Occurrence and Effects of Antimicrobials Drugs in Aquatic Ecosystems

Currently, thanks to the development of sensitive analytical techniques, the presence of different emerging pollutants in aquatic ecosystems has been evidenced; however, most of them have not been submitted to any regulation so far. Among emerging contaminants, antimicrobials have received particular attention in recent decades, mainly due to the concerning development of antibiotic resistance observed in bacteria, but little is known about the toxicological and ecological impact that antimicrobials can have on aquatic ecosystems. Their high consumption in human and veterinary medicine, food-producing animals and aquaculture, as well as persistence and poor absorption have caused antimicrobials to be discharged into receiving waters, with or without prior treatment, where they have been detected at ng-mg L−1 levels with the potential to cause effects on the various organisms living within aquatic systems. This review presents the current knowledge on the occurrence of antimicrobials in aquatic ecosystems, emphasizing their occurrence in different environmental matrixes and the effects on aquatic organisms (cyanobacteria, microalgae, invertebrates and vertebrates).

Forest defoliator outbreaks alter nutrient cycling in northern waters

Insect defoliators alter biogeochemical cycles from land into receiving waters by consuming terrestrial biomass and releasing biolabile frass. Here, we related insect outbreaks to water chemistry across 12 boreal lake catchments over 32-years. We report, on average, 27% lower dissolved organic carbon (DOC) and 112% higher dissolved inorganic nitrogen (DIN) concentrations in lake waters when defoliators covered entire catchments and reduced leaf area. DOC reductions reached 32% when deciduous stands dominated. Within-year changes in DOC from insect outbreaks exceeded 86% of between-year trends across a larger dataset of 266 boreal and north temperate lakes from 1990 to 2016. Similarly, within-year increases in DIN from insect outbreaks exceeded local, between-year changes in DIN by 12-times, on average. As insect defoliator outbreaks occur at least every 5 years across a wider 439,661 km2 boreal ecozone of Ontario, we suggest they are an underappreciated driver of biogeochemical cycles in forest catchments of this region.

Soil structure: its importance to resilient pastures in New Zealand (review)

Soil structure is critical to soil quality due to its influence on many soil processes and functions, including water storage and transport, the oxygen supply, the emission of greenhouse gases, and biological processes such as carbon and nitrogen mineralisation, nitrification and denitrification. These soil functions underpin key ecosystem services such as pasture production, nutrient cycling and mitigation of contaminant losses to receiving waters. The paper discusses key soil physical indicators relevant to pasture performance and the environment, including soil porosity, bulk density and hydraulic conductivity. In regions with robust programs for monitoring soil quality, e.g., Waikato, Canterbury, Auckland, Marlborough and Wellington, soil compaction is found to be widespread under pastoral land-use. The specific consequences of degraded soil quality on pasture production and financial implications remain unclear, at farm, regional and national levels. The range of impacts of soil structural damage on pasture yield, persistence, farm system response, and management practices that minimise or repair damage are presented. Knowledge gaps and further research needs are also summarised.

Antibiotics in Aquaculture Wastewater: Is It Feasible to Use a Photodegradation-Based Treatment for Their Removal?

Aquacultures are a sector facing a huge development: farmers usually applying antibiotics to treat and/or prevent diseases. Consequently, effluents from aquaculture represent a source of antibiotics for receiving waters, where they pose a potential threat due to antimicrobial resistance (AMR) induction. This has recently become a major concern and it is expectable that regulations on antibiotics’ discharge will be established in the near future. Therefore, it is urgent to develop treatments for their removal from wastewater. Among the different possibilities, photodegradation under solar radiation may be a sustainable option. Thus, this review aims at providing a survey on photolysis and photocatalysis in view of their application for the degradation of antibiotics from aquaculture wastewater. Experimental facts, factors affecting antibiotics’ removal and employed photocatalysts were hereby addressed. Moreover, gaps in this research area, as well as future challenges, were identified.

