SBBGR technology for reducing waste sludge production during plastic recycling process: Assessment of potential increase in sludge hazardousness.

Sludge production in the wastewater treatment sector is consistently increasing and represents a critical environmental and economic issue. This study evaluated an unconventional approach for treating wastewater generated from the cleaning of non-hazardous plastic solid waste during the plastic recycling process. The proposed scheme was based on sequencing batch biofilter granular reactor (SBBGR) technology, which was compared with the activated sludge-based treatment currently in operation. These treatment technologies were compared regarding sludge quality, specific sludge production, and effluent quality to highlight whether the reduced sludge production shown by SBBGR corresponded to an increase in the concentration of hazardous compounds in the sludge. The SBBGR technology showed remarkable removal efficiencies (TSS, VSS, and NH3 > 99 %; COD >90 %; TN and TP > 80 %) and a sludge production six-fold lower than the conventional plant (in terms of kgTSS/kg CODremoved). Biomass from the SBBGR did not show a significant accumulation of organic micropollutants (i.e., long-chain hydrocarbons, chlorinated pesticides and chlorobenzenes, PCB, PCDD/F, PAH, chlorinated and brominated aliphatic compounds, and aromatic solvents), whereas a certain accumulation of heavy metals was observed. Furthermore, an initial attempt to compare the operating costs of the two treatment approaches revealed that the SBBGR technology would provide 38 % savings.

Use of constructed wetlands to prevent overloading of wastewater treatment plants.

The fluctuation in the number of people in tourist areas affects the wastewater quality and quantity. Constructed wetlands (CWs) aim to simulate physical, chemical, and biological processes occurring in natural environments for wastewater treatment and are considered a sustainable system. The current study aimed at evaluating the effectiveness of in-vessel CWs for supporting the wastewaters treatment plants in periods of overloading. Such approach can be quickly implementable, economic, and the CWs can be fast regenerated in the framework of sustainable good practices. Three pilot scale CWs were prepared in as many containers layering 10 cm of gravel, 60 cm of sand and 10 cm of gravel, and placing pieces of giant reed rhizomes in the upper layers. The bottom of each CW had a tap, and CWs were irrigated with a real municipal sewage three times a week. Before each new irrigation, the tap was opened, and the effluent collected for determining gross parameters, elemental composition, and contaminants of emerging concern (CECs). CWs significantly reduced almost all gross parameters considered and half the CECs, except for a couple of metabolites of corresponding parental compounds. With regards to the potentially toxic elements, all reduced their concentration from the influents to the effluents. The results of this study were promising and highlighted good efficiency of constructed wetlands as pre-treatment of real municipal sewage to reduce the overloading of the wastewater treatment plant.

Treating and reusing wastewater generated by the washing operations in the non-hazardous plastic solid waste recycling process: Advanced method vs. conventional method.

The effectiveness of an advanced treatment of wastewater generated by non-hazardous plastic solid waste (PSW) washing, based on the Sequencing Batch Biofilter Granular Reactor (SBBGR), was assessed in terms of gross parameters, removal efficiencies and sludge production. The proposed treatment was also compared with the conventional treatment, which was based on primary and secondary treatments, using the activated sludge process, performed by Recuperi Pugliesi, a leading company in the plastic recycling industry located in Bari, Italy. The company produces low-density polyethylene (LDPE) regenerated granules from PSW used in agricultural and floricultural greenhouse activities and industrial packaging after a washing stage in the aqueous phase. The latter generates large volumes of wastewater, the conventional treatment of which is characterised by large quantities of sludge and the associated disposal problems. Under steady-state conditions, the SBBGR provided impressive removal efficiencies regarding the main gross parameters (over 90% for COD and TKN, over 99% for BOD5, TSS, VSS and NH3, and over 80% for TN) with a statistically better effluent quality than that of the conventional treatment. The SBBGR effluent quality was modelled in terms of washing water characteristics by using generalized additive models (GAMs). The SBBGR treatment was characterised by a specific sludge production five times lower than that of the conventional treatment (0.21 kg TSS vs. 1.0 kg TSS per m3 of wastewater treated). Compared with the conventional treatment, the proposed process showed a five-fold reduction in the cost of sludge disposal, which saved 50% of the operating cost.

Full-scale sludge reduction in the water line of municipal wastewater treatment plant.

