Nutrient Removal Efficiency Research Articles

Biomass Accumulation, Contaminant Removal, and Settling Performance of Chlorella sp. in Unsterilized and Diluted Anaerobic Digestion Effluent

Microalgae demonstrate significant efficacy in wastewater treatment. Anaerobic digestion effluent (ADE) is regarded as an underutilized resource, abundant in carbon, nitrogen, phosphorus, and other nutrients; however, the presence of inhibitory factors restricts microalgal growth, thereby preventing its direct treatment via microalgae. The purpose of this study was to dilute ADE using various dilution media and subsequently cultivate Chlorella sp. to identify optimal culture conditions that enhance microalgal biomass and water quality. The effects of various dilution conditions were assessed by evaluating the biomass, sedimentation properties, and nutrient removal efficiencies of microalgae. The results demonstrate that microalgal biomass increases as the dilution ratio increased. The microalgae biomass in the treatments diluted with simulated wastewater was significantly higher than that with deionized water, but their effluent quality failed to meet discharge standards. The treatment diluted with deionized water for 10 times exhibited abundant microbial biomass with strong antioxidant properties. The corresponding total phosphorus concentration in the effluent (6.96 mg/L) adhered to emission limits under the Livestock and Poultry Industry Pollutant Emission Standards (8 mg/L), while ammonia nitrogen concentration (90 mg/L) was near compliance (80 mg/L). The corresponding microbial biomass, with a sludge volume index (SVI30) of 72.72 mL/g, can be recovered economically and efficiently by simple precipitation. Its high protein (52.07%) and carbohydrate (27.05%) content, coupled with low ash (10.75%), makes it a promising candidate for animal feed and fermentation. This study will aid in understanding microalgal growth in unsterilized ADE and establish a theoretical foundation for cost-effective ADE purification and microalgal biomass production.

Electrochemical Methods for Nutrient Removal in Wastewater: A Review of Advanced Electrode Materials, Processes, and Applications

In response to the increasing global water demand and the pressing environmental challenges posed by climate change, the development of advanced wastewater treatment processes has become essential. This study introduces novel electrochemical technologies and examines the scalability of industrial-scale electrooxidation (EO) methods for wastewater treatment, focusing on simplifying processes and reducing operational costs. Focusing on the effective removal of key nutrients, specifically nitrogen and phosphorus, from wastewater, this review highlights recent advancements in electrode materials and innovative designs, such as high-performance metal oxides and carbon-based electrodes, that enhance efficiency and sustainability. Additionally, a comprehensive discussion covers a range of electrochemical methods, including electrocoagulation and electrooxidation, each evaluated for their effectiveness in nutrient removal. Unlike previous studies, this review not only examines nutrient removal efficiency, but also assesses the industrial applicability of these technologies through case studies, demonstrating their potential in municipal and industrial wastewater contexts. By advancing durable and cost-effective electrode materials, this study emphasizes the potential of electrochemical wastewater treatment technologies to address global water quality issues and promote environmental sustainability. Future research directions are identified with a focus on overcoming current limitations, such as high operational costs and electrode degradation, and positioning electrochemical treatment as a promising solution for sustainable water resource management on a larger scale.

Effects of Temperature and Light on Microalgal Growth and Nutrient Removal in Turtle Aquaculture Wastewater

The aim of this study was to explore the effects of temperature and light on microalgal growth and nutrient removal in turtle aquaculture wastewater using a single-factor experiment method. Results showed that the growth process of Desmodesmus sp. CHX1 in turtle aquaculture wastewater exhibited three stages, namely adaptation, logarithmic, and stable periods. Temperature and light significantly influenced the growth and protein and lipid accumulation of Desmodesmus sp. CHX1. The optimal conditions for the growth and biomass accumulation of Desmodesmus sp. CHX1 included a temperature of 30 °C, a photoperiod of 24L:0D, and a light intensity of 180 μmol photon/(m2·s). Increased temperature, photoperiod, and light intensity enhanced nutrient removal efficiency. Maximum nitrogen removal was achieved at a temperature of 30 °C, a photoperiod of 24L:0D, and a light intensity of 180 μmol photon/(m2·s), with the removal efficiency of 86.53%, 97.94%, 99.57%, and 99.15% for ammonia, nitrate, nitrite, and total phosphorus (TP), respectively. Temperature did not significantly affect TP removal, but increased photoperiod and light intensity improved the removal efficiency of TP. The development of microalgae biomass as a feed rich in protein and lipids could address feed shortages and meet the nutritional needs of turtles, offering a feasible solution for large-scale production.

