Nutrient Removal Capability Research Articles

Refining the Farm Aquaculture Resource Management Model for Shellfish Nitrogen Removal at the Local Scale

Nutrient-related environmental degradation in coastal waters is a continuing global problem. Bivalve shellfish farms show nutrient removal capabilities similar to some traditional management strategies and in some places have been incorporated into nutrient management programs to help achieve water quality goals. Bioextractive nutrient removal varies by farmed species and is influenced by environment parameters; thus, data and information for both are needed to estimate nutrient mitigation potential of shellfish farms. The Farm Aquaculture Resource Management (FARM) model, calibrated for farmed species, uses local environmental and farming practice data to simulate interactions between the farmed population and the local environment and to optimize cultivation practices for economic gain. We calibrated the model to predict nitrogen removal by Eastern oyster (Crassostrea virginica) farms with specific field and experimental data on oysters, their local environment, and farm practices in Long Island Sound, CT, USA. Previous FARM applications were not validated for nitrogen removal with local data. In the harvest when ready (HWR) model scenario (oysters are harvested when they reach harvest size), the farm removed 159 kg N ha−1 year−1 while the non-HWR scenario (all oysters are harvested at one time) removed 274 kg N ha−1 year−1. These estimates are within the range of previously reported in-water bioextraction studies in the Northeastern USA. The robust outputs from this validated model can be reliably used in marine spatial planning efforts and by nutrient managers to predict the nitrogen removal benefits that could be achieved through new or expanded eastern oyster farms in eutrophic environments.

Calcium Alginate Core–Shell Liquid Beads Encapsulated with Microalgae for Wastewater Treatment

Liquid beads are core–shell particles with a liquid core and a solid shell. Calcium alginate liquid beads have been emerging as a promising platform for cell encapsulation. These beads have demonstrated their capability of encapsulating and culturing a wide range of human cells for tissue engineering. However, a significant research gap remains in the application of alginate liquid beads for encapsulating photosynthetic microorganisms. Herein, fast‐growing microalgae strain Chlorella vulgaris is encapsulated into calcium alginate liquid beads to facilitate the removal of nutrients from wastewater, minimizing the risk of eutrophication. Liquid bead‐microalgae systems are prepared, using different calcium ion concentrations as crosslinking ions. It has been thoroughly characterized for their morphologies, cell growth patterns, nutrient removal capabilities, and overall stability throughout the wastewater treatment process, with upflow anaerobic sludge blanket effluent as the wastewater model. The results indicate that the liquid bead‐microalgae system with the highest calcium ion concentration (5%) performs more efficiently, exhibiting a well‐formed crosslinking structure, leading to rapid cell growth with the highest cell density and the most effective removal of nutrients. The findings from this study provide valuable insights for future optimization and upscaling efforts in wastewater treatment systems based on calcium alginate liquid beads.

Metagenomic analysis of microbial consortia native to the Amazon, Highlands, and Galapagos regions of Ecuador with potential for wastewater remediation.

Native microbial consortia have been proposed for biological wastewater treatment, but their diversity and function remain poorly understood. This study investigated three native microalgae-bacteria consortia collected from the Amazon, Highlands, and Galapagos regions of Ecuador to assess their metagenomes and wastewater remediation potential. The consortia were evaluated for 12 days under light (LC) and continuous dark conditions (CDC) to measure their capacity for nutrient and organic matter removal from synthetic wastewater (SWW). Overall, all three consortia demonstrated higher nutrient removal efficiencies under LC than CDC, with the Amazon and Galapagos consortia outperforming the Highlands consortium in nutrient removal capabilities. Despite differences in α- and β-diversity, microbial species diversity within and between consortia did not directly correlate with their nutrient removal capabilities. However, all three consortia were enriched with core taxonomic groups associated with wastewater remediation activities. Our analyses further revealed higher abundances for nutrient removing microorganisms in the Amazon and Galapagos consortia compared with the Highland consortium. Finally, this study also uncovered the contribution of novel microbial groups that enhance wastewater bioremediation processes. These groups have not previously been reported as part of the core microbial groups commonly found in wastewater communities, thereby highlighting the potential of investigating microbial consortia isolated from ecosystems of megadiverse countries like Ecuador.

