Water resources are threatened globally and declining water quality is primarily due to stormwater, agricultural, urban, and mining runoffs. Steamboat Creek in Nevada is the largest non point source (NPS) of pollution to the Truckee River. Treatment wetlands are a cost-effective and reliable technique to control NPS pollution, therefore, a large-scale wetland along Steamboat Creek has been proposed as a component of a regional watershed restoration plan. This study used ten parallel pilot-scale wetland mesocosms, and tested the effects of drying and rewetting, hydraulic retention time (HRT), and high nitrogen loading on the efficiency of nutrient and total suspended solids (TSS) removal. Drying and rewetting produced noticeable effects on nutrient retention, but the effect was short-lived. During longer HRT period nutrient removal in manipulated mesocosms with an 8 h HRT were higher than controls with a 4 h HRT. Reducing the HRT from 4 h to 30 min further decreased nutrient interception. During increased influent nitrogen loading (9.5?±?2.4 mg l?1), manipulated mesocosms functioned as sinks for total nitrogen (TN) with removal efficiency increasing from 45?±?13% to 87?±?9%. The average change in TN concentration was 9.1?±?2.2 mg l?1. Drying/rewetting and varying HRT influenced total phosphorus (TP) and TSS similarly, and TP removal was associated with TSS removal. Results can help make decisions regarding wetland construction, management, and operation more effective in order to reduce nutrient loads to the Truckee River. 相似文献
Removal of nitrogen and phosphorus from a domestic wastewater using a sequencing batch reactor (SBR) was evaluated at solid retention times (SRTs) of 9.3, 13.8, and 18.3 days respectively. Oxygen uptake rates (OURs) and sludge settling characteristics were determined at each SRT investigated. COD removal, nitrification, denitrification, and phosphorus removal were accomplished by using the following operating cycle: 15-min unmixed fill; 2-hr mixed anaerobic period; 3-hr mixed aerobic period; 3-hr mixed anoxic period; 0.5-hr reaeration period; 1-hr settling period; 1-hr decant period; and a 1.5-hr idle period. Advanced wastewater treatment (AWT) standards of 5/5/3/1 mg L-1 for biochemical oxygen demand (BOD5), suspended solids (SS), total nitrogen (TN), and total phosphorus (TP) could not be achieved with the bench-scale SBR. 相似文献
Static granular bed reactor (SGBR) and upflow anaerobic sludge blanket (UASB) reactor were demonstrated at mesophilic condition for the treatment of pulp and paper mill wastewater. The hydraulic retention times (HRTs) were varied from 4 to 24 h following 29-day start-up period. The overall chemical oxygen demand (COD) removal efficiency of the SGBR was higher than the UASB during this study. At 4 h HRT, the COD removal was greater than 70 % for the SGBR and 60 % for the UASB. Biomass yield and volatile fatty acids concentration of SGBR were slightly less than UASB at organic loading rates ranging from 1.2 to 5.1 kg/m3/day. The results indicated that the SGBR system can be considered a viable alternative system for anaerobic treatment for pulp and paper wastewater. 相似文献
Two horizontal constructed wetlands with subsurface flow (CWs) of different age were monitored in a 2-year study. One of the CWs was new, while the second one had been in operation for 5 years in the first year of study. Transformations of C, P, and N were measured in each CW in the substrate of the vegetated bed under both aerobic and anaerobic conditions, and their rates were compared. C was mineralized in both CWs under both aerobic and anaerobic conditions, but mineralization rates differed between the CWs; they were cca ten times higher in the established CW compared to the new CW. Dissolved reactive phosphorus (DRP) was immobilized under aerobic conditions but was mobilized under anaerobic conditions. DRP transformation was cca five times faster in the established CW. Nitrification occurred under aerobic conditions at similar rates in both CWs. NH4+ concentration decreased under both aerobic and anaerobic conditions, but there was large variability. The age of the CW affected C mineralization rates and DRP immobilization rates under aerobic conditions and mobilization rates under anaerobic conditions; they increased as the CWs maturated, while no effect of CW age was observed on nitrogen removal rates. 相似文献
