Development of steady-state phosphate concentrations in septic system plumes

Long-term monitoring of PO₄⁻³ behaviour in a well-defined septic system plume on calcareous sand (Cambridge site) shows that, after 17 yr of system operation, a distinct PO₄⁻³ plume (PO₄⁻³−P > 1 mg L⁻¹) is present extending 20 m downgradient from the infiltration bed. The PO₄³⁻ plume migration velocity is 1 m yr⁻¹, reflecting retardation by a factor of 20 compared to the groundwater velocity. During monitoring between years 10 to 17, an expanding steady-state zone was noted below the infiltration bed where PO₄³⁻ −P levels remained consistently near 4 mg L⁻¹, a value 25% lower than the average effluent value (6.3 mg L⁻¹). The pattern of attenuation — a 25% mass loss in the 2-m-thick vadose zone, then little further attenuation along the flowpath — is suggestive of a condition of equilibrium with a controlling phosphate mineral phase. Chemical equilibrium modelling shows supersaturation with respect to hydroxylapatite and variscite. Four other field sites are identified from the literature and from our work where similar steady-state PO₄³⁻ zones are present in septic system plumes. In these, steady-state levels range from 15% to 68% of effluent values, with lower concentrations observed in the more acidic plumes, again indicative of a mineral solubility control, possibly variscite.PO₄³⁻ behaviour in these plumes suggests that, although P migration velocity is controlled by the processes of sorption, the magnitude of PO₄³⁻ that is present is governed by the constraints of phosphate mineral solubility. When septic systems on sands are located relatively close to sensitive surface water bodies and when long-term downgradient impact is the primary concern, more attention should be focused on the geochemical conditions that control PO₄³⁻ mineral solubility rather than only on the sorption characteristics of the sediment.     

Geochemistry of a septic-system plume in a coastal barrier bar, Point Pelee, Ontario, Canada

The major ion and trace metal geochemistry of a septic system plume in a shallow sand aquifer was characterized to assess geochemical processes controlling the transport of nutrients and their release to a nearby wetland. The plume was generated from a 16-year-old tile bed, and is more than 60 m long, 40 m wide and 7 m thick. The groundwater pH at the site is near neutral, but up to 0.4 units lower in the plume core as a result of H⁺ generated from NH₃ and DOC oxidation in the unsaturated zone. The plume can be divided into distinct redox zones, which show differences in nutrient mobility. Proximal to the tile bed, there is a shallow suboxic zone, with intermediate Eh values (>400 mV), low concentrations of dissolved oxygen (<1.0 mg/l), and elevated concentrations of Mn (1–3 mg/l) and nutrients (10–80 mg/l NO₃–N, 1–15 mg/l NH₃–N, 0.1–1.5 mg/l PO₄–P, 6–13 mg/l dissolved organic carbon). At the base of the aquifer, there is a reduced zone (Eh<200 mV) with elevated concentrations of Fe (1–14 mg/l), PO₄ and NH₃, but negligible concentrations of NO₃ (<0.01 mg/l N). Distal from the tile bed, the shallow groundwater is suboxic to oxic, and has elevated concentrations of NO₃ and NH_3, but negligible PO₄. In the lower reduced zone, elevated concentrations of PO₄ occur up to 60 m away. The release of groundwater containing even very low concentrations of PO₄ (<0.02 mg/l P) can lead to the development of eutrophic conditions in surface water bodies. Geochemical calculations indicate that, in the Mn-rich zone, the groundwater is close to saturation or supersaturated with respect to hydroxyapatite, rhodochrosite, calcite and ferrihydrite. In the reduced zone, the groundwater is close to saturation or supersaturated with respect to hydroxyapatite, vivianite, calcite and siderite. Formation of these phases, or related phases, are likely limiting the concentrations of dissolved PO₄, Fe and Mn and controlling the geochemical evolution of the plume.     

