RESUMEN
The discharge of ammonia-nitrogen (NH3-N), total nitrogen (TN), chemical oxygen demand (COD), and total phosphorus (TP) in rural sewage usually exceeds the Pollutant Discharge Standard for Urban Sewage Treatment Plants (GB18918-2002). Efficient and cost-effective removal of these pollutants cannot be simultaneously realized using conventional rural sewage treatment methods. Thus, an assembled biological filter (D50 × W50 × H113 cm), including a phosphorus removal layer filled with solid polymeric ferric sulfate and alternating aerobic-anaerobic layers, is proposed herein. The aerobic (anerobic) layers were filled with zeolite (zeolite and composite soil) at different intervals. This system was used for the treatment of synthetic sewage having COD: 122.0-227.0 mg/L; NH3-N: 29.1-47.0 mg/L; TN: 28.0-58.0 mg/L; and TP: 2.0-3.8 mg/L. Based on optimal operation conditions (40 L/h reflow rate, without artificial aeration, and 12-h operation cycle), the system showed NH3-N, TN, COD, and TP removal efficiencies of 87.1 ± 8.1, 83.4 ± 7.9, 91.0 ± 9.4, and 80.0 ± 6.4%, respectively. Further, in the pilot-scale test, under the same optimal parameters, the removal efficiencies of NH3-N, TN, COD, and TP were 78.9 ± 8.1, 75.4 ± 7.9, 82 ± 9.4, and 76 ± 6.4%, respectively. Furthermore, in the different functional units of the system, a large number of functional bacteria capable of efficiently facilitating the simultaneous removal of the different pollutants from sewage were identified. Therefore, this proposed system, which complies with current environmental discharge regulations, can be a more sustainable approach for the treatment of unattended rural sewage.
Asunto(s)
Fósforo , Aguas del Alcantarillado , Amoníaco , Biodegradación Ambiental , Reactores Biológicos , Nitratos , Nitrógeno , Eliminación de Residuos LíquidosRESUMEN
The decentralized bioreactor is a promising process for landfill leachate (LL) treatment, however, it is often confronted with various forms of shock loadings. To explore the robustness of bioreactors to the long-lasting substrate shocks, a long-term study of over 90 days was carried out to investigate the effects of nitrogen (mainly ammonium nitrogen, NH4-N) and organic (in terms of chemical oxygen demand, COD) shock loading on an engineered zeolite-based biofilter with alternative soil-mixed block (SMB) (EZS-biofilter) for treating matured LL. The low-, mid-, and high-strength intensity of matured LL was theoretical defined mainly according to the content of total nitrogen (TN) and COD. The experiment proved that the EZS-biofilter could effectively absorb the substrate shocks in a range of 104, 408, and 1357 mg/L as TN and 178, 590, and 1050 mg/L as COD, corresponding to the low-, medium-, and high-strength LL, respectively. A modified sensitivity index reflected that the nitrogen shock loadings exerted much more predominant influence than COD shock due to the great variation of nitrification/denitrification. The provided information in this study are beneficial for the practical engineered operation of biofilters for treating matured LL.
Asunto(s)
Compuestos de Amonio/metabolismo , Nitrógeno/metabolismo , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/metabolismo , Análisis de la Demanda Biológica de Oxígeno , Reactores Biológicos , Filtración , NitrificaciónRESUMEN
We studied the effect of electron competition on chromate (Cr(VI)) reduction in a methane (CH4)-based membrane biofilm reactor (MBfR), since the reduction rate was usually limited by electron supply. A low surface loading of SO42- promoted Cr(VI) reduction. The Cr(VI) removal percentage increased from 60 to 70% when the SO42- loading increased from 0 to 4.7 mg SO42-/m2-d. After the SO42- loading decreased back to zero, the Cr(VI) removal further increased to 90%, suggesting that some sulfate-reducing bacteria (SRB) stayed in the reactor to reduce Cr(VI). However, a high surface loading of SO42- (26.6 mg SO42-/m2-d) significantly slowed down the Cr(VI) reduction to 40% removal, which was probably due to competition between Cr(VI) and SO42- reduction. Similarly, when 0.5 mg/L of Se(VI) was introduced into the MBfR, Cr(VI) removal percentage slightly decreased to 60% and then increased to 80% when input Se(VI) was removed again. The microbial community strongly depended on the loadings of Cr(VI) and SO42-. In the sulfate effect experiment, three genera were dominant. Based on the correlation between the abundances of the three genera and the loadings of Cr(VI) and SO42-, we conclude that Methylocystis, a type II methanotroph, reduced both Cr(VI) and sulfate, Meiothermus only reduced Cr(VI), and Ferruginibacter only reduced SO42-.
