Fermentative hydrogen gas production using biosolids pellets as the inoculum source

Biosolids pellets produced from anaerobically digested municipal wastewater sludge by drying to greater than 90% total solids at 110-115 degrees C for at least 75 min, were tested for their suitability as an inoculum source for fermentative hydrogen production. The hydrogen recoveries (mg gaseous H(2) produced as COD/mg added substrate COD) for glucose-fed batch systems were equal, 20.2-21.5%, between biosolids pellets and boiled anaerobic digester sludge as inoculum sources. Hydrogen recoveries from primary sludge were 2.4% and 3.5% using biosolids pellets and boiled sludge, respectively, and only 0.2% and 0.8% for municipal wastewater. Biosolids pellets should be a practical inoculum source for fermentative hydrogen reactors, although the effectiveness will depend on the wastewater treated.     

Treatment of hydroponic wastewater by denitrification filters using plant prunings as the organic carbon source

This study investigated the feasibility of using pre-treated plant liquors as organic carbon sources for the treatment of hydroponic wastewater containing high nitrate-N (>300 mg N/L). The waste plant material was pre-treated to extract organic carbon-rich liquors. When this plant liquor was used as an organic carbon source in denitrification filters at the organic carbon:nitrogen dose rate of 3C:N, nitrate removal efficiencies were >95% and final effluent nitrate concentrations were consistently <20mg N/L. However, at this dose rate, relatively high concentrations (>140 mg/L) of organic carbon (fBOD5) remained in the final effluents. Therefore, a 'compromise' organic carbon:nitrogen dose rate (2C:N) was trialled, at which nitrate removal efficiencies were maintained at >85%, final effluent nitrate concentrations were consistently below 45 mg N/L, and effluent fBOD5 concentrations were <25mg/L. This study has demonstrated that waste plant material is a suitable carbon source for the removal of nitrate from hydroponic wastewater in a denitrification filter.     

Potential soil reinforcement by biological denitrification

Currently new ground reinforcement techniques are being developed based on microbially induced carbonate precipitation (MICP). Many studies on MICP use microbially catalyzed hydrolysis of urea to produce carbonate. In the presence of dissolved calcium this process leads to precipitation of calcium carbonate crystals, which form bridges between the sand grains and hence increase strength and stiffness. In addition to urea hydrolysis, there are many other microbial processes which can lead to the precipitation of calcium carbonate. In this study the theoretical feasibility of these alternative MICP processes for ground reinforcement is evaluated. Evaluation factors are substrate solubility, CaCO₃ yield, reaction rate and type and amount of side-product. The most suitable candidate as alternative MICP method for sand consolidation turned out to be microbial denitrification of calcium nitrate, using calcium salts of fatty acids as electron donor and carbon source. This process leads to calcium carbonate precipitation, bacterial growth and production of nitrogen gas and some excess carbon dioxide. The feasibility of MICP by denitrification is tested experimentally in liquid batch culture, on agar plate and in sand column experiments. Results of these experiments are presented and discussed.     

Systematic review: External carbon source for biological denitrification for wastewater

Nitrogen mitigation is serious environmental issue around the globe. Several methods for wastewater treatment have been introduced, but biological denitrification has been recommended, particularly with addition of the best external carbon source. The key sites of denitrification are wetlands; it can be carried out with different methods. To highlight the aforementioned technology, this paper deals to review the literature to evaluate biological denitrification and to demonstrate cost effective external carbon sources. The results of systematic review disclose the denitrification process and addition of different external carbon sources. The online literature exploration was accomplished using the most well-known databases, that is, science direct and the web of science database, resulting 625 review articles and 3084 research articles, published in peer-reviewed journals between 2015 and 2021 were identified in first process. After doing an in-depth literature survey and exclusion criteria, we started to shape the review from selected review and research articles. A number of studies confirmed that both nitrification and denitrification are significant for biological treatment of wastewater. The studies proved that the carbon source is the main contributor and is a booster for the denitrification. Based on the literature reviewed it is concluded that biological denitrification with addition of external carbon source is cost effective and best option in nitrogen mitigation in a changing world. Our study recommends textile waste for recovery of carbon source.     