Influence of detergent formulation on nutrient movement through sand columns simulating mound and conventional septic system drainfields

The effects of phosphate (P) and zeolite (Z) -built detergents on leaching of N and P through sand columns simulating septic system drainfields were examined in laboratory columns. To simulate mound septic system drainfields, paired sets of columns were dosed intermittently with septic tank effluent from households using P- or Z-built detergent. Two other paired sets of columns were flooded with P- or Z-effluent to simulate new conventional septic system drainfields; after clogging mats or “crusts” developed at infiltration surface, the subsurfaces of the columns were aerated to simulate mature (crusted) conventional septic system drainfields. NO₃ loading in leachate was 1.1 times higher and ortho-P loading was 4.3 times lower when columns were dosed with Z- than with P-effluent. Dosed columns removed P poorly; total phosphorus (TP) loading in leachate was 81 and 19 g m⁻² yr⁻¹ with P- and Z-effluent, respectively. In flooded columns 1.3, 2.0 and 1.8 times more NH₄, organic nitrogen (ON) and total nitrogen (TN) respectively, were leached with Z- than with P-effluent; NO₃ leaching was similar. Flooded columns removed P efficiently; TP leached through flooded systems was 2.5 and 1.4 g m⁻² yr⁻¹ with P- and Z effluent, respectively. Crusted columns fed Z-effluent leached 1.2, 2.6, 1.4 and 2.1 times more NH₄, NO₃, ON and TN, respectively, than those with P-effluent but 1.8 times less TP. Crusted columns removed P satisfactorily: 8.2 and 4.6 g m⁻² yr⁻¹ TP with P- and Z-effluent, respectively. The P-built detergent substantially improves the efficiency of N removal with satisfactory P removal in columns simulating conventional septic system drainfield. Simultaneous removal of N and P under flooded conditions might be explained by precipitation of struvite-type minerals. Dosed system drainfields were less efficient in removing N and P compared to flooded and crusted system drainfelds.     

Arsenic strongly associates with ferrihydrite colloids formed in a soil effluent

Arsenic mobility may increase in liquid phase due to association with colloidal Fe oxides. We studied the association of As with Fe oxide colloids in the effluent from water-saturated soil columns run under anoxic conditions. Upon exfiltration, the solutions, which contained Fe²⁺, were re-aerated and ferrihydrite colloids precipitated. The entire amount of effluent As was associated with the ferrihydrite colloids, although PO₄³⁻, SiO₄⁴⁻, CO₃²⁻ and dissolved organic matter were present in the effluent during ferrihydrite colloid formation. Furthermore, no subsequent release of As from the ferrihydrite colloids was observed despite the presence of these (in)organic species known to compete with As for adsorption on Fe oxides. Arsenic was bound via inner-sphere complexation on the ferrihydrite surface. FTIR spectroscopy also revealed adsorption of PO₄³⁻ and polymerized silica. However, these species could not impede the quantitative association of As with colloidal ferrihydrite in the soil effluents.     

Comparative studies of the Fe–UV, H2O2–UV, TiO2–UV/vis systems for the decolorization of a textile dye X-3B in water

The degradation of a common textile dye, Reactive-brilliant red X-3B, by several advanced oxidation technologies was studied in an air-saturated aqueous solution. The dye was resistant to the UV illumination (wavelength λ  320 nm), but was decolorized when one of Fe³⁺, H₂O₂ and TiO₂ components was present. The decolorization rate was observed to be quite different for each system, and the relative order evaluated under comparable conditions followed the order of Fe²⁺–H₂O₂–UV  Fe²⁺–H₂O₂ > Fe³⁺–H₂O₂–UV > Fe³⁺–H₂O₂ > Fe³⁺–TiO₂–UV > TiO₂–UV > Fe³⁺–UV > TiO₂–visible light (λ  450 nm) > H₂O₂–UV > Fe²⁺–UV. The mechanism for each process is discussed, and linked together for understanding the observed differences in reactivity.     

Chemical characteristics of precipitation at metropolitan Newark in the US East Coast

