Techno-environmental and economic assessment of color removal strategies from textile wastewater.

The textile industry is one of the most chemical-intensive processes, resulting in the unquestionable pollution of more than a quarter of the planet's water bodies. The high recalcitrant properties of some these pollutants resulted on the development of treatment technologies looking at the larger removal efficiencies, due to conventional systems are not able to completely remove them in their effluents. However, safeguarding the environment also implies taking into account indirect pollution from the use of chemicals and energy during treatment.

Extractive membrane bioreactor to detoxify industrial/hazardous landfill leachate and facilitate resource recovery.

Landfill leachate is a highly polluted and toxic waste stream harmful to the environment and human health, its biological treatment, even if challenging, offers the opportunity of recovering valuable resources. In this study, we propose the application of an extractive membrane bioreactor equipped with a polymeric tubing, made of Hytrel, as an innovative device able to remove specific organic toxic compounds of the leachate and, at the same time, to produce an effluent rich in valuable chemicals suitable for recovery. The leachate treatment consists in a two-step process: the extraction of specific toxic compounds through the polymeric tubing based on the affinity with the polymer, and their subsequent biodegradation in controlled conditions in the bulk phase of the extractive membrane bioreactor, thus avoiding the direct contact of the microbial consortium with the toxic leachate.

Anaerobic biodegradation of phenol in wastewater treatment: achievements and limits.

Anaerobic biodegradation of toxic compounds found in industrial wastewater is an attractive solution allowing the recovery of energy and resources but it is still challenging due to the low kinetics making the anaerobic process not competitive against the aerobic one. In this review, we summarise the present state of knowledge on the anaerobic biodegradation process for phenol, a typical target compound employed in toxicity studies on industrial wastewater treatment. The objective of this article is to provide an overview on the microbiological and technological aspects of anaerobic phenol degradation and on the research needs to fill the gaps still hindering the diffusion of the anaerobic process.

Anaerobic phenol biodegradation: kinetic study and microbial community shifts under high-concentration dynamic loading.

The anaerobic biodegradation of phenol has been realised in a sequencing batch reactor (SBR) under anaerobic conditions with phenol as sole carbon and energy source and with glucose as co-substrate. A step-change increase of phenol loading (from 100 up to 2000 mg/L of phenol concentration in the feed solution) has been applied during the acclimation phase in order to progressively induce the development of a specialised microbial consortium. This approach, combined with the dynamic sequence of operations characterising SBRs and with the high biomass retention time, led to satisfactory phenol and COD removal efficiencies with values > 70% for the highest phenol input (2000 mg/L) fed as the single carbon and energy source.

Self-regenerating tubing bioreactor for removal of toxic substrates: Operational strategies in response to severe dynamic loading conditions.

A tubing TPPB (Two-Phase Partitioning Bioreactor) was operated with the objective of verifying the effective treatment of a phenolic synthetic wastewater with simultaneous polymeric tubing bioregeneration by introducing tubing effluent recycle and modifications to the Hydraulic Retention Time (HRT). 2,4-dichlorophenol (DCP) was employed as the target substrate and the bioreactor was operated for a 3 month period under severe loading conditions (from 77 to 384 mg/L d) with HRT in the tubing in the range of 2-4 h. Tubing effluent recycle (recycle flow rate/influent flow rate ratio = 0.

Post-aerobic treatment to enhance the removal of conventional and emerging micropollutants in the digestion of waste sludge.

Low content of micropollutants in sewage sludge, essential to allow its safe re-use in agriculture, requires effective removals during the digestion phase. To this purpose, we investigated the performance of the anaerobic-aerobic sequential digestion process applied to real waste sludge in the removal of several classes of standard pollutants, i.e.

Anaerobic-aerobic sequential treatment: Temperature optimization and cost implications.

Traditionally, aeration units, used as a polishing stage after anaerobic digestion (AD) of wastes, are operated at ambient temperature. Yet, when effluent quality is the main design criterion, raising the temperature of the aeration stage can be justified by improved removal efficiencies. In this study, an anaerobic-aerobic sequential system (AASS) was operated to co-digest raw wastewater and food waste.

Polymer extraction and ex situ biodegradation of xenobiotic contaminated soil: Modelling of the process concept.

An integrated model of a two-step process for the ex situ bioremediation of xenobiotic contaminated soil has been formulated. The process is characterized by an initial extraction step of the organic contaminants from the polluted soil by contact with inexpensive and commercially-available polymer beads, followed by release and biodegradation of the xenobiotics, with parallel polymer bioregeneration, in a Two-Phase Partitioning Bioreactor (TPPB). The regenerated polymer is cyclically reused in the extraction step, so reflecting the robust and otherwise-inert properties of such polymers.

On the applicability of a hybrid bioreactor operated with polymeric tubing for the biological treatment of saline wastewater.

Effective biological treatment of high salt content wastewater requires consideration of both salt and organic toxicity. This study treated a synthetic saline wastewater containing NaCl (100gL) and 2,4-dimethylphenol (1.2gL) with a hybrid system consisting of a biological reactor containing spiral-coiled polymeric tubing through which the mixed feed was pumped.

A novel continuous two-phase partitioning bioreactor operated with polymeric tubing: Performance validation for enhanced biological removal of toxic substrates.

