Complete Mass Balance Research Articles

Concurrent nitrate and Fe(III) reduction during anaerobic biodegradation of phenols in a sandstone aquifer

The biodegradation of phenols (∼5, 60, 600 mg l −1) under anaerobic conditions (nitrate enriched and unamended) was studied in laboratory microcosms with sandstone material and groundwater from within an anaerobic ammonium plume in an aquifer. The aqueous phase was sampled and analyzed for phenols and selected redox sensitive parameters on a regular basis. An experiment with sandstone material from specific depth intervals from a vertical profile across the ammonium plume was also conducted. The miniature microcosms used in this experiment were sacrificed for sampling for phenols and selected redox sensitive parameters at the end of the experiment. The sandstone material was characterized with respect to oxidation and reduction potential and Fe(II) and Fe(III) speciation prior to use for all microcosms and at the end of the experiments for selected microcosms. The redox conditions in the anaerobic microcosms were mixed nitrate and Fe(III) reducing. Nitrate and Fe(III) were apparently the dominant electron acceptors at high and low nitrate concentrations, respectively. When biomass growth is taken into account, nitrate and Fe(III) reduction constituted sufficient electron acceptor capacity for the mineralization of the phenols observed to be degraded even at an initial phenols concentration of ∼60 mg l −1 (high) in an unamended microcosm, whereas nitrate reduction alone is unlikely to have provided sufficient electron acceptor capacity for the observed degradation of the phenols in the unamended microcosm. For microcosm systems, with solid aquifer materials, dissolution of organic substances from the solid material may occur. A quantitative determination of the speciation (mineral types and quantity) of electron acceptors associated with the solids, at levels relevant for degradation of specific organic compounds in aquifers, cannot always be obtained. Hence, complete mass balances of electron acceptor consumption for specific organic compounds degradation are difficult to confine. For aquifer materials with low initial Fe(II) content, Fe(II) determinations on solids and in aqueous phase samples may provide valuable information on Fe(III) reduction. However, in microcosms with natural sediments and where electron acceptors are associated with the sediments, complete mass-balances for substrates and electron acceptors are not likely to be obtained.

Carbon flows in Baltic Sea food webs — a re-evaluation using a mass balance approach

The brackish Baltic Sea has been seen as particularly suitable for studies of food webs. Compared to fully marine ecosystems, it has low species diversity, which means fewer trophic linkages to analyse. The Baltic Sea is also one of the best-studied areas of the world, suggesting that most data requirements for food web models should be fulfilled. Nevertheless, the influence of physical and biological factors on trophic interactions and biogeochemical patterns varies spatially in the Baltic Sea, adding considerable complexity to food web studies. Food web structure and processes can be described and compared quantitatively between areas by estimating the flow of matter or energy through the organisms. Most such models have been based on carbon, though studies of complementary flows of other elements limiting production, such as nitrogen and phosphorus would be desirable. However, since ratios between carbon and other elements are used in calculating these flows, it is crucial, as a first step, to quantify the flows of carbon as accurately as possible. In this study, we used the EcopathII software (ver 3.1) to analyse models of carbon flow through the food webs in the three main areas of the Baltic Sea; the Baltic proper, Bothnian Sea and Bothnian Bay. A previously published study on carbon flow in the Baltic Sea [Elmgren, R. 1984. Trophic dynamics in the enclosed, brackish Baltic Sea. Rapp. P.-V. Reun. — Cons. Int. Explor. Mer. (183) 152–169.] was complemented with the data on respiration and flow to detritus [Wulff, F., Ulanowicz, R. 1989. A comparative anatomy of the Baltic Sea and Chesapeeake Bay ecosystems. In: F. Wulff, J.G. Field, K.H. Mann (Eds.), Flow Analysis of Marine Ecosystems: Theory and Practice. New York: Springer-Verlag.] in order to present complete mass balance models of carbon. The purpose of re-evaluating previous models with new analytic tools was to check how well their carbon flows balance, and to provide a basis for improved mass balance models using more recent data, including nutrients other than carbon. The resulting mass balance networks for the Baltic proper, Bothnian Sea and the Bothnian Bay were shown to deviate from steady state. There was an organic carbon surplus of 45, 25 and 18 g C m −2 year −1 in the pelagic zones of the Baltic proper, Bothnian Sea and Bothnian Bay, respectively. The Ecopath network analysis confirmed that the overall carbon flow was highest in the Baltic proper, somewhat lower in the Bothnian Sea and much lower in the Bothnian Bay. The only clear differences in food web structure between the basins was that the average trophic level was lower for demersal fish in the Bothnian Sea and higher for macrofauna in the Bothnian Bay, compared to the other basins. The analysis showed weakness in our current understanding in Baltic Sea food webs and highlighted areas where improvements could be made with more recent data.