To investigate the chemical characteristics of precipitation in the polluted coastal atmosphere, a total of 46 event-based precipitation samples were collected using a wet-only automatic precipitation collector from September 2006 to October 2007 at metropolitan Newark, New Jersey in the US East Coast. Samples were analyzed by ion chromatography for the concentrations of major inorganic ions (Cl⁻, NO₃⁻, SO₄²⁻, F⁻, NH₄⁺, Ca²⁺, Mg²⁺, Na⁺, K⁺) and organic acid species (CH₃COO⁻, HCOO⁻, CH₂(COO)₂²⁻, C₂O₄²⁻). Selected trace metals (Sb, Pb, Al, V, Fe, Cr, Co, Ni, Cu, Zn, Cd) in samples were determined by ICPMS. Mass concentration results show that SO₄²⁻ was the most dominant anion accounting for 51% of the total anions, controlling the acidity of the precipitation. NH₄⁺ accounted for 48.6% of the total cations, dominating the precipitation neutralization. CH₃COO⁻ and HCOO⁻ were the two dominant water-soluble organic acid species, accounting for 42% and 40% of the total organic acids analyzed, respectively. Al, Zn and Fe were the three major trace metals in precipitation, accounting for 34%, 27%, and 25% of the total mass of metals analyzed. The pH values in precipitation ranged from 4.4 to 4.9, indicating an acidic nature. Enrichment Factor (EF) Analysis showed that Na⁺, Cl⁻, Mg²⁺ and K⁺ in the precipitation were primarily of marine origin, while most of the Fe, Co and Al were from crust sources. Pb, V, Cr, Ni were moderately enriched with EFs ranging 43–410, while Zn, Sb, Cu, Cd and F⁻ were highly enriched with EFs > 700, indicating significant anthropogenic influences. Factor analysis suggests 6 major sources contributing to the observed composition of precipitation at this location: (1) nitrogen-enriched soil, (2) secondary pollution processes, (3) marine sources, (4) incinerations, (5) oil combustions, and (6) malonate–vanadium enriched sources. To further explore the source–precipitation event relationships and seasonality, cluster analysis was performed for all precipitation events. Results show that about half of the precipitation events were characterized by mixed sources. Significant influences of nitrogen-enriched soil and marine sources were associated with precipitation events in spring and autumn, while secondary pollution processes, incineration and oil combustion contributed greatly in summer.     

Iron isotopic fractionation in industrial emissions and urban aerosols

A study on tropospheric aerosols involving Fe particles with an industrial origin is tackled here. Aerosols were collected at the largest exhausts of a major European steel metallurgy plant and around its near urban environment. A combination of bulk and individual particle analysis performed by SEM–EDX provides the chemical composition of Fe-bearing aerosols emitted within the factory process (hematite, magnetite and agglomerates of these oxides with sylvite (KCl), calcite (CaCO₃) and graphite carbon). Fe isotopic compositions of those emissions fall within the range (0.08‰ < δ⁵⁶Fe < +0.80‰) of enriched ores processed by the manufacturer (−0.16‰ < δ⁵⁶Fe < +1.19‰). No significant evolution of Fe fractionation during steelworks processes is observed. At the industrial source, Fe is mainly present as oxide particles, to some extent in 3–4 μm aggregates. In the close urban area, 5 km away from the steel plant, individual particle analysis of collected aerosols presents, in addition to the industrial particle type, aluminosilicates and related natural particles (gypsum, quartz, calcite and reacted sea salt). The Fe isotopic composition (δ⁵⁶Fe = 0.14 ± 0.11‰) measured in the close urban environment of the steel metallurgy plant appears coherent with an external mixing of industrial and continental Fe-containing tropospheric aerosols, as evidenced by individual particle chemical analysis. Our isotopic data provide a first estimation of an anthropogenic source term as part of the study of photochemically promoted dissolution processes and related Fe fractionations in tropospheric aerosols.     

Investigation of the removal mechanism of Cr(VI) in groundwater using activated carbon and cast iron combined system

Zero-valent iron (Fe⁰) has been widely used for Cr(VI) removal; however, the removal mechanisms of Cr(VI) from aqueous solution under complex hydrogeochemical conditions were poorly understood. In this research, the mixed materials containing cast iron and activated carbon were packed in columns for the treatment of aqueous Cr(VI)-Cr(III) in groundwater with high concentration of Ca²⁺, Mg²⁺, HCO₃ ⁻, NO₃ ⁻, and SO₄ ²⁻. We investigate the influences of those ions on Cr(VI) removal, especially emphasizing on the reaction mechanisms and associated precipitations which may lead to porosity loss by using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) techniques. The results show that the precipitations accumulated on the material surface were (Fe/Cr) (oxy)hydroxide, mixed Fe(III)-Cr(III) (oxy)hydroxides, Fe₂O₃, CaCO₃, and MgCO₃. During these reactions, the Cr(VI) was reduced to Cr(III) coupled with the oxidated Fe⁰ to Fe(II) through the galvanic corrosion formed by the Fe⁰-C and/or the direct electron transfer between Fe⁰ and Cr(VI). In addition, Cr(VI) could be reduced by aqueous Fe(II), which dominated the whole removal efficiency. The primary aqueous Cr(III) was completely removed together with Cr(III) reduced from Cr(VI) even when Cr(VI) was detected in the effluent, which meant that the aqueous Cr(III) could occupy the adsorption sites. In general, the combined system was useful for the Cr(VI)-Cr(III) treatment based on galvanic corrosion, and the hardness ions had a negative effect on Cr(VI) removal by forming the carbonates which might promote the passivation of materials and decrease the removal capacity of the system.

