Plastic packaging waste in Europe: Addressing methodological challenges in recording and reporting.

A reliable comparison of European Union (EU) Member States' reporting of statistics on plastic packaging waste generation, recycling and recovery is necessary if there is to be a fair transition to a circular economy across the EU. It is a priority for there to be an improvement in the quality and validity of these statistics to assess each Member State's performance in relation to EU targets. This article explores the quality of national reporting based on the two main approaches which are used to calculate packaging waste generation, namely 'placed on the market' and 'waste analysis'. The findings outline how Member States apply a variety of approaches leading to different packaging waste statistics which makes reported data difficult to compare. Often, it is not clear what approach is applied in different counties. Factors such as freeriding, non-compliance and de minimis have represented the primary weaknesses in evaluating and reporting packaging waste statistics as producers have financial incentives for under-reporting. This article highlights the need to inform circular economy strategies by addressing the challenge of comparing data on packaging and plastic packaging waste generation across the EU.

Spatial Variation of the Microbial Community Structure of On-Site Soil Treatment Units in a Temperate Climate, and the Role of Pre-treatment of Domestic Effluent in the Development of the Biomat Community.

The growth of microbial mats or "biomats" has been identified as an essential component in the attenuation of pollutants within the soil treatment unit (STU) of conventional on-site wastewater treatment systems (OWTSs). This study aimed to characterize the microbial community which colonizes these niches and to determine the influence of the pre-treatment of raw-domestic wastewater on these communities. This was achieved through a detailed sampling campaign of two OWTSs. At each site, the STU areas were split whereby half received effluent directly from septic tanks, and half received more highly treated effluents from packaged aerobic treatment systems [a coconut husk media filter on one site, and a rotating biodisc contactor (RBC) on the other site]. Effluents from the RBC had a higher level of pre-treatment [~90% Total Organic Carbon (TOC) removal], compared to the media filter (~60% TOC removal). A total of 92 samples were obtained from both STU locations and characterized by 16S rRNA gene sequencing analysis. The fully treated effluent from the RBC resulted in greater microbial community richness and diversity within the STUs compared to the STUs receiving partially treated effluents. The microbial community structure found within the STU receiving fully treated effluents was significantly different from its septic tank, primary effluent counterpart. Moreover, the distance along each STU appears to have a greater impact on the community structure than the depth in each STU. Our findings highlight the spatial variability of diversity, Phylum- and Genus-level taxa, and functional groups within the STUs, which supports the assumption that specialized biomes develop around the application of effluents under different degrees of treatment and distance from the source. This research indicates that the application of pre-treated effluents infers significant changes in the microbial community structure, which in turn has important implications for the functionality of the STU, and consequently the potential risks to public health and the environment.

The influence of pre-treatment on biomat development in soil treatment units.

Soil treatment units (STUs) receiving effluent from on-site wastewater treatment systems (OWTSs) rely on the gradual development of a microbial biomat/biozone at the infiltrative surface for optimal effluent distribution and pollutant attenuation. Here, we present the first direct measurement of gradual biomat development in the field in STU trenches receiving either primary (PE) or secondary treated effluent (SE) under identical environmental, hydrological and subsoil conditions. Two domestic OWTSs were constructed in Ireland and monitored over a period of >2 years using an automated, three-dimensional network of buried soil water content sensors tracking water flow and retention within the soil underneath the infiltrative surface. While trenches receiving PE expressed signs of biomat formation along the entire length of STU trenches, biomats in trenches receiving SE were significantly muted and did not extend further than 10 m from the inlet at the end of the study. The presence of a mature biomat helped to retain soil moisture above background levels and made the system more resilient towards drought events and desiccation stress but led, in one case, to effluent ponding within the trenches. A growth-limited non-linear model fit revealed that biomats in SE trenches are expected to remain considerably shorter and will not spread along the entire trench design length, even after 10 years of operation, which is contrary to prevalent design assumptions. Muted biomat growth, on the contrary, might lead to localized hydraulic and pollutant overloading and has been shown previously to negatively affect the ability to attenuate pollutants effectively within the soil profile before the effluent reaches the groundwater.

Spatial and temporal variation of CO2 and CH4 emissions from a septic tank soakaway.

CO2 and CH4 flux measurements over a septic tank soakaway located in a northern maritime climate (Ireland) were conducted for a period of 81 days using a multi-chamber automated soil gas flux chamber system with high spatial and temporal resolution. Overall median CO2 fluxes were 7.28; 6.40 µmol CO2 m-2 s-1 from the soakaway and control soil, respectively. Overall median CH4 fluxes were - 0.28; -0.67 nmol CH4 m-2 s-1 from the soakaway and control soil, respectively. While CO2 fluxes expressed strong diurnal variability driven by soil temperature, CH4 fluxes were less affected by environmental factors and effectively limited to the first few meters from the septic tank. However, localised CH4 degassing events were observed during drying conditions with up to 60-times higher fluxes compared to the overall median. The soakaway was found to be a net emitter of both CO2 and CH4, releasing a total of 7.327 kg CO2 yr-1 and 0.033 kg CO2Eq. yr-1, respectively. The apparent spatio-temporal heterogeneity of observed soil gas fluxes identified in this study emphasises the importance of integrating measurements with both high spatial and temporal resolution from on-site installations as engineered nature-based solutions.

Methane-derived carbon in the benthic food web in stream impoundments.

Methane gas (CH4) has been identified as an important alternative source of carbon and energy in some freshwater food webs. CH4 is oxidized by methane oxidizing bacteria (MOB), and subsequently utilized by chironomid larvae, which may exhibit low δ(13)C values. This has been shown for chironomid larvae collected from lakes, streams and backwater pools. However, the relationship between CH4 concentrations and δ(13)C values of chironomid larvae for in-stream impoundments is unknown. CH4 concentrations were measured in eleven in-stream impoundments located in the Queich River catchment area, South-western Germany. Furthermore, the δ(13)C values of two subfamilies of chironomid larvae (i.e. Chironomini and Tanypodinae) were determined and correlated with CH4 concentrations. Chironomini larvae had lower mean δ(13)C values (-29.2 to -25.5 ‰), than Tanypodinae larvae (-26.9 to -25.3 ‰). No significant relationships were established between CH4 concentrations and δ(13)C values of chironomids (p>0.05). Mean δ(13)C values of chironomid larvae (mean: -26.8‰, range: -29.2‰ to -25.3‰) were similar to those of sedimentary organic matter (SOM) (mean: -28.4‰, range: -29.3‰ to -27.1‰) and tree leaf litter (mean: -29.8 ‰, range: -30.5‰ to -29.1‰). We suggest that CH4 concentration has limited influence on the benthic food web in stream impoundments.