Search Results (20)

Wastewater treatment plants (WWTPs) play a crucial role in mitigating microplastic (MP) release to the environment. In this paper, a WWTP of a textile manufacturing plant in Guangdong, China, was investigated to identify MP characteristics and the effectiveness of wastewater treatment within the plant. Laser Direct Infrared (LDIR) and Liquid Chromatography with Mass Spectrometry (LC-MS/MS) were applied to quantify both the number and the mass of the microplastics in the effluent of the textile manufacturing plant where most of the wastewater were from three printing and dyeing lines. The study further investigated the MP removal efficiency of each wastewater treatment process of the industry-owned WWTP and analysed the removal mechanism of each step, highlighting limitations in detecting and eliminating MPs. It is observed that (1) the results from LDIR and LC-MS/MS can be complementary to each other; (2) the MP concentration in the influent was 1730 n/L by number and 13.52 µg/L by mass; (3) the total removal efficiency of the WWTP were 99% by the number of MPs and 67.7% by the mass of MPs; (4) nine types of polymers have been identified in the influent, of which Polyamide (PA) was dominating; (5) hydrolysis acidification removed PA most; (6) aerobic tank, sand filter, and biological aerated filter (BAF) showed low removal efficiency; (7) coagulation and sedimentation tank had the highest removal efficiency to PET than any other processes. Full article

To achieve the in situ capacity expansion of the post-denitrification biological aerated filter (BAF-DN), the integration of BAF with the anammox process (BAF/AX) was proposed. With the objective of maximizing retaining ammonia nitrogen, the operational optimization of BAF was achieved by two distinct strategies. The treatment performance of BAF demonstrated that the removal efficiencies of chemical oxygen demand (COD) and ammonia nitrogen (${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$) was 66.3~67.3% and 4~12%, respectively, under conditions of low aeration intensity (0.4 m³·m⁻²·h⁻¹) or a shortened empty bed residence time (EBRT) of 30 min. Residual ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ in the BAF effluent served as the ammonia substrate for the subsequent anammox process, which was successfully launched by using ceramic particles and sponges as carriers. Notably, the sponge carrier facilitated a shorter start-up period of 41 to 44 days. Furthermore, the sponge-based anammox reactor exhibited a superior ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ removal capacity (≥85.7%), under operations of a shorter EBRT of 40 min, low influent ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ concentrations (≤30 mg/L), and COD levels of ≤67 mg/L. In addition, a comprehensive evaluation of the BAF/AX process was conducted, which considered performance, cost-effectiveness, and engineering feasibility. The performance results illustrated that the effluent quality met the standard well (with a COD level of ≤ 50 mg/L, and a TN of ≤3.1~10.5 mg/L). Following a comparison against the low aeration intensity operation, it was recommended to operate BAF at a low EBRT within the BAF/AX process. Consequently, the treated volume was double the volume of the standalone BAF-DN, synchronously achieving low costs (0.413 yuan/m³). Full article

The advanced treatment of proprietary Chinese medicine secondary effluent (PCMSE) was strongly needed with the recent implementation of a more stringent discharge standard. Based on the features of PCMSE and the reuse of Al³⁺ from wastewater from soaking of Pinellia Ternata with alumen (WSPTA), three new combined processes were designed for the advanced treatment of PCMSE on a larger pilot scale. A pilot scale study showed that compared with two other combined processes, the new coupling of a biological-aerated filter with Al³⁺ addition (BAFA)-O₃/H₂O₂ with microbubble (OHOMB) (CBAFAOHOMB) obtained the maximum pollutant removal (with removals of 91.71%, 94.64%, and 82.32% being observed for color, total phosphorus (TP), and chemical oxygen demand (COD), respectively) and acquired the lowest Al³⁺ residual in the effluent. During CBAFAOHOMB treatment of PCMSE, the vast majority of TP elimination, 35.20% of COD removal, and 49.40% of color removal were achieved by BAFA; OHOMB obtained 64.80% of COD removal and 60.60% of color removal, and biofilm activity in BAFA slightly changed under a 10 mg/L Al³⁺ dose. Furthermore, microbubble aeration was more efficient in removing organics than conventional bubble aeration during O₃/H₂O₂ oxidation, and suspended solid (SS) relatively significantly lowered oxidation ability in the OHOMB system. These results indicated that CBAFAOHOMB markedly integrated advantages of BAFA and OHOMB, and was a proposed process for the advanced treatment of PCMSE. Meanwhile, it was feasible that WSPTA was reused for PCMSE treatment as an Al³⁺ source. Full article

