ISSN:1061-4303    

DOI:10.2175/WER.65.2.1

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
Upflow anaerobic filters fed acetate and propionate, and completely mixed, suspended growth reactors fed acetate, propionate, lactate, and glucose were used to investigate the effect of electron donor and reactor type on the interaction between sulfate‐reducing bacteria (SRB) and methanogens. Organic loading rates of 0.25–0.50 g chemical oxygen demand (COD)/L · d were used in suspended growth systems and 1.0–5.0 g COD/L · d in filters. COD/sulfur ratios ranged from 20/1 to 2/1 for completely mixed reactors, and 20/1 to 8/1 for anaerobic filters. Results indicated that organisms involved in the conversion of lactate and glucose into simpler products were not affected by sulfide toxicity. Levels of 60–75 mg sulfur/L of hydrogen sulfide and 150–200 mg/L of dissolved sulfide (DS) caused stress in all suspended growth reactors; 100–150 mg sulfur/L of hydrogen sulfide and 200–400 mg DS/L could be tolerated in lactate and glucose systems, although with diminished COD and sulfate removal. For similar loading conditions, lactate and glucose systems had higher DS levels than acetate and propionate systems. A cyclic pattern of variation of DS and hydrogen sulfide with volatile‐acids COD (VACOD) was observed in long‐term experiments with suspended growth reactors. Anaerobic filters were able to tolerate higher DS and hydrogen sulfide levels than suspended growth reactors. A propionate‐fed filter could withstand more than 150 mg hydrogen sulfide/L of hydrogen sulfide and 1000 mg DS/L, and an acetate‐fed filter could tolerate more than 125 mg sulfur/L of hydrogen sulfide and 400 mg DS/L.

ISSN:1061-4303    

DOI:10.2175/WER.65.2.2

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
The effects of temperature and mean cell residence time (MCRT) on biological nitrogen and phosphorus removal were investigated by operating two pilot‐scale continuous‐flow reactors in parallel over a range of temperatures and MCRTs. One system was operated as a high‐rate Virginia Initiative Plant (VIP) biological nutrient removal (BNR) process, and the other was operated as a conventional, fully aerobic activated sludge process for comparison. Results showed that less aerobic volume was needed for complete nitrification in the BNR process than in the conventional process when conditions of temperature and MCRT were suitable for complete nitrification. However, the BNR system was more prone to nitrifier washout than the conventional system. Nitrification rates and the degree of nitrification achieved by the BNR system and the conventional system were equal when compared on the basis of aerobic MCRT. Enhanced biological phosphorus removal (EBPR) was adversely afFected by colder temperatures, with lower MCRTs being most affected. EBPR was not possible at a 5 day system MCRT and 10°C. Nitrification, however, was more sensitive to MCRT and temperature effects than EBPR under all conditions studied. Operation of the BNR process at the lowest MCRT that provided complete nitrification provided the best combined nitrogen and phosphorus removal when EBPR was chemical oxygen demand (COD)‐limited. Higher MCRTs were considered optimal when EBPR was limited by phosphorus because of lower sludge productions.

ISSN:1061-4303    

DOI:10.2175/WER.65.2.3

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
Contamination of individual wells in rural areas from leaking petroleum storage tanks poses unique problems for regulatory agencies, utilities, and potentially responsible parties. A potential solution is the use of point‐of‐entry (POE) treatment techniques. Results indicate POE systems using aeration followed by granular activated carbon (GAC) are a viable, cost effective, short‐term solution while ground water remediation is performed or an alternate drinking water supply is secured. Selection and design of POE systems should consider variations in water usage and contaminant concentrations. Iron and manganese did not affect POE system performance at the ten sites studied. However, iron precipitation was observed and may pose problems in some POE applications. Increased concentrations of nonpurgeable dissolved organic carbon consisting primarily of methy‐t‐butyl ether (MTBE) and hydrophilic petroleum hydrocarbons were found in the raw waters but did not affect volatile organic chemical (VOC) removals by aeration or GAC. Microbial activity as measured by heterotrophic plate count significantly increased through four of the ten POE systems studied. Reliability of the POE systems will best be achieved by specifying top quality system components, educating POE users, and providing routine maintenance and VOC monitoring.

ISSN:1061-4303    

DOI:10.2175/WER.65.2.4

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
A solution of seven metal salts was dosed into batch and continuous‐flow dynamic wastewater experiments at bench‐ and pilot‐scale to calibrate a computer‐based mathematical model for predicting the fate of metals in municipal water pollution control plants (WPCPs). The model accounts for both precipitation and sorption onto primary and secondary sludges, and predicts the concentrations of metals in the primary sludge, return activated sludge, and secondary clarifier effluent. In dynamic step experiments, six of seven metals were removed substantially (55–99%) by the pilot activated sludge system. Lead and chromium were removed to the greatest extent while nickel was least removed. With the exception of nickel, a large fraction of the effluent metal concentrations were in particulate form. Below the solubility limits, a linear sorption model generally was able to simulate the observed effluent response to a step input. Sampling at a full‐scale WPCP was conducted for testing the steady‐state model's predictive capability. Except for lead, the predicted effluent concentrations agreed well with observed values.

