Measurement of organic nitrogen and phosphorus fractions at very low concentrations in wastewater effluents

The purpose of this study was to develop simple, accurate, and inexpensive measurement protocols for dissolved organic nitrogen (DON) and dissolved non-reactive phosphorus (DNRP) at low levels in wastewater effluents. Two protocols are presented--one to measure DON exclusively, and the other to measure DON and DNRP simultaneously. Currently, DON and DNRP are calculated indirectly by subtracting the dissolved inorganic fractions from the total dissolved concentration, resulting in significant errors. To increase the accuracy of DON measurements, effluent sample pretreatment using ion exchange to remove nitrate was applied. Spectrometric methods were selected to measure the inorganic fractions-the second derivative UV spectroscopy method for nitrate, and the malachite green method for orthophosphate. These methods, combined with the optimized persulfate digestion of the samples, can be used to measure total dissolved nitrogen and phosphorus accurately. The measurement ranges attained were 0.05 to 3 mg N/L for DON and 0.01 to 0.5 mg P/L for DNRP.     

Aerobic and anaerobic membrane bioreactors for municipal wastewater treatment.

An aerobic bioreactor and an anaerobic bioreactor, each coupled with a microfiltration membrane filter (MBR), were operated at different hydraulic retention times (HRTs) with primary effluent from the City of Elmhurst, Illinois, municipal-wastewater-treatment plant. The soluble chemical oxygen demand (COD) removal performance of the anaerobic MBR system was similar to that of the aerobic MBR under the same operational conditions, without the added cost of aeration. The results indicated that the solids deposition rate on the membrane surface was lower in the case of anaerobic MBR compared to the aerobic MBR, indicating possible lower loss in water-flux rates. This research found that an anaerobic MBR is a feasible and economical option for municipal-wastewater-treatment plants seeking COD removal by a biological process followed by a separate nitrification and denitrification system.     

Stabilization and solidification of metal-laden wastes by compaction and magnesium phosphate-based binder

Bench-scale and full-scale investigations of waste stabilization and volume reduction were conducted using spiked soil and ash wastes containing heavy metals such as Cd, Cr, Pb, Ni, and Hg. The waste streams were stabilized and solidified using chemically bonded phosphate ceramic (CBPC) binder, and then compacted by either uniaxial or harmonic press for volume reduction. The physical properties of the final waste forms were determined by measuring volume reduction, density, porosity, and compressive strength. The leachability of heavy metals in the final waste forms was determined by a toxicity characteristic leaching procedure (TCLP) test and a 90-day immersion test (ANS 16.1). The structural composition and nature of waste forms were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. CBPC binder and compaction can achieve 80-wt% waste loading and 39-47% reduction in waste volume. Compressive strength of final waste forms ranged from 1500 to 2000 psi. TCLP testing of waste forms showed that all heavy metals except Hg passed the TCLP limits using the phosphate-based binder. When Na2S was added to the binder, the waste forms also passed TCLP limits for Hg. Long-term leachability resistance of the final waste forms was achieved for all metals in both soil and ash wastes, and the leachability index was approximately 14. XRD patterns of waste forms indicated vermiculite in the ash waste was chemically incorporated into the CBPC matrix. SEM showed that waste forms are layered when compacted by uniaxial press and are homogeneous when compacted by harmonic press.     

Odor emission rate estimation of indoor industrial sources using a modified inverse modeling method

Odor emission rates are commonly measured in the laboratory or occasionally estimated with inverse modeling techniques. A modified inverse modeling approach is used to estimate source emission rates inside of a postdigestion centrifuge building of a water reclamation plant. Conventionally, inverse modeling methods divide an indoor environment in zones on the basis of structural design and estimate source emission rates using models that assume homogeneous distribution of agent concentrations within a zone and experimentally determined link functions to simulate airflows among zones. The modified approach segregates zones as a function of agent distribution rather than building design and identifies near and far fields. Near-field agent concentrations do not satisfy the assumption of homogeneous odor concentrations; far-field concentrations satisfy this assumption and are the only ones used to estimate emission rates. The predictive ability of the modified inverse modeling approach was validated with measured emission rate values; the difference between corresponding estimated and measured odor emission rates is not statistically significant. Similarly, the difference between measured and estimated hydrogen sulfide emission rates is also not statistically significant. The modified inverse modeling approach is easy to perform because it uses odor and odorant field measurements instead of complex chamber emission rate measurements.     