Temperature is an important factor influencing the treatment effect of biological aerated filters (BAFs). In this study, BAFs incorporating biological manganese oxides (BMOs) were used to treat micro-polluted source water containing organic masses and ammonia, and the influence of temperature on the removal efficiency of the pollutants was investigated. The results showed that after the formation of biogenic manganese oxides (BMOs) in the filter layer, the removal efficiency of CODMn significantly improved. When the water temperature was approximately 24 °C, 16 °C, and 6~8 °C, the removal rates of COD_Mn, ammonia, and manganese were 60.64, 42.55, and 20.48; 98.40, 95.58, and 85.04; and 98.70, 97.63, and 96.38%, respectively. The influence of water temperature on the removal efficiency of the pollutants was hierarchically structured as follows: COD_Mn > ammonia > manganese. Analysis of the removal efficiencies of the pollutants along the filter layer showed that COD_Mn had been eliminated in every filtration layer, and ammonia and manganese were mainly removed in the 0~0.4 m and 0~0.8 m regions of the filter layer, respectively. With a decreasing water temperature, the concentrations of COD_Mn, ammonia, and manganese along the filter layer increased. The biological COD_Mn, manganese, and ammonia removal processes were all first-order kinetic reactions. With a decreasing water temperature, the kinetic constant k gradually decreased, and the reaction half-life (t_1/2) gradually increased. Full article

Algal cell proliferation has posed significant problems for traditional water treatment facilities; these problems are attributed to surface hydrophilicity and electrostatic repulsion. Biological aerated filters (BAFs) have been extensively used in wastewater treatment to remove pollutants such as algal cells by utilizing the adsorption and separation capabilities of the filter media. In this study, a BAF was supplemented with biological filter medium (Marchantia polymorpha) to assess its effectiveness of pretreating aquaculture wastewater. In terms of process performance, steady and consistent treatment was achieved by the BAF with M. polymorpha (BAF2) under an algal cell density as high as 1.65 × 10⁸ cell/L, with average removal rates for NH₄⁺-N and algae cells of 74.4% and 81.9%, respectively. The photosynthetic activity parameters (rETRmax, α, Fv/Fm, and I_k) of the influent and effluent were quantitatively assessed, and M. polymorpha was found to remove algae by disrupting the photosynthetic system of the algal cells. Furthermore, the addition of the M. polymorpha filter medium enhanced the community structure of the functional microbes in the BAF system. The highest microbial community richness and diversity were observed in the BAF2. Meanwhile, M. polymorpha promoted an increase in the abundance of denitrifying bacteria, including Bdellovibrio and Pseudomonas. Overall, this work offers a unique perspective on the aquaculture wastewater pretreatment process and BAF design. Full article

