Fate of Anionic Surfactants in a 38?ML/Day UASB-Based Municipal Wastewater Treatment Plant: Case Study

The outcome of a 15-month monitoring study (August 2004–October 2005) on the anionic surfactants (AS), at the 38?ML/day up-flow anaerobic sludge blanket (UASB)-based sewage treatment plant (STP) is described. The average removal of AS was only around 57%. Appreciable concentration of AS was being discharged to the watercourse (average 2.41?mg/L; range 0.63–5.16?mg/L). On an average dried sludge contained 1,560?mg?AS?kg?1 dry weight. Mass balance indicated that, AS load of the orders of 23 and 33% is removed by adsorption in UASB reactors and polishing ponds (PP), respectively. Biodegradation of AS under anaerobic conditions in UASB reactors and PP does not seem to take place. In the sludge stream, appreciable biodegradation ( ≈ 70%) of adsorbed AS under aerobic conditions on the sludge drying beds takes place. If influent AS mass flux is normalized to 100?units, than 43 and 7?units are discharged with treated effluent and dried sludge, respectively, whereas 33 and 16?units are adsorbed/settled in PP and aerobically biodegrade on sludge drying beds, respectively.     

Investigation of factors affecting pellet strength in straight grate induration machine

Abstract

During induration in a straight grate machine, the green pellets pass through four different thermal treatments, namely drying, preheating, heating and cooling. The pellet bed is fired with downdraught firing leading to thermal gradients through the bed. Corex sludge, which is used as fuel in the pellet mix, supplies the necessary energy for uniform heating of the pellet. The physicochemical conditions, e.g. the temperature and oxygen partial pressure mainly depend on the amount of fuel incorporated in the pellet mix. As a result the percentage and the distribution of various phases in the pellets vary, leading to deviation in quality. To study the distribution of phases and their impact on cold crushing strength at different carbon levels (1·20 and 1·35%), pellets from different layers of the induration bed in an industrial straight grate were characterised. It was observed that the strength of the pellets varied from 142 to 268 kg/pellet and 128 to 245 kg/pellet across bed, with carbon 1·20 and 1·35% respectively. It was found that middle layer pellets had higher strength compared to top and bottom layers. It was observed that amount of hematite, magnetite, porosity and the pore size plays a significant role on the pellet strength. Pellets with 1·20% carbon showed better physical and microstructural properties across the pellet bed compared to pellets with 1·35% carbon.     

Probability of Aluminum Toxicity from Bhandup Complex Water Treatment Plant, Mumbai: Case Study

Bhandup Complex water treatment plant located in Mumbai, India, supplies water to most of Mumbai. The plant receives raw water from Vehar Lake. Alum has been used as a coagulant in the treatment process for the past 27?years. The backwashed water from the plant is released into Vehar Lake, which carries a significant amount of suspended matter. Therefore, a layer of sludge was deposited on the meeting point of backwashed water and Vehar Lake. The status of aluminum (Al) concentration in sludge deposits, banks, water, and sediment samples of Vehar Lake and its comparison with Al concentration of soil in the area surrounding the plant is presented in this paper. The comparison showed that the surrounding soil samples had the least Al concentration (16,394–26,081??mg/kg), whereas the highest values of 53,882–73,382??mg/kg and 62,096–76,496??mg/kg were reported in upper and lower layers of sludge, respectively. This paper also discusses the detrimental effect of Al when it is available in toxic form at acidic pH.     

Dopexamine hydrochloride in septic shock: effects on oxygen delivery and oxygenation of gut, liver, and muscle

It has been suggested that septic shock is a disorder of microvascular autoregulation. Tissue blood flow is modulated by the state of activation of upstream endothelial receptors controlling the vascular smooth muscle tone. Because vascular receptor populations vary between organs, it should be expected that vasoactive drugs affect tissue oxygenation differently in different organs. We studied the effects of dopexamine HCl (a novel inotrope) and septic shock on oxygen delivery as well as tissue Po2 in gut, liver, and skeletal muscle in anesthetized rabbits. Employing the thermodilution technique, cardiac output was measured across the pulmonary bed and used to calculate oxygen delivery. Three eight-channel Mehrdraht Dortmund Oberfl?che oxygen electrodes were placed on gut serosa, liver, and skeletal muscle surfaces, respectively, and sufficient readings were obtained to calculate tissue Po2 distributions. During septic shock mean arterial pressure, cardiac output, oxygen delivery, and mean tissue Po2 decreased in all organs. Our results suggest that the observed changes in tissue oxygenation during septic shock were caused by defective regulation of microvascular blood flow. In conclusion, during baseline conditions dopexamine HCl caused no statistically significant changes in tissue oxygenation in any organ, except in skeletal muscle at 10 micrograms/kg/min when tissue Po2 increased. During septic shock, however, dopexamine HCl improved oxygenation in all three organs in a dose-dependent manner.     

