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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

An iron-facilitated chemical and biological process for phosphorus removal and recovery during wastewater treatment

Zhao, Kang, 趙鈧 January 2013 (has links)
Phosphorus (P) is an important pollutant of concern in wastewater that causes eutrophication and algal blooms in water body. On the other hand, P is a valuable natural resource for agricultural and industrial use. With the rapid depletion of mineral phosphorus on earth, there is a need to recover phosphorus from wastewater. In this study, a new chemical and biological process facilitated with iron dosing has been developed for P removal and recovery during wastewater treatment. The system consists of a main stream identical to the conventional activated sludge process in an aerobic sequencing batch reactor (SBR) for P removal and a side stream of sludge recirculation through an anaerobic SBR (AnSBR) for P release and recovery from the P-rich sludge. In the aerobic SBR treating a synthetic domestic wastewater, Fe(III) (FeCl3) was dosed to remove P by precipitation and adsorption. Fe(III) dosing at a Fe/P molar ratio of 1.5:1 could reduce the P concentration from more than 10 mg/L to below 1 mg/L in the final effluent. Compared to other dosing periods, dosing Fe(III) right before the SBR settling could achieve the best result in sludge flocculation and P removal. Meanwhile, organic removal was well maintained as 90% of the chemical oxygen demand (COD) was degraded in the aerobic SBR. In the AnSBR, phosphate precipitated with ferric iron in the sludge was released owing to microbial Fe(III) reduction, and a positive correlation was found between the phosphate and ferrous iron concentrations in the sludge suspension. Chemical tests showed that significant P release from Fe(III)-P occurred only if the acidic condition and the reducing condition were combined. For the AnSBR sludge, a higher organic loading, lower pH and higher biomass concentration resulted in a higher level of Fe(III) reduction and P release. Organic acidogenesis prevailed in the reactor and lowered the pH to ~4.5, which facilitated the P release from the solid phase into the liquid phase. With a solids retention time (SRT) of 10 days, the anaerobic supernatant contained a phosphate concentration of up to 70 mg/L, while the settled sludge was returned to the aerobic SBR. The phosphate could be readily recovered from the supernatant with Fe-induced precipitation by aeration and pH adjustment, and the overall P recovery could be achieved at about 70%. In addition to the treatment performance, the speciation of P in the aerobic sludge and the anaerobic sludge also was investigated. A significant change in the immediately available P and the redox-sensitive P was found in the sludge through the aerobic-anaerobic cycle. Such chemical transformation is believed to be crucial to the P removal and recovery during the wastewater treatment process. / published_or_final_version / Civil Engineering / Master / Master of Philosophy
2

An experimental investigation of the effect of phosphorus on separate sludge digestion

Walton, Graham, January 1937 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1937. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 49).
3

Tapered aeration of activated sludge sewage mixtures

Rohlich, G. A. January 1937 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1937. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 54-55)
4

Experimental investigation of the effect of concentration of floc on oxygen utilization by activated sludge

Fluck, William Z. January 1937 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1937. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 45-47).
5

Treatment and disposal of secondary sewage effluent through snowmaking

Zapf-Gilje, Reidar January 1985 (has links)
When secondary sewage effluent is converted to snow, the nutrients and residual organics become concentrated in the early meltwater discharge through melt-freeze processes within the snow-pack. The early season melt comes off relatively slowly. Providing the soil can absorb the early melt, the bulk of the nutrients will be removed even if later season melt rates exceeds the soil's infil-trability. This could provide an inexpensive method for nutrient removal from secondary sewage effluents. Laboratory experiments showed that the degree of impurity concentration was largely independent of the number of diurnal melt-freeze cycles, snow depth, snow temperature and initial concentration of impurity in the snow. As a result, the removal of impurities from a snowpack can be expressed in terms of the cumulative melt discharge. A simple exponential decay process was found to describe the impurity removal well for most cases. The first 20% of the melt removed, on the average, 65% of the phosphorus and 86% of the nitrogen from snow made from sewage effluent; and 92% of the potassium chloride from snow made from potassium chloride solution. Stripping of ammonia during snow production and melting increased the overall nitrogen removal to about 90%. A field investigation of salt movement through a natural snowpack confirmed the laboratory results. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate
6

Use of genetic algorithms in bounded search for design of biological nitrification/denitrification waste treatment systems

Palazolo, Paul Joseph 05 1900 (has links)
No description available.
7

Preparation and laboratory evaluation of stationary-phase iron-oxide-based adsorbents for removal of metals from waste waters

