L. Travieso

Assessment of a microalgae pond for post-treatment of the effluent from an anaerobic fixed bed reactor treating distillery wastewater

Abstract An evaluation of the performance of a laboratory‐scale microalgae pond treating effluent from an anaerobic fixed bed reactor digesting distillery wastewater was carried out. The microalgae pond operated with an effluent recycling (R) of 10:1 with respect to the influent and at surface organic loading rates of 418 kg COD ha−1 day−1 and 92 kg BOD5 ha−1 day−1. During the experiment total chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total solids (TS), total suspended solids (TSS), volatile suspended solids (VSS), total nitrogen, ammonia, total phosphorus, orthophosphate, total chlorophyll (C T) and chlorophyll a (C a ) concentrations were monitored. Overall COD and BOD5 removal efficiencies of 98.2 % and 98.8 % were obtained. The global solids removal efficiencies were of 93.2%, 92.6 % and 97.6 % for TS, TSS and VSS, respectively. The removal efficiencies obtained for organic nitrogen and ammonia were 90.2% and 84.1%, respectively. Finally, the removals for total phosphorus and orthophosphate were 85.5% and 87.3%, respectively. It was demonstrated that microalgae grew in this waste by determination of the total chlorophyll and chlorophyll a in the effluent.

Arthospira sp. intensive cultures for food and biogas purification

SummaryThe main contaminants (CO2 and H2S) in biogas produced by anaerooic digestion can be removed by an intensive mass culture of Arthospira sp.. At the same time productivities of 26–34 g dry mass/m2 -d were reached.

Production of biomass (algae-bacteria) by using a mixture of settled swine and sewage as substrate

This paper presents the use of a mixture of settled swine and sewage as substrate for biomass production, mainly constituted by microalgae Chlorella vulgaris and aerobic bacteria, growing outdoor at different dilution rates in a continuous mode. The experiments were carried out in 16-litre volume laboratory ponds operating at hydraulic retention times (HRT) in a range of 4–14 days equivalent to dilution rates (D) in a range of 0.250–0.071 d−1. Total chemical oxygen demand (TCOD), soluble chemical oxygen demand (SCOD), total biochemical oxygen demand (TBOD5), total suspended solids (TSS), volatile suspended solids (VSS), total Chlorophyll (Σ C), total Kjeldahl nitrogen (TKN), ammonia nitrogen, total phosphorous, orthophosphate and pH were monitored. An empirical relationship between the dilution rate (D) and the removal efficiencies of TCOD, SCOD, TBOD5, TKN and total phosphorous was found. The occurrence of an inhibition process for TCOD, TBOD5, TKN and total phosphorous removals was observed. The Andrews kinetic model was successfully applied to these experimental data, while the Monod model was more suitable for studying the variation of the SCOD removal rate with the effluent SCOD concentration. The maximum microalgal biomass productivity was found to be in the range of 93–98 mg VSSA/L d (37.2–39.2 g/m2d) at dilution rates in the range of 0.167–0.250 d−1, where VSSA is the concentration of microalgae expressed in VSS. In the case of the bacteria, the productivity increased linearly with the dilution rate being maximum at a D value of 0.25 d−1. It was concluded that the mixture of pre-treated swine and sewage used as substrate, contributed to the obtention of a high biomass (microalgae-bacteria) production, providing a simple technology feasible to be applied in developing countries.

Effect of ionic exchanger addition on the anaerobic digestion of cow manure

Abstract The long retention time required for cow manure digestion could be attributed to the presence of complex organic compounds but also, to the high concentration of ammonia (NH4 + plus free NH3) that affects the anaerobic digestion. Both problems could be ameliorated by the utilization of ionic exchanger supports. The subject of the present work was the evaluation of the natural zeolite as ionic exchanger. It was observed that the digester with zeolite addition had the best behaviour during the experiments while inhibition of anaerobic degradation was obtained in a control digester with suspended biomass.

Kinetics of anaerobic degestion of cow manure with biomass immobilized on zeolite

This papar describes a kinetic study of anaerobic digestion of cow manure (chemical oxygen demand (COD)  47.1 g 1−1), a process usually inhibited due to the presence of complex organic compounds and high concentrations of ammoniacal nitrogen. Two fluidized bed reactors were used for the study, one with freely suspended biomass as a control, and the other with biomass supported on zeolite. The results obtained are evaluated using the Chen-Hashimoto methane production model to obtain values for the maximum specific growth rate μmax and kinetic constant K of the process for each case studied. Use of the support produced a 59% and 35% increase in the values of these parameters, respectively. This behaviour is believed to be due to the exchange of ammoniacal nitrogen that occurs in this type of digester between the support and the medium. Anaerobic digestion is shown to be a useful method for purifying the wastewater in question since this method results in a 93%–94% reduction of the initial COD, leaving a final COD of between 2.7 and 3.0 g 1−1.

