ISSN:1061-4303    

DOI:10.1002/j.1554-7531.1996.tb00171.x

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Phosphate release and phosphate fixation during sludge treatment of waste activated sludge (WAS) was investigated with a pilot plant for enhanced biological phosphorus removal (EBPR), complemented by laboratory investigations of sludge samples from different large EBPR plants. The major part of the eliminated phosphorus in the pilot plant was due to the storage of polyphosphate (poly‐P) in the WAS and was accompanied by an uptake of magnesium and potassium. Thickening and stabilizing WAS from the EBPR pilot plant results in a hydrolysis of poly‐P which could be modeled with first‐order kinetics and the Arrhenius relationship for the temperature dependence of the reaction constant. As a result of poly‐P hydrolysis in stabilizing systems, phosphate, magnesium, and potassium are released, but only potassium remains in solution, whereas magnesium and a part of the released phosphate were precipitated as struvite. Another large fraction of the released phosphate was fixed by aluminium.

ISSN:1061-4303    

DOI:10.2175/106143096X127983

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Nitrite and free available chlorine (FAC) are reported to cause errors in total residual chlorine (TRC) measurements when following the Standard Methods back‐titration procedure with iodate titrant. Nitrite caused elevated TRC results when using either phenylarsine oxide or thiosulfate, which are the alternative reducing reagents specified in the procedure. FAC caused no error when phenylarsine oxide was used; however, TRC results were low when using thiosulfate. These errors are explained based on studies of the analysis chemistry, and method modifications are suggested for eliminating those errors. Thus, when using phenylarsine oxide, errors from nitrite were prevented by sulfamic acid, which was used to destroy nitrite. However, sulfamic acid could not be used with thiosulfate because the acidity of sulfamic acid induced a reaction between nitrite and thiosulfate. Errors from FAC are traced to an upset in the analysis reaction stoichiometry. With FAC present in samples, thiosulfate was not exclusively oxidized to tetrathionate. Instead, thiosulfate was partially converted to sulfate due to the strong oxidizing power of FAC. However, errors from FAC were eliminated by changing the order of reagent addition used in the analysis.

ISSN:1061-4303    

DOI:10.2175/106143096X127992

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

A potential alternative technology for wastewater treatment streams involves coprecipitation with colloidal iron hydroxide followed by aging at elevated temperatures and high pH to produce crystalline iron oxides. The resultant crystalline oxides, in addition to having reduced sludge volume, may chemically/physically incorporate metal ions and/or metalloid oxyanions. The increased stability of the crystalline solids may be advantageous in reducing the rate of release of the contaminants to groundwater. The rate of transformation of iron hydroxide model wastewater treatment solids contaminated with arsenate into crystalline products was measured at 60 and 70°C. The rate of transformation was found to be described by either a solid‐state reaction equation for powdered compacts or a zero‐order reaction controlled by desorption. X‐ray diffraction demonstrates that, after crystallization has occurred, no solid solutions involving iron oxides and arsenate are formed.

ISSN:1061-4303    

DOI:10.2175/106143096X128009

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Oxygen uptake at clarifier weirs was investigated for both clean water and primary wastewater. A pilot‐scale model with cross‐sectional geometry similar to clarifier weirs was constructed to carry out the study. The drop height, type of flow regime over the weir, hydraulic loading, and weir shape were identified as important parameters influencing mass transfer. Empirical correlations predicting oxygen uptake were developed for different weir configurations. A correlation using theα‐factor was developed to predict the oxygen transfer in primary wastewater using clean water. These correlations are a first step in estimating volatile organic compound emissions for wastewater flows over clarifiers at wastewater treatment plants.

ISSN:1061-4303    

DOI:10.2175/106143096X128018

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Abandoned mine pit lakes in Minnesota are being used for intensive aquaculture, and this has resulted in real and perceived water‐quality impacts. In current net pen aquaculture operations, metabolic wastes and uneaten food are dispersed into previously oligotrophic lakewater, resulting in increased levels of phosphorus and nitrogen, oxygen depletion, and increased deposition of organic matter. Conditions necessary for algal blooms have been infrequent due to light limitation from intensive artificial aeration and circulation. Highly emotional conflicts arose over the novel use of a few of these man‐made water bodies by an industry commonly perceived to be relatively “green” and heavily promoted by state and federal governments as a rapid growth industry. The combination of the industry's “newness” on the regulatory scene, coupled with the current regulatory push toward antidegradation of groundwater and regulation of agriculture, necessitated consideration of carcinogenesis, Alzheimer's disease, and antibiotic resistance transfer in addition to more conventional considerations, such as eutrophication and wildlife impacts.

