Environmental and Socioeconomic Impacts of Poly(ethylene terephthalate) (PET) Packaging Management Strategies in the EU.

Plastics are a challenge for the circular economy due to their overall low recycling rate and high dependency on primary resources. This study analyzes the EU demand for poly(ethylene terephthalate) (PET) packaging from 2020 to 2030 and quantifies the potential environmental and societal savings by changing the waste management and consumption patterns compared with business-as-usual practices. The results of the life-cycle assessment and life-cycle costing show that a maximum of 38 Mt of CO2-eq and 34 kt of PM2.5-eq could be saved with a more efficient waste management system and a robust secondary material market while also avoiding 8.3 billion EUR2019 in societal costs (cumulative 2020-2030). However, limiting annual PET consumption growth appears to have a similar profound effect on improving the efficiency of waste management systems: 35 Mt of CO2-eq, 31 kt of PM2.5-eq, and 25 billion MEUR2019 societal costs could be saved, simply by keeping EU consumption of PET constant.

Managing the analytical challenges related to micro- and nanoplastics in the environment and food: filling the knowledge gaps.

This paper identifies knowledge gaps on the sustainability and impacts of plastics and presents some recommendations from an expert group that met at a special seminar organised by the European Commission at the end of 2018. The benefits of plastics in society are unquestionable, but there is an urgent need to better manage their value chain. The recently adopted European Strategy for Plastics stressed the need to tackle the challenges related to plastics with a focus on plastic litter including microplastics. Microplastics have been detected mainly in the marine environment, but also in freshwater, soil and air. Based on today's knowledge they may also be present in food products. Although nanoplastics have not yet been detected, it can be assumed that they are also present in the environment. This emerging issue presents challenges to better understand future research needs and the appropriate immediate actions to be taken to support the necessary societal and policy initiatives. It has become increasingly apparent that a broad and systematic approach is required to achieve sustainable actions and solutions along the entire supply chain. It is recognised that there is a pressing need for the monitoring of the environment and food globally. However, despite the number of research projects increasing, there is still a lack of suitable and validated analytical methods for detection and quantification of micro- and nanoplastics. There is also a lack of hazard and fate data which would allow for their risk assessment. Some priorities are identified in this paper to bridge the knowledge gaps for appropriate management of these challenges. At the same time it is acknowledged that there is a great complexity in the challenges that need to be tackled before a really comprehensive environmental assessment of plastics, covering their entire life cycle, will be possible.

Polyethylene recycling: Waste policy scenario analysis for the EU-27.

This paper quantifies the main impacts that the adoption of the best recycling practices together with a reduction in the consumption of single-use plastic bags and the adoption of a kerbside collection system could have on the 27 Member States of the EU. The main consequences in terms of employment, waste management costs, emissions and energy use have been quantified for two scenarios of polyethylene (PE) waste production and recycling. That is to say, a "business as usual scenario", where the 2012 performances of PE waste production and recycling are extrapolated to 2020, is compared to a "best practice scenario", where the best available recycling practices are modelled together with the possible adoption of the amended Packaging and Packaging Waste Directive related to the consumption of single-use plastic bags and the implementation of a kerbside collection system. The main results show that socio-economic and environmental benefits can be generated across the EU by the implementation of the best practice scenario. In particular, estimations show a possible reduction of 4.4 million tonnes of non-recycled PE waste, together with a reduction of around €90 million in waste management costs in 2020 for the best practice scenario versus the business as usual scenario. An additional 35,622 jobs are also expected to be created. In environmental terms, the quantity of CO2 equivalent emissions could be reduced by around 1.46 million tonnes and the net energy requirements are expected to increase by 16.5 million GJ as a consequence of the reduction in the energy produced from waste. The main analysis provided in this paper, together with the data and the model presented, can be useful to identify the possible costs and benefits that the implementation of PE waste policies and Directives could generate for the EU.

Relevance of two-dimensional Brownian motion dynamics in applying nanoparticle tracking analysis.

