Organic Matter Removal Efficiency Research Articles

Laser-Engineered Graphene on Wood Enables Efficient Antibacterial, Anti-Salt-Fouling, and Lipophilic-Matter-Rejection Solar Evaporation.

Advances in solar steam generation have made a promise in mitigating the water scarcity problem. However, their practical use could be curtailed by the vaporized pollutants and the longevity limited by biofouling and salt-fouling that are often overlooked. Here, a flake of wood is reported to be engineered into a miniaturized solar water treatment device by a laser engraving process and demonstrates advantages over common solar systems. The device is structured to mimic the centralized water treatment plants, which contains a superhydrophilic graphene bottom layer for lipophilic organic matter rejection and antifouling, an intrinsic wood microchannels layer for water transport and thermal management, and a hydrophobic graphene top layer for solar-driven desalination while inhibiting salt deposition. The pore size of wood differentiates the water flux and hence the evaporation performance, and the balsa wood with a larger pore size possesses a higher evaporation rate of 1.6 ± 0.02 kg m-2 h-1 compared with pine wood. The hierarchical design achieves a solar energy conversion efficiency of 110% and a lipophilic organic matter removal efficiency of >90% and significantly improves longevity even at high salinity. This work illuminates a sustainable and cost-effective pathway for water treatment and shows potential for wastewater reuse.

Evaluation of the effect of reaction time on nutrients removal from secondary effluent of wastewater: Field demonstrations using algal-bacterial photobioreactors.

Real field demonstrations to assess the removal efficiency of nutrients and organic matter from domestic wastewater were carried out using algal-bacterial photobioreactors. The reactors which consisted of three basins of 200 L were fed with secondary effluent of domestic wastewater and operated under natural day light/dark cycles. The results demonstrated that reaction time (RT) has a substantial role on the whole process performance. Whereas inoculation with nitrifiers affected the process only in some aspects. The enhancement in the dissolved oxygen production rate (1.15 mg O2. L−1.h−1) was in alignment with growing higher algal biomass concentrations due to the increase in RT. COD removal rates were significantly increased (p < 0.05) with increasing the RT, and removal rates of 27%, 46% and 50% were obtained under RTs of 2, 3 and 4hrs. respectively. Meanwhile, 30%, 84% and 95% of the phosphorus was removed under the same studied RTs. No significant effect was recorded due to the addition of nitrifying bacteria on the removal of both COD and phosphorus. Ammonium (NH4+-N) removal rates were also increased with increasing RT and by the addition of nitrifiers, such that removal rates of 13%, 21% and 31% were obtained in basins inoculated with nitrifiers, but 11%, 14% and 19.5% were obtained in non-inoculated basins under RT of 2, 3, and 4 hrs. respectively. These results provide some new insights into algal-bacterial symbiosis systems under real field conditions which could be helpful for further process development.

Comparative removal efficiencies of natural organic matter by conventional drinking water treatment plants in Zimbabwe and South Africa.

Natural organic matter (NOM) influences the quality and treatability of drinking water; therefore, its removal is paramount. A few studies exist on NOM removal in developing countries, and comparative studies are even fewer globally. This study compared the removal efficiencies for bulk NOM and biodegradable organic carbon (BDOC) fractions of drinking water treatment plants in Zimbabwe (Z) and South Africa (S). NOM removal efficiency at the coagulation stage of plant Z and plant S was 11% and 13%, respectively. The fluorescence index (FI) for the raw water feeding plant Z (1.66) indicated a mixture of both microbial and terrestrially derived NOM, whereas for plant S the FI (4.08) showed terrestrially derived NOM. Based on the log-transformed absorbance at the disinfection stage, plant S had a 58% greater opportunity to produce disinfection by-products than plant Z. The BDOC results for plant Z showed humic fractions were the major substrates for bacterial assimilation, whereas the heterotrophic bacteria in plant S were not particularly selective toward DOC fractions. Overall, the plants had comparable NOM removal performances. PRACTITIONER POINTS: NOM removal efficiency at the coagulation stage of plant Z and plant S was 11% and 13%, respectively. Plant Z had a mixture of both microbial and terrestrially derived NOM, whereas plant S had terrestrially derived NOM. Plant S had a 58% greater opportunity to produce disinfection by-products than plant Z. Humic fractions were the major substrates for bacterial assimilation for plant Z, whereas the heterotrophic bacteria in plant S were not selective towards DOC fractions.

