Francesco Avezzu

To centralise or to decentralise: An overview of the most recent trends in wastewater treatment management

An overview of recent trends in wastewater management is proposed concerning the role of centralisation and decentralisation in wastewater treatment. The main advantages, criticisms and limitations considering social, economic and environmental issues have been summarised. It resulted that none of the approaches could be excluded a priori, but were generally shown to integrate one another on the basis of the specific required situation.

Seawater ecotoxicity of monoethanolamine, diethanolamine and triethanolamine.

Monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) are compounds with potential acute, sub-chronic and chronic toxicity effects towards aquatic species. A literature review highlighted the existence of a gap in the knowledge on their toxicity with saltwater testing species. A battery of toxicity tests including the alga Phaeodactylum tricornutum Bohlin, the bivalve molluscs Crassostrea gigas (Thunberg) and Mytilus galloprovincialis (Lmk), and the crustacean Artemia franciscana, was considered to update and improve the existing ecotoxicological information. Data were provided as the Effective Concentration that induces a 50% effect in the observed population (EC50), Lowest Observed Effect Concentration (LOEC) and No Observed Effect Concentration (NOEC). EC50, LOEC and NOEC values were compared with a reviewed database containing the existing ecotoxicological data from saltwater organisms.

Lignin and tannin toxicity to Phaeodactylum tricornutum (Bohlin)

Lignin and tannin are widespread natural compounds traditionally used in tannery industries. Their presence is commonly detected in textile wastewater showing potential toxicity effects within various endpoints onto sea water organisms that generally represent the ultimate target of discharged effluents. Most data are available only as nominal concentrations or percentage volume of wastewater having an unknown lignin and tannin content. The aim of this study was to provide the ecotoxicological characterisation of both compounds considering as testing species the marine alga Phaeodactylum tricornutum (Bohlin). Lignin and tannin showed an E(r)C(50) of 113.84(100.90-128.45)mg/L and 26.04(20.10-33.95)mg/L, respectively. NOEC and LOEC values were together <0.1mg/L and 0.1mg/L, in that order. Moreover, it was observed a morphological change of the algae fusiform shape occurring only at tannin concentrations ≥ 75 mg/L and <185 mg/L.

Behaviour of Heavy Metals in Activated Sludge Biological Treatment of Landfill Leachate

The behaviour of heavy metals was studied by carrying out a series of experiments with an activated sludge biological reactor (with pure oxygen), fed with different types of landfill leachate. The leachates used had been previously treated by the wet oxidation process and also by ammonia stripping. The experimentation aims were to evaluate both BOD and COD removal rates and the distribution of heavy metals concentrations between the liquid and solid phases. This latter data was used to confirm a mathematical model which predicts the distribution of heavy metals between the liquid and solid phases of a biological process.

Toxicity removal efficiency of decentralised sequencing batch reactor and ultra-filtration membrane bioreactors

As a consequence of the Water Framework Directive and Marine Strategy Framework Directive, there is now more focus on discharges from wastewater treatment plants both to transitional and marine-coastal waters. The constraint to encourage sustainable water policy to prevent water deterioration and reduce or stop discharges has entailed new requirements for existing wastewater treatment plants in the form of advanced wastewater treatment technologies as further suggested by the Integrated Pollution and Prevention Control Bureau. A whole toolbox of physico-chemical and ecotoxicological parameters to investigate commercial and mixed domestic and industrial discharges was considered to check the efficiency of an Activated-Sludge Sequencing Batch Reactor (AS-SBR) and two Ultra-Filtration Membrane Biological Reactors (UF-MBRs) on a small scale decentralised basis. All discharges were conveyed into Venice lagoon (Italy), one of the widest impacted Mediterranean transitional environment. The UF-MBRs were able to provide good quality effluents potentially suitable for non-potable reuse, as well as reducing specific inorganic micro-pollutants concentration (e.g. metals). Conversely, the AS-SBR showed unpredictable and discontinuous removal abilities.

Performance assessment of AS-SBR and UF-MBR for hotel wastewater treatment

A large number of tourist structures in Venice (Italy) have small sized on-site treatment systems for their wastewater. Due to its historical characteristics, the city has no public sewerage system and untreated hotel wastewater represents a serious hazard for its lagoon environment. This study focused on the wastewater facilities installed in two hotels adopting an Activated Sludge Sequencing Batch Reactor (AS-SBR) and an Ultra-Filtration Membrane Biological Reactor (UF-MBR). Their performance was checked in terms of both traditional physico-chemical and ecotoxicological parameters, the importance of which has recently been recognised by EU regulatory dispositions and OSPAR indications. Acute and sub-chronic endpoints were both considered on a whole effluent toxicity basis by means of Vibrio fischeri and Crassostrea gigas, respectively. The two months monitoring survey evidenced that the UF-MBR was more efficient than the AS-SBR in providing high-quality discharges under both chemical and ecotoxicological viewpoints.