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PubMed2006

Biological phosphate uptake and release: effect of pH and magnesium ions.

Enhanced biological phosphorus removal (EBPR) is based on poly-phosphate accumulating organisms' (PAOs) unique features of "luxury" phosphate uptake during aerobic conditions and phosphate release in anaerobic conditions. It is believed that poly-phosphate accumulation is accompanied by the uptake and accumulation of potassium ions (K+) and magnesium ions (Mg2+). The release of phosphate under anaerobic conditions is also accompanied by the release of both cations. The objective of this research was to evaluate the effect of pH and Mg2+ on the biological phosphate uptake and release behavior of activated sludge mixed liquor during aeration and sedimentation. Research results indicate that Mg2+, supplied either by magnesium chloride (MgCl2) or magnesium hydroxide [Mg(OH)2], stimulated phosphate uptake during the aeration period, while pH increase, caused by the application of Mg(OH)2, enhanced phosphate release during the sedimentation period. It is also noted in our experiments with MgCl2 that Mg2+ slightly inhibited anaerobic phosphate release.

Bacteria, Aerobic↗
PubMed2006

Food-service establishment wastewater characterization.

Food-service establishments that use on-site wastewater treatment systems are experiencing pretreatment system and/or drain field hydraulic and/or organic overloading. This study included characterization of four wastewater parameters (five-day biochemical oxygen demand [BOD5]; total suspended solids [TSS]; food, oil, and grease [FOG]; and flow) from 28 restaurants located in Texas during June, July, and August 2002. The field sampling methodology included taking a grab sample from each restaurant for 6 consecutive days at approximately the same time each day, followed by a 2-week break, and then sampling again for another 6 consecutive days, for a total of 12 samples per restaurant and 336 total observations. The analysis indicates higher organic (BOD5) and hydraulic values for restaurants than those typically found in the literature. The design values for this study for BOD5, TSS, FOG, and flow were 1523, 664, and 197 mg/L, and 96 L/day-seat respectively, which captured over 80% of the data collected.

Food Services↗
PubMed2006

Performance of a submerged membrane bioreactor system for biological nutrient removal.

A pilot submerged membrane bioreactor coupled with biological nutrient removal was used to treat the primary effluent at a municipal wastewater treatment plant. Long-term experiments were conducted by varying hydraulic retention time from 6 to 8 hours and solids retention time from 20 to 50 days, respectively. The performance was assessed by monitoring key wastewater parameters, including chemical oxygen demand (COD), nitrogen, and phosphorus concentration in individual anoxic, anaerobic, aerobic, and membrane separation zones. Results showed that the tested system can consistently achieve COD, nitrogen, and phosphorus removal efficiencies at 80 to 98%, 70 to 93%, and 89 to 98%, respectively. Effluent COD remained low as a result of efficient solid retention, even though there was great variation in influent quality. However, total nitrogen increased proportionally with influent concentration. At a 50-day solids retention time, higher COD and nitrogen oxides specific utilization rates in the anoxic zone resulted in a high production of nitrogen oxides in the subsequent aerobic zone.

Bioreactors↗
PubMed2006

Full-scale class A biosolids production by two-stage continuous-batch thermophilic anaerobic digestion at the hyperion treatment plant, Los Angeles, California.

The City of Los Angeles Hyperion Treatment Plant (HTP) (California) converted its anaerobic digesters to thermophilic operation to produce Class A biosolids. Phase IV tests demonstrated compliance of a two-stage, continuous-batch process with Alternative 1 of U.S. Environmental Protection Agency 40 CFR Part 503 (U.S. EPA, 1993), which defines the time-temperature requirement for batch treatment (T > or = 56.3 degrees C at 16-h holding). Fecal coliforms, Salmonella sp., viable helminth ova, and enteric viruses were not detected in biosolids in the postdigestion train, including the truck-loading facility and the farm for land application as the last points of plant control where compliance is to be demonstrated. The same results were achieved during Phase V tests, after lowering the second-stage holding temperature to 52.6 degrees C to reduce the elevated methyl mercaptan production that was observed during Phase IV. Hence, the Phase V process complied with Alternative 3 of 40 CFR Part 503. Currently, HTP operates its digesters under the same conditions as tested in Phase V. In 2003, monthly monitoring of the biosolids at the truck-loading facility and the farm for land application demonstrated consistent compliance with Alternative 3.