Transforming wastewater-derived algae biodiesel with ammonium hydroxide emulsion for enhanced energy efficiency and emission reduction

The growing demand for sustainable energy has prompted a search for alternative fuels, with microalgae-based biodiesel emerging as a promising option. However, improving its energy efficiency and minimizing environmental impacts remain key challenges. This study presents a novel approach by integrating wastewater-derived algae cultivation with ammonium hydroxide emulsion to enhance biodiesel performance. Chlorella vulgaris microalgae were grown in a medium of diluted human urine, where nutrient removal efficiency was evaluated, and biooil was extracted via solvent extraction. The resulting biodiesel was analyzed for elemental, chemical, and physicochemical properties. A 30 % blend of Chlorella vulgaris algae biodiesel (CVAB) with normal diesel fuel (NDF) was prepared. To further boost energy efficiency and emissions performance, ammonium hydroxide emulsion was added at concentrations of 5 % and 10 %. Results confirmed that wastewater-sourced algae cultivation is a viable method for sustainable biodiesel production. While CVAB's combustion characteristics were similar to NDF's, it exhibited a 7 % decrease in brake thermal efficiency and a 5 % increase in nitrogen oxide emissions. The addition of ammonium hydroxide emulsion notably improved both energy efficiency and emission profiles. This study highlights a breakthrough in using ammonium hydroxide emulsion to enhance algae biodiesel, making it a more competitive alternative to fossil fuels. Economically, this approach offers a dual advantage: utilizing low-cost wastewater for biodiesel production while improving fuel performance and reducing emissions.

Sustainable remediation of piggery wastewater using a novel mixotrophic Chlorella sorokiniana Cbeo for high value biomass production

Piggery wastewater (PW) contains high density of organic carbon (COD), nitrogen (NH4+-N and TN) and phosphorous (TP), which are essential nutrients for microalgae growth. This work was attempted to use a newly isolate Chlorella sorokiniana Cbeo for recovery these compounds into its biomass via mixotrophic cultivation. Critical factors including level of ammonia, C/N ratio, pH, light intensity, sterilized/unsterilized media, and indoor/outdoor cultivations affecting biomass production and nutrients removal efficiencies were investigated. Data revealed that C. sorokiniana Cbeo achieved the optimal growth in the unsterilized medium at NH4+-N concentration, C/N ratio, initial pH, and light intensity of 250mg/L, 10/1, 7, and 150 μmol/m2/s, respectively. Under the optimal conditions, dry cell weight (DCW) reached the maximal level of 4.30g/L, which was slightly higher than 4.14g/L determined for the sterilized medium. In 30 L-scale photobioreactor, C. sorokiniana Cbeo grown under indoor and outdoor achieved DCW of 3.61 and 3.19g/L, respectively. COD, NH4+-N, TN, TP removal efficiencies for both conditions were determined as 91.9–96.7, 96.6–99.7, 96.2–96.4, and 98.2–100%, respectively. The C. sorokiniana Cbeo biomass contained 14–27% lipid, 25–32% carbohydrate, 44–48% protein, and 0.25–0.97% lutein. Interestingly, α-Linolenic acid (C18:3n3) was 19.84 –27.0% of the total fatty acids. C. sorokiniana Cbeo is the promising algal strain for development of a sustainable biorefinery of PW.

Prioritizing conservation sites for multi-pond systems to maintain protection of water quality in a fragmented agricultural catchment

