RESUMEN
Phosphorus (P) is a valuable, nonrenewable resource in agriculture promoting crop growth. P losses through surface runoff and subsurface drainage discharge beneath the root zone is a loss of investment. P entering surface water contributes to eutrophication of freshwater environments, impacting tourism, human health, environmental safety, and property values. Soluble P (SP) from subsurface drainage is nearly all bioavailable and is a significant contributor to freshwater eutrophication. The research objective was to select phosphorus sorbing media (PSM) best suited for removing SP from subsurface drainage discharge. From the preliminary research and literature, PSM with this potential were steel furnace slag (SFS) and a nano-engineered media (NEM). The PSM were evaluated using typical subsurface drainage P concentrations in column experiments, then with an economic analysis for a study site in Michigan. Both the SFS and generalized NEM (GNEM) removed soluble reactive phosphorus from 0.50 to below 0.05 mg/L in laboratory column experiments. The most cost-effective option from the study site was the use of the SFS, then disposing it each year, costing $906/hectare/year for the case study. GNEM that was regenerated onsite had a very similar cost. The most expensive option was the use of GNEM to remove P, including regeneration at the manufacturer, costing $1641/hectare/year. This study suggests that both SFS and NEM are both suited for treating drainage discharge. The use of SFS was more economical for the study site, but each site needs to be individually considered.
Asunto(s)
Fósforo , Agua , Adsorción , Agricultura , Humanos , Michigan , Fósforo/análisis , Movimientos del Agua , Purificación del AguaRESUMEN
Land application of domestic and food processing wastewater is used due to its low cost, energy use, and maintenance. Design procedures are generally based on empirical relationships that may not account for critical site and waste-specific conditions. A mathematical model was utilized to simulate the complexity of wastewater land application. Multiple scenarios were run to determine system performance as measured by chemical oxygen demand (COD) and the nitrification/denitrification process. The modeling results showed that COD and nitrification occurred within the first 15.4 cm of a sandy loam soil. Increasing the dosing frequency slightly reduced the COD effluent concentration. Complete denitrification does not occur in a typical land application wastewater treatment system. In a domestic wastewater land application system, up to 32% of nitrate can be removed by increasing the dosing frequency and providing more organic carbon. In a food processing wastewater land application system, up to 56% of nitrate can be removed by increasing the dosing frequency and hydraulic and organic loadings. HYDRUS CW2D modeling is a valuable design tool to simulate multiple operation strategies and predict carbon degradation, nitrification, and denitrification. The model result can provide operational strategies to maximize the treatment while minimizing environmental impacts.
Asunto(s)
Carbono/análisis , Simulación por Computador , Modelos Teóricos , Nitrógeno/análisis , Suelo/química , Eliminación de Residuos Líquidos/métodos , Aguas Residuales/química , Análisis de la Demanda Biológica de Oxígeno , Desnitrificación , Nitratos/análisis , NitrificaciónRESUMEN
When a fast-food restaurant's wastewater containing fats, oil and grease (FOG) is discharged into a collection system, it builds up over time and clogs pipes. Similarly, when such wastewater flows into a septic soil treatment system, it adheres to the surface of inlet pipes, gravel/distribution media and soil, restricting the flow and eventually clogging the septic soil treatment system. In this study, an enzymatic pretreatment system was tested on wastewater from a fast-food restaurant to determine its effectiveness in preventing septic soil treatment system clogging. This system used aeration equipment, baffles and a one-time inoculum that excretes enzymes to reduce the molecular weight and number of double bonds associated with FOG. FOG containing triglycerides having lower molecular weights and fewer double bonds are less sticky. The enzymatic pretreatment system was found to cause these changes as verified by measuring the types of triglycerides (compounds in FOG) using liquid chromatography/mass spectrometry. A unique bench-scale septic soil treatment system (soil trench) was also used. Each contained six soil moisture sensors to enable the determination of moisture saturation trends among the five tested conditions: sanitary wastewater only, a combination of sanitary and kitchen wastewater, enzymatically pretreated sanitary and kitchen wastewater, kitchen wastewater, and enzymatically pretreated kitchen wastewater. For all influent types, a significant amount of FOG and other pollutants were removed, regardless of the initial concentrations. Moisture sensor readings showed differences among the tested conditions, indicating that septic soil treatment system clogging was delayed. Inspection of the influent pipe and gravel at the end of testing verified these differences as did the measurements of volatile solids.