A novel jet-loop anaerobic filter membrane bioreactor treating raw slaughterhouse wastewater: Biological and filtration processes

Results from raw slaughterhouse wastewater treatment in a new jet-loop Anaerobic Filter Membrane Bioreactor (AnFMBR) are presented. The innovation consists in integrating an attached growth anaerobic reactor and a filtration tank as an external loop gas-lift bioreactor, taking advantage of the gas-lift effect caused by the gas sparging used for fouling mitigation. A jet-loop AnFMBR pilot plant was operated for 18 months with a hydraulic retention time of 19.5–21.3 h, a solid retention time of 60d and organic loading rates between 3.5 and 7.4 kgCOD/m3·d, depending on the wastewater concentration, with peaks of up to 10.9 kgCOD/m3·d. Organic matter removal efficiency was maintained between 92 and 97%. Most of the biomass in the jet-loop AnFMBR, 82%, was retained by the carrier material so the membrane was in contact with low concentration biomass suspension.Effects of different backwash scenarios and filtration fluxes on reversible and irreversible fouling rates were studied by short-term and mid-term assays, using Box-Behnken experimental designs. Fouling consolidation due to the fouling layer compression was the main cause of irreversible fouling. Pilot-scale results have shown that jet-loop AnFMBR is a promising technology for real scale complex wastewater treatment.

Effect of operating pressure on direct biomethane production from carbon dioxide and exogenous hydrogen in the anaerobic digestion of sewage sludge

The development of biological Power-to-Methane in-situ technologies aimed at producing biomethane directly in a single anaerobic digestion unit by the supply of external hydrogen, find its limiting step in the gas-to-liquid mass transfer of poorly soluble hydrogen. Increasing the operating pressure with an exogenous hydrogen supply could enhance transfer rates of hydrogen and carbon dioxide (enriching gas phase with methane) and simultaneously control the liquid media pH because the methanation of hydrogen and carbon dioxide prevents the acidification caused by carbon dioxide/bicarbonate equilibrium displacement. Thus, the feasibility of operating the anaerobic digestion of sludge at a pressure higher than the atmospheric pressure with an exogenous hydrogen supply to improve the solubilisation of hydrogen and subsequent bioconversion of hydrogen and carbon dioxide into methane by methanogenic archaea was studied. A mesophilic sludge digester (35 L) was operated at variable absolute pressure up to 300 kPa. Hydrogen was continuously supplied through the sludge recirculation stream, coupled to a static mixer. Hydrogen conversion increased with the operating pressure (up to 99%), and the methane concentration in the digester off-gas averaged 92.9 ± 2.3% at 300 kPa (maximum of 95.2%). pH approached 7 under such conditions, and the efficiency of organic matter removal was similar to that observed during conventional anaerobic digestion at atmospheric pressure without a detrimental accumulation of volatile fatty acids. This study confirmed that increasing the system pressure (mass transfer driving force) can be a viable alternative to high energy-consuming mixing methods to enhance the hydrogen gas-liquid mass transfer.

