Effective removal of iron, nutrients, micropollutants, and faecal bacteria in constructed wetlands cotreating mine water and sewage treatment plant effluent.

Regulators in England and Wales have set new targets under the Environment Act 2021 for freshwater quality by 2038 that include halving the length of rivers polluted by harmful metals from abandoned mines and reducing phosphorus loadings from treated wastewater by 80%. In this context, an intriguing win-win opportunity exists in the removal of iron from abandoned mines and phosphate from small sewage treatment plants by coprecipitation in constructed wetlands (CWs). We investigated such a CW located at Lamesley, Northeast England, which cotreats abandoned coal mine and secondary-treated sewage treatment plant effluents. We assessed the removal of nutrients, heavy metals, organic micropollutants, and faecal coliforms by the CW, and characterized changes in the water bacteriology comprehensively using environmental DNA. The CW effectively removed ammonium-nitrogen, phosphorus, iron, and faecal coliforms by an average of 86, 74, 98, and 75%, respectively, to levels below or insignificantly different from those in the receiving river. The CW also effectively removed micropollutants such as acetaminophen, caffeine, and sulpiride by 70-100%. Molecular microbiology methods showed successful conversion of sewage and mine water microbiomes into a freshwater microbiome. Overall, the CW significantly reduced impacts on the rural water environment with minimal operational requirements.

Environmental DNA clarifies impacts of combined sewer overflows on the bacteriology of an urban river and resulting risks to public health.

There is no reference of microbiological water quality in the European Union's Water Framework Directive, adapted into English law, and consequently microbial water quality is not routinely monitored in English rivers, except for two recently designated bathing water sites. To address this knowledge gap, we developed an innovative monitoring approach for quantitative assessment of combined sewer overflow (CSO) impacts on the bacteriology of receiving rivers. Our approach combines conventional and environmental DNA (eDNA) based methods to generate multiple lines of evidence for assessing risks to public health. We demonstrated this approach by investigating spatiotemporal variation in the bacteriology of the Ouseburn in northeast England for different weather conditions in the summer and early autumn of the year 2021 across eight sampling locations that comprised rural, urban, and recreational land use settings. We characterized pollution source attributes by collecting sewage from treatment works and CSO discharge at the peak of a storm event. CSO discharge was characterized by log10 values per 100 mL (average ± stdev) of 5.12 ± 0.03 and 4.90 ± 0.03 for faecal coliforms and faecal streptococci, and 6.00 ± 0.11 and 7.78 ± 0.04 for rodA and HF183 genetic markers, for E. coli and human host associated Bacteroides, respectively, indicating about 5 % sewage content. SourceTracker analysis of sequencing data attributed 72-77 % of bacteria in the downstream section of the river during a storm event to CSO discharge sources, versus only 4-6 % to rural upstream sources. Data from sixteen summer sampling events in a public park exceeded various guideline values for recreational water quality. Quantitative microbial risk assessment (QMRA) predicted a median and 95th percentile risk of 0.03 and 0.39, respectively, of contracting a bacterial gastrointestinal disease when wading and splashing around in the Ouseburn. We show clearly why microbial water quality should be monitored where rivers flow through public parks, irrespective of their bathing water designation.

Valorisation of agricultural waste derived biochars in aquaculture to remove organic micropollutants from water - experimental study and molecular dynamics simulations.

In this work, we evaluated the valorisation of agricultural waste materials by transforming coconut husks and shells, corncobs and rice straw into biochar for water treatment in aquaculture. We compared the biochars' suitability for removal of organic micropollutants (acetaminophen, oxytetracycline, tetracycline, enrofloxacin, atrazine, diuron and diclofenac) from surface water needed for aquaculture. The biochars were prepared by three methods ranging from inexpensive drum kilns (200 °C) to pyrolysis with biogasfication (350-750 °C). Overall, antibiotics tetracycline and enrofloxacin were the most strongly sorbed micropollutants, and coconut husk biochar prepared at 750 °C was the best sorbent material. Molecular Dynamics simulations indicated that the major sorption mechanism is via π-π stacking interactions and there is a possibility of multilayer sorption for some of the micropollutants. We observed, a strong impact of ionic strength (salinity), which is an important consideration in coastal aquaculture applications. High salinity decreased the sorption for antibiotics oxytetracycline, tetracycline and enrofloxacin but increased diclofenac, atrazine and diuron sorption. We considered coconut husk biochar produced in drum kilns the most practical option for biochar applications in small-scale coastal aquacultures in South Asia. Pilot trials of canal water filtration at an aquaculture farm revealed that micropollutant sorption by coconut husk biochar under real-world conditions might be 10-500 times less than observed in the laboratory studies. Even so, biochar amendment of sand enhanced the micropollutant retention, which may facilitate subsequent biodegradation and improve the quality of brackish surface water used for food production in coastal aquaculture.

Coconut husk biochar amendment enhances nutrient retention by suppressing nitrification in agricultural soil following anaerobic digestate application.

Anaerobic digestate and biochar are by-products of the biogasification and pyrolysis of agricultural wastes. This study tested the hypothesis that combined application of anaerobic pig/cattle manure digestate and coconut husk (CH) biochar can improve soil nutrient conditions, whilst minimizing atmospheric and groundwater pollution risks. Microcosms simulated digestate application to agricultural soil with and without CH biochar. Ammonia volatilization and nutrient leaching were quantified after simulated heavy rainfalls. Archaeal and bacterial community and abundance changes in soils were quantified via next generation sequencing and qPCR of 16S rRNA genes. Nitrifying bacteria were additionally quantified by qPCR of functional genes. It was found that CH biochar retarded nitrate leaching via slower nitrification in digestate-amended soil. CH biochar reduced both nitrifying archaea and bacteria abundance in soil by 71-83 percent in the top 4 cm soil layer and 66-80 percent in the deeper soil layer one month after the digestate application. Methanotroph abundances were similarly reduced in the CH biochar amended soils. These findings demonstrate combined benefits of anaerobic digestate and CH biochar application which are relevant for the development of a more circular rural economy with waste minimization, renewable energy production, nutrient recycling and reduced water pollution from agricultural land.