Enhancing biomass and lipid accumulation by a novel microalga for unsterilized piggery biogas slurry remediation.

The cost and efficiency of an algal-BS treatment system are determined by the specific microalgal species and BS pretreatment method. This study examines the growth of a novel algae Chlorella sp. YSD-2 and the removal of nutrients from the BS using different pretreatment methods, including dilution ratio and sterilization. The highest biomass production (1.84 g L-1) was achieved in the 1:2 unsterilized biogas slurry, which was 2.03 times higher than that in the sterilized group, as well as higher lipid productivity (17.29 mg L-1 d-1). Nevertheless, the sterilized biogas slurry at a 1:1 dilution ratio exhibited the most notable nutrient-removal efficiency, with COD at 71.97%, TP at 91.32%, and TN at 88.80%. Additionally, the analysis of 16S rRNA sequencing revealed a significant alteration in the indigenous bacterial composition of the biogas slurry by microalgal treatment, with Proteobacteria and Cyanobacteria emerging as the predominant phyla, and unidentified_Cyanobacteria as the primary genus. These findings suggest that Chlorella sp. YSD-2 exhibits favorable tolerance and nutrient-removal capabilities in unsterilized, high-strength biogas slurry, along with high productivity of biomass and lipids. Consequently, these results offer a theoretical foundation for the development of an efficient and economically viable treatment method for algal-BS.

Review of emerging technologies for nutrient removal in wastewater treatment

The burgeoning global population and industrial activities have significantly increased the generation of wastewater laden with nutrients, posing severe environmental and public health concerns. Traditional wastewater treatment methods often fall short in effectively removing nutrients like nitrogen and phosphorus, leading to eutrophication of water bodies and endangering aquatic ecosystems. In response, emerging technologies for nutrient removal in wastewater treatment have gained traction in recent years, offering innovative and efficient solutions to mitigate nutrient pollution. This comprehensive review explores the latest advancements in nutrient removal technologies, encompassing biological, physical, and chemical processes. Biological treatment methods, including activated sludge, sequencing batch reactors (SBRs), and membrane bioreactors (MBRs), have been extensively studied and optimized for nutrient removal. Novel biofilm-based systems, such as moving bed biofilm reactors (MBBRs) and integrated fixed-film activated sludge (IFAS), have demonstrated enhanced nutrient removal capabilities and resilience to fluctuations in wastewater composition. Furthermore, the integration of advanced oxidation processes (AOPs) and membrane technologies has revolutionized nutrient removal from wastewater. AOPs, such as ozonation, ultraviolet (UV) irradiation, and photocatalysis, offer effective means to degrade recalcitrant organic pollutants and disrupt nutrient cycles. Membrane-based technologies, including reverse osmosis (RO), nanofiltration (NF), and forward osmosis (FO), enable selective nutrient removal and concentration, thereby producing high-quality effluent suitable for reuse or discharge into sensitive environments. Additionally, the review delves into emerging chemical treatment strategies, such as adsorption, precipitation, and ion exchange, for targeted removal of nutrients from wastewater streams. Advanced adsorbents and nanomaterials exhibit superior adsorption capacities and selectivity for nitrogen and phosphorus compounds, paving the way for cost-effective nutrient recovery and resource recycling. Moreover, the review highlights the importance of process optimization, system integration, and environmental sustainability in the development and deployment of emerging nutrient removal technologies. Life cycle assessments (LCAs) and techno-economic analyses provide valuable insights into the environmental footprint and economic viability of these innovative solutions, guiding decision-makers towards sustainable wastewater management practices. In conclusion, the synthesis of biological, physical, and chemical processes in emerging nutrient removal technologies holds great promise for addressing the challenges of nutrient pollution in wastewater treatment. Future research directions should focus on scalability, energy efficiency, and holistic approaches towards achieving water quality goals and fostering a circular economy.