Nanoparticle Tracking Analysis (NTA) is an image analysis-based technique that deduces the particle size from the changing position of scattering diffusing particles in a sequence of images. It is shown that a basic understanding of the underlying physical principles largely helps to prevent artifacts. In fact, an inappropriate selection of both software parameters, such as maximum particle jump or minimum track length, as well as sample preparation aspects (such as degree of dilution) may give rise to inaccurate or even erroneous results.

Mineralogy and leachability of gasified sewage sludge solid residues.

Gasification of sewage sludge produces combustible gases as well as tar and a solid residue as by-products. This must be taken into account when determining the optimal thermal conditions for the gasification process. In this study, the influence of temperature, heating atmosphere and residence time on the characteristics of the gasified sewage sludge residues is investigated. ICP-AES analyses reveal that the major chemical elements in the char residues are phosphorus, calcium, iron and silicon. Heavy metals such as copper, zinc, chromium, nickel and lead are also present at relatively high levels - from 50 to more than 1000 mg/kg of dry matter. The major mineral phases' identification - before and after heating - as well as their morphology and approximate chemistry (XRD and SEM-EDX) demonstrate that a number of transformations take place during gasification. These are influenced by the reactor's temperature and the oxidative degree of its internal atmosphere. The copper-, zinc- and chromium-bearing phases are studied using chemometric tools, showing that the distribution of those metals among the mineral phases is considerably different. Finally, batch-leaching tests reveal that metals retained in the residue are significantly stabilized after thermal treatment to a higher or lower extent, depending on the thermal conditions applied.

A method for visualising polyelectrolyte distribution after polyelectrolyte conditioning of a biotic sludge.

Charge neutralisation is an important mechanism in (polyelectrolyte) conditioning of biotic sludges and required for efficient sludge dewatering. Based on results from streaming potential and zeta potential measurements, it has been suggested that charge neutralisation is more complete on the outside of the sludge flocs than on the inside. This paper discusses the development of a technique for assessing the spatial distribution of polyelectrolyte (PE) within sludge flocs. After flocculation with a fluorescently labelled PE, fluorescence microscopy can be used to visualise the distribution of the PE in the sludge flocs. Preliminary results indicate that the PE can penetrate relatively deep into the sludge flocs (and flocculi). Inhomogeneity in the PE distribution arises from differences in exposure to PE in different regions, and from differences in the affinity of the PE for different substances.

Microalgal bacterial floc properties are improved by a balanced inorganic/organic carbon ratio.

Microalgal bacterial floc (MaB-floc) reactors have been suggested as a more sustainable secondary wastewater treatment. We investigated whether MaB-flocs could be used as tertiary treatment. Tertiary influent has a high inorganic/organic carbon ratio, depending on the efficiency of the secondary treatment. In this study, the effect of this inorganic/organic carbon ratio on the MaB-flocs performance was determined, using three sequencing batch photobioreactors. The MaB-flocs were fed with synthetic wastewater containing 84, 42, and 0 mg L(-1) C-KHCO(3) supplemented with 0, 42, 84 mg L(-1) C-sucrose, respectively, representing inorganic versus organic carbon. Bicarbonate significantly decreased the autotrophic index of the MaB-flocs and resulted in poorly settling flocs. Moreover, sole bicarbonate addition led to a high pH of 9.5 and significant lower nitrogen removal efficiencies. Sucrose without bicarbonate resulted in good settling MaB-flocs, high nitrogen removal efficiencies and neutral pH levels. Despite the lower chlorophyll a content of the biomass and the lower in situ oxygen concentration, 92-96% of the soluble COD-sucrose was removed. This study shows that the inorganic/organic carbon ratio of the wastewater is of major importance and that organic carbon is requisite to guarantee a good performance of the MaB-flocs for wastewater treatment.

Virus disinfection in water by biogenic silver immobilized in polyvinylidene fluoride membranes.

