Rafael Borja

Aerobic biodegradation and detoxification of wastewaters from the olive oil industry

Growth and polyphenol biodegradation by three microorganisms namely Geotrichum sp., Aspergillus sp. and Candida tropicalis were studied on olive mill wastewater (OMW). These three microorganisms were selected for their tolerance to the polyphenols. The biodegradation process of OMW was investigated in batch regime by conducting experiments where the initial concentration of chemical oxygen demand (COD) was varied. Furthermore, some tests were performed to determine the most important nutrients necessary for aerobic degradation of OMW. Average COD removals were 55.0%, 52.5% and 62.8% in wastewaters fermented with Geotrichum sp., Aspergillus sp. and C. tropicalis, respectively. The maximum removal of polyphenols was 46.6% (Geotrichum sp.), 44.3% (Aspergillus sp.) and 51.7% (C. tropicalis). In addition, significant decolorization was evident.

Influence of ammonia concentration on thermophilic anaerobic digestion of cattle manure in upflow anaerobic sludge blanket (UASB) reactors

Abstract Ammonia concentrations of 5 g N/litre or more inhibited thermophilic anaerobic digestion of cattle manure in upflow anaerobic sludge blanket (UASB) reactors. A stable digestion of cattle manure could be maintained with ammonia concentrations up to 7 g N/litre after 6 months of operation. However, the methane yield was reduced and the concentration of volatile fatty acids increased from 1 to 3 g/litre as acetic acid, compared to controls with an ammonia concentration of 3 g N/litre. The temporary strong inhibition following a one-step increase in ammonia concentration was reduced by applying a gradual increase. The specific methanogenic activity of ammonia-inhibited reactors (7 g N/litre) with acetate or hydrogen as substrate was reduced by 72 and 56%, respectively. Tests of ammonia toxicity on the acetate- and hydrogen-utilizing populations showed a higher sensitivity of the aceticlastic compared to the hydrogenotrophic methanogens; the specific growth rate for the aceticlastic methanogens was halved at ammonia concentrations of 4 g N/litre, compared to 7·5 g N/litre for the hydrogenotrophic methanogens.

Anaerobic treatment of palm oil mill effluent in a two stage up-flow anaerobic sludge blanket (UASB) system

A high rate anaerobic treatment of palm oil mill effluent (POME) was achieved in a two-stage up-flow anaerobic sludge blanket (UASB) reactor. The acidogenic reactor acclimated rapidly to the wastewater and was tolerant to a suspended solids (SS) concentration of 5.4 g l?1 in the influent wastewater. Loading was gradually increased over a period of 100 days resulting in a satisfactory hydrolysis and acidification giving a maximum rate of acid production of 4.1 g l?1 d?1 acetic acid at a loading rate of 16.6 g l?1 d?1 COD at a hydraulic retention time of 0.9 days. An increase in alkalinity throughout the acclimatization maintained the effluent from the reactor at around pH 5.8. The methanogenic reactor was initially fed on dilutions of the effluent from the first stage reactor after pH adjustment. The loading was gradually increased, and then stepwise, to 60 g l?1 d?1 COD at which point COD removal efficiency had declined significantly and an accumulation of long-chain volatile fatty acids was observed. It was concluded that the reactor could work efficiently up to loadings of 30 g 1?1 d?1 COD, whilst producing a good methane yield and a COD reduction of greater than 90%. Effluent recirculation alleviated the need for alkali additions to the feed of the methanogenic reactor and a direct coupling of the two reactors was achieved towards the end of the experimental run of 175 days. Both reactors showed granule formation with distinct morphological characteristics; these were observed to be formed after 80 days in the acidogenic reactor and after 110 days in the methanogenic reactor.

