Woodchip bioreactors provide sustained denitrification of brine from groundwater desalination plants

Dissolved organic matter characteristics linked to bacterial community succession and nitrogen removal performance in woodchip bioreactors

Woodchip bioreactors are an eco-friendly technology for removing nitrogen (N) pollution. However, there needs to be more clarity regarding the dissolved organic matter (DOM) characteristics and bacterial community succession mechanisms and their association with the N removal performance of bioreactors. The laboratory woodchip bioreactors were continuously operated for 360 days under three influent N level treatments, and the results showed that the average removal rate of TN was 45.80 g N/(m3·day) when the influent N level was 100 mg N/L, which was better than 10 mg N/L and 50 mg N/L. Dynamic succession of bacterial communities in response to influent N levels and DOM characteristics was an important driver of TN removal rates. Medium to high N levels enriched a copiotroph bacterial module (Module 1) detected by network analysis, including Phenylobacterium, Xanthobacteraceae, Burkholderiaceae, Pseudomonas, and Magnetospirillaceae, carrying N-cycle related genes for denitrification and ammonia assimilation by the rapid consumption of DOM. Such a process can increase carbon limitation to stimulate local organic carbon decomposition to enrich oligotrophs with fewer N-cycle potentials (Module 2). Together, this study reveals that the compositional change of DOM and bacterial community succession are closely related to N removal performance, providing an ecological basis for developing techniques for N-rich effluent treatment.

A systematic review of strategies to overcome barrier for nitrate separation systems from drinking water: Focusing on waste streams treatment processes

By 2030, the UN General Assembly issued the Sustainable Development Goal 6, which calls for the provision of safe drinking water. However, water resources are continuously decreasing in quantity and quality. NO3- is the most widespread pollutant worldwide, threatening both human health and ecosystems. NO3- separation systems (NSS) using IX and membrane-based techniques (MBT) are considered practical and efficient technologies, but the management of IX waste brine (IXWB) and concentrate streams for MBT (CSM), as well as the high salt requirements for IX regeneration, are challenging from both economic and environmental perspectives. It is essential to classify the different waste management strategies in order to examine the current state of research and identify the best option to address these issues. This review provides harmonized information on IXWB/CSM management strategies. This study is the first systematic review of all papers available in the Web of Science, Scopus, and PubMed databases published until February 2023. 75% of the studies focused on the use of biological denitrification (BD) and catalytic denitrification (CD). Although innovative technologies (bio-regeneration and direct CD) have advantages over indirect processes, they are not yet practical for large-scale plants because their reliability is unknown. Moreover, the generation of NH4+ is the major challenge for application large-scale of chemical reduction. An innovative work flow diagram, challenges, and future prospects are presented. The review shows that integrating modified NSS with IXWB/CSM treatment is a promising sustainable solution, as the combination could be economically and environmentally beneficial and remove barriers to NNS application.

Isolation of a marine-derived yeast with potential applications in industrial nitrite utilizing

The nitrite efficient utilization microorganism Wickerhamomyces anomalus RZWP01 was identified. Using nitrite and ammonium as the sole nitrogen source, the nitrogen removal rate of W. anomalus RZWP01 was 97.4% and 87.1%, respectively. W. anomalus RZWP01 grew well in the nitrite medium with glucose or xylose as the only carbon source. However, the W. anomalus RZWP01 cannot live on the nitrite medium with lactose, citric acid, and methanol as the only carbon source. The maximal cell concentration occurred in the nitrite medium with glucose as the only carbon source at a C/N ratio of 20 for 48 h, reaching 8.92 × 108 cell mL-1. W. anomalus RZWP01 was the first reported yeast that can efficiently utilize nitrite. The isolation and identification of W. anomalus RZWP01 enriched the microbial resources of nitrite-degrading microorganisms and provided functional microorganisms for the water treatment of sustainable aquaculture.

Extreme low-flow conditions in a dual-chamber denitrification bioreactor contribute to pollution swapping with low landscape-scale impact