Anaerobic Thermophilic/Mesophilic Dual-Stage Sludge Treatment

Conventional anaerobic mesophilic (AnM) digestion coupled with anaerobic thermophilic (AnT) pretreatment (AnTAnM system) and anaerobic thermophilic posttreatment (AnMAnT system) of mixed sludge (thickened waste activated sludge and primary sludge) was investigated. The main objectives were to investigate the ability of AnTAnM and AnMAnT systems to produce a product sludge that can meet Class A sludge requirements and to enhance sludge treatment in terms of volatile solids (VS) destruction, gas production, sludge supernatant chemical oxygen demand (COD) reduction, and sludge dewaterability. Lab-scale AnTAnM and AnMAnT systems were operated at a system sludge residence time of 15 days and temperature of 62°C in AnTAnM and AnMAnT thermophilic reactors. A lab-scale control anaerobic digester was operated at a system sludge residence time of 15 days and temperature of 37°C. The AnTAnM and AnMAnT systems and control achieved VS reductions of >38% (Class A sludge vector attraction reduction requirement). Average VS reductions by the AnTAnM (61%) and AnMAnT (63%) systems were significantly higher than VS reduction by the control (50%). The fecal coliform densities in the AnTAnM and AnMAnT system product sludges were below 1,000 most probable number (MPN) per gram total solids (TS) (Class A sludge fecal coliform density limit) compared to 106 MPN∕g TS in the control product sludge. The product sludge from the AnTAnM and AnMAnT systems and the control anaerobic digester met the Class A sludge Salmonella density limit (<3 MPN∕4 g TS) when fed with feed sludge containing 2–12 MPN∕g TS. Average methane production by the AnTAnM mesophilic digester (0.66 ± 0.10 m3∕kg VS destroyed) was higher than those of the AnMAnT (0.51 ± 0.06 m3∕kg VS destroyed) and the control anaerobic mesophilic digesters (0.52 ± 0.03 m3∕kg VS destroyed). The average supernatant CODs in the AnTAnM system product sludge (10,500 ± 200 mg∕L) and AnMAnT system product sludge (10,200 ± 150 mg∕L) were approximately the same and were significantly lower than the supernatant COD in the control anaerobic digester (14,100 ± 350 mg∕L). All three systems were fed with feed sludge containing an average supernatant COD of 22,500 mg∕L. Dewaterability of the product sludges, measured as time to filter, was 244 and 207 s for AnTAnM and AnMAnT systems, respectively, whereas it was 364 s for the control anaerobic digester product sludge.     

Enhancement of Denitrification in Upflow Sludge Bed Reactors with Sludge Wasting

From the performance data of the upflow sludge bed (USB) reactors (with sufficient carbon), the rate-limiting step in denitrification is nitrate reduction. Biological denitrification in the USB reactors (superficial velocity=0.5, 1.0, 2.0, and 4.0 m/h) can be greatly enhanced with sludge wasting from the bioreactor [i.e., maintain granular sludge retention time (GSRT) at 20 days], including high volumetric loading rates of up to 6.61 g NO3?–N/L day, high specific denitrification rates [arithmetic mean=0.31–0.42 g NO3?–N/g volatile suspended solids (VSS) day], high denitrification efficiencies (97.6–97.8%), and relatively low washout rates of biomass granules (arithmetic mean ω?=0.13–0.31 g VSS/L day). The biomass concentration, average granule size (dp), and microbial density of the USB reactors with sludge wasting were greater than those of the USB reactors without sludge wasting (i.e., the former grew more compact granules than the latter). From the granulation experiment, the granule size distribution and dp of the broken-up granules in the sludge-bed zone can restore to those of the original granules in one GSRT, implying that spontaneous flocculation of extra-cellular polymer of denitrifying-bacteria cells occurred in the USB reactor, which may also be accelerated by a rigorous backing-mixing effect of continuous production of biogas. Accordingly, the USB reactor with sludge wasting can be regarded as a promising alternative to treat high-strength nitrate wastewater.     