Enhanced biological denitrification of high concentration of nitrite with supplementary carbon source

Nitrite accumulates during biological denitrification processes when carbon sources are insufficient. Acetate, methanol, and ethanol were investigated as supplementary carbon sources in the nitrite denitrification process using biogranules. Without supplementary external electron donors (control), the biogranules degraded 200 mg l^?1 nitrite at a rate of 0.27 mg NO₂–N g^?1?VSS h^?1. Notably, 1,500 mg l^?1 acetate and 700 mg l^?1 methanol or ethanol enhanced denitrification rates for 200 mg l^?1 nitrite at 2.07, 1.20, and 1.60 mg NO₂–N g^?1?VSS h^?1, respectively; these rates were significantly higher than that of the control. The sodium dodecyl sulfate polyacrylamide gel electrophoresis of the nitrite reductase (NiR) enzyme identified three prominent bands with molecular weights of 37–41 kDa. A linear correlation existed between incremental denitrification rates and incremental activity of the NiR enzyme. The NiR enzyme activity was enhanced by the supplementary carbon sources, thereby increasing the nitrite denitrification rate. The capacity of supplementary carbon source on enhancing NiR enzyme activity follows: methanol?>?acetate?>?ethanol on molar basis or acetate?>?ethanol?>?methanol on an added weight basis.     

Biological denitrification using cross-linked starch/PCL blends as solid carbon source and biofilm carrier

A novel kind of cross-linked starch/polycaprolactone (SPCL11) was prepared and used as carbon source and biofilm attachment carrier for denitrifying bacteria. The results showed that the average denitrification rate was 0.027 mg NO?-N/(g·h) in batch tests. The continuous fixed-bed experiments indicated that more than 90% NO?-N was removed, the denitrification rate reached 26.86 mg NO?-N/(L·h), and NO?-N concentration was below 0.16 mg/L. The formation of NH?-N was observed, but usually below 1.0 mg/L. Rapid biodegradation of starch on the surfaces of SPCL11 granules could cause an initial excess release of dissolved organic compound (DOC), and shortening HRT from 2h to 1h can result in sharp decrease of DOC.     

Carbon source recovery from waste activated sludge by alkaline hydrolysis and gamma-ray irradiation for biological denitrification

The recovery of an organic carbon source from a waste activated sludge by using alkaline hydrolysis and radiation treatment was studied, and the feasibility of the solubilized sludge carbon source for a biological denitrification was also investigated. The effects of an alkaline treatment and gamma-ray irradiation on a biodegradability enhancement of the sludge were also studied. A modified continuous bioreactor for a denitrification (MLE reactor) was operated by using a synthetic wastewater for 47 days. Alkaline treatment of pH 10 and gamma-ray irradiation of 20 kGy were found to be the optimum carbon source recovery conditions. COD removal of 84% and T-N removal of 51% could be obtained by using the solubilized sludge carbon source through the MLE denitrification process. It can be concluded that the carbon source recovered from the waste activated sludge was successfully employed as an alternative carbon source for a biological denitrification.     

Methane fermentation of water hyacinth: effect of solids concentration and inoculum source

Summary Batch anaerobic digestion of water hyacinth (Eichhornia, crassipes) was carried out in the laboratory. Daily gas yields were 18.9, 20.8. and 27.0 l/kg total solids (TS)/day for feedstocks containing 50, 30 and 20 g TS/l, respectively. Percentage decomposition rates of organic solids were 70.1, 72.0 and 75.6 for the 50, 30 and 20 g TS/l slurries, respectively Differences in methane content of the biogas were negligible. The average biogas produced per kg TS was 631 l. Three types of inoculum were used to start digesters freshly charged with 50 g TS/l of water hyacinth slurry: digested domestic sewage sludge (DSS), sheep rumen liquor (RL) and sludge from an old digester working on water hyacinth (WHS). The digester seeded with WHS gave the highest yield of biogas per kg dry water hyacinth, viz. 552 litres. The unseeded control gave only 221 litres/kg. Decomposition of volatile solids was 71.9% for the WHS digester and only 35.0% for the unseeded digester. The DSS and RL digesters gave results between these extremes with respect to both gas yield and percentage utilization of volatile solids.

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Resumen La digestión anaerobia semi-continua de jacintos acuáticos (Eichornia crassipes) se realizó a escala de laboratorio. Los rendimientos en gas fueron de 18.9, 20.8 y 27.0 l/kg de sólidos totales (TS)/día, y las velocidades de descomposición de sólidos, yolátiles, expresadas en porcentajes, fueron de 70.1, 72.0 y 75.6, ambos parámetros relativos a producto inician con un contenido en sólidos totales de 50, 30, y 20g TS/l respectivamente. La cantidad media de biogás generada por KG TS fue de 6311. Se utilization tres tipos de inóculo para iniciar la fermentación en digestores recién cargados con pasta líquida de jacinto acuático: fangos de depuradora doméstica (DSS), extracto de rumen ovino (RL) y residuos de pasta de jacinto ya fermentada (WHS). El digestor sembrado con WHS fue el que produjo mayor cantidad de biogás por kg de materia seca: 552 l; el digestor sin inocular produjo tan solo 221 l/kg. El porcentaje de sólidos volátiles fue de 71.9% para el digestor con WHS y de 35.0% para el control no inoculado. Los digestores con DSS y RL dieron resultados intermedios tanto para la produccción de gas como para la utilización de sólidos volátiles.

