Aerobic Biological Degradation Research Articles

The Design and Performance Prediction Model of an Integrated Scheme of a Membrane Bioreactor and Anaerobic Digester for the Treatment of Domestic Wastewater and Biowaste

An innovative and integrated scheme that encompasses two well-established waste treatment technologies, the aerobic biological degradation of organic matter bioprocess via membranes and anaerobic digestion, was demonstrated as a zero-waste approach that may effectively treat wastewater and biowaste in an integrated and symbiotic manner. Aiming to create a tool for the design, monitoring, and control of the scheme, prediction models were developed, validated, and implemented for the process simulation of the integrated scheme. The minimization of selected objective functions led to the estimation of the models’ parameters. The activated sludge model no. 1 (ASM1) was adopted for the simulation of the aerobic membrane bioreactor. The kinetic parameters were calibrated using volatile suspended solids and total nitrogen as the objective functions permitting the model to simulate the bioprocess satisfactorily (Nash–Sutcliffe efficiency > 0.86) and to calculate the concentration of the active biomass. The predominance of heterotrophic bacteria (4300 to 9770 mg COD/L) over autotrophic biomass (508 to 1422 mg COD/L) was showcased. For the anaerobic process unit, a simplified anaerobic digestion model 1 ADM1-R4 was used, and the first-order hydrolysis constants (kch 0.41 d−1, kpr 0.25 d−1, kli 0.09 d−1) and microbial decay rate (kdec 0.02 d−1) were evaluated, enabling an accurate prediction of biogas production rates. A full-scale implementation of the integrated scheme was conducted for a decentralized waste treatment plant in a small community. Preliminary design calculations were performed in order to estimate the values related to certain process and technical parameters. The performance of this full-scale plant was simulated by the developed model, presenting clear benefits for practical applications in waste treatment plants.

Impact of digestate addition on the biostabilization of undersized fraction from municipal solid waste

Biostabilization is a commonly applied method in mechanical-biological treatment (MBT) plants to process municipal solid waste. In many ways, e.g. by applying additives to waste, MBT plant operators strive to enhance the effectiveness of biostabilization, which leads to reducing the time and energy outlays necessary for the process, as well as to minimizing the amount of final stabilized waste directed to landfills. This paper deals with the impact of digestate waste from agricultural biogas plants used as additive to the biostabilization process of undersized fraction from municipal solid waste (UFMSW) on the intensive phase of the process and properties of stabilized waste. The aim of this study was to assess whether, and if so to what extent, the application of digestate waste affects the process. Five different input compositions were tested (without digestate and with the addition of digestate at: 2.5; 5; 7.5 and 10 wt%). Waste treatment time was 2 weeks. Changes in moisture content, organic matter (OM), respiration activity (AT4), bulk density, air-filled porosity, heavy metal content, pH, carbon to nitrogen ratio, as well as composition of process gases emitted were evaluated. Additionally, microorganisms (including pathogens) inhabiting the processed waste in the aspect of waste sanitation were analyzed. It was found that the addition of digestate at 2.5, 5 and 7.5 wt% extended the duration of the thermophilic phase and decreased the CO2 content in process gases. The addition of digestate at 2.5 wt% and 5 wt%, decreased also OM by approx. 25% of the initial value and AT4 by approx. 30%. It was also proved that the addition of digestate favors the limited sanitation of UFMSW. As a result of the research, it was found that the addition of digestate at 2.5 wt% and 5 wt% is sufficient to accelerate the aerobic biological degradation of UFMSW.

Aerobic biological degradation of organic matter and fracturing fluid additives in high salinity hydraulic fracturing wastewaters

Reuse of hydraulic fracturing wastewaters depends on effective tailored treatment to prepare the water for the intended end use. Aerobic biological treatment of hydraulic fracturing produced water was examined to degrade dissolved organic carbon (DOC) and polyethylene glycols (PEGs). Biological treatment experiments of three produced water samples with DOC concentrations ranging from 22 to 420 mg/L and total dissolved solids (TDS) levels ranging from 26 to 157 g/L were conducted in 48–240 h batches. Samples were not pretreated to remove suspended solids and were inoculated with activated sludge and acclimated over several weeks. Results show that between 50% and 80% of DOC was removed in 12–24 h but a sizeable portion, on a mass basis, remained in the samples with higher DOC concentrations. PEGs were also shown to readily biodegrade into singly- and doubly-carboxylated metabolites, but were not shown to degrade past that point, leading to accumulation of PEG-dicarboxylates (PEG-diCs) in the batch reactors. Possible explanations include residence times that were too long, resulting in starved microbial populations (and thus, a stopping of PEG degradation) or the presence of other ethoxylated additives that degraded into PEGs and PEG-diCs and fed this accumulation. This work demonstrates that a well-acclimated microbial culture is capable of degrading a large portion of DOC in hydraulic fracturing wastewaters across a wide spectrum of TDS concentrations, indicating that biological treatment is a viable option for enabling reuse of produced water.