UASB Treatment of Tapioca Starch Wastewater

Feasibility of the upflow anaerobic sludge blanket (UASB) process was investigated for the treatment of tapioca starch industry wastewater. After removal of suspended solids by simple gravity settling, starch wastewater was used as a feed. Start-up of a 21.5-L reactor with diluted feed of approximately 3,000 mg∕L chemical oxygen demand (COD) was accomplished in about 6 weeks using seed sludge from an anaerobic pond treating tapioca starch wastewater. By the end of the start-up period, gas productivity of 4–5 m3/m3r?day was obtained. Undiluted supernatant wastewater with a COD concentration of 12,000–24,000 mg∕L was fed during steady-state reactor operation at an organic loading rate of 10–16 kg COD/m3r?day. The upflow velocity was maintained at 0.5 m∕h with a recirculation ratio of 4:1. COD conversion efficiencies >95% and gas productivity of 5–8 m3/m3r?day were obtained. These results indicated that removal of starch solids from wastewater by simple gravity settling was sufficient to obtain satisfactory performance of the UASB process.     

热解-金汞齐捕集-原子吸收光谱法测定土壤和沉积物中汞的影响因素及适用性讨论

对热解-金汞齐捕集-原子吸收光谱法测定土壤和沉积物中汞的影响因素进行了讨论,并选取12个含量范围为14～1 700 ng/g的土壤和沉积物标准物质验证了实验方法的适用性;同时对进样量、镍舟的维护、记忆效应的消除等给出了参考建议。正交试验表明:分解温度是主要影响因素,调试仪器应优先设定分解温度;最佳仪器条件为干燥温度250 ℃、干燥时间20 s、分解温度800 ℃和分解时间180 s。验证试验表明:当土壤或沉积物中汞含量大于30 ng/g时,实验方法测定结果的相对误差和相对标准偏差(RSD, n=6)均不大于21.4%和4.3%,满足HJ/T 166-2004《土壤环境监测技术规范》的要求。采用实验方法对冶炼企业周边农田土壤、某水库沉积底泥、某污水场处理污泥中的汞进行测定,测得结果在85.7～9.06×10³ ng/g之间,RSD(n=6)不大于4.4%。     

Empirical Model and Kinetic Behavior of Thermophilic Composting of Vegetable Waste

Laboratory-scale temperature-controlled reactors were used to generate experimental data of thermophilic composting of vegetable waste. By fitting in experimental data of thermophilic composting, the obtained empirical model (also verified by F-test) appeared to be a quadratic form. The empirical model can be used to predict operating conditions (ratio of predried vegetable waste to rice husks, aeration rate, and reaction temperature and time) for thermophilic composting of vegetable waste in the subtropical region. Moreover, an innovative method for investigating kinetic behavior of thermophilic composting (an exoenzyme-catalyzed reaction followed by a multienzyme-catalyzed reaction) is proposed. The two biochemical reactions of thermophilic composting of vegetable waste followed Monod-type kinetics with the specific substrate utilization rate constants k1 and k2 of 0.026 and 4.5 mg COD∕mg VSS∕day, respectively. Accordingly, the exoenzyme-catalyzed reaction kinetically controls the overall process of thermophilic composting of vegetable waste.     

Effect of Carbon Source on PCE Dehalogenation

A laboratory study using the upflow anaerobic sludge blanket reactor for treating high-strength wastewater containing tetrachloroethene (PCE) was carried out to study the effect of carbon source, recycle, and shock loading on dehalogenation of PCE and process performance. The PCE was dehalogenated to trichloroethylene, cis-1,2-dichloroethylene, vinyl chloride, and ethylene. During the study on the effect of carbon source, the PCE and COD removal up to 97% and biogas production of 0.518–0.47 m3∕kg CODrem with methane content up to 66% were achieved under steady-state operating conditions. An increase in the influent COD from 2,000 to 4,000 mg∕L did not show any improvement in the PCE removal. Recycling of effluent at 50% showed the decrease in COD removal and increase in the effluent concentration of dichloroethylene and vinyl chlorides. Around 1–3.5% of influent PCE stripping to biogas was observed. It was observed that methanol has the stimulatory effect on the dehalogenation of PCE. A shock loading study showed that the upflow anaerobic sludge blanket reactor could assimilate 1.5–2 times the original PCE concentration (50 mg∕L) without much effect on the process performance.     