Population Dynamic of Algae and Bacteria in an Oxidation Channel

Abstract A study on algae and bacteria population changes, as a function of time, was carried out in a pilot scale oxidation channel bioreactor using a carrousel system. Total Coliforms, Pseudomonas aeruginosa, and Streptococcus faecalis, the most common bacteria found in sewage, Scenedesmus obliquus and Chlorella vulgaris were the microalgae considered in this work. Physicochemical parameters such as COD, BOD, Chlorophyll a, nitrogen, and phosphorous compounds were studied and determined during the experiments. It was demonstrated that the level of wastewater contamination could be predicted based on the bacterial and algae composition. The relationships between the algae and bacteria population, and the variation of these microorganism populations as a measurement of the level of purification were established. The oxidation channel was able to remove a considerable amount of organic matter and pathogenic microorganisms in a relatively short time. The nitrification process could not be measured. The increase in the relative concentration of microalgae contributed toward improving the global efficiency of the system as well as reducing the pathogenic bacteria population.

Effect of the organic volumetric loading rate on soluble COD removal in down-flow anaerobic fixed-bed reactors

Abstract The organic volumetric loading rate is an important parameter for anaerobic digester design. The effects of the organic volumetric loading rate on the soluble COD (SCOD) removal from settled piggery waste, settled beef cattle manure, screened dairy manure and torula yeast waste were studied. Two models describing the response of the systems were compared: a pseudo first-order and a second-order model.

Effect of the hydraulic retention time on the anaerobic biofilm reactor efficiency applied to screened cattle waste treatment

SummaryIt was found that the increase of the hydraulic retention time improved the organic matter removal and the conversion of organic to ammonia nitrogen. Methane concentration in the biogas was not affected by the hydraulic retention time.The reactor in operation during one year was not clogged.

Evaluation of the quality of the water in El Hondo natural park located in the east of Spain

The purpose of the present work was to evaluate the quality of the water in El Hondo Park, an important wetland located in the east of Spain (province of Alicante) and included on the Ramsar List. The influence of the input of pollutants was assessed over a 14-month period in order to propose remedial action. Three different sources of waters were studied: irrigation water, brackish water and reservoir water. The irrigation water was found to have a high value of conductivity with high concentrations of Cl−, SO4 2 −, Na+ and K+ due to the influence of the brackish water. The concentration of organic matter given as COD T (total chemical oxygen demand) was found to be in the range of 70–600 mg/L of CODT, which was comparable to low-middle strength wastewater. A high concentration of Chlorophyll (a) was found in samples of reservoir water and the eutrophication of this water was thus observed. A high linear relationship was found among CODT, CODF (filtered COD) and BOD5; among electrical conductivity (E.C.), Cl−, SO4 −2, Na+, K+, Ca2+ and Mg2+ and among pH, CO3H− and CO3 2− in all the samples evaluated. Taking this fact into consideration, a simplified water quality index (WQI) was calculated. Using this parameter, the quality of the water from different sources and its variation during the period evaluated was determined to be at a maximum during the months of December to February, which coincided with the period of high precipitations and low temperature. The highest values of this parameter were found in the samples corresponding to the reservoir water while the lowest values were found in the samples of the brackish water. By determination of the WQI, the influence of the brackish water on the quality of water for irrigation and reservoir waters was confirmed.

Evaluation of a laboratory and full-scale microalgae pond for tertiary treatment of piggery wastes.

Piggery wastes tertiary treatment in laboratory and full-scale microalgal ponds was evaluated. COD, BOD, inorganic nitrogen and orthophosphate removals of up to 57 %, 69 %, 79 % and 74 %, respectively, were obtained. The effect of the hydraulic retention time (HRT) on removal efficiencies followed an exponential relationship. COD, BOD and orthophosphate removal rate decreased with increased effluent concentration while the inorganic nitrogen removal rate increased with an increasing effluent substrate concentration at inorganic nitrogen concentration values lower than 0.07 g l-1. Values of maximum substrate removal rate, half rate constant, cell yield coefficient, endogenous constant and maximum specific growth rate were 7.1 ? 0.5 d-1, 0.21 ? 0.02 g l-1, 0.26 ? 0.01 g VSS g-1 COD, 0.012 ? 0.001 d-1 and 1.9 ? 0.9 d-1, respectively. At full-scale, effluent COD, BOD, MPN, inorganic nitrogen and orthophosphate decreased while pH and Chlorophyll a increased with the operation time. It was found that the use of the final effluent as drinking water did not affect pigs growth.