May, Michael Lee 28 October 1998 (has links)
Several potential sorbent materials containing iron oxides were prepared and evaluated for potential to remove divalent metals from waste waters. These included a ferrihydrite-coated sand, maghemite incorporated in Dowex[Trademark] ion exchange resin, gothite and two thermally activated ferrihydrites. Attempts to prepare sorbents from steel shot by coating with ferrihydrite or by thermal oxidization resulted in cemented solids rather than pellets. Ferrihydrite activated at 295��C had a surface area of 113-202 m��/g, followed by gothite at 72-92 m��/g and ferrihydrite-coated sand at 0.78-1.4 m��/g. Zinc adsorption was evaluated by placing 5 g ferrihydrite-coated sand, 0.1 g maghemite in Dowex or 0.1 g gothite in batch reactors containing 40-50 mL of zinc solution, adjusting to various pH values, allowing to react for 96 hours, and analyzing the supernatant for zinc. The data fitted poorly to an ion exchange model using nonlinear regression. The adsorption site densities determined from the regression analysis were 8.0x10������ moles per gram of ferrihydrite-coated sand and 4.1x10������ moles per gram of White. Maghemite in Dowex did not provide any additonal zinc removal capacity in excess of the ion exchange capacity of the resin. Kinetic experiments showed that zinc adsorption onto ferrihydrite-coated sand was 86% complete after 96 hours. Based upon this study, the most promising sorbent appears to be gothite, although the "activated ferrihydrites" are also worthy of further study. Neither ferrihydrite-coated sand and maghemite in Dowex appear to be practical sorbents, based on their low zinc adsorption site density. Maghemite in Dowex might be useful in applications requiring magnetic sorbents. / Graduation date: 1999
8

CONTINUOUS LOADING OF COMPLETELY MIXED, HIGH-RATE ANAEROBIC DIGESTERS

Dea, Stanley Jepong, 1939- January 1966 (has links)
No description available.
9

Oxygenation in column reactor sewage treatment

Neleigh, James Edward, 1945- January 1973 (has links)
No description available.
10

Soil and grass filtration of domestic sewage effluent for the removal of trace elements.

Lehman, Gordon Stanley,1935- January 1968 (has links)
Soil and grass filtration of a domestic sewage effluent for trace element removal was investigated by applying oxidation-pond-treated waste water to twelve 2.44-meter-long, 30.5-cm-diameter, lysimeter columns and to a half-acre plot planted to common bermudagrass. Bermudagrass was also planted on the soil columns to aid in the removal of accumulated metals, thus prolonging the filtering capacity of the soil system. Four irrigation patterns, continuous flooding, alternate day flooding, one day wet-three days dry cycles and two days wet-five days dry cycles, were employed during the eleven week lysimeter test. Water samples were extracted from the soil columns at eight sampling depths to determine the soil depth at which the various trace metals were removed from the filtrate by the processes of adsorption, absorption and biological assimilation. Atomic absorption spectrophotometric techniques were used to determine the concentrations of iron, manganese, hexavalent chromium, nickel, copper, zinc, lead, cadmium, cobalt and strontium in the applied effluent, filtrate, soil and grass clippings. Filtrate samples for trace metal analysis were also extracted at shallow depths and from two groundwater zones at 9.1 and 15.2 meters depth under the grass plot. In the lysimeter study, iron, manganese, nickel, copper, zinc, lead and cadmium were removed from the filtrate at, or near, the soil surface. Some copper, zinc and cobalt were found in the deeper filtrate samples during periods of high infiltration rates and in the presence of anaerobic conditions. Smaller amounts of manganese, nickel and lead were also found at the deeper sampling points. Strontium was not removed from the water percolating through the calcareous soil employed in this study. Chromium and cobalt were not present in measurable quantities in the applied effluent. Iron and manganese were removed from the soil system in the grass clippings in the greatest amounts. Traces of copper, zinc and cadmium were also detected in the grass clippings. Larger quantities of iron, manganese and copper were detected in the filtrate at the grass plot than at comparable depths of the lysimeter columns, probably due to effluent applications at the grass plot over a period of two years. Lower quantities of nickel and lead in the filtrate at the grass plot were attributed to leaching by effluent during grass filtration tests, prior to the trace metal experiments. The concentrations of trace metals in the filtrate at the bottom of the lysimeter columns and in the groundwater zones at the grass plot were irsignificant by United States Public Health Service drinking water standards (1962) and would meet most other water supply requirements. The total nitrogen and nitrate contents were successfully reduced when a combination of aerobic and anaerobic environments were present in the soil system. Total nitrogen and nitrate levels were not reduced by grass filtration through 304.8 meters of dense grass. Fewer total coliform organisms were detected in the aerobic lysimeter columns than in the continuously flooded columns. The majority of coliform organisms detected in the filtrate at the 61 cm depth were believed to be of non-fecal origin. The chemical oxygen demand of the applied effluent was reduced to as low as 105 mg/L by grass filtration. A substantial portion of the remaining COD was attributed to high algal concentrations. The most effective treatment employed in this study was the one day wet-three days dry irrigation cycles. This treatment provided the necessary aerobic environment for trace metal removal from the effluent, nitrification of reduced nitrogen compounds and coliform organism elimination. The flooding period provided the anaerobic conditions required for denitrification losses of nitrate.

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