     

Microbial characterization of nitrification in a shallow, nitrogen-contaminated aquifer, Cape Cod, Massachusetts and detection of a novel cluster associated with nitrifying Betaproteobacteria

Groundwater nitrification is a poorly characterized process affecting the speciation and transport of nitrogen. Cores from two sites in a plume of contamination were examined using culture-based and molecular techniques targeting nitrification processes. The first site, located beneath a sewage effluent infiltration bed, received treated effluent containing O₂ (> 300 µM) and NH₄⁺ (51–800 µM). The second site was 2.5 km down-gradient near the leading edge of the ammonium zone within the contaminant plume and featured vertical gradients of O₂, NH₄⁺, and NO₃⁻ (0–300, 0–500, and 100–200 µM with depth, respectively). Ammonia- and nitrite-oxidizers enumerated by the culture-based MPN method were low in abundance at both sites (1.8 to 350 g^− 1 and 33 to 35,000 g^− 1, respectively). Potential nitrifying activity measured in core material in the laboratory was also very low, requiring several weeks for products to accumulate. Molecular analysis of aquifer DNA (nested PCR followed by cloning and 16S rDNA sequencing) detected primarily sequences associated with the Nitrosospira genus throughout the cores at the down-gradient site and a smaller proportion from the Nitrosomonas genus in the deeper anoxic, NH₄⁺ zone at the down-gradient site. Only a single Nitrosospira sequence was detected beneath the infiltration bed. Furthermore, the majority of Nitrosospira-associated sequences represent an unrecognized cluster. We conclude that an uncharacterized group associated with Nitrosospira dominate at the geochemically stable, down-gradient site, but found little evidence for Betaproteobacteria nitrifiers beneath the infiltration beds where geochemical conditions were more variable.     

X-ray absorption and photoelectron spectroscopy investigation of selenite reduction by Fe-bearing minerals

The long-lived radionuclide ⁷⁹Se is one of the elements of concern for the safe storage of high-level nuclear waste, since clay minerals in engineered barriers and natural aquifer sediments strongly adsorb cationic species, but to lesser extent anions like selenate (Se^VIO₄²⁻) and selenite (Se^IVO₃²⁻). Previous investigations have demonstrated, however, that Se^IV and Se^VI are reduced by surface-associated Fe^II, thereby forming insoluble Se⁰ and Fe selenides. Here we show that the mixed Fe^II/^III (hydr)oxides green rust and magnetite, and the Fe^II sulfide mackinawite reduce selenite rapidly (< 1 day) to FeSe, while the slightly slower reduction by the Fe^II carbonate siderite produces elemental Se. In the case of mackinawite, both S^−II and Fe^II surface atoms are oxidized at a ratio of one to four by producing a defective mackinawite surface. Comparison of these spectroscopic results with thermodynamic equilibrium modeling provides evidence that the nature of reduction end product in these Fe^II systems is controlled by the concentration of HSe⁻; Se⁰ forms only at lower HSe⁻ concentrations related to slower HSeO₃⁻ reduction kinetics. Even under thermodynamically unstable conditions, the initially formed Se solid phases may remain stable for longer periods since their low solubility prevents the dissolution required for a phase transformation into more stable solids. The reduction by Fe²⁺-montmorillonite is generally much slower and restricted to a pH range, where selenite is adsorbed (pH < 7), stressing the importance of a heterogeneous, surface-enhanced electron transfer reaction. Although the solids precipitated by the redox reaction are nanocrystalline, their solubility remains below 6.3 × 10^− 8 M. No evidence for aqueous metal selenide colloids nor for Se sorption to colloidal phases was found. Since Fe^II phases like the ones investigated here should be ubiquitous in the near field of nuclear waste disposals as well as in the surrounding aquifers, mobility of the fission product ⁷⁹Se may be much lower than previously assumed.     