Treatment of a Worn mineral oil Effluent by Electrocoagulation using aluminium Electrodes

Water pollution by oils is more and more a preoccupation because of its increasing occurrence and the hazard to human life and environment. Depollution of oily effluents can sometimes generate a secondary pollution (with chemical coagulation / flocculation processes) or be very costly (ultracentrifugation). In this work, electrocoagulation with aluminium electrodes was applied to the treatment of a worn mineral oil effluent. For this to be achieved, the influence of the pH and the current density on the turbidity and organic matter was first investigated. A liquid-liquid extraction was then carried out on the oil samples in order to isolate hydrocarbons and study their behaviour. Finally, these hydrocarbons were analysed by gas chromatography (GC-FID) to evaluate their removal efficiency. The results obtained showed that optimal conditions were as follows: initial pH=7 and current density = 10.98 mA.cm-2. The results obtained with a supporting electrolyte concentration set at 0.5 mg.L-1 showed that optimal conditions were as follows: initial pH=7 and current density = 10.98 mA.cm-2.) In these conditions, the turbidity was almost totally eliminated and organic matter removal efficiency was 93.30%. Analyses of the various chromatograms showed that 98.83, 99.56 and 93.02% respectively of aliphatic fraction, unsaturated hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) were eliminated during electrocoagulation of the worn mineral effluent. However, the absence of regular peaks was observed on the chromatograms, and that was due to unidentified heavy PAHs. Thus, FID did not seem sensitive enough to identify and characterize PAHs compounds based only on retention.

Understanding the microbial trends in a nitritation reactor fed with primary settled municipal wastewater

Partial nitritation was pointed out as the key step to implement the autotrophic nitrogen removal processes at low temperature. This study investigated the initiation and maintenance of a nitritation process with simultaneous COD removal in a sequencing batch reactor (SBR) run at 15 °C and fed with primary settled urban wastewater characterized by 42 ± 10 mg TOC/L and 45 ± 4 mg NH4+-N/L. A nitrite accumulation ratio of nearly 100% was observed and the long-term (354 days) process stability was successfully maintained despite the municipal wastewater composition fluctuations. The absence of nitrite oxidizing bacteria (NOB) activity was attributed to the free nitrous acid (FNA) in-situ accumulated at high levels (0.02–0.20 mg HNO2-N/L). Despite nitrate production was not observed, the quantification of bacterial groups indicated that NOB were present in the SBR sludge throughout the entire operational period. Ammonium oxidizing bacteria (AOB) abundance and community structure were significantly influenced by the organic matter present in the feeding. Average organic matter removal efficiencies of 80% were obtained without observing any detrimental effect over the nitritation process performance, due to the functional redundancy within both the chemoheterotrophic and AOB communities.

Removal of the Colloidal Suspension from Dam Water Using Mineral Coagulants Prepared by Co-Precipitation

In this work, we were interested in eliminating the organic and mineral compounds that pose problems in obtaining drinking water using the method of coagulation. These substances are stable in the medium due to their colloidal sizes and surface loads, which require appropriate treatment. For this purpose, we explored the removal of colloidal suspension using a coagulant formed by co-precipitation of AlCl3.6H2O in an alkaline medium. This practice leads to the formation of polymeric species mixtures such as Al45O45(OH)45Cl and Al2O3.H2O after washing. The removal efficiency of mineral and organic matter is evaluated by measuring the turbidity and permanganate index by varying the concentration of the coagulant from 0.04 to 0.4 g.1−1. It has been shown that the effectiveness of the treatment had been increased in parallel with the concentration. The preliminary hydrolysis of aluminium leads to a fixation of the pH throughout the concentration range. This character had solved the problem of direct use of aluminium salts (conventional method) resulting in a modification of the pH and subsequently, variable efficiency. The refined coagulant (after washing) reaches the removal of 97% turbidity and almost all oxidisable matter using only a mass of 0.08 g.1−1. However, using the crude coagulant (without washing) containing a significant amount of NaCl requires 0.4 g.1−1 to reach only 87% removal of turbidity as well as 35% of oxidisable matter, with an increase of conductivity compared with that of the refined coagulant.