Comparison of two dynamic measurement methods of odor and odorant emission rates from freshly dewatered biosolids

Odor and odorant emission rates from freshly dewatered biosolids in a dewatering building of a Water Reclamation Plant (WRP) are measured using the EPA flux chamber and wind tunnel methods. Experimental results are compared statistically to test whether the two methods result in similar emission rates when experiments are performed under field conditions. To the best of our knowledge the literature is void of studies comparing the two methods indoors. In this paper the two methods are compared indoors where the wind velocity and air exchange rate are pertinent field conditions and can be measured. The difference between emission rates of odor and hydrogen sulfide measured with the two methods is not statistically significant (P values: 0.505 for odor, 0.130 for H(2)S). It is concluded that both methods can be used to estimate source emissions but selection of the most effective or efficient method depends on prevailing environmental conditions. The wind tunnel is appropriate for outdoor environments where wind effects on source emissions are more pronounced than indoors. The EPA flux chamber depends on the air exchange rate of the chamber, which simulates corresponding conditions of the indoor environment under investigation and is recommended for estimation of indoor pollution sources.     

Adaptation to the Impacts of Sea Level Rise in Egypt

Assessment of the vulnerability and expected socioeconomic losses over the Nile delta coast due to the impact of sea level rise is carried out in details. Impacts of sea level rise over the Governorates of Alexandria and Port Said in particular, are evaluated quantitatively. Analysis of the results at Alexandria Governorate indicate that, if no action is taken, an area of about 30% of the city will be lost due to inundation. Almost 2 million people will have to abandon their homeland; 195,000 jobs will be lost and an economic loss of over $3.5 Billion is expected over the next century. At Port Said Governorate results indicate that beach areas are most severely affected (hence tourism), followed by urban areas. The agriculture sector is the least affected sector. It is estimated that the economic loss is over $ 2.0 Billion for 0.50 m SLR and may exceed $ 4.4 Billion for 1.25 m SLR. Options and costs of adaptation are analyzed and presented. Multi-criteria and decision matrix approaches, based on questionnaire surveys are carried out to identify priorities for the two cases. Analysis of these techniques of two options; the current policy (hard protection measures on some vulnerable areas) and no action (stopping these activities) have the lowest scores. Beach nourishment and integrated coastal zone management (ICZM) have the highest scores, however ICZM has high cost measures. The most cost-effective option is the land-use change, however with relatively very high cost measure. It is recommended that an ICZM approach be adopted since it provides a reasonable trade off between costs and cost effectiveness.     

Stabilization and Solidification of Metal-Laden Wastes by Compaction and Magnesium Phosphate-Based Binder

ABSTRACT

Bench-scale and full-scale investigations of waste stabilization and volume reduction were conducted using spiked soil and ash wastes containing heavy metals such as Cd, Cr, Pb, Ni, and Hg. The waste streams were stabilized and solidified using chemically bonded phosphate ceramic (CBPC) binder, and then compacted by either uniaxial or harmonic press for volume reduction. The physical properties of the final waste forms were determined by measuring volume reduction, density, porosity, and compressive strength. The leachability of heavy metals in the final waste forms was determined by a toxicity characteristic leaching procedure (TCLP) test and a 90-day immersion test (ANS 16.1). The structural composition and nature of waste forms were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively.