Anaerobiosis↗
PubMed2006

Steam-explosion pretreatment for enhancing anaerobic digestion of municipal wastewater sludge.

This study evaluated the use of steam explosion as a pretreatment for municipal wastewater treatment sludges and biosolids as a technique for enhancing biogas generation during anaerobic digestion. Samples of dewatered anaerobic digester effluent (biosolids) and a mixture of thickened waste activated sludge (TWAS) and biosolids were steam-exploded under differing levels of intensity in this study. The results indicate that steam explosion can solublize components of these sludge streams. Increasing the intensity of the steam-explosion pressure and temperature resulted in increased solublization. The steam-explosion pretreatment also increased the bioavailability of sludge components under anaerobic digestion conditions. Increasing the steam-explosion intensity increased the ultimate yield of methane during anaerobic digestion. Batch anaerobic digestion tests suggested that pretreatment at 300 psi was the most optimal condition for enhanced biogas generation while minimizing energy input. Semicontinuous anaerobic digestion revealed that the results that were observed in the batch tests were sustainable in prolonged operation. Semicontinuous digestion of the TWAS/biosolids mixture that was pretreated at 300 psi generated approximately 50% more biogas than the controls. Semicontinuous digestion of the pretreated biosolids resulted in a 3-fold increase in biogas compared with the controls. Based on capillary suction test results, steam-explosion pretreatment at 300 psi improved the dewaterability of the final digested sludge by 32 and 45% for the TWAS/ biosolids mixture and biosolids, respectively, compared with controls. The energy requirements of the nonoptimized steam-explosion process were substantially higher than the additional energy produced from enhanced digestion of the pretreated sludge. Substantial improvements in energy efficiency will be required to make the process viable from an energy perspective.

Bacteria, Anaerobic↗
PubMedDate not supplied

The performance and kinetic study of membrane anaerobic system in treating POME. Palm oil mill effluent.

The application of the three known kinetic models on MAS (membrane anaerobic system) process treating the POME and the overall MAS treatment efficiency were investigated. The MAS consists of a cross-flow ultrafiltration membrane (Model Micro 240) for solid-liquid separation. Six steady states were attained over a range of mixed liquor suspended solids of 12,681 - 30,460 mg/l. The study showed a good fitting of the Monod Model (91.1%), Contois Model (98.5%) and Chen and Hashimoto Model (95%) for the MAS treating raw POME at organic loadings between 1.5 kgCOD/m3/d to 6.5 kgCOD/m3/d. The growth yield coefficient, Y, was found to be 0,604 kg VSS/kgCOD while the specific microorganism decay rate was 0.099 day(-1). The k values were in the range of 0,242 to 0.425 mg COD/mg VSS.d and the microm values were between 0.145 to 0.257 day(-1). Throughout the study, the removal efficiency of COD was 83.2 to 97.97%. The methane production rate was between 0.262 to 0.473 l/g-COD-utilised/d. The MAS treatment efficiency was greatly affected by SRT and OLRs. In the study, membrane fouling and polarization at the membrane surface played a significant role in the formation of the strongly attached cake layer limiting membrane permeability

Anaerobiosis↗
PubMed1986

Hospitals and hazardous wastes.

Much attention surrounds the volatile subject of hazardous waste management in our society--What is it? What can/should we do about it? How should we pay for it? What happens when these wastes are mismanaged? Experience shows that in hospitals: (1) There is a great deal of confusion and misinformation about the extent of responsibility for hazardous waste disposal; and (2) There are direct violations of regulations ranging from minor administrative infractions to ones that seriously threaten the environment and human life. This article examines the confusion surrounding the management of hazardous waste by hospitals and offers some management guidance.