Recent trends in chemical composition of bulk precipitation at Estonian monitoring stations 1994–2001

Monthly and annual means of main anions (SO₄²⁻, NO₃⁻, Cl⁻) and summed base cations (Ca²⁺, Mg²⁺, K⁺, Na⁺) in bulk precipitation were studied at 10 stations during an 8-year monitoring period. The data showed statistically significant decreasing trends in most cases. Average declines of mean annual volume-weighted concentrations for both anions and cations were about two-fold. Despite the decrease, the loads of S and cations are still relatively high in Estonia (about 4–14 kg S ha⁻¹ and 0.6–1.2 keq ha⁻¹, respectively) compared with the loads in Finland and Sweden. Estimated linear decline trends followed the same pattern as annually combusted oil shale from Estonian power plants and emissions of SO₂ and fly ash. Recent trends in chemical composition of bulk precipitation at the monitoring stations reflected economic changes in Estonia as well as transboundary fluxes from neighbouring countries.     

Quality of roof runoff waters from an urban region (Gda sk, Poland)

The paper presents the results of testing of roof runoff waters from buildings in the city of Gda sk (Poland), carried out as a part of a broader research project aimed at the determination of pollutant levels in precipitation. The analytes determined included volatile organohalogen compounds, petroleum hydrocarbons, Na⁺, K⁺, NH₄⁺, Mg²⁺, Ca²⁺, F⁻, Cl⁻, NO₂⁻, NO₃⁻, PO₄³⁻, SO₄²⁻ ions, as well as organonitrogen, organophosphorus and organochlorine pesticides. In addition, the toxicity and pH of the samples were examined. The samples were collected over a period of six months, during or immediately following precipitation events. More than half of the samples (25) were found to be toxic, with inhibition exceeding 20%. The toxicity was weakly correlated to the levels of organonitrogen and organophosphorus pesticides in runoff waters. It was established that at least in some cases the roofing material affected the levels of the pollutants found in the samples.     

Geochemical stability of phosphorus solids below septic system infiltration beds

Review of 10 mature septic system plumes in Ontario, revealed that phosphorus (P) attenuation commonly occurred close to the infiltration pipes, resulting in discrete narrow intervals enriched in P by a factor of 2-4 (. MSc thesis, Dept. Earth Sci., University of Waterloo, Waterloo, Ont.; Ground Water 36 (1995) 1000; J. Contam. Hydrol. 33 (1998) 405). Although these attenuation reactions appeared to be sustainable under present conditions, the potential for remobilization of this P mass, should geochemical conditions change, is unknown. To test the stability of these P solids, dynamic flow column tests were carried out using sediments from three of the previously studied sites (Cambridge, Langton and Muskoka) focusing on sediments from the 'High-P' and underlying (Below) zones. Tests were continued for 166-266 pore volumes (PVs), during which time varying degrees of water saturation were maintained. During saturated flow conditions, relatively high concentrations of PO4 were eluted from the Cambridge and Langton High-P zones (up to 4 and 9 mg/l P, respectively), accompanied by elevated concentrations of Fe (up to 1.4 mg/l) and Mn (up to 4 mg/l) and lower values of Eh (<150 mV). The Below zones from Cambridge and Langton, however, maintained lower concentrations of P (generally<2 mg/l), Fe (<0.2 mg/l) and Mn (<1 mg/l) and maintained higher Eh (>250 mV) during saturated flow conditions. During unsaturated flow, P and Fe declined dramatically in the High-P zones (P<1 mg/l, Fe<0.2 mg/l), whereas concentrations remained about the same during saturated and unsaturated flow in the Below zones. This behavior is at least partly attributed to the development of reducing conditions during saturated flow in the High-P zones, leading to reductive dissolution of Fe (III)-P solids present in the sediments. Reducing conditions did not develop in the Below zones apparently because of lower sediment organic carbon (OC) contents (0.03-0.04 wt.%) compared to the High-P zones (0.2-0.65 wt.%). At the Muskoka site, where the sediments were noncalcareous, low values of P (<0.2 mg/l) were maintained in both the High-P and Below columns and reducing conditions did not develop. Results indicate the possibility of remobilizing P accumulated below septic system infiltration beds should conditions become more reducing. This could occur if sewage loading patterns change, for example when a seasonal use, lakeshore cottage is converted to a permanent dwelling.     