Asunto(s)
Cromatos/química , Electrones , Metano/química , Fenómenos Fisiológicos Bacterianos , Biopelículas , Reactores Biológicos/microbiología , Oxidación-ReducciónRESUMEN
Concentrated turtle aquaculture effluent poses an environmental threat to water bodies, and therefore needs to be treated prior to disposal. This study was conducted to assess the effect of multi-soil-layer (MSL) systems treating turtle aquaculture effluent with adding different amounts of sludge. Four MSL systems were constructed with dry weight ratios of sludge with 0%, 5%, 10%, and 20% (MSL 1, MSL 2, MSL 3, and MSL 4, respectively). The turtle aquaculture effluent had an average chemical oxygen demand (COD), ammonia nitrogen (NH4(+)-N) and total nitrogen (TN) concentration of 288.4, 213.4, and 252.0 mg/L, respectively. The COD/TN (C/N) ratio was 1.2. The results showed that the four MSL systems could effectively treat the COD, NH4(+)-N, and TN, and MSL 4 showed significantly improved NH4(+)-N removal efficiency, suggesting the potential of sludge addition to improve the turtle aquaculture effluent treatment. The average COD, TN, and NH4(+)-N removal efï¬ciencies of MSL 4 were 70.3%, 66.5%, and 72.7%, respectively. To further interpret the contribution of microorganisms to the removal, the microbial community compositions and diversities of the four MSL systems were measured. Comparisons of the denaturing gradient gel electrophoresis (DGGE) profiles revealed that the amount of nitrifying bacteria and diversity in MSL 4 were higher than those in the other three systems. We concluded that adding 20% of sludge improved the NH4(+)-N removal and stability of the system for nitrification, due to the enrichment of the nitrifying bacteria in MSL 4.
Asunto(s)
Acuicultura/métodos , Nitrógeno/aislamiento & purificación , Suelo/química , Tortugas/crecimiento & desarrollo , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodos , Animales , Nitrógeno/química , Aguas Residuales/químicaRESUMEN
To evaluate the feasibility of using multi-soil-layer (MSL) system and subsurface flow constructed wetland to treat the wastewater of marine cultured Penaeus vannamei and to determine the suitable process for the local aquaculture wastewater pollution characteristics. In this study, MSL system and four constructed wetland systems with Spartina anglica, Phragmites australis, Typha latifolia and unplanted system were evaluated for their potentials of pollutants removal capacity. The results showed the average removal rates of chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH(4)+ -N) and nitrate (NO-(3) -N) by MSL system were 80. 38% ± 2. 14% , 68. 14% ± 3.51% , 40.79% ± 3. 10% , 42. 68% ± 2.90% and 54. 19% ± 5. 15% , respectively. Additionally, the ability of pollutants removal of other four wetland systems decreased in the order: Spartina anglica, Phragmites australis, Typha latifolia and unplanted system.
Asunto(s)
Acuicultura , Eliminación de Residuos Líquidos/métodos , Humedales , Análisis de la Demanda Biológica de Oxígeno , Nitrógeno/análisis , Fósforo/análisis , Poaceae , Suelo , TyphaceaeRESUMEN
Sedum alfredii Hance is a fast-growing and high-biomass zinc (Zn) hyperaccumulator native to China. A compound containing substituted indole ligand was isolated from this Zn hyperaccumulator plants by sonication/ethanol extraction, macroporous resin column as well as preparative HPLC (P-HPLC). Hydroponic experiment showed that the concentrations of both Zn and the compound containing substituted indole ligand were remarkably increased in stems and leaves of both hyperaccumulator and non-hyperaccumulator as Zn rising from 0.5 to 50 micromol L(-1), with much more in the stems of hyperaccumulator than non-hyperaccumulator. At 50 micromol L(-1) Zn, hyperaccumulator grew normally but its non-hyperaccumulator suffered from strongly Zn-induced toxicity. This suggested that there was a positive correlation between the compound containing substituted indole ligand and Zn concentration in shoots of hyperaccumulator S. alfredii.