Anaerobic co-digestion of leachate and glycerol for renewable energy generation

ABSTRACT Anaerobic digestion is a versatile biotechnology that produces bioenergy, biogas, from wastewater. Biogas production and wastewater treatment can be optimized by associating substrates with complementary characteristics. In this context, the aim of this study was to evaluate the performance of the anaerobic co-digestion of different contents of landfill leachate and crude glycerol compared to the organic matter removal and specific biogas production, the effects of the factors (time, glycerol content and substrate/inoculum ratio) and their interactions on kinetic parameters of specific biogas production using the modified Gompertz model. A Central Composite Rotational Design (CCRD) was performed for the experimental variables: time (16.6, 20, 25, 30 and 33.4 days), glycerol content (0.43, 0.70, 1.10, 1.50 and 1.77%) and substrate/inoculum ratio (0.23, 0.30, 0.40, 0.50 and 0.57 g COD/g VSS). From the optimization, it was possible to maximize the efficiency of organic matter removal (90.15%) and specific biogas production (403.15 mL/g VSS) in the conditions of 33.2 days, glycerol content of 1.71% and substrate/inoculum ratio of 0.37 g COD/g VSS. Concerning the modified Gompertz model of the optimal condition performed, an average of 20.3 times higher specific biogas production was obtained when compared to the monodigestion of leachate. Therefore, the association of leachate and glycerol was found to be feasible in terms of stability, biodegradability and biogas production.

Evaluation of a novel anaerobic co-digestion system for disposal of dead swine and manure: An important tool in animal production

Purpose The anaerobic digester for dead animals is the most eco-friendly and cost-effective way to dispose of this waste. The aim of this study was to evaluate the removal efficiency of organic matter and pathogenic microorganisms by an anaerobic co-digestion of whole dead animals and manure, both of swine origin. Methods Two test digesters coated with geomembrane were used. Samples were obtained from a private pig farm with 2000 sows in Southern Brazil from April to June of 2017. The analyses were performed in triplicate, at six treatment points and physicochemical and microbiological analyses were performed to evaluate the efficiency of the anaerobic co-digester system. Results We found the efficiency in the removal of chemical oxygen demand (87.88%), biological oxygen demand (83.57%) and total solids (75%), accorded with levels proposed in Resolution 430/2011 of the Brazilian National Environment Council. Furthermore, macro- and micronutrient values also accorded with the environmental parameters proposed by Brazilian legislation. Based on the total nitrogen (2222.00 mg L-1) and environmental critical phosphorus values (333.30 mg dm-³), a subsequent agronomic evaluation is suggested prior to the release of this effluent into the soil. The absence of Salmonella spp. and helminth eggs reinforced the notion of suitability of the system for the treatment of dead animals. Total coliform counts and E. coli counts were within the expected standards. Conclusion Treatment of dead animals and effluents using an anaerobic digestion process was efficient, suggesting that it could replace other methods such as composting and incineration.

Submerged module of outer selective hollow fiber membrane for effective fouling mitigation in osmotic membrane bioreactor for desalination

This paper investigated the membrane fouling mitigation efficacy and performance of a home-made submerged module containing outer selective hollow fiber thin film composite forward osmosis (OSHF TFC FO) membrane in osmosis membrane bioreactor (OMBR) system treating municipal wastewater for desalination. Initial tests, optimization of draw solution flowrate and pumping mode for the submerged module were carried out before it was applied into the OMBR system. Overall, the OMBR system exhibited an initial water flux of approximately 6.3 LMH using 35 g/L NaCl as draw solution, and high removal efficiencies of bulk organic matter and nutrients. Moreover, membrane fouling was effectively mitigated with slow rate of flux decline during 33-day operation of the OMBR system. These results indicated that the submerged membrane module of OSHF TFC FO membrane has stable and reliable performances making it suitable for OMBR supplication without the need of air scouring to prevent membrane fouling.

Characterization and evaluation of biogas generation of Arba Minch Town slaughterhouse wastewater, Ethiopia

Abstract This study was carried out to characterize raw and treated Arba Minch town slaughterhouse wastewater and to assess its methane generation potential with lab-scale anaerobic batch reactors. The methane was collected by downward displacement of an alkaline water column. The methane generation potential of the slaughterhouse wastewater was 270.6 mL methane per gram of volatile solids at hydraulic retention time (HRT) of 20 days at 37 °C. The organic loading rate was 0.48 g and the organic matter removal efficiency of the reactor was COD (93.5%), BOD5 (88.5%), and TVS (94.7%). The result demonstrated that installation of a biogas reactor to treat slaughterhouse wastewater can recover methane, reduce pollutants and protect the environment. The result can be a demonstration for untreated slaughterhouse wastewaters in developing countries like Arba Minch Town to use anaerobic treatment and supplement their scarce energy options.

