Search Results (29)

Removal of micropollutants using biological treatment systems remains a challenge, since conventional bioprocess systems require adaptations to provide more advanced treatment. An ambient temperature upflow anaerobic sludge blanket (UASB) reactor was employed, followed by a two-stage (saturated and unsaturated) vertical subsurface flow (VSSF) constructed wetland (CW) system, to treat domestic wastewater from a nearby settlement and investigate the occurrence and fate of 10 contaminants of emerging concern (CECs) in decentralized, non-conventional treatment systems. The integrated UASB—two-stage CW system achieved high performance regarding abatement of target CECs across all periods. Removal efficiencies ranged from 78% ± 21% (ketoprofen) to practically 100% (2-hydroxybenzothiazole). The pilot system was found to be robust performance-wise and provided enhanced treatment in comparison to a conventional wastewater treatment plant operating in parallel. Most of the target CECs were successfully treated by UASB, saturated and unsaturated CWs, while ibuprofen, bisphenol A and diclofenac were mostly removed in the unsaturated CW. Environmental risk assessment revealed that triclosan poses a significant ecological risk to algae during treated wastewater disposal into the aquatic environment. Additionally, cumulative risk quotient indicated that the potential for mixture toxicity should be carefully considered across all trophic levels. Full article

An integrated hybrid system was developed, incorporating sedimentation, anaerobic digestion, biological filtration, and a two-stage hybrid subsurface flow constructed wetland, horizontal subsurface flow constructed wetland (HSSFCW) and vertical subsurface flow constructed wetland (VSSFCW), to treat rural sewage in southern Jiangsu. To optimize nitrogen and phosphorus removal, the potential of six readily accessible industrial and agricultural waste byproducts—including plastic fiber (PF), hollow brick crumbs (BC), blast furnace steel slag (BFS), a zeolite–blast furnace steel slag composite (ZBFS), zeolite (Zeo), and soil—was systematically evaluated individually as substrates in vertical subsurface flow constructed wetlands (VSSFCWs) under varying hydraulic retention times (HRTs, 0–120 h). The synergy among substrates, plants, and microbes, coupled with the effects of hydraulic retention time (HRT) on pollutant degradation performance, was clarified. Results showed BFS achieved optimal comprehensive pollutant removal efficiencies (97.1% NH₄⁺-N, 76.6% TN, 89.7% TP, 71.0% COD) at HRT = 12 h, while zeolite excelled in NH₄⁺-N/TP removal (99.5%/94.5%) and zeolite–BFS specializing in COD reduction (80.6%). System-wide microbial analysis revealed organic load (sludges from the sedimentation tank [ST] and anaerobic tanks [ATs]), substrate type, and rhizosphere effects critically shaped community structure, driving specialized pathways like sulfur autotrophic denitrification (Nitrospira) and iron-mediated phosphorus removal. Annual engineering validation demonstrated that the optimized strategy of “pretreatment unit for phosphorus control—vertical wetland for enhanced nitrogen removal” achieved stable effluent quality compliance with Grade 1-A standard for rural domestic sewage discharge after treatment facilities, without the addition of external carbon sources or exogenous microbial inoculants. This low-carbon operation and long-term stability position it as an alternative to energy-intensive activated sludge or membrane-based systems in resource-limited settings. Full article

Mangroves are one of the world’s most productive and ecologically important ecosystems, and they are threatened by the widespread invasion of Spartina alterniflora Loisel in China. As few studies have examined the spatial pattern differences of S. alterniflora invasion and the nearby mangroves in different latitudes, we chose the Zhangjiang Estuary and the Dandou Sea, two representative mangrove–salt marsh ecotones in the north and south of the Tropic of Cancer, as the study areas for comparison. The object-based image analysis and visual interpretation methods were combined to construct fine-scale mangrove and S. alterniflora maps using high-resolution satellite imagery from 2005 to 2019. We applied spatial analysis, centroid migration, and landscape indexes to analyze the spatio–temporal distribution changes of mangroves and S. alterniflora in these two ecotones over time. We used the landscape expansion index to investigate the S. alterniflora invasion process and expansion patterns. The annual change rates of mangrove and S. alterniflora areas in the Zhangjiang Estuary showed a continuous growth trend. However, the mangrove areas in the Dandou Sea showed a fluctuating trend of increasing, decreasing, and then increasing again, while S. alterniflora areas kept rising from 2005 to 2019. Spartina alterniflora showed larger annual change rates compared with mangroves, indicating rapid S. alterniflora invasion in the intertidal zones. The opposite centroid migration directions of mangroves and S. alterniflora and the decreasing distances between the mangrove and S. alterniflora centroids indirectly revealed the fierce competition between mangroves and S. alterniflora for habitat resources. Both regions saw a decrease in mangrove patch integrality and connectivity. The integrality of mangrove patches in the Zhangjiang Estuary was always higher than those in the Dandou Sea. We observed the growth stage (2011–2014) and outbreak stage (2014–2019) of S. alterniflora expansion in the Zhangjiang Estuary and the outbreak stage (2005–2009) and plateau stage (2009–2019) of S. alterniflora expansion in the Dandou Sea. The expansion pattern of S. alterniflora varies in time and place. Since the expansion of S. alterniflora in the outbreak stage is rapid, with a large annual change rate, early warning of S. alterniflora invasion is quite important for the efficient and economical removal of the invasive plant. Continuous and accurate monitoring of S. alterniflora is highly necessary and beneficial for the scientific management and sustainable development of coastal wetlands. Full article