Seven experimental pilot-scale subsurface vertical-flow constructed wetlands were designed to assess the effect of plants [Typha latifolia L. (cattail)], intermittent artificial aeration and the use of polyhedron hollow polypropylene balls (PHPB) as part of the wetland substrate on nutrient removal from eutrophic Jinhe River water in Tianjin, China. During the entire running period, observations indicated that plants played a negligible role in chemical oxygen demand (COD) removal but significantly enhanced ammonia–nitrogen (NH4–N), nitrate–nitrogen (NO3–N) total nitrogen (TN), soluble reactive phosphorus (SRP) and total phosphorus (TP) removal. The introduction of intermittent artificial aeration and the presence of PHPB could both improve COD, NH4–N, TN, SRP and TP removal. Furthermore, aerated wetlands containing PHPB performed best; the following improvements were noted: 10.38 g COD/m2 day, 1.34 g NH4–N/m2 day, 1.04 g TN/m2 day, 0.07 g SRP/m2 day and 0.07 g TP/m2 day removal, if compared to non-aerated wetlands without PHPB being presented. 相似文献
Stormwater runoff is a known pollutant source capable of causing surface water degradation, especially in highly populated areas such as Central Florida. Wet detention ponds manage this stormwater, but most of the ponds do not remove enough nutrients, specifically nitrogen and phosphorus, to meet total maximum daily load regulations. This paper presents the use of a chamber upflow filter and skimmer (CUFS) filled with a specific green sorption medium as process modification of stormwater retention ponds, which can increase the removal of nitrogen and phosphorus in the stormwater runoff. Green sorption medium consists of recycled and natural materials that provide a favorable environment for pollutant removal. Water enters the system through the skimmer, which floats on the surface of the detention pond. It travels from the skimmer to the bottom of the chamber where heavier particles settle out before entering the upflow filter. The upflow filter contains 61 cm (24 in.) of green sorption medium providing physicochemical and microbiological processes to remove nitrogen and phosphorus under anoxic/anaerobic conditions. After this treatment, water flows up through the filter and out of the system and eventually travels to Lake Jesup, a eutrophic lake in Central Florida. A total of 28 storm events and seven baseflows were sampled from the site in Seminole County, and ten storm events were sampled from a pilot study of CUFS for statistical analysis and performance evaluation. Significant reductions by the CUFS were confirmed in terms of turbidity, orthophosphorus, total phosphorus, and total suspended solids when the mean values were compared at a 95% confidence level. Reductions also occurred for total nitrogen (TN), but could not be proved by the mean comparison in the field test, whereas the pilot-scale application of the CUFS proved effective for reducing TN at a 95% confidence level. Hydraulic retention time should be increased so as to improve the design for TN removal in future applications. 相似文献
Hydraulic retention time (HRT) influence improving sludge flocculation with adding the polyelectrolytes (non-ionic, anionic, and cationic) was studied on an activated sludge (AS) system fed with synthetic domestic wastewater (SDW), dairy industry wastewater (DIW), and caramel industry wastewater (CIW). The sludge volumetric index, food/microorganism ratio (F/M), and mixed liquor volatile suspended solids at different HRTs (6, 8 and 10 h) were monitored on an experimental model. Results showed that both SDW and IW had the best sludge flocculation conditions at 8 h and 100 mL of non-ionic polyelectrolyte (0.2 mg L?1). In addition, this phenomenon reached the organic matter removal efficiencies of 95.9, 95.7, and 94.2% for SDW, DIW, and CIW, respectively. Therefore, optimum HRT increased the organic matter removal efficiencies by 10%, sludge concentration by 37% (22–55%), and F/M ratio by 70%. Moreover, the polyelectrolytes used in AS improved the sludge flocculation by 2.9 times. 相似文献
In recent years, moving bed systems have been shown as an efficient technology in wastewater treatment and particularly in
the treatment of urban effluents. This paper presents the results obtained for three different carriers in organic matter
removal, analysing the influence of hydraulic retention time (HRT) and the filling ratio, as well as the kinetic constants
of each carrier used. During the research, differences in the organic matter removal were observed under different conditions
studied as a result of physical and geometrical characteristics of each carrier and their hydraulic behaviour. Two of the
three carriers studied in this research had similar yields compared to the third carrier that presented lower rates of organic
matter removal and lower kinetic constants than the other two. Carriers 1 and 2 obtained removal rates of organic matter in
the form of soluble chemical oxygen demand (sCOD) above 50% for intermediate and higher filling ratios with HRTs of 15, 10
and 15 h, respectively. The maximum values obtained for carrier 1, 2 and 3 were 56.97%, 58.92% and 46.13%, respectively, under
15 h of HRT and 50% of filling ratio. The kinetic constants obtained by respirometry showed a similar trend to the values