Towards a complete mass balance and model for PCBs and PAHs in a small rural lake, Cumbria U.K.

This paper summarizes the processes of exchange/fluxes for polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in a small well‐studied rural lake, Esthwaite Water in northwest England. Measurements of PCB and PAH concentrations have been made in rain, air, water, dated sediment cores, and sediment trap samples over a 2‐yr study period and used to determine fluxes to and from the lake. A steady state mass balance model was used to construct an input‐output budget for the chemicals and to investigate the relative importance of transport into and out of the lake. The hydraulic transport from the lake was the most important loss mechanism for both PCBs and PAHs. Volatilization, not sedimentation, is currently the dominant loss process for PCBs in the water column, whereas, sedimentation exceeds volatilization for PAHs. The data further suggest that the current sediment‐water flux is upward for PCBs and downwards for PAHs, indicating that the sediments might be acting as a secondary source for PCBs but continue to act as a sink for PAHs. Riverine, catchment runoff, or both are believed to be the most important input for PCBs and PAHs to the lake although direct aerial deposition to the lake is also important for PCBs. Differences in the mixtures of compounds in the various compartments suggests significant fractionation of PCBs and PAHs in the air‐water‐sediment system in the lake.

Mass balance for wastewater nitrogen in the Central Arizona–Phoenix ecosystem

A complete nitrogen mass balance for all wastewater generated in the Central Arizona–Phoenix ecosystem was developed using data from the 18 largest wastewater treatment plants (99% of flow). Components included total N in raw wastewater, denitrification in wastewater treatment plants, biosolids production, and effluent (reuse, recharge, and discharge). Denitrification and biosolids production remove 81% of wastewater N. Nearly all biosolids are recycled to cotton fields within the ecosystem. Most effluent is recycled within the ecosystem. As the result of wastewater management practices developed to reuse wastewater, wastewater N is either deliberately volatilized or accumulates within the system; only 4% of the original wastewater N is exported via the Gila River.

Nitrogen Distribution in the Pyrolysis Products of a Type II Kerogen (Cenomanian, Italy). Timing of Molecular Nitrogen Production versus Other Gases

A type II kerogen (NN8, Cenomanian, Italy) was submitted to isothermal closed pyrolyses, in sealed gold tubes, under various temperature/time conditions (ranging from 280 to 550 °C and from 1 to 72 h). Nitrogen distributions were determined, via independent measurements, in the different pyrolysis fractions. Complete nitrogen mass balances were thus obtained, for the first time to the best of our knowledge, for pyrolyses of a type II kerogen. The nature and the abundance of the individual gases generated under each temperature/time condition were also examined. Taken together the above results provided information on (i) the amounts of N_2, CH_4, CO_2, and H_2S produced from the NN8 kerogen upon thermal stress, (ii) the timing of such productions, and (iii) the composition to be expected for the gas fractions generated from such a type II kerogen at different stages of natural maturation. In addition, these observations were compared with those derived from a similar study recently carried out on a type I kerogen.