Asunto(s)
Lípidos/química , Eliminación de Residuos Líquidos/métodos , Contaminantes del Agua/química , Restaurantes , Suelo , Aguas ResidualesRESUMEN
Farmstead runoff poses significant environmental impacts to ground and surface waters. Three vegetated filter strips were assessed for the treatment of dairy farmstead runoff at the soil surface and subsurface at 0.3- or 0. 46-m and 0. 76-m depths for numerous storm events. A medium-sized Michigan dairy was retrofitted with two filter strips on sandy loam soil and a third filter strip was implemented on a small Michigan dairy with sandy soil to collect and treat runoff from feed storage, manure storage, and other impervious farmstead areas. All filter strips were able to eliminate surface runoff via infiltration for all storm events over the duration of the study, eliminating pollutant contributions to surface water. Subsurface effluent was monitored to determine the contributing groundwater concentrations of numerous pollutants including chemical oxygen demand (COD), metals, and nitrates. Subsurface samples have an average reduction of COD concentrations of 20, 11, and 85% for the medium dairy Filter Strip 1 (FS1), medium dairy Filter Strip 2 (FS2), and the small Michigan dairy respectively, resulting in average subsurface concentrations of 355, 3960, and 718 mg L COD. Similar reductions were noted for ammonia and total Kjeldahl nitrogen (TKN) in the subsurface effluent. The small Michigan dairy was able to reduce the pollutant leachate concentrations of COD, TKN, and ammonia over a range of influent concentrations. Increased influent concentrations in the medium Michigan dairy filter strips resulted in an increase in COD, TKN, and ammonia concentrations in the leachate. Manganese was leached from the native soils at all filter strips as evidenced by the increase in manganese concentrations in the leachate. Nitrate concentrations were above standard drinking water limits (10 mg L), averaging subsurface concentrations of 11, 45, and 25 mg L NO-N for FS1, FS2, and the small Michigan dairy, respectively.
Asunto(s)
Plantas/metabolismo , Calidad del Agua , Agua/química , Arsénico/análisis , Arsénico/aislamiento & purificación , Arsénico/metabolismo , Agua Subterránea/química , Concentración de Iones de Hidrógeno , Manganeso/análisis , Manganeso/aislamiento & purificación , Manganeso/metabolismo , Nitrógeno/análisis , Nitrógeno/aislamiento & purificación , Nitrógeno/metabolismo , Oxígeno/química , Fósforo/análisis , Fósforo/aislamiento & purificación , Fósforo/metabolismo , Suelo/químicaRESUMEN
The research reported here examined the use of hydraulic loading strategies to maximize nitrogen removal from onsite-generated wastewater. These strategies are made practical by the inherently intermittent flow of onsite-generated wastewater. Experimentation was conducted at the Western Regional Wastewater Pretreatment Facility in Montgomery County, Ohio, with an established, full-scale onsite wastewater treatment system rated at 500 gallons per day. The onsite wastewater treatment unit was fed primarily with domestic wastewater that had passed through fine screens and grit removal. The dosing schedule was intermittent, representing what would be expected from onsite-generated wastewater. Oxidation occurred in the aeration tank and potentially on the solid-liquid filtration socks within the aeration tank. All major wastewater characterization parameters were monitored during the approximately one-year study, including five-day biochemical oxygen demand (BOD;), total suspended solids (TSS), nitrate, total nitrogen, pH, and alkalinity. Excellent removal of BOD5 and TSS resulted, with the effluent concentration of each parameter substantially and consistently below 10 mg/L for all operating conditions. Excellent total nitrogen removal occurred, typically to below 10 mg/L of nitrogen when the instantaneous flow of wastewater was low, even when the daily hydraulic loading was high. The removal of nitrogen was attributed to microbial biodegradation. This result indicates that the onsite wastewater treatment unit has an inherent denitrification capacity that can be matched with an equalized-hydraulic-loading strategy. The practical ability to equalize and reduce instantaneous loading results from the inherently intermittent nature of the flow associated with onsite wastewater treatment.