Biodegradation of Mixtures of Phenolic Compounds in an Upward-Flow Anaerobic Sludge Blanket Reactor

The anaerobic biodegradability of mixtures of phenolic compounds was studied under continuous and batch systems. Continuous experiments were carried out in up-flow anaerobic sludge bed (UASB) reactors degrading a mixture of phenol and p-cresol as the main carbon and energy sources. The total chemical oxygen demand (COD) removal above 90% was achieved even at organic loading rates as high as 7 kg COD/m3/day. Batch experiments were conducted with mixtures of phenolic compounds (phenol, p-cresol, and o-cresol) to determine the specific biodegradation rates using unadapted and adapted anaerobic granular sludge. Phenol and p-cresol were mineralized by adapted sludge with rates several orders of magnitude higher than unadapted sludge. Additionally, an UASB reactor was operated with the mixture phenol, p-cresol, and o-cresol. After 54 days of operation, 80% of o-cresol (supplied at 132 mg/L) was eliminated. The phenol biodegradation was not affected by the presence of o-cresol. These results demonstrate that major phenolic components in petrochemical effluents can be biodegraded simultaneously during anaerobic treatment.     

不锈钢酸洗污泥微波场中升温特性的研究

本文就酸洗污泥微波场中的升温特性进行了系统研究,旨在为探求酸洗污泥微波辐射深度脱水新工艺提供理论依据.结果表明,酸洗污泥干泥在微波场中的升温特性为先缓慢升温至拐点温度后开始快速升温;酸洗污泥湿泥在微波场中的升温特性为先快速升温至110℃左右后开始缓慢升温,直至水分蒸发完才出现拐点温度并开始快速升温.     

EDTA, NTA, Alkylphenol Ethoxylate and DOC Attenuation during Soil Aquifer Treatment

Removals of dissolved organic carbon (DOC), ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and carboxylated alkylphenol polyethoxylate metabolites (APECs) were studied at the Sweetwater (Tucson, Ariz.) soil aquifer treatment site that treated chlorinated secondary effluent. The site was operated in a first phase by flooding irregularly for weeks interrupted by days of drying and in a second phase by a regular schedule of flooding for 3 days and drying for 4 days. The average hydraulic loading rates were 0.13 and 0.17?m/day in the first and second phases, respectively. During drying, oxygen intruded at least 3?m deep into the unsaturated subsurface causing nitrification of the ammonium that was retained in the top layer during flooding. Nitrification increased nitrate concentrations to >200?mg/L but most was removed to <10?mg/L during transport to 38?m depth. At 38?m depth, removals of DOC, EDTA, NTA, and APECs during the first phase were 85, 80, 90, and 98%, slightly higher (<7%) than during the second phase. Most of the DOC removal occurred during transport to 3?m and most of the trace organics removal occurred during transport from 3 to 38?m depth.     

磁铁矿石球团的干燥过程解析

对磁铁矿石球团进行了单球干燥实验，结果表明：球团的干燥过程包括很短的恒速段与较长的降速段。把屋脊形斜面上球团的干燥按物料移动型穿流式干燥处理。对球团的干燥过程解析得到：影响球团干燥过程的主要因素有干燥床面积，球团料层厚度，球团初始含水量，干燥气的温度，流量等。     

