Nitrification and denitrification in a system of reciprocating jet bioreactor

Concept of separation of stages coupled with novel design of reciprocating jet bioreactor have been incorporated in this research for the development of high efficiency treatment system for contaminated wastewaters.Evaluation of pilot plant data reveals that a three stage reciprocating jet bioreactor system could be effectively employed for nitrification and denitrification of highly polluted wastewater obtained from Berlin wastewater treatment plant. Such a system with COD destruction stage (residence time 1–3 hours) followed by nitrification stage (residence time 3–4.5 hours) and denitrification stage (residence time 0.3 hours) gives COD destruction rate upto 58 kg COD/(m³ day), nitrification rate upto 3.2 NH ₄ ⁺ -N/(m³ day) and denitrification rate upto 28 kg NO ₃ ^– -N/(m³ day) while providing COD, NH ₄ ⁺ -N and NO ₃ ^– -N conversion of more than 90%.Nitrification and denitrification of wastewater at such a short residence time is possible mainly due to the employment of reciprocating jet bioreactor system.Paper presented at the Third Joint Schlesinger Seminar on Transport phenomena and processes in biological systems, Technion — Israel Institute of Technology, Haifa, Israel, May 8–9, 1990     

Performance of two laboratory‐scale horizontal wetlands under varying influent loads treating artificial sewage

The performance of two laboratory‐scale horizontal subsurface‐flow constructed wetlands(CWs) treating artificial sewage in response to varying influent components and loads was investigated. Acidification with a pH of 3.0 was detected under an organic carbon load of 100 mg/day, which further inhibited the activity of the denitrification process. With an increase in the carbon load to 240 mg/day, the pH was significantly elevated to 6.0. However, a negative effect of sulphide as a product of sulphate reduction was observed on the removal of ammonium, the plants (Juncus effusus), and the organic carbon degradation. With a produced sulphide concentration of about 3.5 mg/L, the ammonium removal decreased from 100% to 30% under an inflow load of 100 mg/day, and the number of healthy stalks of J. effuses was reduced from about 14 000/m² to less than 6000/m². The removal of organic carbon decreased from 94% to 68% under an influent load of 240 mg/day, when the sulphide concentrations reached up to about 8–10 mg/L. The production of sulphide was not immediately controlled by stopping the inflow sulphate load to remove the negative effect of the sulphide toxicity, thus indicating an immobilization of the deposited reduced sulphur compounds. Moreover, the effect of a nitrate dosage on the sulphide control was also examined, but was shown to be only evident under the conditions of a low organic carbon input.     

Immobilized cell reactors in mineralization of dicarboxylic acid solid waste

Dicarboxylic acid solid waste containing phthalic acid, malic acid, quinone, saturated and unsaturated dicarboxylic esters etc., are discharged in huge quantities during the crackdown of benzene over the catalyst vanadium at temperatures greater than 500 °C in a dicarboxylic acid manufacturing industry. Concern over the biological effects of these compounds underlines the necessity to treat this solid waste. The role of yeast Saccharomyces cerevisiae and anaerobic mixed bacterial cultures immobilized in activated carbon, in sequential two stage anoxic reactors, were investigated for the degradation of dicarboxylic acid solid waste (DASW). In the first stage, DASW was dissolved in water to yield a concentration of 0.5% w/v and was treated in yeast Saccharomyces cerevisiae immobilized reactor at an optimum residence time of 24 h. The yeast fermented samples were further treated in an upflow anaerobic reactor containing mixed culture immobilized in activated carbon at an Hydraulic Retention Time (HRT) of 0.2076 days at an hydraulic flow rate of 14.6×10⁻³ m³/day and Chemical Oxygen Demand (COD) loading rate of 4.3 kg/m³/day. The intermediates that were formed during the yeast fermentation and the anaerobic degradation of DASW were characterized by HPLC, proton NMR, C¹³ NMR and mass spectrometry.     

A preliminary carbon budget for a part of the Ems estuary: The Dollard

During 1975, measurements were made to quantify all sources of input of organic matter in the Dollard. This made a comparison possible between in situ primary production, import from natural sources and organic waste discharges in terms of organic carbon. In order to make a carbon budget, mineralization and the amount of organic matter buried in the sediment was also measured. Input of organic carbon was mainly based on primary production on the tidal flats (measured in situ as O₂ production, 9.3×10⁶ kg C · year^–1), accumulation of suspended matter originating from the North Sea and the River Ems (maximal 37.1×10⁶ kg C · year^–1) and discharge of heavily polluted water (33.0×10⁶ kg C · year^–1). Input from primary production in the water phase was negligibly low (0.7×10⁶ kg C · year^–1). Loss of organic carbon was due to mineralization in the sediment (measured in situ as oxygen consumption, 18.2×10⁶ kg C · year^–1), mineralization in the water phase (using the BOD technique, 7.2×10⁶ kg C · year^–1) and burying of organic matter in the sediment (9.9·10⁶ kg C · year^–1). The loss of dissolved organic matter to the adjacent Waddensea was not measured but must be considerable. Allochthonous detritus was the main source of energy for the food-webs in the Dollard. The role of bacteria as an important source of food for higher organisms in the Dollard is discussed.     