Hybrid Constructed Wetland to Improve Organic Matter and Nutrient Removal

Constructed wetlands are one of the best technologies for wastewater treatment in small towns, small businesses or farms and/or livestock breeding. In this work, a wastewater depuration ecological system implemented in a hybrid constructed wetland to remove nutrients and organic matter from small urban agglomerations is studied. It comprises two processing stages: a primary treatment carried out in two hydrolytic up-flow sludge bed digesters working in parallel and a secondary one made up of two vertical flow constructed wetlands, which are alternatively used, followed by a horizontal flow constructed wetland. An internal recirculation system connects the output of the vertical flow constructed wetlands to the input of the hydrolytic up-flow sludge bed digesters with the aim of promoting the nitrification-denitrification process. High nutrients and organic matter removal efficiencies were observed when treating highly polluted wastewater from an animal farm. Therefore, this ecological depuration system, designed with an internal recirculation to enhance nitrogen reduction, may be considered an efficient alternative to treat wastewater from small urban agglomerations and diffuse contamination from agricultural industries and livestock farms polluting surface waters with nitrates, which may cause serious environmental problems, such as eutrophication.

Removal of sulfadiazine from simulated industrial wastewater by a membrane bioreactor and ozonation

Ozonation can be used as a polishing treatment for degrading low-concentration pharmaceutical compounds recalcitrant to biological treatment, when large amounts of biodegradable organics have been previously removed by biological processes. Nevertheless, a systematic investigation has not yet been carried out for the coupled MBR + O3 process through an experimental design approach. Thereby, the purpose of this study is to evaluate the performance of different processes (membrane bioreactor-MBR, ozonation; and integrated MBR + O3) for removing the antibiotic sulfadiazine (SDZ) from a synthetic wastewater matrix of industrial interest. The MBR behavior was monitored over seven months for different parameters (pH, temperature, permeate flow, transmembrane pressure, biological oxygen demand-BOD5, chemical oxygen demand-COD, total organic carbon-TOC, solids, and SDZ concentration). Additionally, the amount of SDZ sorbed onto the sludge was characterized, an issue which is scarcely addressed in most research works. Ozonation experiments were conducted in batch mode in a 2-L glass reactor provided with openings for gas flow. For the MBR + O3 process, the effects of gas flow rate (0.1–1.5 L min−1) and inlet ozone concentration (4–12 mg L−1) on SDZ removal from the MBR permeate were systematically assessed using a Doehlert experimental design and response surface methodology. The results indicated that the MBR system showed good performance regarding organic matter removal efficiency, evaluated in terms of BOD5 (91.5%), COD (93.1%) and TOC (96.3%). In contrast, SDZ was partially removed (33%) by the MBR; in that case, the results indicated that the antibiotic was moderately removed with the sludge and partially biodegraded. In turn, the MBR + O3 system showed excellent performance for removing SDZ (100%), TOC (97%), BOD5 (94%) and COD (97%). The statistical analysis confirmed that the influence of ozone gas flow rate upon the SDZ removal rate was more important than that exhibited by inlet ozone concentration. Therefore, coupling MBR and ozone can be considered a promising alternative for point source treatment of antibiotic production wastewater.