Bioremediation potential of the Chlorella and Scenedesmus microalgae in explosives production effluents

This study explores microalgae-based bioremediation for treating black gunpowder production effluents, an understudied yet environmentally significant stream. Two native microalgae, Chlorella sp. MC18 (CH) and Scenedesmus sp. MJ23-R (SC), were assessed for growth kinetics and nutrient removal capabilities in culture media containing different proportions of untreated raw wastewater. Results show both species thrived in 100 % raw wastewater, displaying robust growth and substantial biomass production in parallelepiped-shaped photobioreactors. SC showed superior performance, with higher maximum specific growth rate (0.549 d−1), biomass yield (454.57 mg L−1) and biomass productivity (64.94 mg L−1 d−1) compared to CH (0.524 d−1, 380.60 mg L−1, 54.37 mg L−1 d−1, respectively). The use of 100 % raw wastewater as a culture medium eliminated the need for additional freshwater input, thus reducing the water footprint. The bioremediation process also resulted in a high removal efficiency in turbidity (>95 % CH, >76 % SC), total suspended solids (>93 % CH, >74 % SC), biochemical oxygen demand (BOD5) (>62 % CH, >93 % SC) and chemical oxygen demand (COD) (>63 % CH, >87 % SC), bringing the effluent into compliance with environmental regulations. Although nitrogen (>45 % CH, >57 % SC) and sulphate (>43 % CH, >35 % SC) removal efficiencies was high, potassium bioremediation was limited (<6 %). The proximate chemical composition of the microalgal biomass revealed different allocations to carbohydrates, lipids and proteins. The results suggest promising applications for biofuel production and aquaculture. This research highlights the potential of microalgae-based bioremediation for sustainable wastewater management in the explosives industry, contributing to the UN Sustainable Development Goals and promoting green industrial practices.

Comparing Vegetation and Substrate Performances on Nutrient Removal and Biomass Establishment Using a Natural Swimming Pool Experiment

Natural swimming pools (NSPs) rely on the interaction of bog vegetation, bacteria, and substrate to maintain water quality. Nitrogen (N) and phosphorus (P) levels in NSPs are critical because of their involvement in eutrophication. We conducted a 15-week greenhouse study to address the significant literature gap regarding nutrient removal capabilities of substrates and vegetation in the low-nutrient environment of NSPs. We used mass balance analyses to compare the performances of four substrates [river gravel (control), recycled glass, expanded clay, expanded shale] and two plant species [blue flag iris (Iris versicolor) and lizard’s tail (Saururus cernuus)] under two flow conditions: free water surface and subsurface flow. At the end of the experiment, except for the recycled glass group, all other substrate groups reduced water nitrate (NO3) levels to less than 30 mg⋅L−1, the standard of the 2011 Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau (FLL) guidelines. However, only the expanded clay group closely approached the P standard (≤0.01 mg⋅L−1). Expanded clay and expanded shale demonstrated potential as substrates for NSP bogs. The final aboveground biomass dry weight was strongly negatively correlated with the final NO3 and P water concentrations. However, direct plant uptake proved insufficient to remove all nutrient inputs, especially for P. Except for the recycled glass group (34%), a significant portion of N (79%–90%) from total N added was removed by aboveground biomass. However, P uptake by biomass was substantially lower (18%–37%). With acceptable vigor and biomass accumulation, blue flag iris may be a suitable species for vegetated NSPs, whereas lizard’s tail is not because of uncertain establishment. Compared with controlling N, managing P for FLL standards in NSPs will be more challenging. Our work begins to fill the essential gap in the NSP literature regarding nutrient removal capabilities of substrates and vegetation. Future work should continue to study alternative substrates and plant species for P removal, particularly in field conditions and over longer periods.

Assessing the impact of increasing phenol loads on the performance and stability of an aerobic granular sludge system

This work evaluated the impact of phenol on the performance and stability of an aerobic granular sludge (AGS) sequencing batch reactor (SBR) operated under alternating anaerobic-aerobic conditions for simultaneous organic matter, nitrogen, and phosphorus removal. The reactor was fed with synthetic wastewater whose phenol concentration was gradually increased from 2 to 200 mg L−1, while the other carbon source (acetate) was reduced proportionally to keep the organic loading rate invariable. Up to 20 mg L−1 of phenol, the average COD removal was above 90%, while practically full ammonium, phosphorus, and phenol removal was achieved. However, at higher phenol concentrations, the activity of polyphosphate-accumulating organisms and nitrifiers was affected. Although the overall COD removal was only slightly affected by increasing phenol loads, replacing the main carbon source from acetate to phenol changed the organic matter removal profile over the cycle, with the latter being converted mainly within the aerated stage of the SBR. As a result, there was filamentous growth that deteriorated the settling properties of the granules. The establishment of an anaerobic feast-aerobic famine regime over the non-aerated and aerated phases of the AGS SBR and the presence of a readily biodegradable substrate (such as acetate) proved to be crucial for maintaining granules stability. Having phenol as the sole organic carbon source led to complete process failure regarding nutrient removal capability.