The influence of variable organic loading on the start-up of an anaerobic fluidised bed reactor

Summary A stepped-loading start-up regime utilising variable organic influent concentrations in the range 1650–11600 mgCOD1^–1 was applied to an anaerobic fluidised bed bioreactor at 37°C. The reactor was sensitive to variable influent COD concentrations, but the stepped-loading aided rapid recovery from transient organic loading shocks. Variable effluent COD levels were produced but a COD removal efficiency of 76% was obtained at a final HRT of 0.5 d and an organic loading rate of 5.3 kg COD m^–3 d^–1.     

Removal of benzene in a hybrid bioreactor

A novel hybrid bioreactor was designed to remove volatile organic compounds from wastewater and its performance was investigated. The bioreactor was composed of a biofilter section and a bubble column bioreactor section. Benzene was used as a model compound and the influent benzene was removed by immobilized cells in a bubble column bioreactor. Gas phase benzene stripped by air injection was removed in a biofilter. When the superficial air flow rate was 21.1 m h⁻¹ (0.76 min of residence time in a biofilter), up to 2.2 ppm of benzene in gas phase was removed completely in a biofilter and the maximum removal rate was 4.71 mg day⁻¹ cm⁻³. The concentration profile of benzene along the biofilter column was dependent on the superficial air flow rate and the degree of microbial adaptation. Air flow rate and residence time were found to be the most important operation parameters for the hybrid bioreactor. By manipulating these operational parameters, the removal efficiency and capacity of the hybrid bioreactor could be enhanced. The organic load on the hybrid bioreactor could be shared by the biofilter and bubble column bioreactors and the fluctuation of load on the hybrid bioreactor could be absorbed by changing the distribution of benzene between biofilter and bubble column bioreactors. The maximum removal capacity of the hybrid bioreactor in the experimental range was obtained when the biofilter took 50.3% of influent benzene while 100% of removal efficiency was achieved when the biofilter took 72.3% of influent benzene.     

Co-digestion of intermediate landfill leachate and sewage sludge as a method of leachate utilization

This study examines the co-digestion of intermediate landfill leachate and sewage sludge from a municipal wastewater treatment plant. Application of leachate as a co-fermentation component increased the concentrations of soluble organic compounds (expressed as total organic carbon), ammonium nitrogen, and alkalinity in the digester influents.The biogas yield obtained from the co-fermentation of a 20:1 sewage sludge: intermediate leachate mixture was 1.30 m³ per kg of removed volatile solids (VS), while that from a 10:1 mixture was 1.24 m³ per kg of removed VS. These values exceeded the biogas yield for the sludge alone by 13% and 8%, respectively. The leachate addition influenced the proportion of methane to a minor extent. Increased methane yields of 16.9% and 6.2% per kg of removed VS were found for the two sewage sluge:intermediate leachate mixtures, respectively.     

Factors controlling seasonal variability of benthic ammonium release and oxygen uptake in Alfacs Bay (Ebro Delta,NW Mediterranean)

The seasonal variability of sediment–water ammonium flux andoxygen uptake was studied in an estuarine bay (Alfacs Bay, Ebro Delta, NWMediterranean) influenced by temporal freshwater discharges. Three stationswith different organic loading were sampled. The relationships of benthicfluxes to bottom water (temperature, dissolved oxygen, ammonium, nitrateplus nitrite) and to sediment (porosity, chlorophyll a derivative pigments,organic carbon and nitrogen) variables were examined. Oxygen uptake rangedfrom 0.3 to 2.5 mmol m^–2 h^–1 and ammoniumrelease ranged from 6 to 230 µmol m^–2 h^–1.The lowest value was recorded at the station furthest from the freshwaterinputs, and the highest was at the littoral station nearest the freshwaterdischarge channels (for oxygen uptake) and at the deep station at the saltwedge front (for ammonium flux). Water temperature and the concentration ofchlorophyll a derivative pigments on the surface sediment were revealed asthe main variables to be taken into account to explain the variabilityfound. Changes in fluxes reflecting temperature changes were found at thestation furthest from the freshwater inputs, while at the other, fluxvariability was found to be related to the cycle of functioning offreshwater discharge channels. The different patterns of variability arediscussed in relation to the dynamics of the estuary and to the mainfeatures of benthic nitrogen cycling.     