obtained from sCOD removal. 相似文献
The potential of ferrihydrite-modified diatomite as a phosphorus co-precipitant was investigated at a laboratory scale. Ferrihydrite-modified diatomite was demonstrated to effectively remove phosphorus from lake water as well as strongly bind phosphorus in sediment under anoxic conditions. Phosphorus removal from the lake water proceeded primarily through phosphorus adsorption onto ferrihydrite-modified diatomite and further phosphorus consumption by stimulated diatom growth. A total phosphorus removal efficiency of 85% was achieved when lake water was dosed with 250 mg/L ferrihydrite-modified diatomite; the residual total phosphorus concentration was 17.0 µg/L, which falls within the range for oligotrophic phosphorus levels. During a 30-day anoxic incubation period, total phosphorus concentrations in lake water treated with 400, 500, or 600 mg/L of ferrihydrite-modified diatomite slightly decreased and maximum total phosphorus concentrations remained below 15 µg/L. Addition of ferrihydrite-modified diatomite resulted in a marked increase in the iron-bound phosphorus fraction, a pronounced decrease in labile phosphorus and organic-bound phosphorus fractions, and stable aluminum-bound phosphorus, calcium-bound phosphorus, and residual phosphorus fractions in the anoxic sediments. Comparable iron-bound phosphorus concentration in the sediment treated by 400 mg/L of ferrihydrite-modified diatomite relative to that of the sediment treated by the combination of 400 mg/L of ferrihydrite-modified diatomite and alum solution at the concentration less than 532 mg/L indicated that ferrihydrite-modified diatomite exhibited a stable phosphorus-binding capacity when dosed at a similar amount. Ferrihydrite-modified diatomite had the potential to be used as an effective phosphorus co-precipitant. 相似文献
The present study aims to investigate the performance of potassium ferrate(VI) in treating decentralized domestic sewage from a rural scattered residential area. Major results were that around 90% of total phosphorus (TP) and 40% of chemical oxygen demand (COD) could be reduced when 25 mg L?1 of ferrate(VI) was applied. The removal of ammonia and total nitrogen (NH3–N and TN) was also monitored. However, the nitrogen removal during the chemical dosing was rather low. Big fluctuations of removal rates were observed against shock pollutants concentrations. Considering its strong ability in removing emerging organic pollutants and P, ferrate(VI) is competitive in the treatment of decentralized domestic sewage as an advanced treatment unit following some traditional treatment units. 相似文献
为了了解太湖地区不同类犁农田排水沟渠对N、P拦截效果的影响,分别在野外构建了3种类型的农田排水沟渠,即生态沟渠、混凝土沟渠和土质沟渠.研究了不同进水N、P浓度、不同水力停留时间和不同进水流速条件下,3种类型沟渠的N、P拦截效果.结果表明:在水力停留时间分别为24 h和48 h静态试验以及在固定进水流速的动态试验中,沟渠对不同进水N、P浓度的N、P去除牢大小顺序是:生态沟渠、土质沟渠和混凝土沟渠,其中,生态沟渠明显优于其他沟渠.在固定进水浓度的条件下,沟渠在不同水力停留时间下的N、P去除率大小顺序为;生态沟渠、土质沟渠和混凝土沟渠,其中,生态沟渠明显好于其他沟渠.在高、低两种进水流速和固定进水浓度条件下.生态沟渠在低进水流速下的N、P去除率明显优于其他沟渠.在不同进水浓度条件下,生态沟渠最佳水力停留时间为48 h. 相似文献
Effects of graphene oxide (GO) on phosphorus removal characteristics and mechanisms of aerobic granular sludge (AGS) were investigated in controlled batch tests. The scanning electron microscope (SEM) image results showed that the surface of AGS appeared wrinkled with coccus and bacillus brevis being wizened and the fungal mycelium being cut into pieces in AGS with 0.06 g/L GO. The anaerobic and aerobic batch tests suggested that the net phosphorus uptake of AGS was 2.60 mg/L for AGS with GO, compared with the value (4.38 mg/L) without GO, and the maximum release and uptake phosphorus rates also remarkably decreased. Intracellular and extracellular phosphorus contents were reduced to 64.67 and 19.74% of that without GO, indicating the nanoparticle might have great effects on extracellular phosphorus. The standards, measurements, and testing (SMT) analysis suggested that the inorganic phosphorus (IP) and organic phosphorus (OP) content decreased compared with the values without GO. The summation of phosphorus fraction associated with Ca (Ca-P) and the phosphorus fraction associated with Al, Fe, and Mn (Fe/Al-P) were 82.09% (without GO) and 94.27% (with GO), suggesting the presence of GO resulted in the decrease of content and species of IP. The extracellular polymeric substances (EPS) were reduced from 173.68 mg/g MLVSS to 137.55 mg/g MLVSS when AGS contacted with GO. The results of this assay had uncovered that 0.06 g/L GO could inhibit the bioactivity of phosphorus-accumulating organisms (PAOs), which resulted in the decrease of Ca-P, Fe/Al-P, and OP. EPS played an essential role on the phosphorus removal and granular stability. The decrease of EPS, which was produced by microorganisms, was contributed to decrease of extracellular phosphorus. This study provided an extensive insight into the influence of GO on phosphorus removal mechanism by AGS.