Precise targeting of conservation practices to the most effective sites in multi-pond systems (MPS) is critical for resource optimization and water quality improvement. Previous studies generally prioritized ponds for conservation practices considering nutrient removal efficiency. However, they have frequently overlooked the role of ponds in sediment interception and the impact of human activities and environmental factors around the pond. Herein, the present study developed and applied a novel framework for pond prioritization by integrating the Pressure-State-Response (PSR) model, graph theory, and K-mean clustering. The framework consists of three components. An indicator system is developed to represent the nutrient removal performance of any MPS, impacts on catchment sediment connectivity, external threats, and human-initiated conservation. A flow path network considering natural and artificial elements was constructed to calculate indicator values. A cluster analysis was conducted on the index values of different ponds, and a hierarchical sorting method were used to prioritize ponds. The framework was applied to the Guilinqiao Catchment, a typical fragmented agricultural catchment in the Yangtze River Basin, China. The study has quantified the Pressure, State, and Response indices of different ponds in this catchment, prioritized the ponds, and drawn recommendations for conserving MPSs based on field surveys and remote sensing data. Ponds with higher Pressure index, higher State index, and lower Response index scores should be targeted as conservation priorities. This framework provides an effective method for ensuring management of MPSs to sustainably maximize water cleanup capacity with limited resources.

Interactions between SDBS and Hydrilla verticillata − epiphytic biofilm in wetland receiving STPs effluents: Nutrients removal and epiphytic microbial assembly

The fate and effects of sodium dodecyl benzene sulfonate (SDBS) in sewage treatment plants (STPs) effluents on nutrients and submerged macrophytes are far from clear in wetlands. This study conducted a 24-day experiment to investigate changes in nutrients and epiphytic biofilm of Hydrilla verticillata in wetlands receiving effluents with 0.5, 2 and 5 mg L−1 SDBS. The decrease of SDBS in overlying water followed pseudo-first-order kinetic equation, with over 80 % of SDBS removal achieved. 2 and 5 mg L−1 SDBS decreased nutrient removal efficiency, induced oxidative stress response and damaged cells of H. verticillata. SDBS altered bacterial and eukaryotic community diversity. 0.5 mg L−1 SDBS can promote carbon fixation and methane oxidation of microorganisms. Network analysis revealed that 0.5 mg L−1 SDBS decreased the stability of epiphytic ecosystems. Mantel tests indicated significant influences of SDBS, temperature, and total nitrogen on epiphytic microbial communities.

Combining fermentation broth with spent water recycling for microalgae cultivation: nutrient reutilization, biodiesel production and techno-economic simulation

This study presents an innovative and promising technology, Water Cycling Combined Fermentation Broth (WC2FB), which offers a sustainable solution to significantly reduce the costs associated with microalgae-based biodiesel production. The innovative approach involves utilising food waste as a nutrient source, supplemented by recycled water after microalgae harvesting, with the goal of improving the viability of industrial biofuel production. The results of nutrient removal efficiency demonstrated that the addition of 15% fermentation broth to the microalgal suspension efficiently utilised volatile fatty acids, resulting in a significant increase in lipid content. Additionally, biocomponent analysis confirmed that the WC2FB mode did not compromise the desirable properties of biodiesel. Through techno-economic simulations, we predicted a 90% probability of achieving net present value (NPV) at a selling price of $5/kg. Finally, we recommended that directing future efforts be directly towards the development of culture devices, low-cost bioflocculation methods, and biorefinery extraction to further advance biodiesel production.

Removal of nutrients and bioelectricity generation from institutional wastewater using constructed wetland-microbial fuel cell

This study evaluated the removal of nutrients from institutional wastewater and the generation of bioelectric power using a microcosm-scale constructed wetland system integrated with a microbial fuel cell (CW-MFC). The research explored the impact of vegetation on both bioelectric production and wastewater treatment within the wetland matrix. Results indicated that the CW-MFC system with vegetation outperformed the unplanted system in terms of treatment efficiency. The planted modules achieved average total nitrogen (TN) and total phosphorus (TP) removal efficiencies of 94.6 % and 90.0 %, respectively, compared to 90.59 % and 83.5 % in the unplanted system. Notably, the CW-MFC planted with Scirpus atrovirens exhibited the highest average output voltage (0.648 V) and power density (232 mW/m³). In contrast, the unplanted CW-MFC produced a maximum voltage of 0.537 V and a power density of 220 mW/m³. These findings suggest that Scirpus atrovirens enhances both the treatment efficiency and bioelectricity generation by facilitating microbial activity involved in the biodegradation of organic compounds and improving electron flow from the anode to the cathode. The significant nutrient removal efficiencies and bioelectric power generation demonstrate the potential of using a vegetated CW-MFC system to achieve sustainable wastewater treatment while simultaneously producing renewable energy, thus contributing to more eco-friendly waste management practices