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Résumé La biométhanisation de la jacinthe d'eau (Eichhornia crassipes) a été conduite en milieu non renouvelé (batch) et à l'échelle du laboratoire. On a obtenu des vitesses de production de 18.9, 20.8 et 27.0 litres de gaz par kg de solides totaux (TS) et par jour pour des liqueurs mixtes contenant initialement respetivement 50, 30 et 20 g de TS par litre. La conversion des solides volatils (matière organique) était respectivement de 70.1, 72.0 et 75.6% pour les liqueurs mixtes contenant initalement 50, 30 et 20 g de TS par litre. Les différences en contenu en méthane du biogaz étaient négligeables. La quantité moyenne de biogaz produite par kg de TS était de 6311. Trois types d'inoculum ont été utilisés pour démarrer les digesteurs qui venaient d'être chargés par un broyat de jacinthe d'eau à 50g de TS par litre: la boue digérée de station d'épuration d'eau résiduaire domestique (DSS), la liqueur mixte du rumen, de mouton (RL) et la boue d'un digesteur alimenté dequis longtemps par la jacinthe d'eau (WHS). Le digesteur ensemencé avec l'inoculum WHS a donné le meilleur rendement en biogaz par kg de jacinthe sèche: 5521. Le contrôle sans ensemencement n'a donné que 2211 par kg. La conversion en solides volatils était de 71.9% pour le digesteur ensemencé avec l'inoculum WHS, tandis qu'elle n'etait que de 35.0% pour le digesteur non ensemencé. Les digesteurs ensemencés soit avec l'inoculum DSS soit avec l'inoculum RL ont donné des résultats intermédiaires entre ces deux extrêmes tant pour le rendement en biogaz que pour la conversion des solides volatils.

     

Nitrate removal from drinking water in a fluidized-bed biological denitrification bioreactor

In most industrially developed countries an increasing degree of nitrification can be observed in potential water reservoirs. High nitrate content is unacceptable by public health standards. Since contamination seems to be unavoidable, the only realistic solution is purification prior to utilization. One of the potential variations is biological denitrification with a highly intensive facility, a fluidized- or expanded-bed bioreactor. Based on laboratory and pilot plant experiments, a detailed analysis is presented on the problems arising and solutions offered in the construction of a purification system meeting high quality requirements of drinking water purification. The crucial point is selection of the denitrifying microorganisms and organic matter required for denitrification, which simultaneously determines the attachment of bacteria to the support material (autoimmobilization), the intensity of nitrate removal and the character of post-purification.     

Removal of nitrate-nitrogen from drinking water using bamboo powder charcoal

The adsorption effectiveness of bamboo powder charcoal (BPC); made from the residual of Moso bamboo manufacturing; in removing nitrate-nitrogen from water has been investigated. Commercial activated carbon (CAC) was also used to compare the effectiveness of adsorption in removal of nitrate-nitrogen. The adsorption effectiveness of BPC was higher than that of CAC; regardless of the concentration of nitrate-nitrogen; in the range of 0-10 mg/l. The effect of temperature on adsorption by BPC and CAC in the range of 10-20 degrees C was also investigated. From the results, it was found that the temperature dependency of the adsorption effectiveness of BPC was weaker than that of CAC. This fact indicates that BPC can be an attractive option for the in situ treatment by adsorption of nitrate-nitrogen-contaminated underground and surface water.     

Habitat selection as a source of biological diversity

Summary Question: What are the conditions required for natural selection to produce phenotypes specially adapted to the various habitats available in nature? Model: Assume there are two habitat types and one or two phenotypes of the same or different species. The phenotypes do not recognize any spatial differences among patches of the same habitat type. Possible evolutionary winners can do better in one habitat only by relinquishing some ability in the other. Results: If only one phenotype is present, it will be an intermediate (unless one of the two habitat types is so rare and unproductive that its effects can be ignored by natural selection). Even if two phenotypes are introduced, natural selection should generally restore monomorphism if habitat selection is not ever favored (e.g. if search costs are high). But if search costs and environmental variation are zero, dimorphism can be expected. And if they are small, then although monomorphism is stable, its basin of attraction is small, and invasion by a second form (such as a sibling species) can provide the discontinuous jump needed to put the system in the other basin of attraction. Once there, dimorphic extremism coevolves. Each successful morph is as specialized as possible on one of the habitats. Competition between the morphs is eliminated. Environmental variation may constrict the basin, but once a point is captured by it, the system approaches dimorphic extremism anyway. In general, whatever promotes the behavior of habitat selection also promotes the evolution of extreme morphologies and physiologies.     