Mathematical modeling of soil carbon turnover in natural Podocarpus forest and Eucalyptus plantation in Ethiopia using compound specific δ13C analysis

Forest soils exhibit huge potential in storing carbon, but may also release large amounts of it if they undergo major changes in land use and environmental conditions. Biogeochemical processes controlling accumulation and release of soil organic carbon (SOC) are not yet sufficiently understood. We investigate the dynamics of SOC depending on its chemical composition below a natural forest (Podocarpus falcatus dominated) and a plantation (Eucalyptus saligna) growing on Nitisols in southern Ethiopia. Soils at the study‐site show a huge shift to less negative δ¹³C values at a depth of 20–30 cm, indicating a change from C4 savanna to C3 forest during the late Holocene. Total organic carbon (TOC), black carbon (BC), and sugars from microbial (rhamnose, fucose) and plant origin (xylose, arabinose) are subjected to compound‐specific stable isotope analysis. Turnover characteristics are calculated using a numerical advection–diffusion–decomposition model. Our measurements show significant differences in carbon storage (P<0.05) for both sites (Podocarpus 23.5 ± 3.2 kg SOC m^?3; Eucalyptus 18.6 ± 2.7 kg SOC m^?3). These differences can be explained with an initial loss of 15–26% of TOC about 50 years ago, induced by clearing the natural forest. After canopy closure, the carbon input below Eucalyptus is 15–34% less than below natural forest. At present, mean residence times (MRTs) of the investigated compounds do not differ between both stands. Sugars show the shortest MRTs in the topsoil with 2–7 years (xylose) and 5–13 years (arabinose) and have been affected the most by clear‐cutting. TOC and BC show MRTs of 13–25 years and 20–34 years, respectively. Old C4 carbon below 20 cm has merely been affected by the land use change. Contrary to expectation, our study does not indicate a pronounced recalcitrance of BC.     

A bioactive foamed emulsion reactor for the treatment of benzene-contaminated air stream

An adapted bioactive foamed emulsion bioreactor for the treatment of benzene vapor has been developed. In this reactor, bed clogging was resolved by bioactive foam as a substitute of packing bed for interfacial contact of liquid to gaseous phase. The pollutant solubility has been increased using biocompatible organic phase in liquid phase and this reactor can be applied for higher inlet benzene concentration. Experimental results showed a benzene elimination capacity (EC) of 220 g m⁻³ h⁻¹ with removal efficiency (RE) of 85% for benzene inlet concentration of 1–1.2 g m⁻³ at 15 s gas residence time in bioreactor. Assessment of benzene concentration in liquid phase showed that a significant amount of transferred benzene mass has been biodegraded. By optimizing the operational parameters of bioreactor, continuous operation of bioreactor with high EC and RE was demonstrated. With respect to the results, this reactor has the potential to be applied instead of biofilter and biotrickling filters.     

Anaerobic Immobilized Yeast Cell Fermentation and Anaerobic Remediation in Hybrid Reactor for Mineralization of Dicarboxylic Acid Solid Waste

Summary The solid resinous product (SRP) containing unsaturated/saturated dicarboxylic acid residues, phthalic acid and maleic acid is discharged as a solid waste during cracking of benzene over vanadium at temperatures above 500°C in the dicarboxylic acid manufacturing industry. In the present study the solid waste was diluted with water to a concentration of 0.5% w/v for microbial degradation. The waste was fermented in a reactor containing mesoporous activated carbon on which was immobilized Saccharomyces cerevisiae at an optimum residence time of 24 h at pH 6.5. The immobilized-yeast-treated samples were further treated in an upflow anaerobic reactor at an hydraulic retention time (HRT) of 0.1038 days at a hydraulic flow rate of 7.34 × 10⁻³ m³/day and chemical oxygen demand (COD) loading rate of 2.19 kg/m³/day. The pathway followed in the degradation of dicarboxylic acid into end products by anaerobic metabolism in the yeast cell fermentor and in the upflow anaerobic reactor was confirmed through HPLC, Fourier transform infra red spectroscopy and proton and ¹³C NMR spectroscopy.     