In order to improve the removal efficiency of refractory organic matters in micro-polluted source water, biological manganese oxides (BMOs) were generated in situ in the biological aerated filter (BAF) (BAF 2^#), which could oxidize the refractory organic matters into biodegradable organic matters. COD_Mn and NH₄⁺-N in the effluent of BAF 2^# both stabilized on the 39th day, while COD_Mn and NH₄⁺-N in the effluent of the control BAF (BAF 1^#) stabilized on the 38th and 42nd days, respectively. In the steady phase, the removal rates of COD_Mn and NH₄⁺-N in BAF 1^# were 41.51% and 94.79%, respectively, while in BAF 2^#, they were 54.52% and 95.55%, respectively. BMOs generated in BAF 2^# evidently improved the efficiency of COD_Mn removal. With the increase in the influent Mn²⁺ in BAF 2^#, the rate of COD_Mn removal was gradually improved to 63.60%, while the efficiency of NH₄⁺-N removal was slightly improved, COD_Mn was evidently removed in each section of the filter layer, and ammonia was mainly removed in the 0~0.8 m layer of the filter. COD_Mn was evidently removed in each section of the filter layer, and NH₄⁺-N was mainly removed in the 0~0.8 m layers of the filter. Biological COD_Mn, Mn²⁺, and NH₄⁺-N removal all followed the first-order kinetic reaction. As the influent Mn²⁺ gradually increased from 0 to about 0.5, 1, and 2 mg/L, the efficiency of COD_Mn removal along the filter layer was significantly improved, but the efficiency of NH₄⁺-N removal was slightly improved. The kinetic constant k of biological COD_Mn removal significantly increased, while the kinetic constant k of biological Mn²⁺ and NH₄⁺-N removal gradually increased. Full article

Wastewater from factories producing polysulfone-based membranes mainly contains the used organic solvent, i.e., dimethylacetamide (DMAc). Due to the environmental impact of DMAc, wastewater treatment is mandatory. Several biological treatment options based on the activated sludge process are described in the literature. Due to artificial aeration, these techniques have high energy requirements. Near-nature processes such as vertical flow constructed wetlands (VF wetlands) have a low energy demand, high tolerance to load fluctuations, and low maintenance requirements. Therefore, high-loaded, two-stage VF wetlands are an efficient option for treating wastewater. However, constructed wetlands have so far only been used to a limited extent for the treatment of industrial wastewater. In the present study, the ability of laboratory-scale, high-load, two-stage VF wetlands to treat DMAc was investigated. This included their DMAc degradation efficiency and corresponding pathways, removal of the total organic carbon (TOC), nitrification and denitrification of the nitrogen, as well as the ecotoxicological effects (mutagenicity, genotoxicity, reactive oxygen species) of untreated and treated wastewater. The focus was to determine the effect of different grain size distributions on removal rates, the maximum inflow loading, and the effect of high inflow concentrations on effluent concentrations. In general, DMAc was completely degraded using VF wetlands, with dimethylamine (DMA) identified as the main intermediate. TOC removal rates reached more than 99%. The nitrogen bound to DMAc was completely nitrified. However, the start-up of the VF wetlands without seeded filter material temporarily leads to high nitrite accumulation. This may affect the mutagenicity of the treated wastewater. The results show that high-loaded, two-stage VF wetlands are an effective option for treating wastewater containing DMAc with higher efficiency than comparable biological processes. Full article

Methane is a potential source of carbon in drinking water. Typically, it is removed at waterworks during an initial treatment step such as aeration or stripping. Remaining methane may be converted by methane-oxidizing bacteria to organic carbon, which is then available for heterotrophic growth and may ultimately contribute to invertebrate growth. We investigated the presence of invertebrates at a waterworks with incomplete methane removal and at a waterworks without methane. Microscopy and analyses of 16S and 18S ribosomal genes were conducted on filter sand from full-scale biological rapid sand filters. Primary filters with methane were dominated by methane- and ammonia-oxidizing bacteria. Upper layers of secondary filters were dominated by heterotrophic bacteria, while the deepest layer contained 92% eukaryote DNA. Rotifers, nematodes, platyhelminths and annelids constituted 22% of the DNA in the secondary filters. Filters with methane contained higher shares of invertebrates (13%) than the filter without methane (7%). Furthermore, pilot studies were conducted to estimate suitable levels of methane when implementing methane removal technologies. Methane concentrations of 0.24 mg/L caused rapid visible growth. Vacuum stripping and nitrogen addition removed methane to 0.018–0.03 mg/L and prevented growth of methane-oxidizing bacteria. Full article