试验设计了一种生物絮凝反应器,用作中试规模循环水养殖系统(recirculating aquaculture system,RAS)的唯一水处理装置,研究其在不同水力停留时间(hydraulic retention time,HRT,12、6、4.5、3 h)条件下的运行效果。试验结果表明,反应器可耐受最小HRT为4.5 h,当HRT降低至3 h,反应器发生不可逆的洗出现象而使试验不能继续进行。反应器絮体沉降性能一般,随着HRT的减小(12、6和4.5 h HRT),絮体体积指数(SVI-30)逐渐降低,但是始终大于150 m L/g,为丝状菌膨胀,主要的丝状细菌由TM7 genera incertae sedis逐渐演变为Haliscomenobacter和Meganema菌属,相对丰度逐渐降低。12 h HRT反应器污染物去除率最高。反应器亚硝氮(NO_2~--N)、硝氮(NO_3~--N)在4.5 h HRT出水质量浓度最低,分别为(0.02±0.01)、(1.70±0.06)mg/L;氨氮(total ammonium nitrogen,TAN)、总氮(total nitrogen,TN)、悬浮颗粒物(suspended solids,SS)出水质量浓度在12 h HRT时最低,分别为(0.48±0.05)、(4.47±1.00)、(14.20±8.14)mg/L,同时未造成有机污染。4.5 h HRT对RAS养殖区污染物的控制效果最佳,TAN、NO_2~--N、NO_3~--N、SS质量浓度分别被控制在0.76、0.10、2.95、60.00 mg/L以下。反应器在不同HRT条件下均以异养细菌为主,主要通过同化作用去除TAN,好氧反硝化细菌和厌氧反硝化细菌同时是反应器的优势菌属。反应器可获得较长的稳定运行状态和良好的水处理效果,具有用作RAS核心水处理装置的可行性,该研究可为其在RAS的进一步研究和应用提供参考。 相似文献
Two series of laboratory-scale vertical flow systems (flooded and nonflooded columns) were designed to compare nitrogen removal performance, nitrous oxide emission, and ammonia volatilization under different water levels upon treating diluted digested livestock liquid. In these systems, influent was supplied at three hydraulic loading rates (HLRs of 1.25, 2.5, and 5 cm day?1) during stage 1 and the rates were doubled during stage 2 when the water levels of nonflooded columns were elevated from zero to half the height of the soil column. After hydraulic loading rates doubled, the average removal rates of total nitrogen in flooded columns varied from 1.27 to 2.94 g?2 day?1 and those in nonflooded columns ranged from 1.23 to 3.88 g?2 day?1. The T-N removal at an HLR of 10 cm day?1 in the nonflooded column with an elevated water table level had higher efficiency than that in the flooded column, suggesting T-N removal is enhanced in the nonflooded column probably due to the improved coupled nitrification–denitrification process under the elevated water table level condition. On the other hand, there was a significant correlation (r2 = 0.532, p < 0.001) between the N2O flux and redox potential that mainly corresponded to water levels and HLRs, suggesting anoxic or aerobic conditions stimulate N2O emission by enhancing the nitrification (nitrification–denitrification) process. In contrast, NH3 volatilization had a high flux in the anaerobic condition mainly because of flooding. Based on the experimental results, it is hypothesized a nonflooded condition with higher water table level (Eh range of ?160 to +260 mV) would be suitable to reduce N2O emission and NH3 volatilization peak value by at least half while maintaining relatively efficient nitrogen removal performance. 相似文献