Nowadays, sludge management represents one of the most critical challenges in the field of sewage treatment for economic and environmental impacts. Therefore, the reduction of sludge has become a major issue for the operators of municipal wastewater treatment plants. In the present paper, a new system, whose acronym is MULESL (MUch LEss SLudge), is proposed and tested at full scale for reducing the quantity of sludge in the water line of the sewage treatment plant. MULESL system takes the advantage of maintenance metabolism to significantly reduce the sludge production. The effectiveness of MULESL system in removing the typical pollutants and reducing sludge production was evaluated at full scale by using 3500 PE unit located in Putignano's WWTP (Puglia, Italy). This unit was obtained by retrofitting an existing activated sludge basin. The results obtained over 1-year period, during which MULESL unit treated the effluent of the preliminary treatment step, have indicated that it was characterized by a specific sludge production as low as 0.13 kg of dry sludge per kg of COD removed; 77% lower than that recorded for primary and secondary treatments of the conventional plant during the same period. This sludge reduction was obtained with a plant volume 27% smaller than that of the conventional water line. Furthermore, the organic matter of the sludge was already stabilized, thus allowing to save investment costs for digestion process facilities. Finally, MULESL unit guaranteed a mean removal efficiency higher than 95% for COD, BOD5, TSS, TKN, NH3 and TN.

Aerobic granular-based technology for water and energy recovery from municipal wastewater.

In the present study, the possibility of recovering both thermal energy and water for agricultural purposes from sewage is evaluated. A treatment plant, based on a sequencing batch biofilter granular reactor (SBBGR) followed by sand filtration and coupled with a solar wastewater source heat pump, was operated from September to November 2018 at a set-point temperature of 14 °C to verify the stability of heat recovery efficiency and the suitability of plant effluent to be reused for irrigation. Heat recovery did not influence the SBBGR treatment and disinfection efficiency, which removed about 90% of suspended solids, chemical and biochemical oxygen demand and ammonia, as well as 70% of total nitrogen, 3 log10 units of Escherichia coli and more than 1 log10 unit of Clostridium perfringens. Furthermore, after sand filtration, water quality complied with the standards for agricultural reuse currently in force in several countries. Energy extracted from SBBGR was mainly influenced by environmental conditions, affecting wastewater temperature, and also by wastewater composition, affecting the energy release due to bacterial metabolic activity for carbon and nitrogen removal. Notably, no evident deterioration of energy extraction efficiency from the SBBGR was observed, suggesting negligible fouling phenomena on the submerged thermal exchanger.

In-house validation and small-scale collaborative study to evaluate analytical performances of multimycotoxin screening methods based on liquid chromatography-high-resolution mass spectrometry: Case study on Fusarium toxins in wheat.

A strong trend toward using highly selective mass spectrometry technologies for screening of multiple mycotoxins has been observed in recent years. In the present study, the process of validation of a multimycotoxin screening method based on liquid chromatography-high-resolution mass spectrometry method is presented. The method was intended for the simultaneous screening of the major Fusarium toxins (deoxynivalenol, 3- and 15-acetyl deoxynivalenol, T-2 and HT-2 toxins, zearalenone, enniatins A, A1, B, and B1, and beauvericin) in wheat. The sample preparation protocol was based on a double extraction (methanol followed by acetonitrile/water mixture) and purification through solid-phase extraction C18 column. To provide insights for full exploitation of the potential of the double-stage high-resolution mass spectrometry detection, a full-scan acquisition event followed by a sequence of 5 fragmentation events (variable data-independent acquisition) was set for mycotoxin detection, the latter to be exploited for confirmatory purposes. Method analytical performances were evaluated through in-house validation and small-scale interlaboratory study, designed according to Commission Regulation 519/2014/EU, setting performance requirements for screening methods for mycotoxins. Screening target concentrations were close to European Union maximum permitted or indicative levels. The in-house validation provided the precision of the response under repeatability conditions and the intermediate precision (both resulting lower than 30%), the cutoff value, and the rate of false suspect results for negative (free of the mycotoxin of interest) samples, which resulted lower than 0.1% in all cases. The collaborative study provided reproducibility and laboratory independent cutoff values. Analysis of reference materials proved method trueness and suitability for screening of the major Fusarium mycotoxins in wheat. Finally, the applicability of the full-scan/variable data-independent acquisition detection approach was successfully tested on a set of naturally contaminated wheat samples, where 2 characteristic product ions could be detected for all identified mycotoxins even at levels in the low µg/kg range.