Phosphorus input with excessive use of fertilizers and manure as one of the main sources of nutrient pollution has increased recently in the wastewater as result of intensive farming and industrialized and densely populated areas. The novelty of the current work lies in improving a Vertical Aerated Rock Filter (VARF) using steel slag and limestone media to enhance the efficiency of a rock filter (RF) to eliminate total phosphorus (TP) from domestic wastewater. RF was designed with steel slag and limestone (calcium hydroxide) as a pilot scale called vertical aerated steel slag filter (VASSF) and optimized based on hydraulic loading rates (HLR) (0.16 to 5.44 m³/m³ day) and airflow rates ranging from 3 to 10 L/min. The highest removal for the design of the laboratory scale steel slag filter (LSSSF) was achieved by approximately 58%, while for the laboratory-scale limestone filter (LSLSF), it was 64%. The VASSF achieved a removal percentage at 30% of TP, biological oxygen demand (BOD; 89%), chemical oxygen demand (COD; 75%), total suspended solids (TSS; 73%), and total coliforms (TC; 96%), recorded with 7 L/min of an airflow rate and 1.04 m³/m³.day of hydraulic loading rate (HLR) at potential of hydrogen (pH) 7.3 and 5.09 mg/L of dissolved oxygen (DO). These findings indicated that the steel slag is higher than limestone in TP removal, because of ion exchange between phosphorus hydrolysis and the adsorption process. Moreover, in the pilot study, the removal efficiency needs more investigation to determine the best conditions for TP considering the temperature, which is unstable, and presence of other pollutants, which might negatively affect the removal efficiency under unstable conditions. Full article

In engineering application, a two-stage biological aerated filter (BAF) has been deployed to achieve the steady nitrogen removal of the wastewater from the mining area of ionic rare earth with a low carbon to nitrogen (C/N) ratio. However, the cost-efficiency of the medium and carbon source casts a shadow over further development. In this study, the influences of four media (i.e., volcanic, zeolite, quartz, and ceramisite) and three soluble carbon sources (i.e., acetate, glucose, and methanol) on the N removal were systematically compared. Applying volcanic and quartz showed a favorable start-up performance due to the biophilic surface and dense packing, respectively. However, regardless of medium type, with [NH₄⁺-N]₀ = 50 and [NO₃⁻-N]₀ = 30 mg/L, the C/N ratio of 3 was required to meet the discharge standards of NH₄⁺-N, TN, and COD, and acetate was confirmed applicable for all the selected medium-packed BAFs. Introduction of sweet potato residues as the solid carbon source decreased the amount of added acetate by more than 13%. The 16S rRNA high-throughput gene sequencing revealed that Sphingomonas and Nitrospira were abundant in the aerobic stages of the volcanic and zeolite-packed BAFs, respectively. Such a community integrated with the extensively distributed Thauera, Clostridium_sensu_stricto, and Proteiniclasticum in the anoxic stage accounted for the efficient N removal. Thus, deploying volcanic as the medium and acetate as the soluble carbon source was proposed. These findings will provide valuable references for the selection of medium and carbon source and, consequently, further optimize the operational performance. 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 use of the plant Chrysopogon zizanioides (vetiver), able to develop under adverse conditions while removing a great number of pollutants, in constructed wetlands (CWs) is widely reported. Regarding the biological trickling filters (BTFs), the selection of the media is one of the most important factors in its performance. We investigated whether the addition of vegetation improves the efficiency of the basic parameters of BTFs with gravel. In addition, due to the properties of light expanded clay aggregate (LECA), we evaluated whether the support media composed of vetiver and LECA is able to increase the media’s oxygenation. The efficiencies were 39, 49, 56, and 49% for biochemical oxygen demand (BOD) and 27, 20, 12, and 31%, for total Kjeldahl nitrogen (TKN) in BTF_LV (vetiver with LECA), BTF_L (LECA only), BTF_GV (vetiver with gravel) and BTF_G (gravel only), respectively. LECA when associated with vetiver may have provided higher aeration of the filter, denoted by the higher nitrate effluent concentration (0.35, against 0.03, 0.06, and 0.10 mg L⁻¹ for BTF_L, BTF_GV, and BTF_G). Vetiver had no improvement on BTFs performance concerning BOD. However, associated with LECA, its use could be viable to remove dissolved forms of nitrogen. Full article