The development of innovative water disinfection strategies is of utmost importance to prevent outbreaks of waterborne diseases related to poor treatment of (drinking) water. Recently, the association of silver nanoparticles with the bacterial cell surface of Lactobacillus fermentum (referred to as biogenic silver or bio-Ag(0)) has been reported to exhibit antiviral properties. The microscale bacterial carrier matrix serves as a scaffold for Ag(0) particles, preventing aggregation during encapsulation. In this study, bio-Ag(0) was immobilized in different microporous PVDF membranes using two different pre-treatments of bio-Ag(0) and the immersion-precipitation method. Inactivation of UZ1 bacteriophages using these membranes was successfully demonstrated and was most probably related to the slow release of Ag(+) from the membranes. At least a 3.4 log decrease of viruses was achieved by application of a membrane containing 2500 mg bio-Ag(0)(powder) m(-2) in a submerged plate membrane reactor operated at a flux of 3.1 L m(-2) h(-1). Upon startup, the silver concentration in the effluent initially increased to 271 µg L(-1) but after filtration of 31 L m(-2), the concentration approached the drinking water limit ( = 100 µg L(-1)). A virus decline of more than 3 log was achieved at a membrane flux of 75 L m(-2) h(-1), showing the potential of this membrane technology for water disinfection on small scale.

Determination of charge density and adsorption behaviour of DMAEA-Q-based cationic polymers by fluorimetric analysis.

In wastewater and sludge treatment, cationic polymers are applied at large scale. A correct determination of the charge density and adsorption efficiency is of high importance for an economic and ecologically sound operation. Although several analytical techniques exist for charge density and polymer concentration determination, they often suffer from laborious sample pretreatment, complex instrumentation or interference from background components present in sludge. In this work, an alternative method has been studied to determine the charge density of an important series of cationic polymers used in water and sludge treatment, viz. copolymers containing quaternised dimethylaminoethylacrylate (DMAEA-Q). The method is based on the basic hydrolysis of the cationic moiety, resulting in choline chloride, which is measured by a fluorimetric technique based on the enzymatic conversion of choline. It was demonstrated that the new technique ensures a highly reliable determination of the charge density of these polymers, based on a comparison with the traditional charge titration technique and the data supplied by the manufacturer. Moreover, the specificity of the enzymatic conversion method also allows the determination of non-adsorbed polymer in conditioned sludge samples, without interference from other components. As a consequence, it enables the determination of the optimal polymer dose in practical conditioning and dewatering operations.

Quantification of hydrolytic charge loss of DMAEA-Q-based polyelectrolytes by proton NMR spectroscopy and implications for colloid titration.

Copolymers of acrylamide and quaternised dimethylaminoethyl acrylate (DMAEA-Q) constitute an economically important range of cationic polyelectrolytes used in sludge conditioning. The latter treatment involves charge neutralisation and bridging induced by these polymers. Since both of these phenomena rely on charge-driven sorption onto the negatively charged colloidal particles, the accurate assessment of their charge density is of primary importance in polyelectrolyte characterisation. The experimental determination of this characteristic generally relies on colloidal charge titration, in which the cationic polymer is titrated against an anionic polymer. Hereby, one of the requirements to have a stoichiometric reaction between the oppositely charged polymers is a sufficiently low polymer concentration. In this study, it is shown that such a low polymer concentration may entail a pronounced hydrolysis effect for DMAEA-Q-based polymers, which leads to a release of the cationic side groups and hence causes considerable errors on the charge titration results. Proton nuclear magnetic resonance spectroscopy was applied to investigate the fast hydrolysis kinetics of DMAEA-Q polymers together with time-dependent charge titration measurements. Diffusion NMR spectroscopy was used to assist in establishing the nature of the hydrolysis compounds. The results from both techniques indicate that a high degree of hydrolysis is reached within minutes after dilution of a concentrated polymer stock solution into aqueous solutions of slightly acidic to neutral pH values. Therefore, a modification to the classic colloid titration procedure is proposed, using a buffered dilution liquid to avoid polymer hydrolysis. It is shown that a buffer pH value of 4.5 avoids not only polymer hydrolysis effects but also possible protonation of the anionic titrant, thereby avoiding overestimation of the charge density. By means of this procedure, reproducible and time-independent charge titration results are obtained.

Optimization of sewage sludge conditioning and pressure dewatering by statistical modelling.