ISSN:1061-4303    

DOI:10.2175/WER.65.2.5

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
This investigation, conducted at 24 full‐scale activated sludge wastewater treatment plants, quantified the extent of floc breakup resulting from the manner in which mixed liquors in aeration basins and conveyance systems are handled. Results showed that the concentration of dispersed solids increases with increasing aeration basin mixing intensity in the case of diffused air aeration systems. Also, the beneficial effect of the tapered aeration mode of operation on the extent of flocculation was shown. In mechanically aerated basins, the location of the aerator nearest the basin discharge point was found to be critical with respect to floc integrity since the degree of solids dispersion was shown to vary inversely with distance from a mechanical aerator. The presence of elbows and free falls of less than 0.5 m in mixed liquor transport systems was found to slightly increase solids dispersion. Free falls greater than 1.2 m however, were observed to cause significant floc breakup. Shear rates normally present in conveyance pipelines resulted in net floc aggregation.

ISSN:1061-4303    

DOI:10.2175/WER.65.2.6

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
Accumulated solids associated with the operation of aerated and facultative lagoons in cold climates were investigated to determine (1) the rate and extent of solids accumulation, (2) the characteristics of the accumulated solids, (3) the potential for in situ stabilization of the accumulated solids, and (4) the effect of lime treatment upon the pathogenic population and subsequent solids drying on sand and soil beds. Accumulated sludges from the Logan and Corinne, Utah, facultative lagoons and the Palmer and Galena, Alaska, partial‐mix aerated lagoons were studied. The rates of accumulation, determined by in situ measurement of the sludge layer in each lagoon, were found to vary with lagoon type and specific operational and environmental conditions. The solids characteristics, determined for samples upon collection and for samples in cold storage over time, were found to be generally comparable to those of conventional primary sludges. Sludge samples were stored for an extended period at temperatures that model winter conditions at the lagoon bottom and were periodically tested to determine if changes were occurring in basic sludge characteristics. With the exception of bacterial concentration reduction, no significant changes were observed, indicating that in situ stabilization of the sludge is probably not occurring in the actual lagoons under low‐temperature conditions. Lime treatment of the lagoon sludges was evaluated by dosing the sludges with lime and applying the limed sludges to bench‐scale sand and soil drying beds. Lime addition produced high pathogen kill levels. The limed sludges readily dewatered on both sand and soil beds.

ISSN:1061-4303    

DOI:10.2175/WER.65.2.7

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
This study reveals that the presence of molecular oxygen (oxic conditions) has a significant impact on the exhibited adsorptive capacity of granular activated carbon (GAC) for several phenolic compounds. The increase in the GAC adsorptive capacity under oxic conditions results from polymerization of these adsorbates on the carbon surface. The mechanism of polymer formation is through oxidative coupling of phenolic molecules. The extent of an increase in the GAC adsorptive capacity is in accordance with the ease of oxidation of these compounds. However, substituting a nitro group on the parent phenol molecule suppressed polymerization reactions and no increase in the GAC adsorptive capacity was observed under oxic conditions for these substituents.

ISSN:1061-4303    

DOI:10.2175/WER.65.2.8

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
A series of constructed and natural wetlands are currently being used by Orange County, Florida to polish reclaimed municipal wastewater. The system consists of constructed wetlands with low organic matter sandy soils, alternating with natural wetlands with organic soils. The hydrologic flow pattern is through constructed wetland → natural wetland → constructed wetland → natural wetland. Nitrogen removal potential of these wetlands was measured in (1) soil microcosms of each wetland batch fed with reclaimed water at a hydraulic retention time (HRT) of 21 days (experiment I), and (2) soil microcosms of each wetland sequentially batch fed for an HRT of 5 days per wetland for a total HRT of 20 days for the system (experiment II). The experiments were conducted in a greenhouse maintained at 18–32°C. Floodwater nitrogen removal, expressed as first‐order rate constants, ranged from 0.086 (±0.030) to 0.214 (±0.020) days−1for the wetland soils studied. Nitrogen removal was more rapid in wetlands with mineral soils than organic soils. Based on these rates, 50% of the inorganic nitrogen loaded to these wetlands would be removed at an HRT of 3–8 days. The firstorder rate constants obtained from experiment I were used to predict the floodwater nitrogen removal in experiment II (sequentially batch fed system) and nitrogen removal at the field site. At ambient nitrogen addition levels, the agreement between predicted and measured values was highly significant (slope = 0.98, R2= 0.98). The overall nitrogen removal efficiency was in the range of 83–89% in the wetlands evaluated. Nitrification and denitrification appear to be major nitrogen removal mechanisms in the wetlands.

ISSN:1061-4303    

DOI:10.2175/WER.65.2.9

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
An ultraviolet (UV) disinfection system was operated under field conditions using both unfiltered and filtered secondary wastewater effluents to assess the feasibility of using UV light to meet the stringent criterion specified in the California Wastewater Reclamation Criteria (CWRC). In the unfiltered wastewater the CWRC criterion that the 7‐day median not exceed 23 total coliform/100 mL was met consistently in effluent exposed to an average UV dose of 60 mW · s/cm2or greater. In the filtered wastewater, the CWRC criterion that the 7‐day median not exceed 23 total coliform/ 100 mL was met consistently in effluent exposed to an average UV dose of 48 mW · s/cm2or greater. The most stringent criteria, that the 7‐day median not exceed 2.2 total coliform/ 100 mL and that the total coliform not exceed 23/100 mL in more than one sample in a 30‐day period, was met consistently in filtered effluent exposed to an average UV dose of at least 97 mW · s/cm2. Filtration of the secondary effluent clearly enhanced the performance of the UV disinfection. Filtration was effective in removing significant amounts of suspended solids, in altering the particle size distribution of the secondary effluent, and in providing a consistently high quality effluent (turbidity<2 NTU).

ISSN:1061-4303    

DOI:10.2175/WER.65.2.10

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY