R. Passino

Combined chemical and biological degradation of tannery wastewater by a periodic submerged filter (SBBR).

The paper reports on the results of an investigation aimed to evaluate the performances of an innovative tannery wastewater process based on the combining biological degradation, carried out in a sequencing batch biofilm reactor, with chemical oxidation, performed by ozone. The combined treatment was carried out at the laboratory scale on real primary effluent coming from a centralised plant treating the wastewater from a large tanning district in Northern Italy. SBBR performances with and without ozonation were compared resulting to be very satisfactory only in the latter instance where recorded COD, NH4-N and TSS average removals were 97%, 98% and 99.9%, respectively. Such efficiencies correspond to specific concentrations in treated effluent well below the limit values fixed by the in-force Italian regulations. Furthermore, it was proved that the combined process is characterised by a very low sludge production. In fact, the measured specific sludge production (0.03 kg TSS/kg COD(removed)) resulted unexpectedly much more lower than the value reported for conventional biological systems (i.e., 0.3-0.5 kg TSS/kg COD(removed)).

Lead removal and recovery from battery wastewaters by natural zeolite clinoptilolite

ABSTRACT Technical feasibility of an ion exchange process for removal and recovery of lead present in battery manufacturing wastewaters is demonstrated. In absence of aluminium and ferric species, lead is quantitatively removed and recovered (≈90%) from the neutralised wastewaters after elution on the natural zeolite clinoptilolite. Control of pH to 5.5-6 is necessary to minimise degradation of the exchanger material. Throughput volumes exceeding 2,700 bed volumes (BV) (flowrate: Fexh10 BV/h) is obtained, when the initial Pb concentration is 4 mg/L, with the metal leakage steadily below the maximum allowable concentration (MAC<0.2 mgPb/L) set by the EU for discharge in rivers, lakes, coastal seawater. Regeneration of the zeolite is carried out by controlled elution of limited amounts of IM NaCl, pH 4.5 (40BV, Freg=5 BV/h) to minimize in situ precipitation of metals and preserve the zeolite from degradation. From spent regeneration eluate lead is recovered to the battery manufacturing operations. This latt...

Coagulants removal and recovery from water clarifier sludge

Several million tons per year of water clarifier sludge are produced in Europe, with forecasts of the figure doubling by the next decade. End disposal of reference sludge is mainly based on controlled landfilling, after conditioning to minimise the volume of solids. The conditioning operation is carried-out in acidic or alkaline media, thus also allowing for coagulants recovery (Al, Fe species). The quality of the chemicals recovered may not be suAcient to justify their reuse, e.g., to water clarification operations. With the aim of improving the purity of coagulants recovered, a new ion exchange process for selective removal, separation and recovery of Al(III) and Fe(III) species from the clarifier sludge is presented. The IERAL (Ion Exchange Recovery of Aluminium) process is based on the use of a commercial weak electrolyte carboxylate resin (Purolite C106, from Purolite Co., UK), allowing for the removal of metals from the clarifier sludge acidic leachate (pH 3.5), followed by selective separation and recovery of the aluminium and ferric species during the resin regeneration step. Together with the performance of a fully automated 50 L/d pilot plant, this paper reports the basic principles of the process. # 2000 Elsevier Science Ltd. All rights reserved

Pb/Fe SEPARATION AND RECOVERY FROM AUTOMOBILE BATTERY WASTEWATERS BY SELECTIVE ION EXCHANGE

ABSTRACT Laboratory scale investigation has been carried out for the optimization of a new process for separation and recovery of Pb/Fe species from automobile battery manufacturing wastewaters. The innovation, based on ion exchange, allows for separation and recovery of the mentioned species by the use of a commercial weak anion resin (Duolite A7 from Rohm&Haas Co, USA), as selective sorbent for the ferric species, and a weak cation resin with carboxylate functionality (Purolite C106 from Purolite Co.,UK) for removal and recovery of lead species. Cl-form anion resin was eluted with real automobile battery wastewaters (pH 3; Fes= 4BV/h; influent Fe concentration: 2 mg/L) for a column throughput exceeding 200 BV (Bed Volumes) with Fe leakage steadily below 0.2 mg/L, (ten times lower the maximum allowable concentration, MAC, for discharge in closed water bodies, enforced by EU legislation). Lead species were removed and recovered on Na/H-form cation resin (pH 6; Fexh=20 BV/h; influent Pb concentration: 4 mg/L) for a column throughput exceeding 15,000 BV at average Pb leakage below 0.03 mg/L (MAC=0.2 mgPb/L). Both sorbents were regenerated by limited amounts of 1M HC1. Specifically, resin Duolite A7 was eluted with 5 BV (Freg =2BV/h), and carboxylate resin was eluted with 30BV

Cr(III)/A1(III)/Fe(III) ion binding on mixed bed ion exchangers. Synergistic effects of the resins behaviour