Evaluating the potential bioextractive capacity of South Florida native macroalgae Agardhiella subulata for use in integrated multi-trophic aquaculture (IMTA)

With the expansion of marine aquaculture throughout the world comes a need for solutions to improve the economic viability and environmental sustainability of farming operations. Integrated multi-trophic aquaculture (IMTA) has been identified as a promising method of farming that typically combines multiple cultured species in connected systems in an effort to decrease the concentration of nutrients expelled as waste products from intensive finfish culture while also increasing commercial profits via subsequent extractive biomass production. This study examined the effectiveness of South Florida native red macroalgal species Agardhiella subulata for use as a productive, nutrient-extracting species for IMTA in the Atlantic, Gulf of Mexico, and Caribbean regions. When cultured in a pilot-scale, land-based IMTA system for replicated 15 day trials with American red snapper, Lutjanus campechanus, A. subulata grew up to 14.4% d−1 and significantly decreased the concentration of all measured dissolved inorganic nutrients in the effluent water. The average percent (% ± SE) removal of nutrients were: 68.8 ± 4.8 ammonia, 94.5 ± 1.3 nitrate, 96.6 ± 2.0 nitrite, and 93.2 ± 3.1 phosphate from primary culture effluents. Further evidence of A. subulata fitness for commercial IMTA practices is shown through significantly high bulk nitrogen tissue concentration of experimental (nutrient-enriched) compared to control (un-enriched) groups. Results of this study demonstrate the efficient growth and nutrient removal capabilities of A. subulata when used in IMTA applications with marine finfish production in warm water environments, as may be encountered in marine aquaculture projects in the Atlantic, Gulf of Mexico and Caribbean regions.

The State-of-the-Art Production of Biofuel from Microalgae with Simultaneous Wastewater Treatment: Influence of Process Variables on Biofuel Yield and Production Cost

Microalgal biofuel production is a useful process to produce sustainable and carbon-neutral biofuels. The choice of microalgal species and the processes adopted in various production stages determine biofuel production. In this review, recent technological advancements made in various stages of microalgal biofuel production are discussed. This review also discussed the recent progress made in harvesting microalgal biomass and lipid extraction. In addition, the viability of using wastewater as a nutrient source for microalgae and its nutrient removal capabilities has been discussed in detail. This is the first study that enlists and compares the minimum achievable cost of biofuel produced in different studies. Also, process optimization strategies adopted to minimize the cost are discussed. The reported biofuel production cost varied from 0.14 $/L to 24.33 $/L based on the variation in the microalgae strains, production method, and optimization strategies.

Comparison of nutrient removal and biomass production between macrophytes and microalgae for treating artificial citrus nursery wastewater

Macrophyte (Lemna minor) and microalgae (Chlorella vulgaris and Scenesdesmus quadricauda) were used for treating artificial wastewater mimicking recirculating soilless citrus nursery system discharge in the laboratory environment. L. minor gave a better dry biomass yield (0.059 ± 0.003 g/L/day) than C. vulgaris (0.033 ± 0.002 g/L/day) and S. quadricauda (0.039 ± 0.001 g/L/day). Furthermore, L. minor had a higher nutrient (total N and P) and soluble minerals (S, K, Ca, Mg, Zn, Cu, and Mn) removal capabilities than microalgae due to a more natural high growth rate in non-optimized culture conditions.