Valorization of abattoir water discharge through phycoremediation for enhanced biomass and biodiesel production

Phycoremediation has been discussed as a multipurpose strategy to refine various waste streams for sustainable algal biomass, value-added compounds, and biodiesel production. While phycoremediation has been explored for various wastewaters, there is still a research gap in systematical understanding the impact of abattoir water discharge (AWD) on both algal growth and biodiesel quality. The present study evaluated the potential of Chlorella sorokiniana to grow at different ratios of AWD, 30–90 %, v/v with conventional growth medium. Results showed that nutrient removal efficiency after 12 days of cultivation reached up to 85 % for total nitrogen, 78 % for total phosphorus, 70 % for potassium, and 65 % for sodium. Thus, all algae-treated AWD samples showed Kelly ratio (KR) values less than 1, confirming their suitability for direct application in soil irrigation. In addition, there were insignificant variations in algal growth and biomass yield across all treatments. Interestingly, carotenoids yield showed significant increase in all AWD ratios, with the highest recorded value of 0.750 mg L−1 at day 12 using 90 % AWD, compared to 0.523 mg L−1 in the control. Among various treatments, C. sorokiniana grown in 90 % AWD exhibited the highest lipid content of 201.6 mg g−1 algal dw (comparing to 180.6 mg g−1 dw in the control). The biodiesel derived from C. sorokiniana at different AWD ratios demonstrated promising characteristics due to enhancement of saturated fatty acids proportion, which resulted in lower iodine value, longer oxidation stability, and higher cetane number than the control.

Growth potential, biochemical properties and nutrient removal efficiency of some freshwater microalgae and their consortia from wastewater

Impact of varying nitrate (NO3-N) and phosphate (PO4-P) concentrations and sewage water (SW) on the growth, nutrient removal, lipid accumulation, enzymatic antioxidant activity and phytochemical contents of the microalgae Scenedesmus dimorphus, Coelastrella tenuitheca, Chroococcus turgidus and Parachlorella kessleri under monoculture and their consortia have been investigated. High growth rates were observed for all the four algae in both mono and mixed culture conditions at enhanced concentrations of N (1500 mg/L NO3-N) and P (40 mg/L PO4-P). The species Scenedesmus dimorphus outperformed other microalgae growing in SW in efficiently removing nitrogen. The algal consortia of mixed species was found to be more effective in phosphorus removal. The carbohydrate and protein contents were highest in Parachlorella kessleri, about 37% and 44%, respectively, in SW cultivation. The algal consortia demonstrated highest starch content (4%) in nitrogen deprived growth medium. Highest lipid production (43%) was observed in the SW culture. The species Coelastrella tenuitheca, Chroococcus turgidus and Scenedesmus dimorphus irrespective of the growth media indicated significant accumulation of phenol, flavonoid and tannin. The DPPH, catalase and ascorbic peroxidase assay showed pronounced antioxidant activity. Nutrient (N and P) enrichment exhibited enhanced antioxidant enzymatic activity and accumulation of cell storage products.

Municipal wastewater treatment using an innovative two-stage sequential microalgal co-cultivation system with different hydraulic retention time: A sustainable approach to circular economy

The present study proposes a sustainable circular bioeconomy approach for municipal wastewater (MWW) treatment, employing a sub-pilot two-stage sequential microalgal co-cultivation system (TSSCS), and evaluates the impact of hydraulic retention time (HRT) on MWW treatment efficiency, as well as biomass and biomolecule productivity. In the first stage of TSSCS, 2 ratios of Tetraselmis indica and one ratio of Picochlorum sp. (2TS:1PC) were used for the treatment of 75% raw MWW + 25% ASN-III, while in the second stage, 2PC:1TS was employed for the treatment of 50% 2TS:1PC effluent+ 50% ASN-III. At the end of the first and second stages of TSSCS, nutrient removal efficiencies were as follows: total nitrate (TN) was <80% and 90% on HRT-10 and HRT-12; total phosphate (TP) was <85% and 95% on HRT-16, and chemical oxygen demand (COD) was <75% and <85% on HRT-14 and HRT-10, respectively. In the TSSCS, 2TS:1PC (S1) and 2PC:1TS (S2) showed maximum biomass productivity of 2.65 and 2.78g/L on /L on HRT-14 and HRT-12, respectively. Additionally, biomass of 2TS:1PC (S1) and 2PC:1TS (S2) contains lipid content (38.67 and 40.67%), β-carotene (4.09 and 3.00mg/g), and astaxanthin (0.69 and 0.31mg/g), respectively.