Asunto(s)
Indoles/aislamiento & purificación , Sedum/química , Zinc/toxicidad , Biodegradación Ambiental , Biomasa , China , Cromatografía Líquida de Alta Presión , Regulación de la Expresión Génica de las Plantas , Hidroponía , Indoles/metabolismo , Ligandos , Hojas de la Planta/efectos de los fármacos , Raíces de Plantas/química , Raíces de Plantas/efectos de los fármacos , Tallos de la Planta/efectos de los fármacos , Sedum/efectos de los fármacos , Sedum/fisiología , Zinc/metabolismoRESUMEN
With two rice genotypes (cv. Zhongbu 51 and Azucena) differing in their root-secreted acid phosphatase activity (APA) under low P condition as test materials, an agar culture experiment was conducted to investigate their P utilization from myo-inositol hexaphosphate (IHP) under conditions of sterilization and inoculating with soil microorganisms. Under sterilization, the shoot dry mass, P absorption and P concentration of test genotypes supplied with hexaphosphate (IHP) as the P source were significantly higher than those with no P supply, but significantly lower than those supplied with inorganic P, indicating that rice plants could partly acquire P from IHP under sterilized condition. The root-secreted APA of the two genotypes was significantly higher under low P than under sufficient P supply, and the higher APA of Zhongbu 51 under low P could be one of the mechanisms of higher P utilization capability of Zhongbu 51 than Azucena under deficient P supply. When supplied with high level IHP (0.96 mmol P x L(-1)), the shoot dry mass, P absorption and P concentration of both Zhongbu 51 and Azucena were higher than those when supplied with low level IHP (0.16 mmol P x L(-1)), indicating that substrate availability could be one of the limiting factors to the utilization of phytate by rice. Inoculation with soil microorganisms had no significant effects on the shoot dry mass, P absorption and P concentration of rice plants, regardless of IHP level and rice genotypes, implying that the utilization of IHP by rice could not be improved via inoculation with soil microorganisms.
Asunto(s)
Fosfatasa Ácida/metabolismo , Organofosfatos/metabolismo , Oryza/enzimología , Oryza/genética , Genotipo , Ácido Fítico/metabolismo , Raíces de Plantas/enzimologíaRESUMEN
Cu and Zn are popularly used as additives in animal feed in China, which could result in their excessive accumulation in manure to a toxic level, and thus, possibly threaten the environment when the manure is applied to farmland. In this paper, the acute and sub-acute lethal effects of pig manure with excessive Cu and Zn on earthworm were studied, and the results indicated that the concentration of Cu and Zn in pig manure had a significantly positive correlation with the mortality of earthworm, while a significantly negative correlation with earthworm growth rate. The individuals of earthworm had different tolerance to excessive Cu and Zn, with the threshold values causing death being 250 mg x kg(-1) and 400 mg x kg(-1) for Cu and Zn, respectively. The LD50 was 646.68 mg x kg(-1) for Cu, and 947.38 mg x kg(-1) for Zn. A strong synergistic effect was observed under the combined pollution of 250 mg x kg(-1) for Cu and 500 mg x kg(-1) for Zn, whereas antagonistic effect happened when 750 mg x kg(-1) for Cu was supplied, suggesting that the joint toxic effects of Cu and Zn on earthworm were closely correlated to their concentrations in pig manure.
Asunto(s)
Cobre/toxicidad , Estiércol/análisis , Oligoquetos/efectos de los fármacos , Zinc/toxicidad , Animales , Dosificación Letal Mediana , PorcinosRESUMEN
Screening and breeding low phosphorous (P) tolerant rice genotype is one of the effective alternatives to alleviate the scarcity of mineral P resource and to increase the utilization efficiency of P fertilizer. Selecting a simple and scientific screening index plays an important role in the screening and breeding program. In this study, a hydroponic culture experiment and a field trial were carried out to approach the screening index for low P tolerant rice genotypes. The results showed that among all the rice characters studied, total dry weight demonstrated a significant genotypic variation at both normal and low P supply (the CV was 21.73% and 19.54%, respectively). Relative total dry weight (low P supply/normal P supply) also demonstrated significant genotypic variation (CV was 19.60%), which was significantly correlated to relative root dry weight, relative plant height, relative total P uptake, relative shoot P accumulation, relative P utilization efficiency and relative P concentration (P < 0.01). Therefore, the relative total dry weight of rice would be an important evaluation or screening index for the low P tolerance ability of rice at its seedling stage. The relative total dry weight of rice in hydroponic culture system was not correlated to the relative grain yield (minus-P/plus-P) in field trial, which meant that it could not be used as an index to evaluate the low P tolerance ability of rice. The internal P utilization efficiency of rice grown in low P solution was significantly correlated to that of rice grown in P-deficient soil (r = 0.798 * *, n = 8). Therefore, screening rice genotypes by using internal P utilization efficiency of rice grown in low P solution at seedling stage as screening index and subsequently testing in field trial would probably be an effective alternative to screen rice genotype with high P utilization efficiency.