A continuous two-phase partitioning bioreactor (C-TPPB), operated with coiled tubing made of the DuPont polymer Hytrel 8206, was tested for the bioremediation of 4-chlorophenol, as a model toxic compound. The tubing was immersed in the aqueous phase, with the contaminated water flowing tube-side, and an adapted microbial culture suspended in the bioreactor itself, with the metabolic demand of the cells creating a concentration gradient to cause the substrate to diffuse into the bioreactor for biodegradation. The system was operated over a range of loadings (tubing influent concentration 750-1500 mg L), with near-complete substrate removal in all cases.

Sequential anaerobic-aerobic decolourization of a real textile wastewater in a two-phase partitioning bioreactor.

This work describes the application of a solid-liquid two-phase partitioning bioreactor (TPPB) for the removal of colour from a real textile wastewater containing reactive azo-dyes. Four polymers were tested over the pH range of 4-9 to select the most effective absorbant to be used as the partitioning phase in the TPPB. The best results were obtained with Hytrel 8206 at pH4 achieving ~70% colour removal, based on the dominant wavelength, in the first 5h of contact time, and 84% after 24h.

Towards a continuous two-phase partitioning bioreactor for xenobiotic removal.

The removal of a xenobiotic (4-chlorophenol) from contaminated water was investigated in a simulated continuous two-phase partitioning bioreactor (C-TPPB), fitted with coiled tubing comprised of a specifically-selected extruded polymer, Hytrel 8206. Wastewater flowed inside the tubing, the pollutant diffused through the tubing wall, and was removed in the aqueous bioreactor phase at typical biological removal rates in the C-TTPB simulated by varying aqueous phase throughput to the reactor. Operating over a range of influent substrate concentrations (500-1500mgL(-1)) and hydraulic retention times in the tubing (4-8h), overall mass transfer coefficients were 1.

Two-stage anaerobic and post-aerobic mesophilic digestion of sewage sludge: Analysis of process performance and hygienization potential.

Sequential anaerobic-aerobic digestion has been demonstrated to be effective for enhanced sludge stabilization, in terms of increased solid reduction and improvement of sludge dewaterability. In this study, we propose a modified version of the sequential anaerobic-aerobic digestion process by operating the aerobic step under mesophilic conditions (T=37 °C), in order to improve the aerobic degradation kinetics of soluble and particulate chemical oxygen demand (COD). Process performance has been assessed in terms of "classical parameters" such as volatile solids (VS) removal, biogas production, COD removal, nitrogen species, and polysaccharide and protein fate.

Regeneration strategies of polymers employed in ex-situ remediation of contaminated soil: Bioregeneration versus solvent extraction.

In this study we evaluated the feasibility of two regeneration strategies of contaminated polymers employed for ex-situ soil remediation in a two-step process. Soil decontamination is achieved by sorption of the pollutants on the polymer beads, which are regenerated in a subsequent step. Tested soil was contaminated with a mixture of 4-chlorophenol and pentachlorophenol, and a commercial polymer, Hytrel, has been employed for extraction.

Pentachlorophenol aerobic removal in a sequential reactor: start-up procedure and kinetic study.

This study has demonstrated the applicability of a simple technology such as the sequencing batch reactor (SBR), operated with suspended biomass, to the aerobic biodegradation of a highly toxic compound, the pentachlorophenol (PCP). An enrichment of a microbial consortium, originated from the biomass of an urban wastewater treatment plant, was performed and 70 days were sufficient to achieve removal efficiencies of ∼90% with the compound fed as only carbon and energy source Once completed the start-up period, the SBR was operated with the acclimatized biomass for 60 days at a feed concentration of PCP in the range of 10-20 mg L(-1). Improved performance was observed at increased influent concentration and the reached removal efficiency for the highest concentrations was stable at values≥90%.

Rapid and effective decontamination of chlorophenol-contaminated soil by sorption into commercial polymers: concept demonstration and process modeling.

Solid phase extraction performed with commercial polymer beads to treat soil contaminated by chlorophenols (4-chlorophenol, 2,4-dichlorophenol and pentachlorophenol) as single compounds and in a mixture has been investigated in this study. Soil-water-polymer partition tests were conducted to determine the relative affinities of single compounds in soil-water and polymer-water pairs. Subsequent soil extraction tests were performed with Hytrel 8206, the polymer showing the highest affinity for the tested chlorophenols.

Ex situ remediation of polluted soils by absorptive polymers, and a comparison of slurry and two-phase partitioning bioreactors for ultimate contaminant degradation.

The present study has provided a comparison between a conventional ex situ method for the treatment of contaminated soil, a soil slurry bioreactor, with a novel technology in which a contaminant is rapidly and effectively removed from the soil by means of absorptive polymer beads, which are then added to a two-phase partitioning bioreactor (TPPB) for biodegradation of the target molecule. 4-nitrophenol (4NP) was selected as a model contaminant, being representative of a large class of xenobiotics, and the DuPont thermoplastic Hytrel™ 8206 was utilized for its extraction from soil over ranges of soil contamination level, soil moisture content, and polymer:soil ratios. Since the polymers were able to rapidly (up to 77% and 85% in 4 and 24h respectively) and selectively remove the contaminant, the soil retained its nutrient and microflora content, which is in contrast to soil washing which can remove these valuable soil resources.