Coupling Pyrite-Fenton Process with Aerobic Biodegradation for the Treatment of 2-Chlorophenol

This study investigates the performance of a sequential pyrite-Fenton and biological process for the treatment of 2-chlorophenol (2-CP) containing wastewater using pyrite-Fenton process as a pretreatment stage. Pyrite was tested as a catalyst material in Fenton reaction due to its low cost and high abundance in the environment. All experiments were run in batch mode. The biodegradation experiments were performed under aerobic conditions using glucose as the co-substrate with untreated or Fenton-pretreated 2-CP. Despite the 100% removal of 2-CP in batch pyrite-Fenton reactors, the total organic carbon (TOC) removal only approached 70%, implying the transformation of 2-CP into some chemically stable intermediate reaction by products during pyrite-Fenton oxidation. In systems with no pyrite-Fenton pretreatment, a combined effect of biotic and abiotic processes including biological degradation, sorption, and volatilization played a significant role on 2-CP removal. The pyrite-Fenton pretreatment of 2-CP significantly improved the performance of aerobic biological reactor relative to system with no pyrite-Fenton pretreatment by (1) reducing the toxicity of 2-CP on aerobic microbial cells and (2) enhancing cell growth. Overall, this study shows that pyrite-Fenton pretreatment coupled with aerobic biological degradation could provide a cost-effective solution for the treatment of wastewater containing low-biodegradable toxic compounds such as chlorophenols.

Aerobic and Anaerobic Biological Degradation of Pharmaceutically Active Compounds in Rice Paddy Soils

One of the concerns against the use of sewage sludge for agricultural purposes is emerging contaminants contained in sewage sludge. Most of the studies on biological degradation of pharmaceutically active compounds in agricultural land were carried out with water-unsaturated soils under relatively aerobic conditions. In this study, the degradation of pharmaceuticals mainly including non-steroidal anti-inflammatory drugs (NSAIDs) was investigated in Asian rice paddy soils that are flooded in anaerobic condition. The experimental results showed that the concentrations of the target pharmaceuticals excluding the exception of naproxen were poorly decreased in anaerobic condition. On the other hand, the microbial communities of the soils contained the aerobic degraders of clofibric acid and diclofenac, which are generally persistent in biological wastewater treatment. The higher degradation rates in aerobic condition suggest the possibility of enhanced degradation of pharmaceuticals by supplying oxygen with plowing anaerobic rice fields or with drying the field in off-season for farming.

Combined treatment of mezcal vinasses by ozonation and activated sludge.

In Mexico, mezcal production generates huge amounts of vinasses (MV) that cause negative environmental impacts. Thus, MV treatment is necessary before discharge to water bodies. Although there is no information for mezcal vinasses, similar effluents have been treated by biological processes (i.e. anaerobic and aerobic) usually complemented by oxidative chemical pretreatments (ozonation) and physico-chemical methods. In this work MV were first ozonated and followed by batch aerobic biological degradation. In the ozonation stage, organic matter removals were 4.5-11 % as COD, whereas the removal of aromatic compounds and phenols were 16-32 % and 48-83 % respectively. In the aerobic post-treatment, COD depletions up to 85 % were achieved; removals in ozone pre-treated vinasses were higher (80 to 85 %) than that of raw vinasse (69 %). It seems that ozonation preferentially attacked the recalcitrant fraction of organic matter present in the vinasses and increased its aerobic biodegradability.

Biological Degradation of 2,4,6-Trichlorophenol by a Sequencing Batch Reactor

2,4,6-trichlorophenol (TCP) is a toxic compound which is released into the environment mainly through industrial wastewater. For aerobic biological degradation of TCP, a modified bench scale SBR was used. The biological sludge of municipal wastewater treatment plant was used to set up the bioreactor. In order to reduce the release of TCP, the SBR was modified by increasing the ratio of constant volume to total volume of the bioreactor, increasing the ratio of height to diameter, reducing the number of operating cycles per day and entering wastewater from the floor of the bioreactor. The amount of TCP volatility with the gases from SBR was determined by adsorbing and extracting it from powder activated carbon column. The modified SBR in TCP concentration of 430 mg/L and HRT of 8 h removed more than 99% of TCP and total phenolic compounds (TP) as well as more than 92% of COD. Also, more than 90% of chloride ions were stoichiometrically released from TCP. Finally, the modified SBR was capable of removing TCP in concentration of 430 mg/L at a low hydraulic retention time (8 h). This is the first study to report these results, where the modified SBR could operate at higher concentrations of TCP and in shorter HRT. Therefore, the modified SBR can be used as a reliable and effective process to remove TCP and other halogenated compounds.