Asunto(s)
Oryza/genética , Fósforo/metabolismo , Genotipo , Oryza/metabolismo , PlantonesRESUMEN
This study was conducted to investigate the effects of temperature and time on the mechanisms of phosphorus removal in swine manure during aeration. Removal of soluble orthophosphates significantly increased with aeration time and temperature. Successive significant ortho-P removals were observed between days one and nine but no significant additional removals were recorded thereafter. Removals were significantly higher at temperatures of 20 and 25 degrees C than at temperatures of 5, 10, and 15 degrees C and ranged between 22.9 to 31.0%. Insoluble inorganic phosphorus also changed significantly with aeration time and temperature and with a similar trend as soluble orthophosphates. The pH of the manure explained 92 and 87% of the content of insoluble inorganic phosphorus at lower temperatures (5, 10, 15 degrees C) and at higher temperatures (20, and 25 degrees C), respectively. Organic phosphorus and aerobes growth patterns were similar to that of soluble orthophosphates removal. The rapid growth of aerobes was most probably the principal factor behind a rapid soluble ortho-P removal above 15 degrees C. The contribution of inorganic phosphates to the removal of soluble orthophosphates was approximately 61% while that due to organic P was approximately 35%. Precipitation was found to be the principal mechanism governing removal of soluble ortho-P in swine manure during aeration treatments.
Asunto(s)
Aire , Estiércol , Fósforo/química , Animales , Precipitación Química , Concentración de Iones de Hidrógeno , Estiércol/análisis , Oxígeno/metabolismo , Solubilidad , Porcinos , Temperatura , Factores de TiempoRESUMEN
A large-volume solution culture and a small-pot soil test were adopted to screen for aluminum tolerance in wheat. Significant correlations were observed between root and shoot tolerance indices in wheat genotypes by using the same or different screening method. It was also shown that root tolerance parameters such as relative root length (RRL) and relative root dry weight (RRW) had more sensitive for differentiating aluminum tolerance in wheat genotypes indicated by higher standard deviation (SD), coefficient of variation (CV), and distribution of data. Although shoot tolerance parameters, such as relative shoot length (RSL) and relative shoot dry weight (RSW) had less sensitive for differentiating aluminum tolerance within wheat genotypes indicated by lower SD, CV, and distribution of data, shoot growth parameters were reliable indicators of Al tolerance because they were sufficient to discriminate Al-tolerant and Al-sensitive genotypes in wheat. Shoot growth especially shoot length could be easily, rapidly, and non-destructively determined, and used effectively to screen for aluminum tolerance in a large-scale screening or breeding program.
Asunto(s)
Aluminio/toxicidad , Raíces de Plantas/crecimiento & desarrollo , Triticum/crecimiento & desarrollo , Triticum/efectos de los fármacosRESUMEN
Manure slurries stored in pits under slatted floors of both finishing and nursery barns were sampled at four different depths to study stratifications of total solids (TS) and nutrients (nitrogen and phosphorus), and to determine the relationship between the stratification of TS and nutrients. The results obtained can be used to improve the management and handling of swine manure in the under-slat storage pits. A management scheme that can be adopted for both the finishing and the nursery barns' pits is the layer-by-layer harvesting of the manure. The thinner manure, which is lower in nutrients, can be spread on land near the production units in larger volumes or it may pumped to land remote from the production units without causing many clogging problems. The thicker manure, higher in nutrients, can be transported to land further away and spread in smaller volumes. The TS content of each stratum can be used to accurately estimate the nitrogen and phosphorus levels in the respective strata so that application rates can easily be adjusted accordingly during the time of land application.
Asunto(s)
Factores de Edad , Estiércol/análisis , Nitrógeno/análisis , Fósforo/análisis , Eliminación de Residuos , Alimentación Animal , Animales , Monitoreo del Ambiente , Tamaño de la Partícula , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Estadística como Asunto , PorcinosRESUMEN
The temperature effect on total anaerobic and aerobic bacterial growth in pig slurry was studied using low level batch aeration treatments. Five bioreactors were built using Plexiglas tubes to perform five temperature treatments (5 degrees C, 10 degrees C, 15 degrees C, 20 degrees C, and 25 degrees C). An airflow rate of 0.129 L/min/L manure was used to aerate manure contained in all reactors. Data showed that temperature had a profound impact on the aerobic counts in pig slurry during the aeration process. When the temperature increased from 15 degrees C to 25 degrees C, the average oxidation-reduction potential decreased from +40 mV to -60 mV, accompanied by a 75% reduction of aerobic bacteria in the manure. At 25 degrees C, the anaerobic counts were consistently higher than aerobic counts for most of days. A quadratic relationship was observed between the aerobic counts and the oxidation-reduction potential with a correlation coefficient of 0.8374. To reduce odor generation potential, the oxidation-reduction potential in the manure should be maintained at +35 mV or higher.