Denitrification bioreactors are an effective edge-of-field conservation practice for nitrate (NO₃) reduction from subsurface drainage. However, these systems may produce other pollutants and greenhouse gases during NO₃ removal. Here a dual-chamber woodchip bioreactor system experiencing extreme low-flow conditions was monitored for its spatiotemporal NO₃ and total organic carbon dynamics in the drainage water. Near complete removal of NO₃ was observed in both bioreactor chambers in the first two years of monitoring (2019-2020) and in the third year of monitoring in chamber A, with significant (p < 0.01) reduction of the NO₃-N each year in both chambers with 8.6-11.4 mg NO₃-N L^-1 removed on average. Based on the NO₃ removal observed, spatial monitoring of sulfate (SO₄), dissolved methane (CH₄), and dissolved nitrous oxide (N₂O) gases was added in the third year of monitoring (2021). In 2021, chambers A and B had median hydraulic residence times (HRTs) of 64 h and 39 h, respectively, due to varying elevations of the chambers, with drought conditions making the differences more pronounced. In 2021, significant production of dissolved CH₄ was observed at rates of 0.54 g CH₄-C m^-3 d^-1 and 0.07 g CH₄-C m^-3 d^-1 in chambers A and B, respectively. In chamber A, significant removal (p < 0.01) of SO₄ (0.23 g SO₄ m^-3 d^-1) and dissolved N₂O (0.21 mg N₂O-N m^-2 d^-1) were observed, whereas chamber B produced N₂O (0.36 mg N₂O-N m^-2 d^-1). Considering the carbon dioxide equivalents (CO₂e) on an annual basis, chamber A had loads (~12,000 kg CO₂e ha^-1 y^-1) greater than comparable poorly drained agricultural soils; however, the landscape-scale impact was small (<1 % change in CO₂e) when expressed over the drainage area treated by the bioreactor. Under low-flow conditions, pollution swapping in woodchip bioreactors can be reduced at HRTs <50 h and NO₃ concentrations >2 mg N L^-1.

Woodchip bioreactors for saline leachates denitrification can mitigate agricultural impacts in mediterranean areas: The Campo de Cartagena-Mar Menor environmental issue

Leachates from intensive agriculture containing high nitrate have been identified as a major cause of the severe eutrophication crisis that impacts Mar Menor (SE Spain), the largest hypersaline coastal lagoon in the Mediterranean basin. A best management practice for removing NO₃^--N is denitrifying bioreactors. This is the first study to assess the efficiency of citrus woodchips bioreactors in treating agricultural leachates that flow to the Mar Menor via surface discharges. Denitrification capacity, woodchip degradation (by weight loss), formation of potentially harmful compounds, and greenhouse gas (GHG) emissions were assessed. Three bioreactors (6 m × 0.98 m x 1.2 m) filled with citrus woodchips (3 m³ d^-1 per bioreactor) through which the untreated ditch water over 1.5 years. Bioreactors were operated at 8 h, 16 h, and 24 h hydraulic residence time respectively, in each bioreactor. The main characteristics of the ditch water were: pH ≈ 7.5-8.0, electrical conductivity ≈ 5-8 dS m^-1, dissolved organic carbon ≈6-10 mg L^-1, and NO₃^--N ≈ 22-45 mg L^-1. Bioreactors were highly efficient in reducing NO₃^--N. The average R_NO3 in effluents was for the complete experimental period 8 g N m^-3 d^-1, 10.9 g N m^-3 d^-1, and 12.6 g N m^-3 d^-1 for 8, 16 and 24 h residence time, respectively. Nitrate reduction efficiency was modulated by seasonal changes in temperature, with an increasing efficiency in warmer periods (maximum ≈ 85-90% for all hydraulic residence time) and decreasing in colder ones (minimum ≈ 12%, 23% and 41% for hydraulic residence time 8, 16 and 24 h respectively). Woodchips degradation was greatest during the first six months (average ≈ 29% weight loss) in the material above the water level, attributable to aerobic mineralization of the organic carbon, while weight loss was ≈11% in woodchip media continuously below the water level. Dissolved organic carbon, sulfide, ammonium, and soluble phosphorus concentrations in the effluents were mostly low, although some peaks in concentrations occurred. Design consideration must be taken to avoid environmental impacts due to the occasional presence of harmful compounds in the effluents.

Use of wood and cork in biofilters for the simultaneous removal of nitrates and pesticides from groundwater

About 13% and 7% of monitored groundwater stations in Europe exceed the permitted levels of nitrates (50 mg NO₃^- L^-1) or pesticides (0.1 μg L^-1), respectively. Although slow sand filtration can remove nitrates via denitrification when oxygen is limited, it requires an organic carbon source. The present study evaluates the performance of the use of wood pellets and granulated cork as carbon sources in bench-scale biofilters operated under water-saturated and water-unsaturated conditions for more than 400 days. The biofilters were monitored for nitrate (200 mg L^-1) and pesticide (mecoprop, diuron, atrazine, and bromacil, each at a concentration of 5 μg L^-1) attenuation, as well as for the formation of nitrite and pesticide transformation products. Microbiological characterization of each biofilter was also performed. The water-saturated wood biofilter achieved the best nitrate removal (>99%), while the cork biofilters lost all denitrification power over time (from 38% to no removal). The unsaturated biofilter columns were not effective for removing nitrates (20-30% removal). As for pesticides, all the biofilters achieved high removal rates of mecoprop and diuron (>99% and >75%, respectively). Atrazine removal was better in the wood-pellet biofilters than the cork ones (68-96% vs. 31-38%). Bromacil was only removed in the water-unsaturated cork biofilter (67%). However, a bromacil transformation product was formed there. The water-saturated wood biofilter contained the highest number of denitrifying microorganisms, with Methyloversatilis as the characteristic genus. Microbial composition could explain the high removal of pesticides and nitrates achieved in the wood-pellet biofilter. Overall, the results indicate that wood-pellet biofilters operated under water-saturated conditions are a good solution for treating groundwater contaminated with nitrates and pesticides.