不同Ca/P比下碳酸根对磷酸钙沉淀反应回收磷的影响

以模拟污水处理厂污泥厌氧消化液为处理对象,进行磷酸钙沉淀除磷小试实验,考察了不同Ca/P物质的量比下碳酸根(CO2-3)对磷酸钙沉淀反应回收磷的影响;利用扫描电镜(SEM)、X射线衍射仪(XRD)和傅里叶变换红外光谱(FTIR)对沉淀产物进行表征。结果表明,磷酸钙沉淀反应是一个快速过程,CO2-3的存在并未改变这一显著特征。磷酸钙沉淀反应过程中,CO2-3的存在降低了磷的去除率,改变了沉淀物形貌、结构和组分;实验设定范围内,磷酸钙的过饱和度越高,越难形成晶体态羟基磷灰石((Ca5(PO4)3OH,HAP);当pH值为9.0,Ca/P比为1.67时,CO2-3取代HAP晶格中的PO3-4,形成碳磷灰石(CHAP);当pH值为9.0,Ca/P比为3.33和5.01时,CO2-3和PO3-4之间竞争,形成碳酸钙(CaCO3);增大Ca/P能有效提高磷的去除率,降低CO2-3对磷酸钙沉淀反应的抑制作用,但综合考虑实际效果,选择Ca/P比为3.33作为适宜的反应条件。     

pH dependence of persulfate activation by EDTA/Fe(III) for degradation of trichloroethylene

The ability of free ferrous ion activated persulfate (S₂O₈²⁻) to generate sulfate radicals (SO₄⁻) for the oxidation of trichloroethylene (TCE) is limited by the scavenging of SO₄⁻ with excess Fe²⁺ and a quick conversion of Fe²⁺ to Fe³⁺. This study investigated the applicability of ethylene-diamine-tetra-acetic acid (EDTA) chelated Fe³⁺ in activating persulfate for the destruction of TCE in aqueous phase under pH 3, 7 and 10. Fe³⁺ and EDTA alone did not appreciably degrade persulfate. The presence of TCE in the EDTA/Fe³⁺ activated persulfate system can induce faster persulfate and EDTA degradation due to iron recycling to activate persulfate under a higher pH condition. Increasing the pH leads to increases in pseudo-first-order-rate constants for TCE, S₂O₈²⁻ and EDTA degradations, and Cl generation. Accordingly, the experiments at pH 10 with different EDTA/Fe³⁺ molar ratios indicated that a 1/1 ratio resulted in a remarkably higher degradation rate at the early stage of reaction as compared to results by other ratios. Higher persulfate dosage under the EDTA/Fe³⁺ molar ratio of 1/1 resulted in greater TCE degradation rates. However, increases in persulfate concentration may also lead to an increase in the rate of persulfate consumption.     

微电解-Fenton深度处理制药废水影响因素与参数控制

采用铁炭微电解-Fenton联合工艺深度处理制药废水生化出水,探讨了初始pH、曝气量、反应时间等因素对微电解出水Fe2+和Fe3+变化规律、COD降解速率以及后续Fenton氧化效果的影响,为优化微电解-Fenton氧化联合工艺提出了微电解间歇加酸的理论。间歇加酸可提高微电解系统中COD降解速率和Fe2+含量,使后续Fenton氧化无需投加FeSO4·7H2O即可达到较好的COD去除效果。结果表明,当初始pH=2.5,曝气量为0.6 m3/h,间歇加酸30 min/次,微电解反应2 h,出水投加1 mL/L的H2O2进行Fenton氧化2 h,COD总去除率可达81.33%;间歇加酸30 min/次可将微电解反应2 h出水Fe2+浓度从50 mg/L提高至151 mg/L,COD降解速率从10.6 mg COD/(L·h)提高至22.2 mg COD/(L·h)。     