Fish canning industry wastewater treatment for water reuse – a case study

Abstract The valorization of wastewaters from the fish canning industry is of great concern, not only because of the high quantities generated, but also economic and environmental benefits may result from a proper treatment approach of the waste generated while reducing costs related to wastewater discharge. A limiting factor for reuse and recycling treated fish canning wastewater into an industrial plant and also for other uses is the high salt content, which persists even after conventional treatment. So, the reuse of fish canning industrial wastewater was assessed by combining conventional treatments, such as sedimentation, chemical coagulation-flocculation and aerobic biological degradation (activated sludge process) followed by a polishing step by reverse osmosis (RO) and ultraviolet (UV) disinfection. In this investigation all these processes were optimized in order to remove essentially the effluent suspended particles (primary treatment), the organic matter content in the biological aerated reactor (secondary treatment) and, finally, the remaining salts and microorganisms (tertiary treatment). The overall removal efficiencies obtained were: 99.9% for dissolved organic carbon (DOC), 99.8% for oil and grease (O&G), 98.4% for total suspended solids (TSS), above 96% for anions and cations and 100% for heterotrophic bacteria expressed as colony-forming units (CFU). The final clarified effluent was found to have the quality requirements to be recycled or reused in the industrial plant, allowing the reduction of the effluent to be discharged, the water use and the costs of tap water for industrial use. As regards the energy and chemicals costs, to obtain a treated effluent to be reused in the process costs 0.85 €/m3. This value can be reduced by about 60% if the goal is only to meet the legislated standards for the effluent discharge into water bodies. Tap water for the industrial plant costs about 2.1 €/m3.

The Biomec process for mechanochemically assisted biodegradation of PCBs in marine sediments

The Biomec process, a two-stage treatment based on a short mechanochemical (MC) pretreatment and then followed by an aerobic biological degradation, was developed and tested for detoxifying marine sediments that were largely contaminated by polychlorobiphenyls (PCBs). Clean marine sediment spiked with PCBs (Aroclor 1260) and, alternatively, with decachlorobiphenyl in slurry conditions was ultramilled for 1 min in a nutational high energy ball mill, then was treated aerobically in a bioreactor with a purposely selected commercial bacterium (Burkholderia xenovorans). With ∼66 % overall PCB biodegradation achieved in less than 3 months, laboratory experiments confirmed the remarkable effectiveness of Biomec process when compared to direct bioremediation. The investigation showed in particular that the MC pretreatment decreased the chlorination degree of high-chlorinated PCB congeners, and consequently their biorecalcitrance, through the substitution of some chlorine atoms with hydroxyl groups. This reaction eases the aerobic degradation of the hydroxyl-substituted PCBs by B. xenovorans, allowing bacteria to skip the cell stressing step of aromatic ring bi-hydroxylation along the biodegradation pathway. After short MC treatment of the sediments, a common biological aerobic treatment can degrade PCB congeners, the highly chlorinated ones were included, in a fast, effective and cheap manner.

Aerobic biological treatment of second cheese whey in suspended and attached growth reactors

AbstractBACKGROUNDSecond cheese whey is a strong organic and saline effluent whose characterization and treatment have not been sufficiently addressed.RESULTSIndigenous microorganisms from second cheese whey were isolated for its aerobic biological degradation. Experiments in suspended and attached growth reactors (lab and pilot scale) were carried out using different feed whey concentrations. These concentrations corresponded to three different dilutions with tap water, using 25%, 50% and 75% whey (concentrations C25, C50 and C75, respectively), as well as without dilution (100% whey, C100). The maximum degradation rate of the organic load obtained in the suspended growth reactors was achieved for the concentration C100 (10.06 g d‐COD L−1 day−1). Degradation was more rapid (26.3 g d‐COD L−1 day−1) in a lab‐scale packed bed reactor with recirculation and concentration C75. Experiments in a pilot‐scale reactor with recirculation were also performed with high degradation rates (6.41 g d‐COD L−1 day−1) under various environmental conditions. The long‐term degradation efficiency (12 month operation period) and the effect of environmental and operating conditions on filter performance were studied.CONCLUSIONSAerobic biological treatment at the proposed pilot‐scale filter proved to be a sufficient method. The simplicity of the installation provides an effective solution to a serious environmental and social problem. © 2014 Society of Chemical Industry

Biotransformation of Benzotriazoles: Insights from Transformation Product Identification and Compound-Specific Isotope Analysis

Benzotriazoles are widely used domestic and industrial corrosion inhibitors and have become omnipresent organic micropollutants in the aquatic environment. Here, the range of aerobic biological degradation mechanisms of benzotriazoles in activated sludge was investigated. Degradation pathways were elucidated by identifying transient and persistent transformation products in batch experiments using liquid chromatography-high-resolution tandem mass spectrometry (LC-HR-MS/MS). In addition, initial reactions were studied using compound-specific isotope analysis (CSIA). Biodegradation half-lives of 1.0 days for 1H-benzotriazole, 8.5 days for 4-methyl-1H-benzotriazole, and 0.9 days for 5-methyl-1H-benzotriazole with activated sludge confirmed their known partial persistence in conventional wastewater treatment. Major transformation products were identified as 4- and 5-hydroxy-1H-benzotriazole for the degradation of 1H-benzotriazole, and 1H-benzotriazole-5-carboxylic acid for the degradation of 5-methyl-1H-benzotriazole. These transformation products were found in wastewater effluents, showing their environmental relevance. Many other candidate transformation products, tentatively identified by interpretation of HR-MS/MS spectra, showed the broad range of possible reaction pathways including oxidation, alkylation, hydroxylation and indicate the significance of cometabolic processes for micropollutant degradation in biological wastewater treatment in general. The combination of evidence from product analysis with the significant carbon and nitrogen isotope fractionation suggests that aromatic monohydroxylation is the predominant step during the biotransformation of 1H-benzotriazole.

Chemical and Biological Treatment of Fish Canning Wastewaters

Abstract — The main environmental problems of fish canning industries are high water consumption and high organic matter, oil and grease and salt content in their wastewaters. This work aims to analyze the situation of different plants located north of Douro river, in Portugal, in order to propose various solutions to their problems. Thus, initially it was made an identification and implementation of prevent and control pollution measures within the industrial units in order to reduce water consumption, minimize the wastewater production and reduce the pollutant load to treat. Then, the wastewater treatability was evaluated through a sedimentation and coagulation-flocculation process and through an aerobic biological degradation. In the sedimentation and coagulation-flocculation process two organic coagulants (RIPOL 070 and RIFLOC 1815), commonly used in wastewater treatment, were tested, leading to good results, especially in terms of oil and grease and total suspended solids removals. The best suspended solids removal efficiencies were 53% and 79%, using 400 mg/L of RIPOL 070 and 150 mg/L of RIFLOC 1815, respectively. At these dosages, both coagulants demonstrated excellent oil and grease removals, about 99% for RIFLOC 1815 and 88% for RIPOL 070. The aerobic biological treatment with activated sludge proved to be very adequate to organic matter removal. Two feed flow rates were tested and the highest TOC removal efficiency (96%) was verified with the lowest one (0.75 L/h), corresponding to a longer hydraulic retention time (8 h). So, the proposed sequential treatment, combining physico-chemical and biological processes, proved to be an effective alternative to start the fish canning wastewaters treatment for further reuse in the industrial process.

Biodegradation of a synthetic co-polyester by aerobic mesophilic microorganisms

The aerobic biological degradation of the synthetic aliphatic–aromatic co-polyester Ecoflex™ (BASF) by 29 strains of enzyme-producing soil bacteria, fungi and yeasts was investigated at moderate environmental conditions. Previous studies had shown that these materials could be degraded but these studies were done under thermophilic conditions. In this paper, a screening procedure was developed to assess the biodegradability of the co-polyester at ambient environmental conditions and to investigate the mechanism of biodegradation. Results showed that the aliphatic–aromatic co-polyester could be degraded by a number of different microorganisms. However, after 21 days exposure to even the most promising cultures of pure microorganisms, only partial degradation of the Ecoflex™ was accomplished and only a few samples showed visible signs of degradation as loosely defined by the mechanical weakening of the films. Weight loss was not as obvious as the visual degradation and suggested broader types of microbial attack. The bacteria studied preferentially degraded the bonds between aliphatic components of the copolymer and the rate of biodegradation of oligomers was appreciably faster than that for the polymer chains. Using GC–MS techniques, degradation intermediates were identified to be the monomers of the co-polyester. Gel permeation chromatography results suggested exo-enzyme type degradation, where the microbes hydrolysed the ester bonds at the termini of the polymeric chains preferentially.

Combination of ozonation with conventional aerobic oxidation for distillery wastewater treatment

Laboratory-scale experiments were conducted in order to investigate the effect of ozone as pre-aerobic treatment and post-aerobic treatment for the treatment of the distillery wastewater. The degradation of the pollutants present in distillery spent wash was carried out by ozonation, aerobic biological degradation processes alone and by using the combinations of these two processes to investigate the synergism between the two modes of wastewater treatment and with the aim of reducing the overall treatment costs. Pollutant removal efficiency was followed by means of global parameters directly related to the concentration of organic compounds in those effluents: chemical oxygen demand (COD) and the color removal efficiency in terms of absorbance of the sample at 254 nm. Ozone was found to be effective in bringing down the COD (up to 27%) during the pretreatment step itself. In the combined process, pretreatment of the effluent led to enhanced rates of subsequent biological oxidation step, almost 2.5 times increase in the initial oxidation rate has been observed. Post-aerobic treatment with ozone led to further removal of COD along with the complete discoloration of the effluent. The integrated process (ozone-aerobic oxidation-ozone) achieved approximately 79% COD reduction along with discoloration of the effluent sample as compared to 34.9% COD reduction for non-ozonated sample, over a similar treatment period.

Effective pine bark composting with the Dome Aeration Technology

In South Africa garden refuse is primarily disposed of in domestic landfills. Due to the large quantities generated, any form of treatment would be beneficial for volume reduction, waste stabilization and resource recovery. Dome Aeration Technology (DAT) is an advanced process for aerobic biological degradation of garden refuse and general waste [Paar, S., Brummack, J., Gemende, B., 1999a. Advantages of dome aeration in mechanical–biological waste treatment. In: Proceedings of the 7th International Waste Management and Landfill Symposium, Cagliari, 4–8 October 1999; Paar, S., Brummack, J., Gemende, B., 1999b. Mechanical–biological waste stabilization by the dome aeration method. Environment Protection Engineering 25 (3/99). Mollekopf, N., Brummack, J., Paar, S., Vorster, K., 2002. Use of the Dome Aeration Technology for biochemical stabilization of waste prior to landfilling. In: Proceedings of the Wastecon 2002, Waste Congress and Exhibition, Durban, South Africa.]. It is a non-reactor open windrow composting process, with the main advantage being that the input material needs no periodic turning. A rotting time of only 3–4 months indicates the high efficiency. Additionally, the low capital/operational costs, low energy inputs and limited plant requirements provide potential for use in aerobic refuse stabilization. The innovation in the DAT process is the passive aeration achieved by thermally driven advection through open windrows caused by temperature differences between the degrading material and the outside environment. This paper investigates the application of Dome Aeration Technology to pine bark composting as part of an integrated waste management strategy. A full-scale field experiment was performed at the Bisasar Road Landfill Site in Durban to assess the influence of climate, waste composition and operational conditions on the process. A test windrow was constructed and measurements of temperature and airflow through the material were taken. The process monitoring revealed that prevailing climatic conditions in a subtropical location do not affect the high efficiency of this technology. However, the composition of the input material can be detrimental for production of high quality compost because of a lack of nitrate.

Catalyzed Hydrogen Peroxide Treatment of Polychlorinated Biphenyl Contaminated Sandy Soils

This paper reports the results of the treatment of polychlorinatedbiphenyl (PCB) contaminated sandy soils (100 mg kg-1 Aroclor 1242) with the Fenton advanced oxidation process (AOP). The results obtained in the various assays permitted the optimization of conditions as follows: 5% H2O2; 100 ppm of Fe3+; and a ratio of sandy soil mass/volume of oxidizing solution (m/V) of 1/3 g mL-1. In addition, these tests established the need for agitation and dispensed with the need for heat. The results obtained confirm that the oxidation process occurs in solid phase (on the PCBs adsorbed to soil particles), producing 98% elimination of the original PCB structure and 82% dechlorination, all within a reaction time of 72 hr. The degree of elimination was found to be dependent on the level of congener chlorination and the process displays a pseudo first order kinetics. In addition, the Fenton chemical oxidation process may be complemented by subsequent aerobic biological degradation which, after 15 days, produces 72% mineralization of the products generated during the chemical oxidation process.

Biological and Physical Attenuation of Endocrine Disruptors and Pharmaceuticals: Implications for Water Reuse

AbstractA select group of endocrine disrupters, pharmaceuticals, and personal care products was studied to determine the degree of biological attenuation in water reuse applications. Laboratory investigations involved both batch reactors using biologically active sand and continuous flow simulated aquifer storage and recovery experiments. All laboratory experiments were conducted using Colorado River water spiked with various target compounds at concentrations between 10 and 100 ng/L. Field studies were also conducted to determine the occurrence and attenuation of target compounds in water reuse applications. Two golf courses irrigated with reuse water were studied to determine if turf applications led to contamination of nearby ground water. A waste water treatment facility that uses rapid infiltration basins seasonally was also tested to determine the degree of attenuation of detectable target compounds along a subsurface flowpath. A qualitative structural activity relationship model was applied to the target compounds to predict the general rate of aerobic biological degradation. Significant attenuation of many target compounds was observed in both laboratory and field experiments. Conversely, several compounds displayed limited removal during these studies. Field experiments were limited to detectable compounds and various nonbiological removal or concentration effects that may impact data interpretations, which are discussed in this paper. The predictive model was found to be moderately accurate within the confines of the project scope.

Removal of estrogenic activity from municipal waste landfill leachate assessed with a bioassay based on reporter gene expression.

The leachate of a municipal waste landfill was tested for estrogenic activity using a reporter-gene-based bioassay with a human breast-cancer-derived cell line (MVLN cells). The leachate was processed with two different membrane-employing processes operating in parallel. One process consists of aerobic biological degradation, ultrafiltration, and subsequent adsorption to activated carbon. The second process was a reverse osmosis treatment of the raw leachate. Both processes are common in the treatment of landfill leachate. Here, the efficacy of the two processes to remove "estrogenicity" was compared. Both treatment processes removed more than 97% of the estrogenic activity, calculated as estradiol equivalents (EEQs), but they were not equally effective. After adsorption to activated carbon, no estrogenicity was detected, whereas concentrated effluent of the reverse osmosis treatment still elicited an estrogenic response in the bioassay. On the basis of chemical analysis, it is proposed that bisphenol A was responsible for the majority of estrogenic activity in the raw and treated leachate. Although the contribution of treated leachate to the estrogenic load on the aquatic environment seems to be low compared to that of sewage treatment works, the high estrogenic activity in raw landfill leachate stresses the necessity for the appropriate treatment of these leachates.

Kinetics of the aerobic biological degradation of shredded municipal solid waste in liquid phase

The organic fraction of municipal solid waste (OFMSW) should be utilised by means of biological methods. The biodegradation of solid wastes can be intensified owing to application of the bioreactors. Estimation of the optimum values of the organic load is one of the most important tasks for the aerobic biodegradation processes. The kinetic model of biological oxidation of the organic wastes has been presented in this paper. The experiments were carried out in batch 6-l working volume stirred tank bioreactors at constant temperature of 25°C. Initial total solids have been at the levels of 15, 19, 34, 55 and 66 g l −1. The kinetics of microbial decomposition of organic substances was described by means of an unstructured model. The satisfactory time courses for substrate chemical oxygen demand in the solid (COD S) and liquid phase (COD L) and biomass concentration (RNA) have been achieved. Also, the influence of the initial TS on the kinetics of the biodegradation process was investigated and the optimum value of initial TS for this type of processes was estimated at 34–55 g l −1.

Treatment of black-olive wastewaters by ozonation and aerobic biological degradation

The degradation of the organic pollutants present in black-olive wastewater was carried out by ozonation, aerobic biological degradation, and the combination of two successive steps: an aerobic biological process followed by an ozonation. Contaminant removal was followed by means of global parameters directly related to the concentration of organic compounds in those effluents: chemical oxygen demand and total aromatic and phenolic contents. In the ozonation, an approximate kinetic study was performed to determine the apparent kinetic constants for the COD reduction, k COD, and for the total aromatic reduction, k A. In the aerobic biological degradation, the kinetic study was performed using the Monod model applied to the experimental data. In the combined process, a higher overall reduction in COD and aromatic content was achieved by the successive stages, and there was improved removal of the organic material during the second treatment. This enhancement was reflected in an increase in the apparent kinetic constants in the ozonation of the wastewater that had previously been treated aerobically, relative to the values obtained for the kinetic parameters in the single process experiment which were carried out under the same operating conditions.