Dynamic Modelling of the Wood Stack in a Wood Drying Kiln

For the design of energy efficient dryers employing heat pump systems, the dynamic response of the product to the kiln conditions must be taken into account. In this paper, the formulation of a dynamic, kiln-wide drying model is described. The model solves the unsteady-state mass, momentum and energy balance equations for both the air flow and the wood boards in drying three types of stack: normal stack, aligned stack and staggered stack. In order to represent the dynamical response of the system, the model equations provide more complete energy and mass balances than those presented in recent publications. The transient profiles of the air humidity, temperature, pressure, and velocity, and the wood temperature and moisture content along the air flow direction within the stack are obtained using this model. To illustrate the use of the model, the drying processes of sapwood boards of Pinus radiata under typical dehumidifier kiln conditions have been calculated, and the modelled results have been discussed in detail. In addition, the model has been tested by using the performance data for a commercial scale kiln. The agreement between the modelled and measured performance results shows that the model is suitable for the design and analysis of dehumidifier wood dryers.

Photocatalytic degradation of polycarboxylic benzoic acids in UV-irradiated aqueous suspensions of titania.: Identification of intermediates and reaction pathway of the photomineralization of trimellitic acid (1,2,4-benzene tricarboxylic acid)

Three polycarboxylic (hemimellitic (Hem), trimellitic (Tri) and pyromellitic (Pyro)) acids, representative of industrial pollutants and of compounds from biomass, were degraded by heterogeneous photocatalysis. The three molecule disappearance rates followed the order Pyro>Hem>Tri. They obeyed a Langmuir–Hinshelwood mechanism. The two competitive initial steps of attack of the molecules corresponded (i) to a hydroxylation reaction induced by photogenerated OH radicals and (ii) by a decarboxylation (photo-Kolbe) reaction resulting from the direct attack of one carboxylic group by a positive photo-hole. A very careful analysis of the degradation intermediates was performed using high performance liquid chromatography (HPLC) and gas chromatograph/mass spectrometer (GC/MS), especially in the case of Tri. The loss of several carboxyl groups leading to benzoic acid formation was observed before the aromatic ring opening. Several aliphatic acidic fragments were detected, such as malonic and succinic acids. Interestingly, a condensation product was detected, which indicated that some carboxylic radicals could attack a Tri molecule and form a Pyr molecule. However, all these acid intermediates could be photodecomposed — in agreement with previous results from the laboratory — into CO2 with a complete carbon mass balance. A detailed degradation pathway could be proposed.Such a reaction demonstrated that complex aromatic water pollutants, originating either from industry or from biomass, could be totally mineralized and that they could produce clean water.

Degradation of 4-fluorobiphenyl in soil investigated by 19F NMR spectroscopy and 10C radiolabelling analysis

The incubation of the model pollutant [U- 14C]′-4-fluorobiphenyl (4FBP) in soil, in the presence and absence of biphenyl (a co-substrate), was carried out in order to study the qualitative disposition and fate of the compound using 14C-HPLC and 19F NMR spectroscopy. Components accounted for using the radiolabel were volatilisation, CO 2 evolution, organic solvent extractable and bound residue. Quantitative analysis of these data gave a complete mass balance. After sample preparation, 14C-HPLC was used to establish the number of 4FBP related components present in the organic solvent extract. 19F NMR was also used to quantify the organic extracts and to identify the components of the extract. Both approaches showed that the composition of the solvent extractable fractions comprised only parent compound with no metabolites present. As the 14C radiolabel was found to be incorporated into the soil organic matter this indicates that metabolites were being generated, but were highly transitory as incorporation into the SOM was rapid. The inclusion of the co-substrate biphenyl was to increase the overall rate of degradation of 4FBP in soil. The kinetics of disappearance of parent from the soil using the data obtained were investigated from both techniques. This is the first report describing the degradation of a fluorinated biphenyl in soil.