Fenton氧化法深度处理抗生素废水二级出水

采用Fenton氧化法对青霉素和土霉素混合废水二级处理出水进行深度处理,通过正交和单因素实验研究了废水初始反应pH值、H2O2投加量、Fe2+/H2O2摩尔比及反应时间等因素对废水处理效果的影响。实验结果表明,Fenton氧化法处理的最佳反应条件为:初始pH值4、H2O2(30%)投加量50 mL/L、Fe2+/H2O2摩尔比1/20和反应时间60 min,处理后出水COD小于120 mg/L,COD去除率在75%以上,急性毒性(HgCl2毒性当量)小于0.07 mg/L,满足《发酵类制药工业水污染物排放标准》(GB21903-2008)表2标准要求。     

The contribution of dry deposited ammonia and sulphur dioxide to the composition of precipitation from continuously open gauges

A series of experiments using bulk precipitation collectors of the type used in the UK precipitation chemistry network measured the amounts of NH₄⁺, SO₄²⁻ and other ions that could be washed from funnels (diameter 15 cm) exposed to a wide range of NH₃ and SO₂ concentrations over periods from hours to days. In dry conditions, the average deposition flux of NH₃ was between 50 and 120 nmol NH₄⁺ funnel⁻¹ d⁻¹ (0.1–0.3 kg N ha⁻¹ yr⁻¹), and was independent of the concentration of NH₃. Dry deposition of NH₃ to wet funnels at small NH₃ concentrations was almost 5 times that to dry funnels under the same conditions (average 240 nmol funnel⁻¹ d⁻¹; 0.7 kg ha⁻¹ yr⁻¹), and increased with increasing NH₃ concentrations. The amount of NH₄⁺ ions remaining on the funnel surface was inversely proportional to the vapour pressure deficit during the experiment. This result was interpreted as a dependence on the duration of surface wetness, with greater deposition of NH₄⁺ when evaporation rates of surface water were small.The amount of SO₂ deposited on funnel surfaces was closely related to the amount of NH₃ deposited, in both wet and dry conditions, but was not strongly correlated with the SO₂ concentration. At low NH₃ and SO₂ concentrations the average deposition to dry funnels was 70 nmol SO₄²⁻ funnel⁻¹ d⁻¹ (0.5 kg ha⁻¹ yr⁻¹), and to wet funnels was approximately 2.5 times larger. The results are interpreted in terms of the balance between the rate of evaporation of surface water, and the rate of oxidation of SO₂, which leads to the ‘fixing’ of NH₄⁺ ions on the surface as involatile salts.It is predicted that dry deposition of NH₃ to funnel surfaces across the UK Secondary Network could account for as much as one-half of the measured bulk wet deposition at sites where wet deposition of NH₄–N is small. The amount of dry deposition depends on how long and how often funnel surfaces are wetted by rain or dew, and on the air concentrations of NH₃. These predictions are based on funnels being wetted only once per day. More frequent wetting would increase the contribution from dry deposition, and the consequent overestimate of wet deposition of NH₄–N across the UK by using data obtained from bulk collectors. To some extent this overestimate may be offset by microbial degradation and loss of NH₄–N in weekly bulk precipitation samples during collection and storage.     

造纸白泥和粉煤灰的添加对污泥消化液中氮磷回收的影响

污泥厌氧消化液中含有丰富的氮磷,若直接排放到环境中,将会对附近水体造成严重污染。由于消化液中Mg^2＋和Ca^2＋的含量很低,严重影响了氮磷的回收效果。把造纸白泥和粉煤灰引入到污泥厌氧消化液氮磷的回收当中,可以明显地提升消化液pH和提高PO4^3-P和NH3-N回收率。实验结果表明：当造纸白泥添加量为4g／（L·h）时,曝气12h后,pH可达10．19,此时PO4^3-P和NH3-N回收率分别达到64％和45％;而当粉煤灰添加量为4g／（L·h）时,曝气12h后,pH达到9．63,PO4^3-P和NH3-N回收率分别为46％和41％。但仅用曝气方式处理,12h后,pH值仅为8．52,PO4^3-P和NH3-N回收率分别只有20％和18％。实验结果还表明,水力停留时间（HRT）越大,pH上升速度越快,幅度越大,氮磷的回收效果就越好。