The present study is based on the characterisation of adobe blocks of the central region of Portugal. It is recognised that the safeguarding of the existing building stock of constructions in the traditional adobe construction technique, through different levels interventions, should also preserve the historical and cultural identity of the area as well as the traditional construction techniques, starting from the ground itself. Soil, as a repository of valuable information on the history of the site, underpins the conservation and preservation process. However, the soil is a local expression of the site, and a precise knowledge of its characteristics is necessary to hypothesise building recovery strategies. For this reason, the characteristics of adobe blocks from old buildings in the village of Torres in Anadia, in a rural area that has not yet been the subject of scientific research, were evaluated. These adobe blocks were taken from the buildings to be used in the laboratory to determine the similar mixing rates for the new adobe mixtures by analysing the material’s chemical, physical, mechanical, and thermal properties, as well as its particle size distribution. In the study area, a wetland was identified characterised by a notable presence of vegetation, namely bunho and junco (Schoenoplectus lacustris L.). These fibres, which can be assimilated to Typha, are wild aquatic plants that can impair the biodiversity of wetlands but which, used as reinforcement for the production of adobe bricks, can stimulate new, more sustainable forms of economy in in the area, which is classified as rural. The fibres were divided into two groups of 10–30 mm and 30–60 mm in length, and compositions with an additional 1 to 3% of fibres were formulated. This experimental approach was useful for understanding how the length and quantity of these fibres influence the performance of the material, thus contributing to improving knowledge about the behaviour of adobe blocks in relation to the incorporation of vegetable fibre reinforcement. The research findings reveal that the length of the fibres and percentage of incorporation have a significant impact on the mechanical behavior of the material, particularly in relation to its compressive strength up to 50%. The tested formulations were also assessed with respect to capillarity, for which most of the formulations were classified as weakly capillary, with a capillary index (Cb) of less than 20. With respect to thermal conductivity, the incorporation of fibres led to a reduction of up to 20%. The characterisations demonstrate that the optimisation of adobe is the initial stage in attaining comprehensive insight into the heritage of traditional construction in the central region of Portugal, with a particular focus on the village of Torres and the ancient adobe construction technique. Full article

In order to clarify the long-term changes in mangroves in the Beibu Gulf of Guangxi and the carbon storage changes after the invasion of Spartina alterniflora (S. alterniflora) in the Dandou Sea area, the Continuous Change Detection and Classification (CCDC) algorithm combined with feature indices was first used to track the changes. Subsequently, the random forest algorithm was applied to classify each change segment, and then sampling was conducted based on the distribution of S. alterniflora in different invasion years. The results showed that the Kappa coefficient of the classification result of the latest change segment was 0.78. The rapid expansion of S. alterniflora, aquaculture pond construction, and land reclamation activities have led to changes in mangroves, causing a decrease in the area of the mangrove region. A total of 814.57 hectares of mangroves has been converted into other land-cover types, with most pixels undergoing one to two changes, and many of these changes were expected to continue until 2022. An analysis of the distribution characteristics and influencing factors of soil organic carbon (SOC) and soil organic carbon storage (SOCS) at different invasion stages revealed that SOC and SOCS were mainly influenced by soil bulk density, soil moisture content, and electrical conductivity. It was found that S. alterniflora had higher SOC content compared to the mudflats. With the increase in invasion years, S. alterniflora continuously increased the SOC and SOCS content in coastal wetlands. Full article

