Effectiveness of Denitrifying Bioreactors on Water Pollutant Reduction from Agricultural Areas

HighlightsDenitrifying woodchip bioreactors treat nitrate-N in a variety of applications and geographies.This review focuses on subsurface drainage bioreactors and bed-style designs (including in-ditch).Monitoring and reporting recommendations are provided to advance bioreactor science and engineering. Denitrifying bioreactors enhance the natural process of denitrification in a practical way to treat nitrate-nitrogen (N) in a variety of N-laden water matrices. The design and construction of bioreactors for treatment of subsurface drainage in the U.S. is guided by USDA-NRCS Conservation Practice Standard 605. This review consolidates the state of the science for denitrifying bioreactors using case studies from across the globe with an emphasis on full-size bioreactor nitrate-N removal and cost-effectiveness. The focus is on bed-style bioreactors (including in-ditch modifications), although there is mention of denitrifying walls, which broaden the applicability of bioreactor technology in some areas. Subsurface drainage denitrifying bioreactors have been assessed as removing 20% to 40% of annual nitrate-N loss in the Midwest, and an evaluation across the peer-reviewed literature published over the past three years showed that bioreactors around the world have been generally consistent with that (N load reduction median: 46%; mean ±SD: 40% ±26%; n = 15). Reported N removal rates were on the order of 5.1 g N m-3 d-1 (median; mean ±SD: 7.2 ±9.6 g N m-3 d-1; n = 27). Subsurface drainage bioreactor installation costs have ranged from less than $5,000 to$27,000, with estimated cost efficiencies ranging from less than $2.50 kg-1 N year-1 to roughly$20 kg-1 N year-1 (although they can be as high as $48 kg-1 N year-1). A suggested monitoring setup is described primarily for the context of conservation practitioners and watershed groups for assessing annual nitrate-N load removal performance of subsurface drainage denitrifying bioreactors. Recommended minimum reporting measures for assessing and comparing annual N removal performance include: bioreactor dimensions and installation date; fill media size, porosity, and type; nitrate-N concentrations and water temperatures; bioreactor flow treatment details; basic drainage system and bioreactor design characteristics; and N removal rate and efficiency

Adoption of precision systems technology in vegetable production

The project ‘Adoption of precision systems technology for vegetable production’ generated significant evidence for precision agriculture (PA) implementation in vegetable systems. Given the relatively low adoption and knowledge base of precision agriculture in vegetable production systems; the project sought to engage producers and commercial providers in order to develop underlying spatial management approaches and evidence of crop variability. This involved establishment of key grower led case study sites across Australia for increased adoption of a broad range of PA technology and approaches. The project significantly increased knowledge and awareness of how PA approaches can be applied to vegetable system using a broad suite of communication products including 12 case studies, 8 factsheets, 4 ‘Youtube’ style videos, 2 webinars and 15 industry magazine articles. The project connected over 900 vegetable industry representatives with the latest application of PA approaches in vegetable systems through 23 face to face extension activities. The project achieved the development of accurate and reliable yield prediction capabilities from remotely sensed satellite imagery in carrots and sweet corn across the country. Overall accuracy of the forecasted yield were 82% (Tasmania) and 91% (Western Australia) and ranged from 74-99% accuracy. The project facilitated increased adoption through a collaborative approach to implement a range of PA technologies and practices across a range of vegetable productions systems. These include: crop sensing imagery, yield forecasting from remotely sensed crop imagery, yield and profit/loss mapping, a range of soil mapping technologies, variable rate application, precision drainage technologies and various drone applications

Moving beyond farm best practice for water quality

Nitrogen use efficiency (NUE) and reducing offsite losses in coastal intensive farming systems presents major challenges for both producers and policy makers. Despite substantial investment over the last two decades into increasing the adoption of best management practices (BMPs), suggests that adoption of BMPs alone will not be adequate to address water quality decline in the Great Barrier Reef (GBR) lagoon. However, in many cases producers and their advisors are being asked to undertake complex nutrient management often without any empirical evidence. This presentation highlights that a mix of approaches will be needed to address this wicked problem. It will highlight how even under conservative nitrogen regimes, losses of nitrogen can be substantial and that a more nuanced understanding the agricultural system can provide opportunity for water quality improvement