Factors affecting pollutants removal and biomass production capability of Chlorella variabilis TH03 in domestic wastewater

Cultivation of microalgae in wastewaters and co-production of algal biomass have been considered as a sustainable approach for wastewater treatment. To achieve desirable biomass productivity and pollutants removal efficiencies, microalgal strain, cultivation mode and culturing conditions should be optimized. This was firstly aimed at examining growth characteristics of Chlorella variabilis TH03 strain under phototrophic, heterotrophic and mixtrophic cultivations using BG-11 medium as the sole of nutrient source. Secondly, the culturing variables such as aeration rate, percent dilution, N/P ratio and supplemented CO2 concentration were optimized to maximize biomass production and nutrient removal efficiencies of the algal strain in domestic wastewater. Thirdly, growth and nutrient removal capability of C. variabilis TH03 were investigated in an outdoor reactor system using domestic wastewater as a culture medium. Data showed that C. variabilis TH03 grew well under phototrophic and mixtrophic conditions but completely inhibited under heterotrophic conditions. In mixtrophic conditions, optimal aeration rate, percent dilution, N/P ratio and supplemented CO2 concentration achieved for the maximum growth and nutrient removal efficiencies were 0.2 vvm, no dilution, N/P = 15:1 and 15% CO2, respectively. Moreover, C. variabilis TH03 also exhibited an outstanding growth and nutrient removal capability in the outdoor reactor system, reaching areal biomass productivity of 39.5 g/m2∙day. Pollutants including COD, TN and TP were removed at efficiencies of 73.9, 97.1 and 99.8%, respectively. Nutrient levels in the effluent dropped below those required by the national technical regulation on domestic wastewater QCVN 14:2008/BTNM and QCVN 14-MT: 2015/BTNMT. The obtained results are useful for further study in large scale cultivation of C. variabilis TH03 for the production of high volume and low price biomass, helping to obtain returns from treatment of the waste stream, which is currently considered as a major source of water pollution in Vietnam.

Enhanced Removal of Phosphorus from Wastewater Using Sequential Electrocoagulation and Chemical Coagulation

An electrokinetic batch treatment scheme was investigated combining sequential electrocoagulation (EC) and chemical coagulation treatment (CC) processes. Synthetic and microbrewery wastewaters were tested in this investigation. The generated results demonstrated the capacity for the integration of EC-CC to effectively remove phosphorus contamination from wastewater under varying operating conditions. The effect of several operational parameters such as current density, conductivity, nutrient loading, and electrolysis time were investigated. The results showed that increased salinity can significantly accelerate the removal of phosphorous during EC treatment with 84.2% and 92.4% removal found for the applied power of 5 and 10 W, respectively. The addition of a sequential chemical coagulant stage following treatment by EC demonstrated the potential for an integrated EC-CC system to lower energy consumption while maintaining effective nutrient removal capabilities. Removal of phosphorous at 95% and 98% was achieved in just 10 min of EC treatment coupled with the addition of 15 mg/L aluminum sulfate. The estimated power consumption over a 10-min period was found to be 0.28 Kwh/m3 with a dissolution rate of 0.28 g/cm2 min held at a constant current density. The experimental anode dissolution rate for the synthetic wastewater ranged between 0.13 and 0.24 g/cm2 min encompassing all salinity levels. The anode dissolution rate increased during treatment of microbrewery wastewater with 0.67 g/cm2 min for 10 W EC treatment. This was attributed to the increase in current density and nutrient loading resulting in increased energy consumption and electrode passivation.

Growth and Nutrient Removal Efficiency of Sweet Wormwood (Artemisia annua) in a Recirculating Aquaculture System for Nile Tilapia (Oreochromis niloticus)

The maintenance of optimal water quality for fish production is one of the major challenges in aquaculture. Aquaponic systems can improve the quality of water for fish by removing the undesirable wastes and in turn produce a second marketable crop. However, there is no information on the growth and nutrient removal capability of Artemisia annua in aquaponic systems. This study evaluated the effect of plant density on water quality, the growth of A. annua and Oreochromis niloticus in a small scale aquaponic system in Kenya. The aquaponic system consisted of three treatments representing different plant densities (D1: 48 plants/m2, D2: 24 plants/m2 and D3:0 plants/m2). The high plant density system contributed significantly (p &lt; 0.05) to the removal of all nutrients. The removal efficiency of ammonia was significantly higher in D1 (64.1 ± 14.7%) than in D2 (44.5 ± 6.8%) and D3 (38.0 ± 12.1%). Nitrates and nitrites were inconsistent, whereas phosphorus increased gradually in all treatments. The productivity of plants was higher in D1 than D2. Fish growth rates were significantly higher in D1 (0.35 ± 0.03 g/d) and D2 (0.32 ± 0.02 g/d) than in D3 (0.22 ± 0.04 g/d). The results show that A. annua can be cultivated in aquaponic systems due to its nitrogen removal capabilities.