Total recycling of CCA treated wood waste by low-temperature pyrolysis

A system to turn a potentially harmful stream of solid waste into a set of substreams with either commercial value or highly concentrated residual streams is presented. The waste which is considered is metal impregnated (in particular Chromated Copper Arsenate (CCA) treated) wood waste and timber, such as telephone poles, railway sleepers, timber from landscape and cooling towers, wooden silos, hop-poles, cable drums and wooden playground equipment. These waste streams sum up to several 100,000 tons of material per year currently to be dumped in every major country of the European Community (EC). Technologies need to be developed to reduce this CCA treated wood waste, such that all of the metals are contained in a marketable product stream, and the pyrolysis gases and/or pyrolysis liquid are used to their maximum potential with respect to energy recuperation. Pyrolysing the CCA treated wood waste may be a good solution to the growing disposal problem since low temperatures and no oxidising agents are used, which result in lower loss of metals compared to combustion. An experimental labscale pyrolysis system has been developed to study the influence of the pyrolysis temperature and the duration of the pyrolysis process on the release of metals and the mass reduction. The macrodistribution and microdistribution of the metals in the solid pyrolysis residue is studied using Inductively Coupled Plasma Mass Spectrometry (ICP–MS) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Analysis (SEM–EDXA). Furthermore, a complete mass balance is calculated over the pyrolysis system. Based on these results a semi-industrial pyrolysis system (pilot plant scale) has been developed consisting of three stages: grinding, packed bed pyrolysis and metal separation. Special types of equipment have been developed to carry out the three stages. A new grinding system has been developed, based on a crushing mechanism rather than a cutting mechanism. The crushed wood is introduced by means of a screw feeding system into a reaction column. In this pyrolysis reactor the wood is heated by subjecting it to a flow of hot gases. This causes an adiabatic pyrolysis, which results in volatilisation of the volatile compounds whereas the mineral compounds (containing the metals) remain entrapped in a coal-type residue which is very rich in carbon. The condensable compounds in the pyrolysis gas condense while leaving the reaction zone due to the inverse temperature gradient. The pyrolysis gas leaving the reactor is used as fuel for the hot gas generator. The charcoal which is extracted at the bottom of the reactor, is cooled, compressed, removed and stored, ready to feed the subsequent stage. A specially developed grinder is used to remove the metal particles from the charcoal and the separation between metal and charcoal particles is accomplished in a pneumatic centrifuge as a result of the difference in density. Using this system the ultimate waste is less than 3% of the initial wood mass. Results obtained with a semi-industrial scale prototype confirm the effectiveness of the process.

Delayed coking: Industrial and laboratory aspects

Delayed coking is a thermal process to convert petroleum residues to a solid coke material. Processes occurring in a delayed coker are complicated and attempts have been made, at the laboratory level, to simulate industrial delayed coking. Although the latter studies are useful, it is impossible to scale-down to the laboratory level. Industrial delayed coking is a turbulent process and such movements cannot be simulated easily in the laboratory. Of industrial importance are the multiphase systems i.e. volumes of unreacted isotropic pitch residue, transported through the bulk, fluid anisotropic mesophase, so creating ordering into acicular structures in the vicinity of the multiphase systems. Four petroleum residues were analysed chemically. Pyrolyses were carried out under pressures of up to 1.0 MPa. Complete mass balances were obtained and the semicokes examined by optical microscopy. Feedstocks for delayed cokers can be blends of petroleum residues, some of which can produce considerable amounts of volatile materials. Volatile evolution, at the optimum operating condition of the delayed coker, can bring about improvements in resultant coke quality. In industrial delayed coking it is important not only to consider the chemistry of the feedstocks, but attention must also be given to the physico-chemical aspects of coker operation.

Interactions between Reactive Aroma Compounds from Model Citrus Juice with Polypropylene Packaging Film

Polypropylene film for food packaging was immersed into an acidic model solution containing 10 aroma compounds (e.g. pinenes, limonene, citrals). Sorption was determined by the use of two complementary methods: solvent extraction and multiple headspace extraction. A complete mass balance of the aroma compounds considering their reactivities in acidic condition was established. It appears that sorption protects the most reactive terpenes from degradation and thus minimizes the formation of compounds which could behave as off-flavors (e.g. α-terpineol). The consequences of this reactivity on the evaluation of the partition coefficient of aroma between juice and packaging are discussed. Keywords: Sorption; aroma compounds; multiple headspace extraction; partition coefficients; polypropylene