Nitrate removal and greenhouse gas production of woodchip denitrification walls under a humid subtropical climate

Denitrification walls are a low-cost technology with the capability to reduce nitrogen (N) loading in shallow groundwater beneath agricultural systems. The aims of this study were to quantify the effect of different carbon (C) substrates on nitrate removal rate (NRR) and greenhouse gas (GHG) production in two soil-capped denitrification walls (volume ≈ 27 m3) under subtropical climate conditions. The relative performance of softwood and hardwood woodchips to promote denitrification was tested over a 2-year program of weekly monitoring, during which water samples were collected for nitrate (NO3−) and dissolved GHG analysis. Both the softwood and the hardwood wall had similar average NRR (2.0 and 1.6 g N m−3 d−1, respectively) but were NO3− limited, and acted as a sink for nitrous oxide (N2O) produced in the walls and dissolved in the aquifer. Both walls produced carbon dioxide (CO2) and methane (CH4), with the hardwood producing respectively 3-fold and 2.5-fold higher fluxes compared to the softwood. Calculation of the Global Warming Potential (GWP) permitted a comparison of the GHG emissions within the walls in terms of CO2 equivalents (CO2-eq). Both the walls emitted CO2-eq lower than natural environments, with the softwood producing null emissions and the hardwood emitting 65-fold higher than softwood. The results of the present study suggest that woodchip bioreactors may be used to reduce nutrient loading from agricultural areas into surrounding aquatic environments as well as to decrease GHG emissions under subtropical climates, with softwood being a preferable substrate.</p

Cooperation between host immunity and the gut bacteria is essential for helminth-evoked suppression of colitis

Abstract Background Studies on the inhibition of inflammation by infection with helminth parasites have, until recently, overlooked a key determinant of health: the gut microbiota. Infection with helminths evokes changes in the composition of their host’s microbiota: one outcome of which is an altered metabolome (e.g., levels of short-chain fatty acids (SCFAs)) in the gut lumen. The functional implications of helminth-evoked changes in the enteric microbiome (composition and metabolites) are poorly understood and are explored with respect to controlling enteric inflammation. Methods Antibiotic-treated wild-type, germ-free (GF) and free fatty-acid receptor-2 (ffar2) deficient mice were infected with the tapeworm Hymenolepis diminuta, then challenged with DNBS-colitis and disease severity and gut expression of the il-10 receptor-α and SCFA receptors/transporters assessed 3 days later. Gut bacteria composition was assessed by 16 s rRNA sequencing and SCFAs were measured. Other studies assessed the ability of feces or a bacteria-free fecal filtrate from H. diminuta-infected mice to inhibit colitis. Results Protection against disease by infection with H. diminuta was abrogated by antibiotic treatment and was not observed in GF-mice. Bacterial community profiling revealed an increase in variants belonging to the families Lachnospiraceae and Clostridium cluster XIVa in mice 8 days post-infection with H. diminuta, and the transfer of feces from these mice suppressed DNBS-colitis in GF-mice. Mice treated with a bacteria-free filtrate of feces from H. diminuta-infected mice were protected from DNBS-colitis. Metabolomic analysis revealed increased acetate and butyrate (both or which can reduce colitis) in feces from H. diminuta-infected mice, but not from antibiotic-treated H. diminuta-infected mice. H. diminuta-induced protection against DNBS-colitis was not observed in ffar2−/− mice. Immunologically, anti-il-10 antibodies inhibited the anti-colitic effect of H. diminuta-infection. Analyses of epithelial cell lines, colonoids, and colon segments uncovered reciprocity between butyrate and il-10 in the induction of the il-10-receptor and butyrate transporters. Conclusion Having defined a feed-forward signaling loop between il-10 and butyrate following infection with H. diminuta, this study identifies the gut microbiome as a critical component of the anti-colitic effect of this helminth therapy. We suggest that any intention-to-treat with helminth therapy should be based on the characterization of the patient’s immunological and microbiological response to the helminth