Aerobic-anaerobic biodegradation of beet molasses alcoholic fermentation wastewater

A study of the aerobic degradation of beet molasses alcoholic fermentation wastewater diluted to 50% (chemical oxygen demand, COD: 82 g/l) was carried out using the following fungi: Penicillium sp., Penicillium decumbens , Penicillium lignorum and Aspergillus niger . These four microorganisms produce a decolorization of the wastewater from the first day of incubation, achieving the maximum decolorization level at the fourth day of treatment in all cases. P. decumbes showed the maximum decolorization with a percentage of 40%. Simultaneously, a significant reduction in the phenolic content of the wastewater was also observed in all cases, reaching average removals of 70% for the four microorganisms studied. Average COD removals were similar in the four cases, achieving maximum values of 52.1 and 50.7%, respectively, on the fifth day of fermentation with Penicillium sp. and P. decumbens . Finally, a comparative study of the mesophilic anaerobic digestion of untreated and previously fermented (with P. decumbens ) beet molasses was carried out in laboratory-scale suspended cell bioreactors. Average COD removals of 93% and methane yield coefficient of 305 ml methane at STP conditions per g of COD removed were found in the anaerobic digestion of pre-treated molasses. The combined aerobic/anaerobic process showed the following advantages in relation to the single anaerobic digestion process: higher average percentages of COD removal (96.5 compared with 90.0%) and a decrease of the hydraulic retention time (HRT) necessary to achieve these COD reductions, increasing the decolorization of the wastewater. # 2002 Elsevier Science Ltd. All rights reserved.

Impact of the main phenolic compounds of olive mill wastewater (OMW) on the kinetics of acetoclastic methanogenesis

Bench-scale tests were conducted to assess the impact of the most representative phenolic compounds present in olive mill wastewater (OMW), two cinnamic acid derivatives (p-coumaric and caffeic acids) and two benzoic acid derivatives (p-hydroxybenzoic and protocatechuic acids), on the kinetics of acetoclastic methanogenesis. Phenolic compounds were added to cultures transferred from an acetate-enriched seed culture reactor. A control without phenolic compound was included as a basis for comparison. Unacclimated cultures were used to minimize the biodegradation of the toxic organic chemicals during the test. A finite-difference, non-linear, least-squares algorithm was used to estimate kinetic parameters by obtaining a best fit of the experimental data to the classical Monod growth and substrate utilization model. Resulting kinetic coefficients revealed substantial changes in both the maximum rate of acetate conversion, k, and the half-velocity coefficient, Ks, when both cinnamic and benzoic acid derivatives were used. The relative effect of the phenolic compound was manifested in a decrease in the value of k or an increase in the value of Ks as the phenolic compound concentration increased. Therefore, mixed inhibition was occurring. In addition, the toxic effects were clearly related to the molecular structure of the phenolic compound in each pair of toxicants studied, the inhibitory impact being greater for the ortho-diphenols (caffeic and protocatechuic acids) in relation to their corresponding monophenolic compounds (p-coumaric and p-hydroxybenzoic acids, respectively).

Response of an anaerobic fluidized bed reactor treating ice-cream wastewater to organic, hydraulic, temperature and pH shocks

Abstract An anaerobic fluidized bed reactor, operating at 35° C, was used to treat ice-cream wastewater with an influent chemical oxygen demand (COD) of 5.2 g l−1. Start-up of the reactor was achieved within 30 days by use of a regime that included stepped increases in influent COD and methanol substitution of the substrate. A steady state was achieved with 94.4% COD reduction at an organic COD loading rate of 15.6 g l−1 d−1 (HRT 8 h). This rate is somewhat faster than those achieved in previously reported studies. The reactor was subjected to transient changes in temperature, pH, influent flow-rate and COD for 6 and 12 h periods. The quality of the effluent deteriorated under these shock load conditions but returned to steady-state values within 6–16 h upon restoring normal conditions. The stability of the reactor under unfavourable process conditions is discussed.