Nitrous Oxide Emissions from Saturated Riparian Buffers: Are We Trading a Water Quality Problem for an Air Quality Problem?

Reestablishing perennial vegetation along riparian areas in agroecosystems reduces nutrient and sediment losses from agricultural lands. However, subsurface (tile) drains bypass traditional buffers routing the majority of shallow groundwater straight to surface waters, limiting their nutrient removal capabilities. Saturated riparian buffers (SRBs) reconnect subsurface drainage water with the soil profile to remove NO in tile water through microbial denitrification. One concern of enhancing denitrification on agricultural landscapes is the potential increase in NO emissions from incomplete denitrification. Our objective was to compare NO emissions from SRBs to traditional buffers and bordering crop fields at two sites, Bear Creek Site 1 and Iowa Site 1, in Central Iowa. We measured NO emissions directly from the soil surface and dissolved in shallow groundwater and estimated indirect emissions from downstream denitrification from 2015 through 2017. Nitrous oxide emissions from soil surfaces were greatest from fertilized corn ( L.). Saturated riparian buffers were only significantly greater ( < 0.05) than traditional buffers in one out of six site-years. Dissolved NO in shallow groundwater seeping from SRBs was not significantly greater ( < 0.05) than dissolved NO from the tile outlet among site years. Indirect NO emissions from rivers and estuaries were significantly reduced from NO removal in both SRBs. Overall, total NO emissions from SRBs were similar to those from traditional buffers and less than those from fertilized corn-soybean [ (L.) Merr.] agriculture. Replacing cultivated land in riparian areas with a SRB has shown potential to subsequently remove NO from surface waters and reduce NO emissions from agricultural landscapes.

Light intensity affects the mixotrophic carbon exploitation in Chlorella protothecoides: consequences on microalgae-bacteria based wastewater treatment.

Microalgal-bacteria consortia application on wastewater treatment has been widely studied, but a deeper comprehension of consortium interactions is still lacking. In particular, mixotrophic exploitation of organic compounds by microalgae affects gas (CO2 and O2) exchange between microalgae and bacteria, but it is not clear how environmental conditions may regulate algal metabolism. Using a respirometric-based protocol, we evaluated the combined effect of organic carbon and light intensity on oxygen production and consumption by C. protothecoides, and found that the chemical oxygen demand (COD) was not consumed when incident light increased. Batch experiments under different incident lights, with C. protothecoides alone and in consortium with activated sludge bacteria, confirmed the results obtained by respirometry. Continuous system experiments testing the combined effects of light intensity and residence time confirmed that, under limiting light, mixotrophy is preferred by C. protothecoides, and the nutrient (COD, N, P) removal capability of the consortium is enhanced.

Phytoremediation capabilities of Spirodela polyrhiza, Salvinia molesta and Lemna sp. in synthetic wastewater: A comparative study

ABSTRACTMacrophytes have been used to mitigate eutrophication and upgrade effluent quality via their nutrient removal capability. However, the available data are influenced by factors such as microbial activities, weather, and wastewater quality, making comparison between nutrient removal performance of different macrophytes almost impossible. In this study, phytoremediation by Spirodela polyrhiza, Salvinia molesta and Lemna sp. were carried out axenically in synthetic wastewater under controlled condition to precisely evaluate nutrient removal efficiency of NO3−-N, PO43−, NH3-N, COD and pH in the water sample. The results showed that ammonia removal was rapid, significant for S. polyrhiza and Lemna sp., with efficiency of 60% and 41% respectively within 2 days. S. polyrhiza was capable of reducing 30% of the nitrate. Lemna sp. achieved the highest phosphate reduction of 86% at day 12 to mere 1.07 mg/L PO43−-P. Correlation was found between COD and TC, suggesting the release of organic substances by macrophytes into the medium. All the macrophytes showed biomass increment. S. polyrhiza outperformed other macrophytes in nutrient removal despite lower biomass production. The acquired nutrient removal profiles can serve as a guideline for the selection of suitable macrophytes in wastewater treatment and to evaluate microbial activity in non-aseptic phytoremediation system.