Use of the upflow sludge blanket (USB) reactor concept for biological wastewater treatment,especially for anaerobic treatment

In recent years considerable effort has been made in the Netherlands toward the development of a more sophisticated anaerobic treatment process, suitable for treating low a strength wastes and for applications at liquid detention times of 3–4 hr. The efforts have resulted in new type of upflow anaerobic sludge blanket (UASB) process, which in recent 6 m³ pilot-plant experiments has shown to be capable of handling organic space loads of 15–40 kg chemical oxygen demand (COD)·m^?3/day at 3–8 hr liquid detention times. In the first 200 m³ full-scale plant of the UASB concept, organic space loadings of up to 16 kg COD·m^?3/day could be treated satisfactorily at a detention times of 4 hr, using sugar beet waste as feed. The main results obtained with the process in the laboratory as well as in 6 m³ pilot plant and 200 m³ full-scale experiments are presented and evaluated in this paper. Special attention is given to the main operating characteristics of the UASB reactor concept. Moreover, some preliminary results are presented of laboratory experiments concerning the use of the USB reactor concept for denitrification as well as for the acid formation step in anaerobic treatment. For both purposes the process looks feasible because very satisfactory results with respect to denitrification and acid formation can be achieved at very high hydraulic loads (12 day^?1) and high organic loading rates, i.e., 20 kg COD·m^?3/day in the denitrification and 60–80 kg COD·m^?3/day in the acid formation experiments.     

Improved biogas production from palm oil mill effluent by a scaled-down anaerobic treatment process

This is a scale-down study of a 500-m³ methane recovery test plant for anaerobic treatment of palm oil mill effluent (POME) where biomass washout has become one of the problems because of the continuous mixing of effluent during anaerobic treatment of POME. Therefore, in this study, anaerobic POME treatment using a scaled down 50-l bioreactor which mimicked the 500-m³ bioreactor was carried out to improve biogas production with and without biomass sedimentation. Three sets of experiments were conducted under different conditions in terms of biomass sedimentation applied to the system. The first experiment was operated under semi-continuous mode whereas the second and third experiments were operated based on mix and settle mode. As expected, biomass retention improved the anaerobic process as the POME treatment incorporated with mix and settle system were able to operate at an organic loading rate (OLR) of 3.5 and 6.0 kg COD/m³/day respectively, while the semi-continuous operated anaerobic treatment only achieved OLR of 3.0 kg COD/m³/day. The highest biogas and methane production rates achieved were 2.42 m³/m³ of reactor/day and 0.992 m³/m³ of reactor/day, respectively at OLR 6.0 kg COD/m³/day. The biomass or solids retention in the reactors was represented by the total solids measured in this study.     

Synthesis of organic compounds from carbon monoxide and water by UV photolysis

The photolysis of water vapor with carbon monoxide at 1849 Å yields alcohols, aldehydes and organic acids, with an overall quantum yield of 3.3×10^–2. This rather high quantum yield could have led to a contribution of 10¹¹ organic molecules cm^–2 sec^–1 to the pool of organic material on the primitive Earth. The reactions are initiated by the photolysis of water molecules and the resulting hydrogen atoms reduce the carbon monoxide to a variety of one and two carbon compounds. The organic molecules are dissolved in water and thus escape destruction by photolysis. Photolysis of water vapor with carbon dioxide did not yield organic compounds under these conditions.     

Continuous biomethanization of agrifood industry waste: A case study in Spain

The anaerobic digestion technology is a biological treatment widely used to reduce the pollution load of wet waste biomass. In this work we present the results obtained by performing extensive experiments of anaerobic digestion of slaughterhouse waste, tomato industry waste and olive oil industry waste in continuous mode, which were designed to demonstrate that anaerobic digestion is an effective technology from an environmental and economic point of view.Biogas yields obtained are between 35.22 and 5.45 Nm³ biogas/m³ olive oil industry waste and tomato industry waste respectively and the slaughterhouse wastes achieve intermediate production, 30.86 Nm³ biogas/m³ municipal slaughterhouse waste and 22.53 Nm³ biogas/m³ Iberian pig slaughterhouse waste. Moreover, it possible to degrade between 63.46 and 75.3% of the initial organic matter.If these results are analyzed, the environmental, energetic economic benefits of anaerobic digestion can be quantified. Biomethanation of all these wastes generated annually in Extremadura could prevent the emission of 134,772 t of equivalent carbon dioxide, generate an energy similar to that provided by 2826 toe and reach payback times from 3.29 to 3.75 years for anaerobic digestion plant designed to treat the wastes generated by a medium-sized industry. So, we have fulfilled all the planned aims.     