Wastewater treatment optimization utilizing polyvinyl alcohol cryogel immobilized microalgae for nutrient removal

This study investigated the use of polyvinyl alcohol (PVA) cryogels to immobilize microalgae for wastewater treatment. Chlorella sorokiniana was successfully entrapped in PVA cryogels via repeated freeze/thaw cycles. The nutrient removal efficiency of these cryogels was tested in a continuously stirred photobioreactor under varying conditions, both with and without the addition of an organic carbon source (sodium acetate). The presence of organic carbon significantly enhanced nutrient removal. Specifically, PVA cryogels with immobilized C. sorokiniana achieved 100% nitrogen removal and 97.2% phosphorus removal under mixotrophic conditions. Furthermore, the maximum nutrient removal capacities of the PVA cryogels were found to be 0.033 mg-N/cube·day for nitrogen and 0.0047 mg-P/cube·day for phosphorus. As the inorganic carbon (bicarbonate) concentration increased from 5 to 100 mg/L, the N/P ratio rose from 6 to 8, with a higher N/P ratio of 10 observed when nitrate nitrogen was used as the nitrogen source, compared to ammonia nitrogen, at 100 mg/L bicarbonate. This study offers an effective method for using microalgae immobilized in PVA cryogels for wastewater treatment. The findings highlight the potential for PVA cryogels to significantly improve nutrient removal efficiency, particularly in the presence of organic carbon sources, thereby enhancing bioreactor performance. High nitrogen and phosphorus removal efficiencies can help reduce eutrophication in water bodies, protect aquatic ecosystems, and enable nutrient recovery and reuse, supporting a circular economy in wastewater treatment practices.

Assessing the nutrient removal performance from rice-crayfish paddy fields by an ecological ditch-wetland system

Agricultural drainage from catchments significantly impacts aquatic ecosystems due to high nitrogen and phosphorus concentrations in runoff. While original ecological ditches and wetlands have demonstrated effectiveness in nutrient load removal, the overall impact of an ecological ditch-wetland system (EDWS) on agricultural nutrient removal has received limited attention. This study conducted a field experiment to investigate the physicochemical conditions and nutrient removal efficiency of an EDWS for purifying nutrient discharge from rice-crayfish paddy fields. Variations in water temperature (WT), dissolved oxygen (DO), pH, and total suspended solids (TSS) within the EDWS were assessed. Nutrient concentrations—including total nitrogen (TN), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), total phosphorus (TP), and soluble reactive phosphorus (SRP)—were monitored from the tillering to the ripening stage of the rice growth cycle. The evaluation of nutrient removal efficiencies in the EDWS revealed that ecological ditches exhibited higher removal efficiencies compared to wetlands. The average total removal efficiencies for TN, NH4-N, NO3-N, TP, and SRP were 37.50 %, 39.38 %, 38.62 %, 37.94 %, and 39.51 %, respectively, with peak removal efficiencies observed at specific growth stages of the rice crop. Furthermore, the study explored the influence of hydraulic retention time on nutrient removal efficiency in the EDWS, indicating higher nutrient discharge removal efficiencies under low water discharge rates. Linear regression analysis identified water discharge, influent nutrient loads, and TSS as significant factors affecting nutrient removal efficiency in the EDWS. This study provides valuable insights into the effectiveness of EDWS in purifying nutrient discharge from rice-crayfish paddy fields, highlighting their potential as sustainable solutions for nutrient management in agricultural landscapes.

Enhancing Wastewater Treatment with Aerobic Granular Sludge: Impacts of Tetracycline Pressure on Microbial Dynamics and Structural Stability.