A mechanistic model was developed to simulate one-dimensional pesticide transport in two-stage vertical flow constructed wetland. The two pesticides taken under study were carbendazim and chlorothalonil. The water flow patterns within the constructed wetland were simulated using the Richards equation. Water content and vertical flux, which are the outputs of the substrate water flow model, were used to calculate the substrate moisture-related parameters and advection term in the solute transport model. The governing solute transport equation took into account a total of six processes: advection, molecular diffusion, dispersion, adsorption to the solid surface, degradation and volatilization. A total of 14 simulation cases, corresponding with available experimental data, were used to calibrate the model, followed by further simulations with standardized influent pesticide concentrations. The simulations indicated that the constructed wetland reached a steady state of pesticide removal after 7 days of operation. Two distinct water flow patterns emerged under saturated and unsaturated conditions. The patterns observed while varying the hydraulic loading rates were similar for each individual saturation condition. Two-factor ANOVA of the simulated data further revealed that the carbendazim and chlorothalonil removal was dependent on the hydraulic loading rates, but it was independent of the influent pesticide concentration. Analysis of the simulated pesticide removal showed that degradation emerged as the predominant removal process over time for both the pesticides. The model developed in this study can be an important tool for the design and construction of treatment wetlands for pesticide removal from wastewater. Full article

The Ethiopian floriculture industry produces large amounts of wastewater, which requires treatment systems with lower retention times, higher hydraulic flow, and higher hydraulic loading rates (HLRs). Unsaturated vertical flow constructed wetlands (UVF-CWs), which represent these characteristics, have not been studied in depth for chlorothalonil remediation from wastewater. In this study, six UVF-CWs and nine pumping stations were organized into three experimental groups as three independent two-stage CW systems. The influent was pumped into the first vertical-flow stage, after which the effluent was collected and pumped into the second vertical-flow stage. The stage A and stage B effluents were tested for chlorothalonil removal at three different HLR of 50, 200, and 400 L d⁻¹ m⁻² and two influent chlorothalonil concentrations of 100 and 500 µg L⁻¹. The chlorothalonil levels for the stage A effluent at an HLR of 50 L d⁻¹ m⁻² for both influent chlorothalonil concentrations were below the detection limit of 0.08 µg L⁻¹. A maximum chlorothalonil concentration of 7.9 and 196 µg L⁻¹ was observed in the stage A effluent for influent concentrations of 100 and 500 µg L⁻¹, respectively. The chlorothalonil levels for the stage B effluent were all below the detection limit of 0.08 µg L⁻¹. A final chlorothalonil removal efficiency of at least 99.9% was observed for both influent chlorothalonil concentrations at the three HLRs used. These results demonstrated that UVF-CWs represent a viable solution for chlorothalonil remediation in the Ethiopian floriculture industry. Full article

As the global population reaches eight billion, large quantities of wastewater (domestic, industrial, livestock) need to be treated in an efficient, green, and environmentally friendly manner. Wastewater hydroponics technology (HP) can efficiently remove various pollutants (conventional and emerging pollutants, heavy metals, and microorganisms) and create economic benefits. This paper aims to systematically review the principles, applications, and limitations of wastewater hydroponics technology in the context of pollution and nutrient removal. Unlike constructed wetlands, wastewater hydroponics has been proven to be effective in removing pollutants through small-scale in situ restoration. For instance, the average removal of COD, total nitrogen (TN), total phosphorus (TP), copper (Cu), and zinc (Zn) was more than 70%, 60%, 80%, 64.2%, and 49.5%, respectively. However, HP technology still has the disadvantages of high energy consumption, complex control parameters, and low public acceptance of using wastewater for planting crops. Therefore, further research is needed to reduce system energy consumption. In addition, hybrid technologies, such as two-stage hydroponics that use aquatic plants (algae or aquatic floating weeds) to recycle pollutant-containing wastewater nutrients for hydroponics, should be further developed. 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