Studies with an anaerobic expanded bed reactor comparing the performances achieved with synthetic waste and domestic sewage

The performance of an anaerobic expanded bed reactor has been examined during the treatment of a synthetic low strength waste whose consistency and composition were constant. The organic loading rates used were in the range 0.2–5 kg total organic carbon m^?3 day^?1 and the removal efficiencies varied from 89 to 52%. Comparing these results with those obtained previously for the treatment of domestic sewage, whose strength and composition was very variable, showed that not only can higher removal efficiencies be achieved with the synthetic waste but also that a significantly better (R² > 0.85, as opposed to <0.5) correlation between data could be obtained. This indicates the potential danger of using synthetic feedstocks for the prediction of reactor performance under real conditions.     

Use of activated carbon as a buffer in biofiltration of waste gases with fluctuating concentrations of toluene

Fluctuations in contaminant concentrations often adversely influence the effectiveness of bioreactors for waste gas treatment. Application of an adsorbent to minimize such fluctuations could improve the overall process. Therefore the buffer capacity of a number of activated carbons and other adsorbents was tested. The buffer capacity of the adsorbents depends on the desired concentration range of the contaminants entering the bioreactor and on the time available for desorption. When fluctuations between 0 and 1000 mg toluene m^–3 were applied to a biofilter this resulted in significant concentrations of toluene leaving the biofilter. Using one selected type of activated carbon it was demonstrated that these fluctuations could be decreased to a value of about 300 mg m^–3, which subsequently completely degraded in the biofilter.     

Nutrient additions by waterfowl to lakes and reservoirs: predicting their effects on productivity and water quality

Lakes and reservoirs provide water for human needs and habitat for aquatic birds. Managers of such waters may ask whether nutrients added by waterfowl degrade water quality. For lakes and reservoirs where primary productivity is limited by phosphorus (P), we developed a procedure that integrates annual P loads from waterfowl and other external sources, applies a nutrient load-response model, and determines whether waterfowl that used the lake or reservoir degraded water quality. Annual P loading by waterfowl can be derived from a figure in this report, using the days per year that each kind spent on any lake or reservoir. In our example, over 6500 Canada geese (Branta canadensis) and 4200 ducks (mostly mallards, Anas platyrhynchos) added 4462 kg of carbon (C), 280 kg of nitrogen (N), and 88 kg of P y^–1 to Wintergreen Lake in southwestern Michigan, mostly during their migration. These amounts were 69% of all C, 27% of all N, and 70% of all P that entered the lake from external sources. Loads from all external sources totaled 840 mg P m^–2 y^–1. Application of a nutrient load-response model to this concentration, the hydraulic load (0.25 m y^–1), and the water residence time (9.7 y) of Wintergreen Lake yielded an average annual concentration of total P in the lake of 818 mg m^–3 that classified the lake as hypertrophic. This trophic classification agreed with independent measures of primary productivity, chlorophyll-a, total P, total N, and Secchi disk transparency made in Wintergreen Lake. Our procedure showed that waterfowl caused low water quality in Wintergreen Lake.Contribution 824 of the National Fisheries Research Center-Great Lakes, 1451 Green Road, Ann Arbor, Michigan 48105, U.S.A. and 722 of the Kellogg Biological Station, Michigan State University.     

Continuous anaerobic treatment of wastewater from a kraft pulp mill

A pilot-scale study of the thermophilic anaerobic digestion of high-strength wastewater (evaporator condensate, EC) discharged from a kraft pulp production process was performed. The system consisted of a microfiltration (MF) membrane module for oily substances removal, a stripping system using evolved gas from the digester for sulfur compounds removal, an anaerobic fixed-bed bioreactor for methane fermentation, and an ultrafiltration (UF) membrane module for retention of a high density of bacterial cells. The bioreactor had a fixed-bed with an effective volume of 5 m³ packed with pumice stone. In a continuous run with only the MF membrane module for oily substances removal, the digester efficiency declined because of methanogenic inhibition by sulfur compounds. After fitting of the stripping system which used evolved gas from the digester, the inhibitive sulfur compounds in the EC were removed more than 80%, and high-loading and high-efficiency operation could be attained. The BOD loading and BOD removal of 35.5 kg BOD/m³/d and 93%, respectively were attained. By anaerobic treatment of the evaporator condensate waste before the conventional aerobic activated sludge method, the total costs would be reduced to ¥3.31/m³ wastewater compared with ¥4.53/m³-wastewater by the aerobic activated sludge method only. The stability of digester performance against interruption by feed stoppage was also examined.