CBPC binder and compaction can achieve 80-wt % waste loading and 39-47% reduction in waste volume. Compressive strength of final waste forms ranged from 1500 to 2000 psi. TCLP testing of waste forms showed that all heavy metals except Hg passed the TCLP limits using the phosphate-based binder. When Na₂S was added to the binder, the waste forms also passed TCLP limits for Hg. Long-term leachability resistance of the final waste forms was achieved for all metals in both soil and ash wastes, and the leachability index was ~14. XRD patterns of waste forms indicated vermiculite in the ash waste was chemically incorporated into the CBPC matrix. SEM showed that waste forms are layered when compacted by uniaxial press and are homogeneous when compacted by harmonic press.     

Anaerobic and aerobic transformations affecting stability of dewatered sludge during long-term storage in a lagoon

The goal of this work was to study long-term behavior of anaerobically digested and dewatered sludge (biosolids) in a lagoon under anaerobic and aerobic conditions to determine the stability of the final product as an indicator of its odor potential. Field lagoons were sampled to estimate spatial and temporal variations in the physical-chemical properties and biological stability characteristics such as volatile solids content, accumulated oxygen uptake, and soluble protein content and odorous compound assessment. The analyses of collected data suggest that the surface layer of the lagoon (depth of above 0.15 m) undergoes long-term aerobic oxidation resulting in a higher degree of stabilization in the final product. The subsurface layers (depth 0.15 m below the surface and deeper) are subjected to an anaerobic environment where the conditions favor the initial rapid organic matter degradation within approximately the first year, followed by slow degradation.     

Bioavailability of dissolved organic nitrogen in treated effluents.

The research objective was to assess dissolved organic nitrogen (DON) bioavailability in wastewater effluents from a pilot-scale nitrification plant and a laboratory-scale total nitrogen (TN) removal plant. The DON bioavailability was assessed using a 14-day bioassay protocol containing bacterial and algal inocula. Nitrogen species, dissolved organic carbon, chlorophyll a, and biomass (as total suspended solids and culturable cell counts) concentrations were measured to assess DON bioavailability. The results showed an increase in algal chlorophyll a concentration, with a concurrent increase in algal biomass over time; increased bacterial counts and a decrease in DON concentration over time; and increased carbon-to-nitrogen ratio at the end of the 14-day bioassay, indicating effluent DON bioavailability to algae and bacteria. Approximately 18 to 61% of the initial DON in low-total-nitrogen wastewater effluent (TN = 4 to 5 mg/L) sample was bioavailable. The results show that bacteria and algae uptake and release DON during their growth.     

Emissions of polychlorinated biphenyls (PCBs) from sludge drying beds to the atmosphere in Chicago

Ambient air PCB concentrations in the Lake Calumet region in Southeast Chicago have been found to be significantly higher than in nearby non-urban areas. This area is highly industrialized and also contains municipal sludge drying facilities and landfills. In an effort to quantify the importance of the sludge drying facilities to the elevated concentrations, upwind/downwind air samples from the Calumet East sludge drying bed were obtained between April and October 2002. For these samples, the downwind minus upwind (downwind-upwind) concentration varied from 0.33 to 1.27ngm(-3) for non-northeast (NE) direction winds suggesting sludge drying is a source of PCBs to the atmosphere. However, the upwind concentrations were higher than the downwind for winds from the NE of the sampling site suggesting more significant source(s), possibly Lake Calumet or the so called "Cluster site" NE of the sludge drying beds. Flux chamber experiments carried out during the sampling period measured average PCB fluxes of 210ngm(-2)h(-1) (range 43-910ngm(-2)h(-1)) which resulted in an overall flux of 0.005kgday (d)(-1) ( approximately 2kgyr(-1)). A developed regression equation between moisture content and sludge concentration estimated higher PCB losses of 0.26kgd(-1) ( approximately 95kgyr(-1)). Although these two approaches yielded different values, they both indicate that the emission from the Calumet East sludge drying beds were of minimal importance when compared to the total estimated amount of 2-70kgd(-1) (700-2100kgyr(-1)) of PCBs entering the Chicago atmosphere.