Numerical Solution of the Complete Mass Balance Equation in Chromatography

A new approach to simulate the movement of bands through a chromatographic column is presented. Similar to the Craig distribution model, the mass balance equation is divided into two equations describing two successive processes. The first equation includes two effects: solute diffusion in the mobile phase and migration of the solute band with the mobile phase. The second equation deals with the distribution of the solute between phases, i.e., the adsorption isotherm. The partial differential equations are integrated numerically over time and space using two methods. The first approach is a finite difference method. In the second approach, the propagation operator is expanded in a Chebyshev series, where large time steps can be used. The rate of adsorption and desorption is determined by the size of the time increment. By varying the size of the time step, it is possible to study kinetic effects. The influences of sample size, injection width, rate of mass transfer, and mobile phase velocity on the elution profile were studied. Simulations using the modified Craig approach with either of the two numerical procedures showed that the solutes behaved in the chromatographically expected manner. Moreover, with linear adsorption isotherms, direct relationships between HETP, as well as retention times, and experimental parameters could be established.

Instability in a combined heat and mass transfer problem in porous media

Exothermic chemical reactions can influence natural convection effects in a porous medium. Such phenomena may occur in tubular reactors, oxidation of solid material in large containers, chemical vapor deposition systems, liquid explosives, and others. Experimental evidence indicates that the influence of natural convection in many chemically reacting systems cannot be neglected. In the present work, transient effects of a two-dimensional convection generated and sustained by an endothermic chemical reaction and a constant heat flux are studied. The Darcy-Boussinesq equations are used to describe fluid flow through porous medium with different orders of chemical reaction ( n). The complete mass, energy, and momentum balance equations are solved with the Arakawa-Dufort Frankel numerical scheme, which is particularly suitable for stationary solutions over a range of various parameters. Flow behavior is governed by several parameters, including thermal ( ra 1) and concentration ( Ra 2) Rayleigh numbers, Lewis number ( Le), Peclet number ( Pe), aspect ratio (α), and angle of inclination, ξ. The solution structure, i.e. the interconnections between the various branches appear quite complicated. Determination of linear stability on these solution branches reveal that all two-dimensional, stationary solutions develop some form of instability at different ranges of thermal or concentration Rayleigh numbers. The nature and frequency of these periodic solutions depend on the route followed in the parameter space of Ra 1, Ra 2, α, and ξ. The various routes to chaos are identified in this parameter space. A detailed study of frequency of oscillations and power spectrum reveals that instability in this system is reached through several routes. However, in most cases, determination of the dimension of chaotic attractors led to the assessment of chaotic flow, whereas frequency analysis detected clearly discernible spectral peaks with little frequency interlocking. This possible contradiction between Reulle-Takens instability with other more conventional approaches is highlighted in this paper. It is pointed out that instabilities due to simultaneous thermal and concentration effects may be unique. A complete stability map for different parameter spaces, e.g. Ra 1and Ra 2, ξ, α, and n is presented. Also presented in this map is the location of different types of instabilities, namely, periodic, quasi-periodic, and chaotic solutions.

Closed pyrolyses of the isoprenoid algaenan of Botryococcus braunii, L race: geochemical implications for derived kerogens

Algaenans, i.e., highly aliphatic, nonhydrolysable, insoluble macromolecular constituents, have been identified in a number of microalga cell walls and their selective preservation shown to play a major role in the formation of numerous kerogens. All the algaenans so far examined comprise a network of long polymethylenic chains, except for the L race of Botryococcus braunii. The resistant macromolecular material isolated from the latter, termed PRB L, is based on C40 isoprenoid chains with a lycopane-type skeleton. Recent comparative studies of PRB L and of Botryococcus-derived sediments provided the first example of kerogen formation via the selective preservation of an “isoprenoid” algaenan. The present study is concerned with PRB L pyrolyses in sealed gold tubes under various temperature/time conditions (260–350°C, 0.5–69 h). For the conversion rates thus obtained, ranging from 30 to 100%, a complete mass balance of the different families of pyrolysis products was established; most of the C1 to C40 pyrolysate constituents were identified and the abundances of the above compounds and their variations with conversion progress were determined. This study thus allowed us (1) to derive further information about PRB L chemical structure (location of the ether bridges, contribution of linear chains and their relationships with the C40 isoprenoid ones), (2) to determine the behaviour of this isoprenoid algaenan to thermal stress (timing of the formation of the different groups of products then released, nature of the primary cleavages, origin and mode of formation of the secondary products, and further degradations), and (3) to show, in connection with previous studies, that PRB L-derived kerogens should exhibit pronounced differences relative to standard type I kerogens, the latter being based on polymethylenic chains, regarding not only the structure of the generated products but also the timing of oil generation (upward shift of the catagenesis zone).