This study evaluated the efficiency of aerobic granular sludge (AGS) technology in treating wastewater contaminated with tetracycline (TC), a common antibiotic. AGS was cultivated under a TC pressure gradient ranging from 5 mg/L to 15 mg/L and compared with conventional wastewater conditions. The results demonstrated that AGS achieved high removal efficiencies and exhibited robust sedimentation performance, with significant differences in average particle sizes observed under both conditions (618.6 μm in TC conditions vs. 456.4 μm in conventional conditions). Importantly, exposure to TC was found to alter the composition and production of extracellular polymeric substances (EPSs), thereby enhancing the structural integrity and functional stability of the AGS. Additionally, the selective pressure of TC induced shifts in the microbial community composition; Rhodanobacter played a crucial role in EPS production and biological aggregation, enhancing the structural integrity and metabolic stability of AGS, while Candida tropicalis demonstrated remarkable resilience and efficiency in nutrient removal under stressful environmental conditions. These findings underscore the potential of AGS technology as a promising solution for advancing wastewater treatment methods, thus contributing to environmental protection and sustainability amid growing concerns over antibiotic contamination.

Study on the purification of aquaculture tailwater under Sulfamethoxazole stress using algae-bacteria biofilms: Nutrient removal efficiency, microbial community, and ARGs

This study explored the dynamic processes of algae-bacteria biofilms in the remediation of aquaculture pond effluents as a novel treatment strategy. The purification capacity of the biofilms, changes in community composition, and their impact on the dissemination of antibiotic resistance genes (ARGs) were investigated under the application of sulfamethoxazole (SMX) at concentrations ranging from 100 to 1000 μg/L. The study also considered the factors influencing the abundance and diversity of ARGs and mobile genetic elements (MGEs) across different seasons, including the roles of environmental parameters and microbial community structure.The results showed that, although exposure to SMX reduced nutrient removal efficiency, photosynthetic activity, and increased oxidative stress levels, the biofilms maintained relatively high purification efficiency (with nutrient removal rates ranging from 67.62 % to 93.23 % and SMX removal rate reaching 50.13 % ± 12.34 %), demonstrating adaptability to SMX stress. Network analysis identified key microbial carriers responsible for ARG dissemination, highlighting the complex interactions between environmental factors, microbial communities, and resistance gene propagation. These findings enhance our understanding of biofilm-based water treatment systems and the seasonal factors affecting the dynamics of ARGs and MGEs.

Improving organic and nutrient removal efficiencies in seafood processing wastewater using anaerobic membrane bioreactor (AnMBR) integrates with anoxic/oxic (AO) processes

Wastewater from seafood processing is a significant source of pollution, containing many harmful organic and inorganic compounds such as proteins, lipids, carbohydrates, nitrogen and phosphorus. This study investigated the enhancement of organic and nutrient removal efficiencies in seafood processing wastewater by integrating an Anaerobic Membrane Bioreactor (AnMBR) with an anoxic/oxic (AO) processes. A pilot-scale system was constructed with a capacity of 0.5 m3/day directly at the factory operated continuously, featuring an AnMBR process with a 24-hour hydraulic retention time (HRT) and an AO process with HRT values and internal recycle changes. The AnMBR system exhibited consistent and high-performance biochemical oxygen demand (COD) elimination, approximately 80 ± 5 %. However, this system demonstrated low-efficiency removal of total nitrogen (TN) at about 20 ± 5 %, and total phosphorus (TP) 15 ± 5 %, under organic loading rates (OLR) of 0.6 to 1.3 kg-COD/(L·d). The AO process was then continually employed to improve the treatment efficacy (at HRT, 5 h in the anoxic phase, and 8.3 h in the oxic phase, at a recycling rate of 300 %) resulting in the final post-treatment concentrations of COD 27–41 mg/L (removal 98.3 ± 0.3 %), TN 12–25 mg/L (90 ± 2 %), and TP 18 ± 2 mg/L (35 ± 5 %). The performance of the integrated AnMBR-AO system met the established Vietnamese discharge standards for seafood processing wastewater, as outlined in QCVN 11-MT: 2015/BTNMT.