By using a quadratic model, an assessment was made of the relative importance of different sludge and polyelectrolyte variables with respect to sludge pressure dewatering. It was seen that the polyelectrolyte characteristics and dose dominated the cake dry matter content and that sludge properties were less important, especially the electrophoretic mobility of the sludge, which showed a restricted natural variability over the 10-month sampling period. The developed quadratic model in this study appeared very well suited to quantitatively predict the pressure dewatering properties of sludge, allowing the selection of the dose and polyelectrolyte type that yield the best dewatering result. It was further shown that relatively small deviations from the optimal polyelectrolyte dose caused only small changes in cake dry matter values. The model appeared to be applicable on a long-term basis, as it was able to predict the dewaterability of several sludge samples from the studied wastewater treatment plant after more than 3 years. Finally, the model also allowed an (simplified) economic evaluation, indicating that for high cake disposal costs, the polyelectrolyte should be taken that guarantees the best dewatering results, even if it has to be applied in high doses.

In situ determination of solidosity profiles during activated sludge electrodewatering.

Two non-invasive techniques were evaluated for the on-line measurement of sludge solidosity profiles during both pressure and electrodewatering operations. In a first approach, a radioactive tracer adsorbed onto the sludge solids was monitored by a gamma camera. Although this technique appeared very flexible in use, the lack of resolution highly limited its usefulness for (electro)dewatering experiments. Improvement in gamma camera resolution by the development of new detectors might, however, increase the future applicability of this technique. In a second technique, nuclear magnetic resonance measurements on a specially designed electrodewatering unit were made. Hereby, reliable on-line measurements of the solidosity profiles of activated sludge during electrodewatering could be made, with a resolution of less than 1mm. Thus, the mechanisms of electroosmotic- and pressure-driven cake dewatering could be illustrated. Given the measurement time required for measuring one sludge profile, both techniques appeared mainly suited for slowly varying processes, such as activated sludge expression, and not for fast changing processes, such as the initial phases of sludge filtration.

Bio-deposition of a calcium carbonate layer on degraded limestone by Bacillus species.

To obtain a restoring and protective calcite layer on degraded limestone, five different strains of the Bacillus sphaericus group and one strain of Bacillus lentus were tested for their ureolytic driven calcium carbonate precipitation. Although all the Bacillus strains were capable of depositing calcium carbonate, differences occurred in the amount of precipitated calcium carbonate on agar plate colonies. Seven parameters involved in the process were examined: calcite deposition on limestone cubes, pH increase, urea degrading capacity, extracellular polymeric substances (EPS)-production, biofilm formation, zeta-potential and deposition of dense crystal layers. The strain selection for optimal deposition of a dense CaCO(3) layer on limestone, was based on decrease in water absorption rate by treated limestone. Not all of the bacterial strains were effective in the restoration of deteriorated Euville limestone. The best calcite precipitating strains were characterised by high ureolytic efficiency, homogeneous calcite deposition on limestone cubes and a very negative zeta-potential.

Effect of polyelectrolyte conditioning on the enhanced dewatering of activated sludge by application of an electric field during the expression phase.

Activated sludge is known to be poorly dewaterable due to its high surface charge density and the extreme solids compressibility, even after polyelectrolyte conditioning. The application of an electric field during pressure dewatering (PDW) of sludge can enhance the dewaterability by the electroosmosis effect. A comparative study was conducted to investigate the additional effect of an electric field, applied during the expression phase, on the dewatering course of polyelectrolyte conditioned sludge, compared to mere PDW. It was found that the application of an electric field markedly improved the dewatering kinetics for all sludge samples, regardless of the conditioning treatment. Although the conditioning polyelectrolyte characteristics and dose had a major effect on the PDW of sludge, the conditioning history did not have a significant effect on the electroosmotic water transport efficiency during the sludge expression phase. By means of on-line streaming potential measurements and fractionated filtrate electrophoretic mobility measurements, it could be demonstrated that even at high polyelectrolyte doses, leading to positively charged sludge flocs, negative surface charges were still present inside the sludge matrix. During the expression of the sludge cake, when liquid is forced to move through the floc inside pores, these negative surface charges hampered PDW, but enhanced electroosmotic dewatering. Electroosmosis is therefore an appropriate technique to remove the water fraction that is associated with these negative surface charges.