Ammonia removal from anaerobically treated piggery manure by ion exchange in columns packed with homoionic zeolite

Abstract Piggery manure digested in an anaerobic fixed bed reactor was treated by ion exchange for ammonia removal using potassic zeolite (K-Zeo), magnesic zeolite (Mg-Zeo), sodic zeolite (Na-Zeo) and calcic zeolite (Ca-Zeo). The best results were obtained with the use of Na-Zeo. The exchange K-NH 4 was affected by the low mobility of K in the zeolite structure. The exchanges Ca-NH 4 and Mg-NH 4 were affected by the high concentration of suspended solids and the viscosity of the influent, which led to a low mobility of these cations in the liquid phase. The effect of the flow rate was evaluated at bed heights of 6, 9, 18 and 27 cm for Na-Zeo. It was found that increasing the height improved the ammonia removal efficiency but the pressure drop was augmented. It was determined that the increase of the flow rate over 1.6 bed volumes per hour increased the dispersion coefficient and reduced the exchange capacity of the bed.

Anaerobic digestion of slaughterhouse wastewater using a combination sludge blanket and filter arrangement in a single reactor

A laboratory-scale anaerobic reactor, in which the bottom two-thirds were occupied by a sludge blanket and the upper one-third by submerged small cubes of polyurethane foam, was evaluated for the anaerobic treatment of slaughterhouse wastewater. The reactor was operated at 35°C during the two experimental studies. In the first study, the chemical oxygen demand (COD) concentration of the wastewater was increased from 3·74 to 10·41 g l−1 whilst maintaining a constant hydraulic retention time (HRT) of 1·5 days. In the second, the HRT was decreased from 1·35 to 0·50 days, whilst maintaining a constant influent COD concentration of 10·41 g l−1. The results showed that this type of reactor was suitable for the anaerobic treatment of this wastewater and demonstrated a high COD removal of between 90·2 and 93·4% at organic loading rates between 2·49 and 20·82 g COD l−1 day−1. At an HRT of 0·5 days, the reactor achieved a methane yield of 0·345 l CH4 STP per gram of COD removed. This yield is higher than the values reported in previous studies.

Effect of organic loading rate on anaerobic treatment of slaughterhouse wastewater in a fluidised bed reactor

COD removed efficiencies in the range 75·0NDASH;98·9% were achieved in an anaerobic fluidised-bed reactor treating slaughterhouse wastewater, when evaluated at organic loading rates (OLR) of between 2·9 and 54·0 g COD/l.d, hydraulic retention times (HRT) of between 0·5 and 8 h and feed COD concentrations of between 250 and 4500 mg/l. More than 94% of feed COD could be removed up to OLR of about 27 g COD/l.d. Up to 0·320 litres of methane were produced per gram of COD removed and this methane production rate was independent of the OLR applied in this investigation. Volatile fatty acid (VFA) concentration in the reactor increased sharply at an OLR of about 30 g COD/l.d and, therefore, sufficient alkalinity should be provided to prevent pH from dropping to an undesirable level. The anaerobic fluidised-bed system can be operated at a significantly higher liquid throughput than other previously reported systems while maintaining its excellent efficiency.

Heavy metals removal from acid mine drainage water using biogenic hydrogen sulphide and effluent from anaerobic treatment: Effect of pH

Four alternatives (runs A, B, C and D) for heavy metals removal (Fe, Cu, Zn and Al) from acid mine drainage water (AMDW) produced in the mining areas of the Huelva Province, Spain, were evaluated. In run A, the anaerobic effluent from the treatment of acid mine drainage water (cheese whey added as a source of carbon) was mixed with the raw AMDW. The pH increased to 3.5 with the addition of KOH. In run B, biogas with around 30% of hydrogen sulphide obtained in the anaerobic reactor was sparged to the mixture obtained in run A, but in this case at a pH of 5.5. In run C, the pH of the raw AMDW was increased to 3.5 by the addition of KOH solution. Finally, in run D, the pH of the raw AMDW was increased to 5.5 by the addition of KOH solution and further biogas was sparged under the same conditions as in run A. It was found that heavy metal removal was a function of pH. At a pH of 3.5 most of the iron was removed while Zn and Cu were partially removed. At a pH of 5.5 the removal of all metals increased considerably. The best results were obtained in run B where the percentages of removal of Fe, Cu, Zn and Al achieved values of 91.3, 96.1, 79.0 and 99.0%, respectively. According to the experimental results obtained tentative schemas of the flow diagram of the processes were proposed.