Pilot Plant Study of Simultaneous Sewage Sludge Digestion and Metal Leaching

This research is related to a preindustrial pilot scale study of the performance of the simultaneous sewage sludge digestion and metal leaching (SSDML) process for decontamination and stabilization of sewage sludge. Ten batch tests were carried out in two 4?m3 bioreactors under various conditions of operation. Results indicated that the addition of 1.0 to 1.5?g?S0/L, which is the equivalent of approximately 30 to 50?kg?S0 per tons dry sludge, is sufficient to obtain conditions of acidity (pH<2.5) and oxido-reduction potential greater than 500 mV necessary for an effective solubilization of toxic metals. The final average of metal solubilization in the output sludge during the SSDML process varied in the following ranges: 25–78% Cd, 9–32% Cr, 48–100% Cu, 77–99% Mn, 15–53% Ni, 12–47% Pb, and 66–100% Zn. The N, P, and K contents were also preserved in the decontaminated sludge. Moreover, the use of low concentrations of elemental sulfur makes it possible to obtain decontaminated sludge with a low total sulfur content (1.4–1.5% S) compatible with agricultural use. The suspended solids removal calculated for the SSDML process was slightly lower, (2.5±0.4)% volatile suspended solids per day, than those reached using standard aerobic digestion. Finally, the SSDML process was found to be effective in removing bad odors and in the destruction (99–100%) of indicator bacteria.     

Removal of Arsenic from Ground Water by Manganese Dioxide–Coated Sand

In a laboratory study, manganese dioxide–coated sand (MDCS), prepared by reacting potassium permanganate with manganese chloride under an alkaline condition and in the presence of sand, showed promise as a medium for use in small systems or home-treatment units in developing areas of the world, for removing arsenic(III) and arsenic(V) from ground water. In ten cycles of downflow column tests [bed depth 400 mm; empty-bed contact time 74 min; influent arsenic 0.5 mg As∕L of arsenic(III) and 0.5 mg As∕L of arsenic(V)], breakthrough bed volumes at the World Health Organization guideline value of 0.01 mg As∕L for arsenic in drinking water were in the range of 153–185 per cycle. During regeneration (backwashing with 2 L of a 0.2 N sodium hydroxide solution), 85.0% of the removed arsenic was recovered in the first cycle, and 94.6–98.3% was recovered in subsequent cycles. A low-cost, simple home arsenic removal unit, containing 6 kg (4 L) of the MDCS medium and operated at 6 L∕h, produced 740 and 700 L of water in two cycles of runs when the influent arsenic concentration was 0.5 mg As∕L of arsenic(III) and 0.5 mg As∕L of arsenic(V). No arsenic(III) or leaching of manganese from the medium was detected in the effluent. A detailed study addressing the effects of some important factors (water pH, concentration and type of competing anions, and cations) on the process is needed. The home arsenic removal unit should be subjected to field trials to assess the long-term effects on performance.     

Temperature and SRT Effects on Aerobic Thermophilic Sludge Treatment

Laboratory-scale experiments were conducted to determine optimum sludge residence time (SRT) and temperature of aerobic thermophilic pretreatment (ATP) of mixed sludge (thickened waste activated sludge and primary sludge) to achieve maximum pathogen reduction and best process performance. 4-L laboratory-scale ATP reactors were operated at SRTs of 0.6, 1.0, and 1.5 days and temperatures of 55, 58, 62, and 65°C. ATP at temperatures ≥62°C and SRT ≥0.6 day reduced the feed sludge fecal coliform density from 107 MPN∕g total solids (TS) to <104 MPN∕g TS. Salmonella in the feed sludge was reduced to <1 MPN∕4 g TS from 2 to 18 MPN∕4 g TS by ATP at temperatures ≥55°C and SRT ≥0.6 day. ATP was able to increase sludge volatile acids concentration by 100–200% over the feed sludge volatile acid concentration and to reduce sludge supernatant chemical oxygen demand from 20,000 to 22,000 mg∕L in the feed to 13,000–17,000 mg∕L in the ATP reactor. Volatile solids reduction by ATP increased from 25 to 40% when SRT was increased from 0.6 to 1.5 days, and a 5% increase in volatile solids reduction was seen at SRTs of 0.6, 1.0, and 1.5 days when ATP temperature was increased from 55 to 65°C.     