In order to satisfy the requirements of rural domestic sewage, a bio-ecological combination system was proposed, including a biological treatment section (anaerobic hydrolysis tank and aerobic tank) and an ecological post-treatment section. This study observed the application potential of constructed wetlands (CW) on different operation modes for biologically pre-treated rural domestic wastewater. The organics and nutrient removal efficiency of the tidal flow constructed wetland (TFCW) and the horizontal subsurface flow constructed wetland (HFCW) were compared at a temperature range of 20–40 °C. During the stable phase, the higher chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N), and total phosphorus (TP) removal efficiencies existed in TFCW than HFCW, corresponding to the efficiency of COD 69.46%, NH₄⁺-N 96.47%, and TP 57.38%, but lower performance on COD (61.43%), NH₄⁺-N (84.99%), and TP (46.75%) removal in HFCW, which should be attributed to the increasement of aerobic heterotrophic bacteria (Arthrobact and Sphingomonas), nitrifiers (Nitrospira), and phosphate accumulating organisms (PAOs) (Pseudomonas). The microbial biomass was also increased from 2.13 ± 0.14 mg/g (HFCW) to 4.64 ± 0.18 mg/g (TFCW), which proved to strengthen the formation and growth of biofilm under a better oxygen supplement. Based on the relative abundance of functional genera in the microbial community, it showed that TFCW was more favorable for promoting the growth of heterotrophic bacteria, nitrifiers, and phosphate-accumulating organisms (PAOs). When temperature changed from −4 °C to 15 °C, the two-stage constructed wetlands (TFCW-HFCW and HFCW-TFCW) were used for improving the performance of pollutants removal. The results demonstrated that the effluent concentrations of TFCW-HFCW and HFCW-TFCW met the Class 1A discharge standard of DB32/3462-2020 in JiangSu Province, China. Therefore, this study will provide a useful and easy-to-implement technology for the operation as an ecological post-treatment section. Full article

Dry detention basins (DB) are commonly used to reduce the rate of runoff in urban areas and may provide open space for recreation between storms. However, most are not effective at nitrogen removal in comparison to other measures, such as constructed wetlands. The study goal was to assess the nitrogen treatment efficiency of a DB that exhibited some wetland characteristics, including saturated soil near the inlet and wetland vegetation that covered 40% of the surface area. Influent and effluent samples were collected during multiple stages of eight storm events for nitrogen concentration analyses. High-frequency water stage, pH, dissolved oxygen (DO), and temperature loggers were deployed at the inlet and outlet prior to anticipated rain. As stormwater passed through the DB, the event mean concentrations (EMCs) and masses of TN declined by 20.7% and 52.3%, respectively, while the DO and pH dropped by 62% and 20.5%, respectively. Load reductions of TN exceeding 93% were observed during two small storms with rain depths of less than 0.16 cm and when the outflow volumes were reduced by greater than 82%. Temperature was significantly correlated (p < 0.001; r = 0.964) with volume reductions (via infiltration and evapotranspiration), and, thus, the treatment was better during warmer periods. The DB was effective at removing inorganic nitrogen, likely via nitrification, denitrification, and immobilization, but frequently exported higher EMCs of organic nitrogen. Overall, the DB exceeded the 10% TN removal expectation for dry basins. The findings from this study suggest that the TN treatment efficiency of DBs may be improved by incorporating wetland characteristics. Full article

In this paper, a fuzzy mathematical programming method is introduced on the basis of the interval two-stage stochastic programming (ITSP) optimisation model for the wetland ecological water replenishment scheme in Boluo Lake National Nature Reserve. The minimum ecological water supply is taken as the objective function, and the lake bubble water diversion capacity, lake bubble water supply capacity, water diversion sequence, ecological service value, and minimum capacity of the wetland water supply are taken as constraints. The ecological water replenishment schemes of five lakes in the Boluo Lake National Nature Reserve are optimised at the levels of low flow years, normal flow years, and high flow years, and an optimised model for the wetland ecological water replenishment scheme in Boluo Lake National Nature Reserve based on the interval fuzzy two-stage stochastic programming (IFTSP) method is constructed. The model fully considers the waste of water resources and the protection of migratory bird habitat and makes rational allocation of water resources to make full use of flood resources. The IFTSP model proposed herein fully considers the fuzzy and uncertain characteristics of the planning area in the lake bubble area of Boluo Lake National Nature Reserve and improves the decision-making efficiency of decision-makers by providing technical support for smooth implementation of the ecological water replenishment project in nature reserves. The model can also be used as a theoretical guide for ecological recharge projects in other regions of the world. Full article