A mathematical model of suspension with saltation

A theoretical approach to the treatment of wind erosion data, particularly from a wind tunnel, is presented. Considerations are given to the utilisation of a real data set in validation of the model, data that will be presented in a forthcoming paper. Following this, the physics of particle suspension, saltation and the turbulent boundary layer are examined. Two different mathematical models evolve: one considers only suspension, another evokes Bagnold's observation that eroding material merely shifts the velocity profile and the effect of the airborne material on the effective density of the air parcel. These produce a final, relatively simple expression that credibly fits the data of Gerety and Slingerland. A critique of the approach reveals it to be an adequate expression of the known mechanisms of suspension and saltation. Derived algebraic forms for integrated collectors show several of the same “logarithmic power” dependences. Importantly, the results show little influence of saltation itself on the profile. It appears that the saltation process is responsible for a feedback such that the eddy diffusion process for particle movement is effectively enhanced. The combination of an appropriate correction of the pitot data (following Scott and Carter) and a complete mass balance has removed the “kink” from the velocity profile and also the need to consider the saltation process itself in the particle mass balance.

A comparison of two photochemical reaction mechanisms using mass balance and process analysis

Abstract Output from air quality models typically consists of model species concentrations given as a function of time or location. When two different photochemical reaction mechanisms are used in the same air quality model, predictions of species concentrations may differ. Explaining why the models predict differently is difficult using only the typical output. We have developed a process analysis method in which a complete mass balance is used to quantify characteristics values of the reacting system. We have modified both Lagrangian and Eulerian air quality models to calculate the integrated rate, i.e. the mass throughout for each chemical reaction and each physical process. The integrated rates are written to an external file, and a post processing program is used to perform a detailed mass balance on the model simulation. Using the mass balance information, we compute characteristic values that describe the reacting system. In this paper we describe the method and give an example analysis comparing two photochemical reaction mechanisms, the Carbon Bond IV and the SAPRC90 mechanism in a Lagrangian model simulation. This analysis method significantly increases our ability to explain the predictions of air quality models. In addition the method reveals several significant reactivity parameters that can be used to compare different reaction mechanisms and that suggest additional measurements that might distinguish between the different representations.

Comments on the analysis of tritium content in electrochemical cells

Expressions are given for the tritium distribution between gas and liquid phases arising from prolonged electrolysis of D 2O on Pd electrodes saturated with absorbed deuterium. Errors associated with commonly employed experimental procedures and their interpretation using a simple model for the distribution between the gas and liquid phases are evaluated. With regard to tritium production, an unambiguous resolution requires a complete mass balance. Conclusions based on partial data, such as the measurement of the tritium content in a single cell component (e.g. electrode, electrolyte or “electrolytic” gas phase), may be misleading, particularly if production rates are either low or intermittent.

Disposition of azole antifungal agents. II. Hepatic binding and clearance of dichlorophenyl-bis-triazolylpropanol (DTP) in the rat.