The purification effect of a biological aerated filter (BAF) mainly comes from the microorganisms in the reactor. Understanding the correlation between microbial community characteristics and environmental factors along the filter has great significance for maintaining good operation and improving the removal efficiency of the filter. A two-stage BAF was employed to treat domestic sewage under organic loads of 1.02 and 1.55 kg/m³·d for 15 days each. 16S rDNA high-throughput sequencing technology and redundancy analysis were applied to explore the correlation between microbial community characteristics and environmental variables. The results showed that: (1) the crucial organic-degrading bacteria in the A-stage filter were of the genus Novosphingobium, which had a significant increase in terms of relative abundance at sampling outlet A3 (135 cm of the filling height) after the increase of organic load; (2) the microbial communities at different positions in the B-stage filter were similarly affected by environmental factors, and the main bacteria associated with nitrogen removal in the B-stage filter were Zoogloea and Rhodocyclus; and (3) to improve the pollutant removal performance of this two-stage biological aerated filter, a strategy of adding an internal circulation in the B-stage filter can be adopted. Full article

A membrane bioreactor enhances the overall biological performance of a conventional activated sludge system for wastewater treatment by producing high-quality effluent suitable for reuse. However, membrane fouling hinders the widespread application of membrane bioreactors by reducing the hydraulic performance, shortening membrane lifespan, and increasing the operational costs for membrane fouling management. This study assesses the combined effect of membrane surface corrugation and a tilted panel in enhancing the impact of air bubbling for membrane fouling control in activated sludge filtration, applicable for membrane bioreactors. The filterability performance of such a system was further tested under variable parameters: Filtration cycle, aeration rate, and intermittent aeration. Results show that a combination of surface corrugation and panel tilting enhances the impact of aeration and leads to 87% permeance increment. The results of the parametric study shows that the highest permeance was achieved under short filtration–relaxation cycle of 5 min, high aeration rate of 1.5 L/min, and short switching period of 2.5 min, to yield the permeances of 465 ± 18, 447 ± 2, and 369 ± 9 L/(m²h bar), respectively. The high permeances lead to higher operational flux that helps to lower the membrane area as well as energy consumption. Initial estimation of the fully aerated system yields the energy input of 0.152 kWh/m³, much lower than data from the full-scale references of <0.4 kWh/m³. Further energy savings and a lower system footprint can still be achieved by applying the two-sided panel with a switching system, which will be addressed in the future. Full article

Wastewater treatment plants (WWTPs) are points of control for the environmental dissemination of antimicrobial resistant bacteria. Vancomycin-resistant enterococci (VRE) were used as indicators of antimicrobial resistance (AMR) in two WWTPs (biologically aerated filter (BAF) and conventional activated sludge (CAS)) in the same municipality. The removal and abundance of enterococci and VRE as well as the species and antimicrobial resistance profiles of VRE were assessed. Enterococci and VRE from the primary and final effluents were enumerated. Results were assessed from an ecological context. VRE was not selected for by either WWTP but the BAF system outperformed the CAS system for the removal of enterococci/VRE. Enterococcus faecalis (n = 151), E. faecium (n = 94) and E. casseliflavus/E. gallinarum (n = 59) were the dominant VRE species isolated. A decrease in levofloxacin resistance in enterococci was observed in the BAF WWTP. An increase in nitrofurantoin resistant (p < 0.001) and a decrease in quinupristin/dalfopristin (p = 0.003) and streptomycin (p = 0.022) resistant enterococci were observed in the CAS WWTP, corresponding to a shift of VRE from E. faecalis to E. faecium. Wastewater treatment processes can be managed to limit the dissemination of antimicrobial resistance determinants into the surrounding environment. Full article