The influence ofPythium on the growth of barley seedlings as affected by soil water and inoculum density

Summary Pythium spp. were more abundant in the southerly and more temperature regions of the barley growing region of South Australia than in the drier and hotter north. Populations were more abundant in the top 10 cm than in the 10 to 20 cm soil zone. Eleven species ofPythium were identified from barley crops.P. irregulare appeared to be the most abundant and was one of the most pathogenic species on barley.P. volutum was also highly pathogenic; it had not been recorded in South Australia before. A factorial experiment using ninePythium spp. and four levels of soil water indicated that unlike other species,P. irregulare, P. volutum andP. graminicolum were most pathogenic in soils with a water content close to field capacity. A factorial experiment usingP. irregulare at four levels of soil water and six inoculum levels showed that inhibition of growth in barley seedlings byP. irregulare increased as the level of water in the soil increased. The experiments support the hypothesis that inhibition of growth of barley seedlings byPythium spp. is most severe in the southerly parts of the barley growing area of South Australia particularly where there is a combination of high soil water and high population densities.     

Evaluation of hairy nightshade as an inoculum source for aphid-mediated transmission of potato leafroll virus

Potato leafroll virus (PLRV) causes one of the most serious aphid-transmitted diseases affecting yield and quality of potatoes, Solanum tuberosum (L.), grown in the United States. The green peach aphid, Myzus persicae (Sulzer), is considered to be by far the most efficient vector of this virus. Even the most strict aphid control strategy may not prevent the spread of PLRV unless measures also are taken to keep virus source plants within and outside the crop at a minimum. Hairy nightshade, Solanum sarrachoides (Sendtner), is one of the preferred weed hosts for green peach aphid. The potential of this weed as an aphid reservoir and virus source and its spread or perpetuation were investigated. With the use of double antibody sandwich enzyme-linked immunosorbent assay, it was confirmed that green peach aphid can transmit PLRV to hairy nightshade and that aphids can become viruliferous after feeding on infected hairy nightshade plants. Transmission from hairy nightshade to potato is 4 times the rate of potato to potato or potato to hairy nightshade. The green peach aphid preferred hairy nightshade over potato plants and reproduced at a higher rate on hairy nightshade than on potato. Therefore, a low level of PLRV-hairy nightshade infection could enhance the disease spread in the field.     

T1 bacteriophage as an indicator for decontamination of laminar-flow biological safety cabinets.

Type 1 coliphage dried onto a glass surface was used as an indicator to monitor decontamination of biological safety cabinets. When desiccated virus was treated with formaldehyde vapor (5,000 or 10,000 ppm) adjusted to 70 to 90% relative humidity immediately before testing, viral inactivation was slow for the first 50 min but then accelerated, being complete in the next 10 min. However, when virus was incubated in an atmosphere containing 70% humidity for 1 h before formaldehyde was added, inactivation was complete within 3 min, indicating that careful attention must be paid to relative humidity in decontamination of safety cabinets.     

Optimization of anaerobically digested distillery molasses spent wash decolorization using soil as inoculum in the absence of additional carbon and nitrogen source

The aim of this study was to achieve maximum decolorization of molasses spent wash (MSW) in absence of any additional carbon or nitrogen source using soil as inoculum. Soil samples were collected from the MSW disposal site. Colored soil samples exhibited higher pH, sugar and protein as compare to less colored samples. A decolorization of 69% was obtained using 10% (w/v) soil and 12.5% (v/v) MSW after 7 days incubation. Optimized parameters including days--6 days, pH--6, MSW--12.5% and soil concentration--40%, were obtained for maximum decolorization. A decolorization of 81% was achieved using 10% soil and 12.5% MSW after 18 days incubation in absence of any media supplement. Nearly 12% reduction in decolorization activity of the soil sample was observed over a period of 12 months when stored at 6 degrees C. It could be concluded that the decolorization of MSW might be achieved using soil as inoculum without addition of chemical amendments.