Asunto(s)
Nitrógeno/aislamiento & purificación , Eliminación de Residuos Líquidos/métodos , Filtración , Oxidación-Reducción , Movimientos del Agua , Abastecimiento de AguaRESUMEN
The need to improve on-site wastewater treatment processes is being realized as populations move into more environmentally sensitive regions and regulators adopt the total maximum daily load approach to watershed management. Under many conditions, septic systems do not provide adequate treatment; therefore, advanced systems are required. These systems must remove significant amounts of biochemical oxygen demand (BOD) and suspended solids, and substantially nitrify, denitrify, and remove phosphorus. Many existing advanced on-site wastewater systems effectively remove BOD, suspended solids, and ammonia, but few substantially denitrify and uptake phosphorus. The purpose of this research was to design and test modifications to an existing on-site wastewater treatment system to improve denitrification and phosphorus removal. The Nayadic (Consolidated Treatment Systems, Inc., Franklin, Ohio), an established, commercially available, extended-aeration, activated sludge process, was used to represent a typical existing system. Several modifications were considered based on a literature review, and the option with the best potential was tested. To improve denitrification, a supplemental treatment tank was installed before the Nayadic and a combination flow splitter, sump, and pump box with a recirculation system was installed after it. A recirculation pump returned a high proportion of the system effluent back to the supplemental treatment tank. Two supplemental treatment tank sizes, three flowrates, and three recirculation rates were tested. Actual wastewater was dosed as brief slugs to the system in accordance with a set schedule. Several ion-exchange resins housed in a contact column were tested on the effluent for their potential to remove phosphorus. Low effluent levels of five-day biochemical oxygen demand, suspended solids, and total nitrogen were achieved and substantial phosphorous removal was also achieved using a 3780-L supplemental treatment tank, a recirculation ratio of 5:1, and a fine-grain activated aluminum-oxide-exchange media. Good results were also obtained with an 1890-L supplemental treatment tank and a recirculation ratio of 3:1. The most significant benefit of the supplemental treatment tank, in combination with the recirculation system, appears to be the low nitrogen concentration dosed to the Nayadic. By reducing the nitrogen concentration and spreading out its mass over time during no-flow periods, the Nayadic's inherent low-level denitrifying capacity was more closely matched and effective treatment was achieved.
Asunto(s)
Carbono/aislamiento & purificación , Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificación , Aguas del Alcantarillado/química , Aguas del Alcantarillado/microbiología , Eliminación de Residuos Líquidos/métodos , Aluminio/química , Intercambio Iónico , Movimientos del Agua , Purificación del Agua/métodosRESUMEN
A dual-media fluidized bed is a unique reactor design containing two distinct media that results in two segregated treatment zones. By the strategic use of these two zones, this design has the potential to remove both BOD and nutrients (nitrogen and phosphorus) in a single compact reactor. Three operational strategies are conceivable. The first is to maintain a microbiological zone close to the influent to achieve BOD and nitrogen removal. The zone above would contain an exchange media to remove phosphorous. In another scenario, the lower zone would be kept aerobic and the higher zone anoxic. This would enhance denitrification. In the third scenario, the first two are combined by having the exchange media serve as the anoxic zone or including an independent third zone (aerobic, anoxic, and exchange). This scenario could result in the comprehensive treatment of BOD, nitrogen, and phosphorus removal. This proof-of-concept research primarily investigated the first scenario and provided preliminary data for the other two. A low-loaded operating strategy was used to minimize the inherent disadvantages of a fluidized bed reactor, primarily caused by excessive biofilm growth. The reactor was operated for approximately 1 year using sand and activated alumina as the two media. Good separation with minimum mixing at the interface resulted. BOD and phosphorus removal and nitrification were consistently very good during non-transitional periods. Denitrification varied depending on the influent concentration, dissolved oxygen, and oxidation/reduction potential. Preliminary data also indicated that when a low recirculation ratio is used, denitrification could be enhanced. There appears to be a potential difficulty, however, in exchanging phosphorous using activated alumina under low oxidation/reduction potential conditions.
Asunto(s)
Reactores Biológicos , Carbono/aislamiento & purificación , Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificación , Eliminación de Residuos Líquidos/métodos , Óxido de Aluminio/química , Intercambio Iónico , Oxidación-Reducción , OxígenoRESUMEN
This laboratory proof-of-concept research examined the feasibility of adding solid, slow-release macronutrients to a biofilm reactor system to achieve the effective biodegradation of a predominately organic polluted storm water. The target scenario was treating ethylene glycol in storm water, representing the runoff of airport deicing and anti-icing fluids. However, the results can also be generalized for any water polluted with a predominately carbonaceous material. The use of a solid, slow-release nutrient source, compared to amending with a soluble solution in proportion to influent flow, would be ideal for storm water applications and other specialized wastewater flows when maintenance requirements and operational support must be minimized. Several commercially available fertilizers were preliminarily examined to determine which had the best potential to provide the required amount of nutrients. A time-released, polymer-coated granular fertilizer was ultimately selected. Based on laboratory studies, it was found that this fertilizer could provide a controllable source of macronutrients that enabled treatment to a similar degree as if the macronutrients had been dissolved in the influent. The only major operational problem was reduced nutrient delivery from the fertilizer after it became coated with a thick biofilm. However, the inherent intermittent nature of storm water production resulting in wet/dry cycles may minimize the development of a thick biofilm.