Nutrient overload promotes the transition from top-down to bottom-up control and triggers dystrophic crises in a Mediterranean coastal lagoon

The excess input of nutrients that triggers eutrophication processes is one of the main destabilizing factors of coastal ecosystems, being coastal lagoons prone to suffer these effects and present dystrophic crises. This process is aggravated by the current trend of rising temperatures and more frequent torrential rains due to climate change. We observed that the Mar Menor lagoon had a great capacity for self-regulation of its trophic web and resistance to the eutrophication process, but after 30 years of nutrient input due to the change in the agricultural regime in its drainage basin in the 1990s, the lagoon ecosystem has suffered several of these events. In this work, we characterize the seasonal dynamic of the pelagic system during the last dystrophic crises. Phosphorus and nitrogen alternate as the limiting nutrient for phytoplankton proliferation. The entrance of phosphorus is mainly related to vacation periods, while nitrogen inputs, both superficial and sub-superficial, are more related to chronic high nitrates concentration in the water table after the agricultural activities carried out in the area changed. Our analysis reveals that the summer season is prone to suffer periodical hypoxia events when the N/P ratio decreases, and the temperature rises. In the Mar Menor, the ecological balance has been maintained in recent decades thanks to, among other mechanisms, the spatial and temporal segregation of top-down control over phytoplankton exerted by three species of jellyfish. However, the deep reduction in the abundance of the summer jellyfish species and the excessive proliferation of phytoplankton has meant the loss of this control. Moreover, we have registered a decline in the abundance of all the other zooplanktonic groups during the dystrophic crises. We suggest that management actions should address the input sources of water and nutrients, and an integrated management of the activities carried out throughout the watershed.

Review: Brine Solution: Current Status, Future Management and Technology Development

Desalination brine is extremely concentrated saline water; it contains various salts, nutrients, heavy metals, organic contaminants, and microbial contaminants. Conventional disposal of desalination brine has negative impacts on natural and marine ecosystems that increase the levels of toxicity and salinity. These issues demand the development of brine management technologies that can lead to zero liquid discharge. Brine management can be productive by adopting economically feasible methodologies, which enables the recovery of valuable resources like freshwater, minerals, and energy. This review focuses on the recent advances in brine management using various membrane/thermal-based technologies and their applicability in water, mineral, and energy recoveries, considering their pros and cons. This review also exemplifies the hybrid processes for metal recovery and zero liquid discharge that may be adopted, so far, as an appropriate futuristic strategy. The data analyzed and outlook presented in this review could definitely contribute to the development of economically achievable future strategies for sustainable brine management.

Nitrate Removal and Woodchip Properties across a Paired Denitrifying Bioreactor Treating Centralized Agricultural Ditch Flows

Treatment of nitrate loads by denitrifying bioreactors in centralized drainage ditches that receive subsurface tile drainage may offer a more effective alternative to end-of-pipe bioreactors. A paired denitrifying bioreactor design, consisting of an in-ditch bioreactor (18.3 × 2.1 × 0.2 m) treating ditch base flow and a diversion bioreactor (4.6 × 9.1 × 0.9 m) designed to treat high-flow events, was designed and constructed in an agricultural watershed (3.2 km2 drainage area) in Illinois, USA. Flow and water chemistry were monitored for three years and the woodchip and bioreactor-associated soil were analyzed for denitrification potential and chemical properties after 25 months. The in-ditch bioreactor did not significantly reduce nitrate concentrations in the ditch, likely due to low hydraulic connectivity with stream water and sedimentation. The diversion bioreactor significantly reduced nitrate concentrations (58% average reduction) but treated only ~2% of annual ditch flow. Denitrification potential was significantly higher in the in-ditch bioreactor woodchips versus the diversion bioreactor after 25 months (2950 ± 580 vs. 620 ± 310 ng N g−1 dry media h−1). The passive flow design was simple to construct and did not restrict flow in the drainage ditch but resulted in low hydraulic exchange, limiting nitrate removal.