Hospital Administration↗
PubMed2000

Anaerobic digestion technologies for closing the domestic water, carbon and nutrient cycles.

Sustainable wastewater treatment requires that household wastewater is collected and treated separately from industrial wastewater and rainwater run-offs. This separate treatment is, however, still inadequate, as more than 70% of the nutrients and much of the chemical oxygen demand (COD) and potential pathogens of a domestic sewage system are confined to the few litres of black water (faeces, urine and toilet water). Whilst grey water can easily be filter treated and re-used for secondary household purposes, black water requires more intensive treatment due to its high COD and microbial (pathogens) content. Recently developed vacuum/dry toilets produce a nutrient rich semi-solid waste stream, which, with proper treatment, offers the possibility of nutrient, carbon, water and energy recovery. This study investigates the terrestrial applicability of Life Support System (LSS) concepts as a framework for future domestic waste management. The possibilities of treating black water together with other types of human-generated solid waste (biowastes/mixed wastes) in an anaerobic reactor system at thermophilic conditions, as well as some post treatment alternatives for product recovery and re-use, are considered. Energy can partially be recovered in the form of biogas produced during anaerobic digestion. The system is investigated in the form of theoretical mass balances, together with an assessment of the current feasibility of this technology and other post-treatment alternatives.

Bacteria, Anaerobic↗
PubMed2001

Secondary wastewater disposal for crop irrigation with minimal risks.

A critical objective for any wastewater reuse program is to close the gap between supply of and demand for water and to minimize health and environmental hazards. Thus, the effects of treated effluent on crops, soils and community health must be considered carefully. When applying wastewater to soil-plant systems, it is to be noted that the passage of water through the soil reduces considerably the number of microorganisms carried out by the reclaimed wastewater. Nevertheless, there is a need to study the real rate of organism decay subject to water quality, soil and vegetable characteristics, and irrigation method. The aim of this work is to determine the fate of the fecal coliforms, coliphages F+ and CN13, and helminth eggs survival during the application of reclaimed wastewater in a vineyard orchard near the City of Arad (Israel) via onsurface and subsurface drip irrigation systems. Wastewater obtained from a stabilization pond, and soil samples were tested and an important decrease of microorganisms was reached in both cases, with the better values obtained with the sub-surface drip irrigation system.

Agriculture↗
PubMed2001

Wastewater quality relationships with reuse options.

The trend towards reuse of effluent for land application of domestic and industrial wastewater is driven by the need to maximise limited water resources and benefit from the plant nutrients available in the effluent. Of significant impact upon the value of the wastewater for reuse is its chemical properties as well as biochemical oxygen demand and suspended solids. While the sewage treatment plant is expected to treat all wastewater received to a minimum environmental standard, no efforts are given to reducing the chemical load derived from uses of chemicals in the domestic household. That the regulation of industry and commerce far exceeds those of the combined effects of thousands of household is remiss of environmental regulators. This paper examines the results of research into the more common sources of chemical additives to the wastewater stream. Twenty five potable water supplies are examined for their salt load, 20 liquid and 40 powder laundry detergents and five dishwashing products were used to simulate discharges to the sewer, measured for their phosphorus, salt and sodium concentrations. The results of the research indicate that choices in the products available for general use within the house can be made only where product labelling and consumer education is improved. Technical improvements in wastewater treatment are not the answer. The improvement in effluent quality will have significant beneficial effects upon land application areas and expand the range of reuse options available for commercial operations.

Australia↗
PubMed1998

Mineral recovery system for a Closed Ecology Experiment Facility (CEEF).

A unique recovery system, which consists of electrodialysis (ED) and crystallization processes, is proposed for NaCl (salt) from waste water after oxidation of urine. NaCl recovery characteristics from the oxidized urine, which contains KCl and NO3- impurities, were experimentally evaluated. Concentrated NaCl/KCl mixed solution was obtained using the ED process from simulated oxidized urine and sweat. Large amounts of NO3- were contained in the concentrated solution. After the crystallization process, NaCl salt of 90% purity, containing less than 5% NO3-, could be recovered by crystallization from the solution at 90 degrees C because NaNO3 or KNO3 salt has high solubility in water at that temperature. The results show that the proposed mineral recovery system can recover NaCl from waste water in the CEEF.