Abstract Ion exchange, as a conservative technology, allows for removal and recycling of metals from liquid effluents. Chelating exchangers may be used to the purpose due to their specificity toward metal species. The specificity, related to the metal-functional group affinity and thus the high stability of the complexes formed, is paid in terms of regeneration levels necessary to reverse the exchange reaction by mass action. Moreover, the liquid-phase speciation of the metals with organic and inorganic ligands, commonly present in industrial effluents, determines the active metal concentrations at the binding sites and thus the removal efficiency of the chelating resins which is, in general, more affected by stereochemical factors during the interaction of the active species at the functional groups. In this context, we investigated the behaviour of a mixed bed weak electrolyte anion (amino) and cation (carboxylate) conventional ion-exchangers as an alternative to chelating resins. The synergistic effects of the two functional groups to selectively remove, separate and recover Cr(III), Al(III), Fe(III) from segregated industrial effluents are discussed. The exhaustion behaviour of the carboxylate resin toward chromic and aluminum species is synergized by the cooperative presence of the anion resin, this latter being able to selectively retain ferric species. Difficult regeneration behaviour of the metal-form carboxylate resin is also favored by the presence of the weak base amino functional groups in the free base form.

Aluminum recovery from water clarifier sludges by ion exchange: Comparison of strong and weak electrolyte cation resins performances

Abstract Technical feasibility of an ion exchange based process for removal and recovery of the coagulating principle (Al, Fe chemicals) from water clarifier sludges is illustrated. The innovation is a typical example of `conservative technology applied to the solution of environmental problems, thus allowing for the minimization of the environmental impact related to the disposal of the solid wastes, through conditioning and detoxification of the sludges for land application, and simultaneous recovery of valuable products from non-conventional sources. The paper illustrates laboratory scale comparative experiments between weak (carboxylate) and strong (sulphonic) cation resins performances in reference to a typical acidic leachate from water clarifier sludges (pH 3.5). Together with mechanistic interpretation of the multicomponent-polyvalent Al/Fe/Na ionic system involved, in this paper indications for process optimization are also given.

ANAEROBIC PROCESS CONTROL BY AUTOMATED BICARBONATE MONITORING

An instrument, which allows the automatic semi-continuous determination of bicarbonates in complex organic solutions and its development for anaerobic process control, is described. n nThe analyser is based on the application of physico-chemical equilibria in gas-liquid systems, and measures the overpressure created by the bicarbonates decomposed to carbon dioxide by strong acid addition. n nThe instrument has also been adapted to control anaerobic digesters and tested on reactors fed with olive oil mill effluents. The selected process control strategy maintains constant bicarbonate concentration in the effluent by addition of alkali solutions. In this study a proportional control law has been used. n nPreliminary results on laboratory scale reactors indicate that automatic process control based on bicarbonate monitoring and control is feasible and effective.

Conservative technologies for environmental protection based on the use of reactive polymers

Abstract Biodegradation of organic pollutants is based on ‘destructive’ technologies leading to the formation of low-molecular-weight compounds and carbon dioxide or methane depending on the process red-ox conditions. This is not possible for persistent pollutants (e.g., heavy metals, biorefractory organics, complex organometals) independent of the origin and structure of the chemical substrate. Reference compounds can only be recovered and eventually recycled to the production lines of origin and/or to related industrial activities. However, the quality of the recovered products must justify the recycling operation. Sorption techniques (ion exchange, carbon adsorption) and membrane technology as typical ‘conservative’ unit operations allow for removal of pollutants to the strictest limits imposed by enforced legislation and simultaneous recovery and recycling. We discuss two examples of conservative environmental technologies, based on ion exchange and the use of reactive polymers. The first relates to metal-laden effluents from the tannery industry, and the second to the management of residues (clarifier sludge) from the drinking water industry. Both processes are aimed at the minimization of environmental impact resulting from the production lines (Cr(III)- and Al(III)-containing wastes, respectively) and the recovery of valuable by-products with the related economic revenues associated with their commercial value.

Modelling of two stage single sludge system for nitrogen removal.

Abstract In this paper a general design procedure of activated sludge plants for nitrogen removal is presented. The general criteria followed involve solving the algebraic system obtained considering the kinetic, stoichiometric and mass balance equations for all the components. The equation used to describe the nitrification and denitrification processes kinetics is the‐classic Michaelis & Menten expression for the enzyme catalyzed reactions considering only the active fraction of the biomass. This fraction has been evaluated introducing a corrective factor (

Low Lime Coagulation for the Enhancement of Primary Treatment of Urban Wastewater

Pollutants in municipal sewage include a complex mixture of soluble and insoluble constituents ranging in size from less than 0.001 μm up to over 100 μm [1]. Several studies have been addressed to the classification of contaminants in wastewater in terms of particle size. Balmat [2], Heukelekian and Balmat [3] and Rickert and Hunter [4], using a sequence of sedimentation, centrifugation and filtration, separated the contaminants into four size fractions: settleable (> 100 μm), supracolloidal (1–100 μm), colloidal (0.08–1 μm), and soluble ( 106 μm), supracolloidal (3-106 μm), colloidal (0.025–3 μm), and soluble (< 0.025 μm). Notwithstanding the differences in the operating definition of the size ranges, these studies do agree that only a quarter or less of the COD of the raw sewage may be considered truly soluble [6]. The majority of the pollutant load is actually in suspended form, and is not easily biodegradable. In addition, other contaminants, such as heavy metals, bacteria and viruses, and organic micro pollutants (PCB, PAH) are strongly associated with the suspended phase.