Possibilities for detection of the change of biodegradability of wastewater by dielectric constant measurements

Nowadays, the development of rapid and non-destructive measurement methods have high importance. The dielectric measurement is a promising technique to detect the chemical and physicho-chemical change of different materials. The dielectric behavior of pure water is widely investigated for decades, but there is very few information available related to the dielectric parameters of wastewater. Our study aims to investigate the applicability of dielectric measurements for the detection of the change of biodegradability of wastewater. In the experiments the change of organic matter solubility and biodegradability of sugar beet processing wastewater, meat processing wastewater, dairy industry wastewater and municipal wastewater was examined. Our results show that dielectric constant - measured at the frequency of 2400 MHz - has a strong linear correlation with the soluble chemical oxygen demand (SCOD), which makes possible the fast detection of disintegration efficiency of different wastewater and sludge treatment processes, or the organic matter removal efficiency of wastewater purification technologies. Furthermore, our results verified that the change of aerobic biodegradability (expressed in BOD5/SCOD ratio) show also good linear correlation with the dielectric constant. These preliminary results enable to develop a dielectric behavior based detection method for the estimation of the efficiency of wastewater treatment processes.

Surfactant removal from wastewater using photo-cathode microbial fuel cell and laterite-based hybrid treatment system.

Sodium dodecyl sulfate (SDS) is a widely used anionic surfactant, which finds its way to the receiving water body due tothe incapability of conventional wastewater treatment systems to completely remove it. A hybrid treatment system consisting of upflow microbial fuel cell (MFC) with titanium dioxide (TiO2) as a photocathode catalyst was developed for treating synthetic wastewater spiked with SDS (10.00 ± 0.46mg L-1). Effluent from anodic chamber of MFC was passed through raw laterite soil filter followed by the photo-cathodic chamber with TiO2-coated cathode irradiated with theUV spectrum. This hybrid system was operated under varying hydraulic retention time (HRT) in anodic chamber of MFC. The SDS removal efficiency of more than 96% along with organic matter removal efficiency of more than 71% was obtained by this hybrid system at different HRTs. The MFC having cathode coated with TiO2 could generate a maximum power density of 0.73Wm-3 and 0.46Wm-3 at the HRT of 12h and 8h, respectively, showing the adverse effect of increased SDS loading rate on the electrical performance of MFC. This investigation highlighted the importance of HRT in anodic chamber of MFC and offered solution for effective removalof surfactant from wastewater.

The Use of Organic Coagulants in the Primary Precipitation Process at Wastewater Treatment Plants

Measurements for determining the effect of chemically enhanced primary treatment (CEPT) on the efficiency of pollutant removal from wastewater were carried out using conventional inorganic coagulants PIX113 with polymer A110 (Kemipol, Police, Poland) and unconventional cationic organic coagulants Cofloc (Attana, Coalville, UK) C29510 (Kemipol, Police, Poland) and Sedifloc 575 (3F Chimica, Sandrigo, Italy). The average removal efficiency in the 2-h sedimentation process was 46%, 34%, 8%, 12% for the total suspended solids, organic matter (COD), total nitrogen, and total phosphorus, respectively. The use of organic coagulants contributed to 14–81% increase of pollutant removal efficiency. Substantial discrepancies in biological nutrient removal processes were not discovered in two-phase (anaerobic-anoxic) experiments without and with the addition of the organic coagulants. The increase in organic matter removal efficiency as a result of the CEPT process may contribute to a 65–80% increase in biogas production. The conducted research confirms the possibility of using organic coagulants in the primary precipitation process in wastewater treatment plants (WWTPs) in accordance with the principles of maximum energy recovery, thereby promoting renewable energy sources. Additionally, organic coagulants, as opposed to inorganic ones, do not cause a significant increase of chloride and sulfate ion concentrations, which facilitates the use of treated wastewater in the water reuse systems, such as irrigation of agricultural crops.