Growth characteristics and nutrient removal capability of eco-ditch plants in mesocosm sediment receiving primary domestic wastewater.

Eco-ditches are being explored to maximize their capability of capturing pollutants and mitigate any harmful side effects in rivers. In this study, mesocosm plastic drum sediment and field experiments were set up to screen 18 plant species found in ditches and identify those with potential for high biomass production and nutrients removal. Terrestrial plants grown in the mesocosm system were shown to be able to acclimate to aquatic conditions and to survive in primary domestic sewage. About 73-95% increase in plant biomass was recorded. Removal efficiencies for total nitrogen, total phosphorus, and ammonium-nitrogen from the sewage of 72-99%, 64-99%, and 75-100%, respectively, were recorded. Furthermore, complete removal of the applied nitrate-nitrogen load was achieved in mesocosm systems. Findings also show that all species, but especially Acorus calamus, Canna indica, Canna lily, Cyperus alternifolius, Colocasia gigantea, Eichhornia crassipes, Iris sibirica, and Typha latifolia had the highest efficiencies for nitrogen and phosphorous removal. The N and P mass balance analysis demonstrated that plant uptake and sediment N and P accumulation accounted for 41-86% and 18-49% of the total influent TN and TP loads, respectively. In addition, the amounts of nitrogen and phosphorous uptake by these plant species were influenced significantly by biomass. The field-culture experiment further identified Canna indica followed by Cyperus alternifolius as the most promising for high biomass production and nutrients uptake. Therefore, these plants may be recommended for extensive use in treating highly eutrophicated rivers. Outcomes of this work can be useful for model design specifications in eco-ditch mitigation of sewage pollution.

Bioremediation of Wastewater by Iron Oxide-Biochar Nanocomposites Loaded with Photosynthetic Bacteria.

It has been reported that bacteria-mediated degradation of contaminants is a practical and innocuous wastewater treatment. In addition, iron oxide nanoparticles (NP) are wastewater remediation agents with great potentials due to their strong adsorption capacity, chemical inertness and superparamagnetism. Therefore, a combination of NPs and microbes could produce a very desirable alternative to conventional wastewater treatment. For this purpose, we first prepared Fe3O4/biochar nano-composites, followed by loading photosynthetic bacteria (PSB) onto them. It was found that Fe3O4/biochar nano-composites exhibited a high adsorption capacity for PSB (5.45 × 109 cells/g). The efficiency of wastewater pollutants removal by this PSB/Fe3O4/biochar agent was then analyzed. Our results indicated that when loaded onto Fe3O4/biochar nano-composites, PSB’s nutrient removal capability was significantly enhanced (P < 0.05). This agent removed 83.1% of chemical oxygen demand, 87.5% of NH4+, and 92.1% of PO43- from the wastewater in our study. Our experiments also demonstrated that such composites are outstanding recyclable agents. Their nutrient removal capability remained effective even after five cycles. In conclusion, we found the PSB/Fe3O4/biochar composites as a very promising material for bioremediation in the wastewater treatment.

Evaluation of passive reduction of nitrate from greenhouse effluent by planted bioreactors

Abstract A number of pilot-scale gravel and wood-chip hybrid bioreactors planted with select species, together with unplanted units, were evaluated for their nutrient removal capabilities from the typical greenhouse effluent with high levels of nitrate and salts. Two levels of nutrient solution (high and low loading: HL/LL) were prepared to simulate the typical characteristics of the greenhouse effluent. The wood-chip bioreactor with Typha angustifolia exhibited the highest consistent nutrient treatment with an average nitrate reduction in the LL phase of 88.4% (28.2 g N m−3 media day−1) and phosphate reduction of 34.4%. The nitrate reduction in this bioreactor was the highest among the values reported in the literature. The near-complete denitrification developed provided a nitrate-limiting environment as evidenced by an average 21.5% sulfate reduction. The distinct increase in the outflow organic carbon (as BOD5) from the wood chips in the bioreactor planted with T. angustifolia appeared to be the key explanation for the efficient denitrification, while the other vegetated bioreactors resulted in 19.0%–36.5% nitrate reduction and low outflow BOD5 near the end of the experiment, indicating carbon limitation in these bioreactors.