Larger shrubs can maintain high infiltration and evapotranspiration rates in experimental biofiltration systems impacted by high sediment loads

Biofiltration systems can fail over time due to clogging by fine sediments in stormwater. Infiltration can be maintained by plant roots, but species selection for biofiltration to date has largely been driven by pollutant removal efficiency and tolerance of conditions. As a result, plant species diversity in biofilters is typically low and dominated by sedges and rushes. Increased use of woody species could in theory improve plant diversity, aesthetic appeal, infiltration under high sediment loads and volumetric runoff reduction via higher evapotranspiration, without jeopardising nutrient pollutant removal. We tested whether shrubs could maintain infiltration and evapotranspiration in biofiltration profiles treated with a high sediment load, by comparing them with biofilters subjected to tap water without sediment. Following sediment application, biofilter columns planted with shrubs with high total biomass and total root length showed higher infiltration and evapotranspiration than those receiving tap water. These results indicate that shrub species are likely to alleviate clogging and increase stormwater retention in biofiltration systems. However, shrubs with a high root diameter also had low total biomass and total root length and showed 33–51 % lower infiltration rates after sediment application compared with those receiving tap water. As all shrubs had higher root diameters than typical sedges and rushes, we suggest that shrubs need a combination of higher total biomass, total root length and average root diameter to effectively maintain infiltration. While shrubs which maintained infiltration had traits associated with high nutrient removal, nutrient removal efficiency of shrubs needs to be quantified. Although root traits were related to maintenance of infiltration, above-ground stems likely created flow pathways through sediment which requires further investigation. Overall, selecting shrub species with high total biomass has the potential to maintain infiltration and increase evapotranspiration in biofiltration systems impacted by high sediment loads.

Examining the efficacy of biological filters in the removal of agricultural pesticides and nutrient elements from agricultural drainage water

The high water consumption in agriculture has led to an obvious water crisis in this sector, and the use of unconventional water sources, especially agricultural drains, is considered necessary. For this purpose, the present study was carried out to evaluate the efficiency of biological filters with different types of substrates for treating agricultural wastewater in Khuzestan province, located in the south of Iran, to use receptive resources and reuse them in agriculture. Next, the efficiency of four types of biological filters for treating agricultural drainage water with different retention times was evaluated. Sawdust, cotton stalks, wheat straw, stubble, and rice husk were used as filters. Qualitative factors included agricultural pesticides (Atrazine, Randup, Paraquat, and 2, 4-D) and nutrients (nitrate, nitrogen, phosphate, and phosphorus). By examining the trend of increasing the retention time and the corresponding removal percentage, it was observed that the retention time has a direct relationship with the amount of removal efficiency of nutrients and agricultural toxins. As the residence time increases, the average amount of nutrient compounds in different filters decreases, and their removal percentage increases. The highest removal percentage of nitrate, total nitrogen, phosphate, and total phosphorus was 74.03, 71.66, 57.97, and 61.85% in the sawdust filter and was assigned to 10 days. The highest percentage of removal of Atrazine, Tofudi, Paraquat, and Roundup toxins with a removal efficiency of 91.73, 84.27, 89.81, and 88.46% was also observed in the treatment of sawdust for 10 days. The sawdust filter showed a good performance in removing the parameters of agricultural toxins and nutrient compounds in a retention time of 10 days compared to other filters and retention times. As a general result, the sawdust filter can be cited as a reliable substrate with acceptable efficiency compared to other filters.

Integrated process of Tetrasphaera-dominated in-situ waste activated sludge fermentation, biological phosphorus removal and endogenous denitrification in single reactor for treatment of wastewater with limited carbon sources

An integrated process of sludge in-situ fermentation, biological phosphorus removal and endogenous denitrification (ISFPR-ED) was developed to treat low ratio of chemical oxygen demand to nitrogen (COD/N) wastewater and waste activated sludge (WAS) in a single reactor. Nutrient removal and WAS reduction were achieved due to Tetrasphaera-dominated sludge fermentation provided organic carbon in extending the anaerobic duration. The WAS reduction efficiency, effluent orthophosphate (PO43−-P) and total inorganic nitrogen reached 28.1 %, less than 0.4 and 7.2 mg/L, respectively. While organic carbon was reduced by 67 %. Tetrasphaera, conventional polyphosphate accumulating organisms (PAOs) stored glycogen, amino acids, and PHA for nutrient removal. Excess energy from fermentation enhanced anaerobic PO43−-P uptake by Tetrasphaera. Tetrasphaera was the dominant PO43−-P removal and fermentation bacteria, working synergistically with conventional PAOs and fermenting microorganisms. This integrated process improves nutrient removal efficiency and reduces operating costs for carbon addition and WAS disposal in wastewater treatment.