Two-year performance of single-stage vertical flow treatment wetlands planted with willows under cold-climate conditions

Climate-related issues constitute an important obstacle for the development of treatment wetland (TW) applications in regions with freezing winter temperatures. The aim of the present study was to evaluate the efficiency of a new configuration of TWs based on the vertical flow (VF) configuration. The proposed TWs system is planted with a willow species (Salix miyabeana SX67) and including design adaptations for cold climate operation. Two different flow modes for winter-time operation were proposed: percolated and saturated with continuous artificial aeration. The pilot-scale systems were tested with municipal wastewater, at an organic loading ranging from 5 to 20 g CBOD5 m−2 d−1.The pilot TWs were successfully operated for 22 months despite freezing winter temperatures reaching as low as −32 °C. Willow development was normal, with evapotranspiration ranging from 19 to 23 mm/d in July 2017 for the pilot TWs at an organic loading of 10 g CBOD5 m−2 d−1. Organic matter removal efficiency was high for all pilot TWs, with an average 91% COD and 81% TSS removal. Nitrification was essentially complete during the summer period and remained high for pilot TWs operated under percolating flow mode in winter but was lower for the saturated flow mode, probably due to insufficient air supply. Our study confirms the successful application of a modified version of VF TW in regions with freezing air temperatures.

Enhanced nitrogen removal of aerobic denitrifier using extracellular algal organic matter as carbon source: application to actual reservoir water.

Man-made organic matter acting as carbon source for oligotrophic aerobic denitrification has been studied extensively, while less attention has been paid to the actual organic matter derived from drinking water reservoir. In this study, the effect of extracellular organic matter (EOM) released from Microcystis aeruginosa and Chlorella sp. and organic matter in actual reservoir water on aerobic denitrification performance of Acinetobacter johnsonii strain WGX-9 has been investigated, by measuring nitrogen removal and determining changes in the properties of organic matter. Results indicated that the Acinetobacter johnsonii strain WGX-9 showed effective nitrogen removal efficiency when cultural conditions were low C/N of 5, pH of 5-11, and low temperature of 8°C. The nitrate removal efficiency with EOM as the sole carbon source was relatively higher than that with intracellular organic matter or natural organic matter as the sole carbon source. This is probably due to that EOM exerts a lower molecular weight and better ability of donating electrons. Besides, the findings can elucidate that nitrate and total organic matter removal efficiency with actual high-density algal water as the carbon source was higher than that with actual low-density algal water as the carbon source. This was attributed to that more EOM was released in high-density algal water, which highlighted the aerobic denitrification performance of Acinetobacter johnsonii strain WGX-9. This study will provide a reference for the application of aerobic denitrifier in drinking water reservoirs.

Performance of wood chips/peanut shells biofilters used to remove organic matter from domestic wastewater

Biofiltration is one of the main alternatives developed to improve wastewater quality and increase its recyclability. Support materials are extremely important when using this technology since they impact the cost of the treatment. In this work, we study the use of wood chips/peanut shell as support medium within biofilters incorporating microorganisms (BM), plants and microorganisms (BPM), earthworms and microorganisms (BEM) and all organisms (hybrid biofilters, HB). These typologies were evaluated to remove organic matter from synthetic domestic wastewater. For this purpose, twelve biofilters were operated in parallel under three different nominal hydraulic rates (0.5, 1 and 1.5 m3 m−2 day−1). Previously, support materials were individually characterized and acute/chronic toxicity tests on plants (Eleocharis palustris (L.) Roem. & Schult.) and earthworms (Eisenia foetida Savigny) were driven. Results showed that both materials have good adsorbent properties, providing adequate environmental conditions for biofiltration. Moreover, non toxicological response was reported when a 25 v/v % peanut shell fraction was selected. With this fraction used in every biofilter studied, the average hydraulic conductivity was between 321 and 502 mm h−1, reaching organic matter removal efficiencies close to 80% (measured as COD), and between 40 and 63% (measured as VS). Higher efficiencies, attributed to the longer contact times, and lower clogging were observed at lower hydraulic rates. The incorporation of earthworms and plants improved the solids removal and reduced clogging. The statistical analysis indicated that the results obtained for biofilters operating at 0.5 m3 m−2 day−1 showed significant differences (p < 0.05) with respect to the other rates. Moreover, BEM were the ones that presented significant differences. As a conclusion, low-cost organic materials (wood chip/peanut shell mix) can be successfully used as support medium, since they provide adequate environmental conditions for plants and earthworms, improving the operation and maintaining contaminant (organic matter) removal within biofiltration typologies.