Francesco Zilio-Grandi

Electrochemical treatment of tannery wastewater using Ti/Pt and Ti/Pt/Ir electrodes

Abstract The treatment of tannery wastewater by the electrochemical method using Ti Pt and Ti/Pt/Ir electrodes is investigated. The aim of a satisfactory elimination of NH+4 from wastewaters of different strength was achieved using both types of electrodes. A Ti/Pt/Ir anode proved to have the electrocatalytical properties for NH+4 removal, but it resulted to be more sensitive to poisoning by H2S contained in the wastewater. For both types of the electrodes NH+4 removal followed pseudo-first order kinetics, with the rate decreasing in function of the presence of organic substances. A concurrent removal of COD was observed particularly with a Ti Pt anode, but its magnitude was not sufficient to ensure the discharge limits to be met while treating the raw wastewater only by the electrochemical process. In conclusion the electrochemical process can be applied successfully as a final polishing or an alternative to biological nitrification, but cannot substitute completely the traditional treatment of tannery wastewater.

Application of electrochemical processes for tannery wastewater treatment

Tannery wastewater (real and synthetic) was treated by an electrochemical method with the principal aim of eliminating ammonium. Of various materials tested as electrodes graphite proved the best anode and steel the best cathode. Ammonium elimination was negatively influenced by the presence of organic pollutants and sulphides. The best results were obtained using electroxidation as a polishing step for the final effluents of a biological treatment plant. Ammonium elimination efficiency after 30 min of electrolysis at a current density of 0.44 A/dm2 was equal to 99%. For these conditions energy consumption for the elimination of 1 kg of NH4 + was 132 kwh. The process was less efficient when applied to raw and partially treated wastewater: to achieve the same result, electroxidation time had to be doubled and current density to be increased about threefold. COD removal was satisfactory when the initial values were relatively low (less than 300 mg/l) and only partial (about 70%) while treating wastewater wi...

Characterization of rainwater quality from the Venice region network using multiway data analysis

Abstract The paper describes the results of an exploratory analysis of the relations between variables characterizing the quality of atmospheric precipitation in the Veneto, an Italian region with an area of ∼ 18000 km2 and a population of just over 4.5 million. A network of eight sampling stations for monitoring rainfall was set up in 1988, in line with the EMEP statements. The data consisted of 1174 observations over the period February 1989–December 1991. Principal component analysis (PCA) was used in an attempt to describe the structure of relations between the solutes in wet deposition. Some extensions of PCA (interstructure-compromise-intrastructure method) were considered in order to evaluate differences between relation structures as defined by location, season and volume of precipitations.

PERFORMANCE OF A FULL-SCALE TREATMENT PLANT FOR TEXTILE DYEING WASTEWATERS

The paper contains an analysis of data relating to two years of operation of a biological plant treating textile wastewaters. In addition to traditionally important parameters, such as COD, BOD and different nitrogen forms, parameters such as surfactants and oil and grease and organic matter composition are also considered. Methylene chloride extract was used to estimate total organic content and to perform a qualitative and semi‐quantitative analysis of the chemical composition of raw and treated effluent. The rates of elimination of organic load and of nitrification were determined. Statistical analysis shows that the organic load was biodegradable by acclimatized sludge of the plant. Organics refractory to biodegradation (0.4–1.3% of COD) were only found in certain periods.

Seasonal phosphorus removal in a Phostrip process—I. Two-years' plant performance

Abstract This paper analyses the performance over 2 yr of a treatment plant located in the tourist area of the Adriatic sea, based on a conventional aerobic sludge process. During the peak season excess phosphorus removal is accomplished by use of a PhoStrip unit. The phosphorus elimination rates are discussed in relation to the influence of the characteristics of the incoming wastewater and the occurrence of simultaneous nitrification and denitrification in the plant. The PhoStrip process proved to be a reliable solution when excess phosphorus has periodically to be removed from wastewater with a low organic content and a high presence of nutrients ( TKN COD = 0.23 and P COD = 0.017 ). Concentration of phosphorus in the final effluent below 1 mg l −1 was obtained on 85% and 73% of the days of plant operation, respectively in 2 yr of study.

Seasonal phosphorus removal in a phostrip process. II: Phosphorus fractionation and sludge microbiology during start-up

Abstract This paper presents data related to the start-up of biological phosphorus removal in a plant exhibiting simultaneous nitrification and denitrification in the aerobic basin. No particular selection of bacterial species was observed during the start-up period, leading to the conclusion that the dephosphatation was carried out by the denitrifiers present in the sludge. The time necessary to promote phosphorus removal in the plant corresponded to about 2 anaerobic-aerobic cycles of the sludge. The maximum removal rate of phosphorus was equal to 7 mg P g −1 MLSS d −1 , resulting in the sludge containing about 10% of phosphorus. Chemical speciation of phosphate fractions indicated that when no lime was added to the clarifier, organic phosphates contributed to 52% of the phosphorus present in the sludge. The remaining 48% is to be attributed to the process of co-precipitation. Dosing of lime caused a decrease in the polyphosphate fraction in the sludge and a simultaneous increase in the portion of other fractions. The conditions prior to lime addition were re-established within a few days of stopping the chemical dosing, indicating that the chemical process does not exert an irreversible influence on the enzymatic system of the biological luxury up-take.

Comparison between ion exchange and nanofiltration for softening of industrial water

This article report on a comparison between the competing processes of ion exchange and nanofiltration for the softening of water for industrial use

TEXTILE WASTEWATER TREATMENT BY AN AEROBIC SUBMERGED BIOFILTRATION

In the paper operation of submerged aerobic filtration pilot plant treating textile wastewaters is described. Conventional parameters, such as COD, BOD and different nitrogen forms are considered. The efficiency of organic elimination was determined and followed as the main objective. The organic load is the parameter governing plant performance. The efficiency of COD removal varied from 55.9% to 92.3% for an organic load of 5 and 1 kgCODm‐3 day‐1. The proposed process occupies 5–10 times less space compared to the traditional aerobic activated sludge treatment.

Treatment of wastewaters from ore flotation containing aliphatic amines and hydrofluoric acid

Wastewaters from feldspar flotation containing hydrofluoric acid and amines were effectively purified by neutralization‐clarification with a 10% solution of lime and polyelectrolytes, followed by a coke filtration and/or a Zeolite or Activated Alumina adsorption. A Polish synthetic Ca‐type Zeolite proved to be efficient in the elimination of fluoride ions at the pH of 7.8. At this pH the Zeolite was more efficient than the Activated Alumina N. Wastewaters from feldspar washing were effectively treated by coagulation with A12(SO4)3, yielding final effluents with the characteristics very close to the clarified postilotation wastewaters. After clarification amines and fluoride ions could be removed from feldspar postflotation and feldspar washing effluents mixed together. A final concentration of fluorides and amines in the purified wastewaters was below 2 mg/1.