DTP (dichlorophenyl-bis-triazolylpropanol) was evaluated as a probe of drug-cytochromes P450 interactions in vitro and in vivo. Studies with rat liver microsomes demonstrate that DTP shows similar P450 binding affinity to its analog, ketoconazole, as determined by P450 difference spectra and inhibition of the metabolism of methoxycoumarin. As a more polar azole, DTP shows less affinity for rat plasma albumin (fraction unbound 0.56) than ketoconazole (fraction unbound 0.037). DTP metabolism is simpler than that of ketoconazole, with only one pathway, N-dealkylation which removes a triazole ring to yield DTP glycol. This primary metabolite is further metabolised to a carboxylic acid, a glycol glucuronide and a third unknown secondary metabolite (probably an acid glucuronide). Over a dose range of 0.1-24mg/kg there is complete mass balance recovery in urine via the five metabolites and unchanged drug. However DTP metabolism is dose dependent and while the affinity of DTP for the cytochromes P450 carrying out the initial dealkylation is high (1.5 microM based on unbound blood concentration), the capacity of the reaction is low (1 nmole/min). Under linear conditions, metabolic clearance is low (19ml/h), but ten-fold higher than renal clearance. The liver is the major distribution site for both DTP and ketoconazole. At low DTP concentrations, a specific high affinity process dominates the hepatic binding of DTP resulting in a liver:blood partition coefficient of approximately 30. Hepatic binding is concentration dependent and the progressive decrease in partition coefficient observed as the dose of DTP is escalated is coincident with a decrease in volume of distribution. The two saturable processes involved in the disposition of DTP result in an unusual concentration dependency in the blood concentration-time profile of this azole. Following administration of a high dose (10mg/kg) of DTP the log concentration-time profile is sigmoidal. At high concentrations (above 1mg/L) both the N-dealkylation and the hepatic binding of DTP are saturated, but as concentrations fall to approximately 0.05mg/L the former process becomes linear and the time profile is convex over this concentration range. At later times as DTP concentrations decline further, the tissue binding also reaches the linear region and the time profile becomes concave. Only at low concentrations (below 0.05mg/L) do both processes become first order and the true half life is evident.

LAS removal and biodegradation in a wastewater treatment plant

AbstractLinear alkylbenzene sulfonate (LAS) biodegrades easily and loses its tensioactive properties quickly through a primary biodegradation process, as many works of literature testify. Many studies have been carried out in laboratories or in pilot plants, whereas few have been undertaken in a wastewater treatment plant (WWTP). In Italy, unlike in other countries, no detailed investigation has been made so far to establish LAS biodegradation in real WWTP conditions. EniChem Augusta (EA) and Consorzio Po‐Sangone (CPS) have worked together for over two years on this problem, taking into consideration the large (flow rate: approximately 400 × 103 m3/d) and central active sludge WWTP of the metropolitan area of Torino, north of Italy. Specific LAS data have been obtained, using established HPLC techniques, in influent and effluent streams, in the dissolved (waters) and adsorbed (suspended solids and sludges) phases, to reach a complete mass balance. LAS removal >99% and LAS biodegradation of approximately 85% have been observed. Attention also has been given to LAS intermediates of biodegradation, namely the sulfophenyl carboxylates (SPC), using HPLC and GC‐MS techniques, the latter after derivatization. The SPCs have been found present only in the waters and not in the adsorbed phases (SS and sludges).

Anionic Surfactants Removal and Biodegradation in a Large Treatment Plant

A full scale study was conducted to investigate the destination of LAS (Linear Alkylbenzene Sulfonate) in Italy's greatest WWTP (Waste Water Treatment Plant): the Turin central plant. Specific LAS data, using established HPLC techniques, have been obtained in the influent and effluent streams, in the dissolved phase (waters) and in the adsorbed one (suspended solids and sludges) to reach a complete mass balance. LAS removal higher than 99% and LAS biodegradation ca. 85% have been observed. Attention has been also given to LAS intermediates of biodegradation, namely the sulfo fenil carboxylaters (SPC) resorting to HPLC and GC-MS techniques, the latter after derivatization. On the basis of SPC data it is possible to measure esperimentally also the biodegradation in sewers before the WWTP (at least 12%) and the mineralization degree of LAS in the WWTP (ca. 80% vs. total biodegraded LAS). The impact of the WWTP on the LAS concentration of the Po river waters has been also considered.