Treatment of MTBE-Contaminated Water in Fluidized Bed Bioreactor

Methyl tertiary-butyl ether (MTBE) biodegradation was evaluated in a laboratory-scale granular activated carbon (GAC)-based fluidized bed bioreactor system. The reactor was operated in seven distinct phases during which the MTBE loading rate, hydraulic retention time, cocontaminant loading [butyl, toluene, ethylbenzene, and xylene (BTEX) and tertiary-butyl alcohol (TBA)] and temperature were varied. The reactor was able to treat MTBE to less than 20 ug/L at 25°C and total organic carbon (TOC) loading rates between 0.01 and 1.1 kg/m3 of expanded GAC bed per day (kg/m3?day). Net biomass yield in the reactor under high loading conditions was approximately 0.55 g of total suspended solids (TSS) per gram of TOC consumed. This high yield under the higher loading rates necessitated that biomass be removed from the reactor to control bed expansion. At a loading rate of 1.5 kg/m3?day, MTBE effluents exceeded 20 ug/L. Reactor performance decreased as the reactor temperature was reduced from 25 to 15°C, but even at the lower temperatures MTBE removal efficiency exceeded 99%. Methyl tertiary-butyl ether treatment efficiency was not affected by the addition of TBA or BTEX under the conditions evaluated. Results of this study demonstrate that fluid bed bioreactors inoculated with an appropriate microbial culture can efficiently treat MTBE-contaminated water.     

Increased plasma endothelin-1 concentrations in E. coli septic peritonitis rats with diabetes mellitus

To study the diabetic mellitus (DM) patient's reaction to sepsis, we investigated the survival rate, the bacteremia, plasma endotoxin and plasma endothelin-1 levels in E. coli septic peritonitis rats with or without streptozotocin-induced DM. No significant difference could be detected between the DM and nondiabetic rats in the survival rate, the bacteremia level or the plasma endotoxin level. The DM rat manifested a significant increase compared to the nondiabetic rat in the plasma endothelin-1 level four hours after the outbreak of peritonitis. Endothelin-1 may thus play some role in the E. coli septic peritonitis rat with DM.     

Value of single oral loading dose of propafenone in converting recent-onset atrial fibrillation. Results of a randomized, double-blind, controlled study

OBJECTIVE: To assess the effects of dobutamine at a rate of 5 micrograms/kg/min on hemodynamics and gastric intramucosal acidosis in patients with hyperdynamic septic shock treated with epinephrine. DESIGN: A prospective, interventional, clinical trial. SETTING: An adult, 16-bed medical/surgical intensive care unit of a university hospital. PATIENTS: Twenty septic shock patients with a mean arterial pressure of > 75 mm Hg and a cardiac index of > 3.5 L/min/m2. INTERVENTIONS: After baseline measurements (H0), each patient received dobutamine at a rate of 5 micrograms/kg/min. Baseline measurements included: hemodynamic parameters, tonometric parameters, arterial and mixed venous gases, and arterial lactate concentrations. These measurements were repeated after 1 (H1), 2 (H2), and 3 (H3) hrs. After H2 measurements, dobutamine was stopped. The patients were separated into two groups according to their PCO2 gap (tonometer PCO2-PaCO2). The increased PCO2 gap group was defined by a PCO2 gap > 8 torr (> 1.1 kPa) (n = 13), and the normal PCO2 gap group by a PCO2 gap < or = 8 torr (< or = 1.1 kPa)(n = 7). MEASUREMENTS AND MAIN RESULTS: Dobutamine at 5 micrograms/kg/min had no significant effects on mean arterial pressure, heart rate, cardiac index, systemic vascular resistance, oxygen delivery, and oxygen consumption in epinephrine-treated septic shock. No patients developed arrhythmia or electrocardiographic signs of myocardial ischemia. During dobutamine infusion, arterial lactate concentration decreased from 5.1 +/- 0.4 in the increased PCO2 gap group and 4.2 +/- 0.4 in the normal PCO2 gap group to 3.9 +/- 0.3 and 3.5 +/- 0.3 mmol/L, respectively (p < .01). The PCO2 gap decreased and gastric intramucosal pH increased in the increased PCO2 gap group from 12 +/- 0.8 (1.6 +/- 0.1 kPa) to 3.5 +/- 0.8 torr (0.5 +/- 0.1 kPa) (p < .01) and from 7.11 +/- 0.03 to 7.18 +/- 0.02 (p < .01), respectively, and did not change in the normal PCO2 gap group. After stopping dobutamine infusion, the PCO2 gap and intramucosal pH returned to baseline values in the increased PCO2 gap group. CONCLUSION: The addition of 5 micrograms/kg/min of dobutamine added to epinephrine in hyperdynamic septic shock selectively improved the adequacy of gastric mucosal perfusion without modification in systemic hemodynamics.