Chemical Precipitation↗
PubMed1999

Direct recycling of human hygiene water into hydroponic plant growth systems.

Direct recycling of gray water (human hygiene water) through plant production systems would reduce the need for additional space, mass, and energy for water reclamation in Advanced Life Support (ALS) systems. A plant production system designed to produce 25% of crew food needs could theoretically purify enough water through transpiration for 100% of crew water requirements. This scenario was tested through additions of shower and laundry water to recirculating hydroponic systems containing either wheat or soybean. Surfactant (Igepon TC-42) did not accumulate in the systems, and both the rate of surfactant disappearance and the proportion of Igepon-degrading microorganisms on the plant roots increased with time. A mechanism of surfactant degradation via the microbially ally mediated hydrolysis of the amide linkage and subsequent breakdown of fatty acid components is proposed. Fecal coliforms present in the human gray water were not detectable on the plant roots, indicating that human-associated microorganisms do not grow in the system. Overall plant growth was unaffected by gray water additions, although preliminary evidence suggests that reproduction may be inhibited.

Biomass↗
PubMed1999

Recycling of Na in advanced life support: strategies based on crop production systems.

Sodium is an essential dietary requirement in human nutrition, but seldom holds much importance as a nutritional element for crop plants. In Advanced Life Support (ALS) systems, recycling of gases, nutrients, and water loops is required to improve system closure. If plants are to play a significant role in recycling of human wastes, Na will need to accumulate in edible tissues for return to the crew diet. If crops fail to accumulate the incoming Na into edible tissues, Na could become a threat to the hydroponic food production system by increasing the nutrient solution salinity. Vegetable crops of Chenopodiaceae such as spinach, table beet, and chard may have a high potential to supply Na to the human diet, as Na can substitute for K to a large extent in metabolic processes of these crops. Various strategies are outlined that include both genetic and environmental management aspects to optimize the Na recovery from waste streams and their resupply through the human diet in ALS.

Chenopodiaceae↗
PubMed1999

Extraction and use of nutrients from composted wheat and potato plants.

Human survival on extended-duration space missions will require reliable regenerative life support systems. Biological systems using higher plants could be incorporated into life support systems; however, substantial quantities of inedible crop residues will also be produced. Composting can reduce the volume of crop residues and provide an end product that may be leached to remove soluble nutrients for use in hydroponic plant growth systems. Solubilization can be affected by physical conditions; we investigated several treatments (pH, temperature, agitation, or pretreatment sonication) for aqueous extraction of nutrients from composted inedible potato and wheat biomass. No significant differences were noted in electrical conductivity data. Chemical analyses indicated highly significant differences. Wheat seeds (Triticum aestivum L. cv. Apogee) were germinated in each extract to monitor for potentially inhibitory compounds. Seeds germinated in each extract, but total mean root lengths were affected negatively by sonication before extraction. Aqueous extracts may also support plant growth.

Biomass↗
PubMed1997

Nutrient recycling systems of Biosphere 2. Litterfall, decomposition, and wastewater recycling: results from the 1991-1993 closure experiment.

Important aspects of nutrient recycling in Biosphere 2 were plant litterfall/leaf decomposition in the terrestrial biomes and sewage and wastewater processing by a constructed wetland system. During the second year of closure, annual litterfall ranged from 1317 +/- 283 g/m2 in the lowland rainforest to 141 +/- 58 g/m2 in the desert sand dune area. Litterfall patterns followed different seasonal regimes in the biomes. Leaf decomposition averaged 90%/year in Biosphere 2, with the smallest leaf loss in the desert biome. For maintenance of soil fertility in the agricultural area, inedible crop material and domestic animal manure was composted, and human waste products and wastewater from people, labs, and domestic animals was processed in a 41-m2 constructed wetland. The wetland produced 1200 kg of fodder and remaining nutrients were returned to the soils via irrigation water.

Biomass↗