic filler slightly increased the degree of DOM humification (or maturity) in ABR effluent, but did not change the main source of humus like substance and DOM in ABR effluent. Full article

In this study, the performance of the horizontal sub-surface flow filter (HSSFF) and constructed wetland (HSSFCW) experimental units enhanced with earthworms was investigated for the treatment of construction camp sewage wastewater. All the experimental units (filter and constructed wetland) were filled with the same filler except Eisenia foetida earthworms and Lolium perenne Linn plants. The performance of the earthworm-enhanced filter (EEF) and the earthworm-enhanced constructed wetland (EECW) was compared to that of the blank filter (BF) units. The results revealed that the removal efficiencies for chemical oxygen demand (COD), ammonium-nitrogen (NH_4⁺-N), total nitrogen (TN) and total phosphorus (TP) in EEF were higher than the BF unit. In order to optimize the operating conditions, the experiments were conducted in three different water levels. The results revealed that the removal efficiencies of EEF for these pollutants are the highest in experimental conditions no. 2 (water level ~30 cm; HRT ~3 days; hydraulic load ~4.05 cm/day; and Inflow discharge ~0.27 L/h). Compared to the EEF and BF units, the EECW has higher removal efficiency for COD and TN and has more stable performance than the filters. This work will aid the design and improvement of filters and CWs for treatment of effluent wastewater from construction camps. The selection of appropriate hydraulic parameters and experimental conditions could be very beneficial in achieving the goal of implantation of low impact development (LID). Full article