P. Traverso

State of the art of R&D in the anaerobic digestion process of municipal solid waste in Europe

Abstract The state of the art of R&D in the field of anaerobic digestion of municipal solid waste in Europe is reviewed. A comparison is made of the quality and quantity of refuse produced in different European countries using data available in recent literature. The conclusion to be drawn from this analysis is that in programmes involving demonstration and full scale plants it is necessary to carry out more detailed studies of the process and its control, as well as carrying out further work on the microbiological aspects of anaerobic digestion of municipal solid waste.

Comparison of co‐digestion performance of two differently collected organic fractions of municipal solid waste with sewage sludges

Abstract This paper deals with the comparison of the co‐digestion performances of two digesters treating organic fractions of municipal solid wastes (MSW) and primary and secondary sewage sludges mixed at various ratios between 0 to 100% TS basis. The organic fractions treated differ in their collection procedures, which influence the chemical characteristics of the substrates and then the process performance. These differences and their influence on the anaerobic digestion process are emphasized throughout the paper so as to assist public sector managers in their choise of treatment method from the harvesting procedure to the final disposal technology of MSW.

A new approach to the kinetic study of anaerobic degradation of the organic fraction of municipal solid waste

Abstract The kinetic models proposed by Monod, Chen and Hashimoto and Singh as well as those of a first order and diffusional type have been tested for fit as mathematical descriptions to describe substrate utilization during anaerobic digestion of the organic fraction of source sorted municipal solid waste. A new model, described as step diffusional, is proposed and the results obtained with it are compared with those obtained using previously published models. The new model is found to show a better fit to the experimental result than those obtained with other models. The new model takes into account simple qualitative and quantitative chemical characteristics of the substrate to be digested. Although this new model is more complex than some others since it involves four kinetic constants, conceptually it is simple enough to find practical applications.

Acidogenic fermentation of source separated mixtures of vegetables and fruits wasted from supermarkets

A pilot scale mesophilic anaerobic acidogenic fermenter was fed with mixtures of vegetables and fruits shredded by a hammer mill and mixed in a stock tank, in order to produce a liquid phase suitable as RBCOD source in denitrification and EBPR processes. Different operative conditions were studied working with a HRT in the range 1–:12 days. The effluent coming from the fermenter was screw pressed, and the solid phase was recycled adopting different ratios to the fermenter, in order to define its effect on the final liquid phase composition. The variations of the VFA, lactate, methyl and ethyl alcohol concentrations, TCOD, SCOD and pH during more than one year were analysed and discussed both with reference to the fresh feed, and to the content of the fermenter. It was found that almost all the organic matter in the liquid phase inside the fermenter was represented by VFA (mainly acetate), lactate (in particular) and methyl and ethyl alcohols when HRT was longer than 6 days.

Observations on future sea level changes in the Venice lagoon

‘Venice is sinking while the sea level is rising’ is a common statement in issues concerning the future of the Venice lagoon. The search for a reliable interpretative tool for measured sea-level changes has taken on more urgency since the sea-level rise was indexed as the consequence of global warming—with catastrophic scenarios for both the ecotone and the city, linked to increasing lagoon erosion, sudden modifications of biological equilibriums, loss of wetlands, salt aggression and an increasing frequency of exceptional high tide events. However, the peculiar hydrodynamics of the northern Adriatic Sea, made more complex by the freshwater inflow from the Po River, and the conceptual limits of existing long-term predictive systems, would suggest a more cautious approach to the scenarios yet proposed for the next century.

Anaerobic digestion of the shredded organic fraction of municipal solid waste

Abstract Anaerobic digestion of the shredded organic fraction of municipal solid waste has been investigated in a pilot-scale completely mixed digester, under mesophilic conditions. Detailed comparisons of the size distributions of the particles in the feed and in the digester effluent are reported under varying organic loading rates and hydraulic retention times. About 20% of the particulate matter in the organic feed is refractory and resists hydrolysis. Hence the maximum removal of total volatile solids attainable under hydraulic retention times of practical interest is about 70%. The optimum hydraulic retention time is around 14 to 15 days.

Selected herbicides in treated and untreated surface water

Abstract Atrazine, simazine, propazine, alachlor, and molinate were determined in raw (Po river) and treated waters of an advanced water supply treatment plant (WSTP) equipped with a granular activated carbon (GAC) column. Continous liquid‐liquid (LLE) and C18 solid‐phase (SPE) extractions were used to isolate the herbicides before the gas Chromatographic analysis using nitrogen‐phosphorus (HRGC‐NPD) and mass spectrometry (HRGC‐MS) detection. The concentrations of atrazine in the raw water, in contrast to those of alachlor and molinate, were rather constant over the one year monitoring. The final effluent of the WSTP showed concentrations of the herbicides considered undetectable or far below the EC prescriptions. Adsorption on the GAC columns was the main process responsible for the major removal of atrazine.

Carbon‐limited biological denitrification by a fluidised‐bed reactor fed with industrial wastewaters

Abstract This paper deals with biological denitrification, in “available”; carbon limiting conditions, by a fluidised‐bed plug‐flow reactor. The nitrate and organic feeds were from industrial wastewater. It was seen that a Monod‐type equation was adequate to describe the experimental nitrate profile along the reactor, and that the chosen organic feed compared favourably with methariol, but that only a fraction of its dissolved BOD content was actually available to the denitrifying organisms.