Coagulation-Flocculation of Aquaculture Wastewater Using Green Coagulant from Garcinia kola Seeds: Parametric Studies, Kinetic Modelling and Cost Analysis

To achieve sustainability, it is necessary to use proper treatment methods to reduce the pollutant loads of receiving waters. This study investigates the coagulative reduction of turbidity, COD, BOD and colour from aquaculture wastewater (AW) using a novel Garcinia kola seeds coagulant (GKC). This coagulant was obtained from extraction of Garcinia kola seeds and analysed for its spectral and morphological characteristics through FTIR and SEM. The kinetics of coagulation-flocculation were also investigated in terms of total dissolved and suspended solids (TDSP). The seeds had 11.27% protein and 68.33% carbohydrate, showing usability in adsorption/charges neutralisation as a coagulant to reduce particles. Maximal turbidity reduction = 81.93%, COD = 75.03%, BOD = 72.84% and colour = 56.69% at 0.3 g GKC/L, pH 2, 60 min and 303 K were achieved. Von Smoluchowski’s second-order peri-kinetics theory was used to fit the results, giving R2 > 0.9. At a coagulation order (α) of 2, the reaction rate (KC) and half-life (τS1/2) were 0.0003 L/g·min and 25.3 min at the optimal conditions. The sorption data better fit the Lagergren compared to the Ho adsorption model. Furthermore, the net cost of using GKC to handle 1 L of AW (including electricity and material costs) was calculated to be 1.57 EUR, and the costs of 0.3 g/L GKC preparation and energy were 0.27 and 1.30 EUR, respectively. In summary, these seeds can be used to pre-treat AW.

Micropollutant-loaded powdered activated carbon released from waste water treatment plants: a risk for sediment-dwelling organisms?

Background In order to protect aquatic environments and to reduce the presence of micropollutants in the global water cycle, wastewater treatment plants (WWTPs) often implement an additional treatment step. One of the most effective measures is the use of powdered activated carbon (PAC) as an adsorbent for micropollutants. This method provides sufficient elimination rates for several micropollutants and has been successfully employed in many WWTPs. Despite this success, there might be a drawback as the retention of the PAC in the WWTP can be challenging and losses of micropollutant-loaded PAC into the aquatic environment may occur. Upon emission, micropollutant-loaded PAC is expected to settle to the benthic zone of receiving waters, where sediment-dwelling organisms may ingest these particles. Therefore, the present study investigated possible adverse effects of micropollutant-loaded PAC from a WWTP as compared to unloaded (native) and diclofenac-loaded PAC on the sediment-dwelling annelid Lumbriculus variegatus. Results Native PAC induced the strongest effects on growth (measured as biomass) and reproduction of the annelids. The corresponding medium effective concentrations (EC50) were 1.7 g/kg and 1.8 g/kg, respectively. Diclofenac-loaded PAC showed lower effects with an EC50 of 2.5 g/kg for growth and EC50 of 3.0 g/kg for reproduction. Although tested at the same concentrations, the micropollutant-loaded PAC from the WWTP did not lead to obvious negative effects on the endpoints investigated for L.variegatus and only a slight trend of a reduced growth was detected. Conclusion We did not detect harmful effects on L. variegatus caused by the presence of MP-loaded PAC from a WWTP which gives an auspicious perspective for PAC as an advanced treatment option.

Mesocosm– and Field–Scale Evaluation of Lignocellulose– Amended Soil Treatment Areas for Removal of Nitrogen from Wastewater

Non–proprietary N–removal onsite wastewater treatment systems are less costly than proprietary systems, increasing the likelihood of adoption to lower N inputs to receiving waters. We assessed the capacity of non–proprietary lignocellulose–amended soil treatment areas (LCSTAs)—a 45–cm–deep layer of sand above a 45–cm–deep layer of sand and sawdust—to lower the concentration of total N (TN) in septic tank effluent (STE) at mesocosm and field scales. The mesocosm received wastewater for two years and had a median effluent TN concentration of 3.1 mg/L and TN removal of 60–100%, meeting regulatory standards of 19 mg/L or 50% removal. Removal varied inversely with temperature, and was lower below 10oC. Removal was higher in the mesocosm than in five field sites monitored for 12–42 months. Median effluent TN concentration and removal met the standard in three continuously–occupied homes but not for two seasonally–occupied homes. Sites differed in temporal pattern of TN removal, and in four of five sites TN removal was greater—and effluent TN concentration lower—in the LCSTA than in a control STA containing only sand. The performance of non–proprietary LCSTAs was comparable to that for proprietary systems, suggesting that these may be a viable, more affordable alternative for lowering N inputs to receiving waters.