Wetlands as an important ecosystem type have been damaged in recent years and restoration of wetland ecosystem functions through ecological water replenishment is one of the important ways. The present study involved the construction of a novel ecological water replenishment model for Jilin Momoge National Nature Reserve (JMNNR) using the interval two-stage stochastic programming (ITSP) method. Breaking down traditional economic models that often sacrifice environmental benefits, the model aims to replenish the ecological water in JMNNR, allocate the ecological water resources scientifically, restore the wetland function of the reserve, improve the functional area of the reserve, enhance the net carbon sequestration capacity of the reserve, and complete the reconstruction of the ecosystem, while considering the ecological service value (ESV) of the reserve to achieve a joint increase in the ecological and economic benefits. The ITSP model constructed in the present study overcame the limitation that the original project recommendation was a single recommended value, and the results are presented in the form of intervals to improve flexibility in decision making to allow the individuals responsible for under-taking decisions to bring focused adjustments according to the actual decision-making conditions and increase the selectivity of the decision-making scheme. The present report discusses the construction of an ITSP model for the ecological water replenishment of JMNNR in an attempt to effectively improve both economic benefits and ecosystem restoration of the reserve, achieve the reconstruction of the JMNNR ecosystem, and provide a selective decision space for the key decision-makers to formulate and optimize the project operation and the management plan. The use of the ITSP model as a pre-procedural basis for the implementation of the project and the simulation of the effects of the implementation of the project can effectively avoid the decision limitations that exist when carrying out the project directly. The ITSP model constructed in this paper can also be used as a theoretical guide for water replenishment projects in different areas of the world, and the model parameters can be reasonably adjusted to achieve better results when used according to the actual local conditions. Full article

The quality of micropolluted water is unstable and its substrate concentration fluctuates greatly. The goal is to predict the concentration effect on the treatment of nitrogen in a river with an actual low C/N ratio for the proposed full-scale Xiaoyi River estuary wetland, so that the wetland project can operate stably and perform the water purification function effectively in the long term. Two pilot-scale multistage constructed wetland–pond (MCWP) systems (S1 and S2, respectively) based on actual engineering with the same “front ecological oxidation ponds, two-stage horizontal subsurface flow constructed wetlands and surface flow constructed wetlands (SFCWs) as the core and postsubmerged plant ponds” as the planned process were constructed to investigate the effect of different influent permanganate indexes (COD_Mn) and total nitrogen (TN) contents on nitrogen removal from micropolluted river water with a fixed C/N ratio from summer to winter in the field. The results indicate that the TN removal rate in the S1 and S2 systems was significant (19.56% and 34.84%, respectively). During the process of treating this micropolluted water with a fixed C/N ratio, the influent of S2 with a higher COD_Mn concentration was conducive to the removal of TN. The TN removal rate in S2 was significantly affected by the daily highest temperature. There was significant nitrogen removal efficiency in the SFCWs. The C/N ratio was a major determinant influencing the nitrogen removal rate in the SFCWs. The organic matter release phenomenon in SFCWs with high-density planting played an essential role in alleviating the lack of carbon sources in the influent. This research strongly supports the rule that there is seasonal nitrogen removal in the MCWPs under different influent substrate concentrations, which is of guiding significance for practical engineering. Full article

The Huolin River is an important water supply source for the wetland located in western Jilin province, especially the river flooding in the lower reaches of the basin. In recent years, the degree of aridity and salinization of the wetlands has increased. To prevent the further deterioration of the ecological system, water conservancy projects and irrigation systems were constructed to ensure water safety. What effects on the ecological system and biological diversity were induced by all the measures and constructions is not clear. The “emergency project” of the water recession of the Huolin River is taken as example. In the analysis, the project is divided into two stages, five indicators for criteria tier were selected, and for index tier, 21 indicators during the implementation stage and 15 indicators during the operation stage were selected for constructing the analytic hierarchy process (AHP) model. By using expert scoring to determine the weight of each indicator, the impact index and degree of water conservancy of projects on biodiversity are calculated. The results show that at the level of the impact categories, ecological landscape is identified as a key influence factor. At the index level, the occupied area of the landscape type, the changes in patch number, the water conservation function, and the water purification quality are identified as corresponding key impact indicators. The biodiversity overall impact index is −23.45, which means the negative impact and the degree is medium to low. Meanwhile, for the implementation stage, the index is −51.58, which indicates a medium to low negative impact, while for the operation stage, the index is 33.66, which indicates a medium to low positive impact. These results are analyzed and scientifically evaluated and corresponding protection suggestions for the local area are proposed. Full article