ISSN:1061-4303    

DOI:10.2175/106143096X128027

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

The upstream branches of Newtown Creek, which receive major combined sewer overflow (CSO) discharges, exhibit stratification of salinity, anoxic conditions below the pycnocline, and emission of hydrogen sulfide (H2S) odors throughout the summer. As high sediment oxygen demand (SOD) levels were coincident with these upstream branches, the modeling approach focused on the mechanisms of solids settling, organic carbon flux, and sediment diagenesis for CSO as well as other sources of solids. Extensive field measurements of the CSOs and the water and sediments within Newtown Creek and the adjoining East River were performed to evaluate model parameters and calibrate/verify the models. Continuous simulations of a 4‐mon summer period for existing (baseline) conditions and CSO abatement alternatives projected the water‐quality improvements that could be expected in the Creek. Because of the extremely low dissolved oxygen (DO) in Newtown Creek, the response to CSO abatement is inhibited, as the model's reaction kinetics would indicate; however, measures that would relieve these conditions and increase DO would also enhance the change in DO achievable through CSO abatement.

ISSN:1061-4303    

DOI:10.2175/106143096X128090

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Organic contaminants in sediment were measured in samples collected from five stations in the Newport Submarine Canyon, Calif., and six nominal 60‐m shelf stations (1985–1991); the 60‐m stations included one at the terminus of an ocean outfall. Two hypotheses were tested: there is no increase in sediment contaminant concentration with water depth in Newport Canyon and there is no difference in contaminant concentration between the canyon and adjacent shelf. Based on analyses herein, hypothesis one was accepted and hypothesis two was rejected. Mean DDE, tDDT, and Aroclor 1254 were higher in the canyon (Station C2) and tPCB was higher at the ocean outfall (Station 0). The results presented here show that the canyon serves as a sediment trap for elevated concentrations of both trace metals and organic compounds.
Due to the highly seasonal nature of rainfall and surface runoff in southern California we anticipated finding quantitative seasonal patterns(e.g.,high concentrations during the wet season and low concentrations during the dry season). The present analyses do not support this trend. Remission of the 7‐yr drought with heavy rainfall from December 1992 through February 1993, and in January–March 1995, may provide the opportunity to document this relationship. Comparison of canyon data with other regional studies suggests multiple sources of contaminants (e.g.,Santa Ana River, Newport Bay, offshore dredge disposal, storm runoff, atmospheric fallout) rather than a single source (e.g.,ocean outfall).
Normalization of contaminant concentrations with TOC was done to compensate for grain size differences between the canyon and the shelf. In a few comparisons, TOC normalized data yielded different results than nonnormalized data. While normalization may become a conventional practice in sediment geochemistry, we urge further study of this practice before unreservedly applying it to develop state and federal guidelines of permissible sediment levels of sediment contaminants.

ISSN:1061-4303    

DOI:10.2175/106143096X128036

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Analyses of New York City municipal wastewaters were performed to determine the frequency of detection of organic priority pollutants (OPPs) and to identify which compounds commonly occur. Six sampling events, from 1989 to 1993, representing 168 samples and ∼19 000 analytical determinations, detected very few OPPs regularly in either influent or effluent. Identified OPPs included 41 of 112 possible OPPs, or 37 different compounds (14 volatiles, 13 semivolatiles, and 10 pesticides) detected at least once in influent waters and 32 compounds (12 volatiles, 11 semivolatiles, and 9 pesticides) detected at least once in effluent waters. The frequency of occurrence for the three analyte categories never exceeded 19% for influents or 15% for effluents. More commonly identified OPPs included five volatile compounds, one semivolatile compound, and one pesticide. With few exceptions, volatile and semivolatile concentrations were<100 μg/L, and pesticide concentrations were<0.2μg/L. Comparisons of effluent concentrations to most stringent standards (MSS) for receiving water showed five compounds to occasionally exceed MSS, with only a single volatile compound, tetrachloroethene, exceeding them with any regularity. This study adds to the limited literature on OPPs in the municipal waste stream, confirming the occurrence of most OPPs to be infrequent in water pollution control plants (WPCPs), and when present, to typically be at low concentrations.

ISSN:1061-4303    

DOI:10.2175/106143096X128108

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

The influent flow rate and substrate concentration normally vary with time in a municipal wastewater treatment plant (MWWTP). The treatment units must be operated dynamically to prevent the process from failing, reducing treatment efficiency, and creating a lack of stability. Using real time operation data to control the dynamic activated sludge process (DASP) systematically is an alternative approach to the expert system, which is based on experts' knowledge and/or operators' experiences and whose control rules are typically difficult to be derived by a systematic approach. The fuzzy control theory based on modified Newton's method can make real‐time control feasible and is adopted in this study. The theory is definitely a systematic approach toward deriving optimum control strategies on‐line. The optimum control strategies derived from the proposed approach are verified by experimental results that indicate that the forecast and control abilities of fuzzy model are sufficient. The proposed systematic approach only requires on‐line monitored data, not experts' knowledge and operators' experiences, to adequately control the complex system. This feature is possible despite the fact that the system information is not clearly described, the kinetic model and related parameters are unknown, or the dynamic behaviors of the process are not thoroughly understood. Moreover, a comparison is also made in this study of the results between F:M ratio and fuzzy control strategies. That comparison reveals that the F:M control might not be appropriate for DASP when municipal wastewater is treated. The fuzzy control strategies confirm that the operating concepts for DASP are similar to those for a steady‐state condition and can make the effluent quality better and more stable. The only difference between both systems is that time delay problems arise in DASP, but not in steady‐state ASP.

ISSN:1061-4303    

DOI:10.2175/106143096X128045

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY