Agricultural Runoff Water Research Articles

Phosphorus removal from wastewater using an algal turf scrubber

Algal turf scrubbing is a novel technology for the treatment of agricultural runoff and eutrophic lake water and may have application for wastewater treatment. The algal turf scrubber (ATS)TM consists of a natural, mixed assemblage of attached periphyton, microalgae and bacteria which colonise an inclined floway over which wastewater flows in a series of pulses. A large-scale ATS (152.4 m long 6.5 m wide) was constructed in Patterson, California and tested in conjunction with UV disinfection over one year for its ability to treat secondary effluent from an evaporation pond. The hydraulic loading rate of the wastewater was varied between 436 and 1226 m3 per day and various operational parameters were tested. The biomass was mechanically harvested from the floway at one or two week intervals depending upon the season. This paper will present the results for phosphorus removal and productivity of the algal turf. Phosphorus removal from the secondary wastewater was measured twice a week during four, 8 week quarters corresponding to the solar seasons. The phosphorus content of the harvested solids was also measured during these periods. Based on the mean percentage of P (2.1 %) in the harvested solids and the mean productivity (35 g m−2 d−1), the yearly mean removal of phosphorus was 0.73 ± 0.28 g m−2 d−1. An inverse relationship was found between reduction in hydraulic loading rate and increase in pH, phosphorus removal and hardness reduction by the ATS. This indicated that pH mediated precipitation probably accounts for much of the phosphorus removal by the ATS and for the high mean phosphorus content of the harvested solids. Measurement of nutrient concentrations in influent and effluent of the ATS over 24 hours showed that at night phosphorus removal declined. These results indicate the potential of the ATS for phosphorus removal from wastewaters and suggest that removal may be easily controlled by altering the hydraulic loading rate.

Phosphorus removal from wastewater using an algal turf scrubber

Algal turf scrubbing is a novel technology for the treatment of agricultural runoff and eutrophic lake water and may have application for wastewater treatment. The algal turf scrubber (ATS)™ consists of a natural, mixed assemblage of attached periphyton, microalgae and bacteria which colonise an inclined flowaway wastewater flows in a series of pulses. A large-scale ATS (152.4 m long 6.5 m wide) was constructed in Patterson, California and tested in conjunction with UV disinfection over one year for its ability to treat secondary effluent from an evaporation pond. The hydraulic loading rate of the wastewater was varied between 436 and 1226 m3 per day and various operational parameters were tested. The biomass was mechanically harvested from the floway at one or two week intervals depending upon the season. This paper will present the results for phosphorus removal and productivity of the algal turf. Phosphorus removal from the secondary wastewater was measured twice a week during four, 8 week quarters corresponding to the solar seasons. The phosphorus content of the harvested solids was also measured during these periods. Based on the mean percentage of P (2.1 %) in the harvested solids and the mean productivity (35 g m-2 d-1), the yearly mean removal of phosphorus was 0.73 ± 0.28 g m-2 d-1. An inverse relationship was found between reduction in hydraulic loading rate and increase in pH, phosphorus removal and hardness reduction by the ATS. This indicated that pH mediated precipitation probably accounts for much of the phosphorus removal by the ATS and for the high mean phosphorus content of the harvested solids. Measurement of nutrient concentrations in influent and effluent of the ATS over 24 hours showed that at night phosphorus removal declined. These results indicate the potential of the ATS for phosphorus removal from wastewaters and suggest that removal may be easily controlled by altering the hydraulic loading rate.

U.S. agricultural biotechnology: Status and prospects

Agricultural applications are extending the already impressive record of biotechnology's contributions to medicine. In many ways, agriculture offers a more ready fit for modern genetic techniques, as single gene methods extend directly from traditional breeding techniques. This article describes how the new genetic tools are being applied to enhance many aspects of the food production system. Crop protection through genetic resistance to insects and disease is among the earliest, significant agronomic contributions. Food characteristics, including nutrient composition, fat content, allergenicity, texture, and flavor, are being modified through selectively targeted metabolic changes. Raw materials for food processing and fermentation are similarly modified and improved. New genetic techniques also present opportunities for introducing products of commodity crops into entirely new markets, including industrial oils, plastics, and pharmaceuticals. Taken together, biotechnology's value-added products, improved food and feed, and enhanced agronomic crop performance bolster the economic competitiveness of American farmers. There are also environmental advances, including biological control strategies and the use of microorganisms and plants to remove heavy metals and other contaminants from soil and agricultural run-off and ground waters. The ultimate impact of agricultural biotechnology, however, is far from certain. Several factors, some well defined and others less transparent, affect the directions and pace of development. These include public funding for basic research and for R&D, governmental regulation of research and products, and enhancement of linkages between the research and agriculture sectors. Compared to public investment in human and microbial genetics, federal support for the plant sciences has been dismal. USDA and EPA have proposed and implemented new regulatory requirements that are remarkable both for their lack of focus on genuine biosafety risks and for their unequivocal anti-innovation and anti-competitiveness effects. The relatively short history of U.S. policy on agricultural biotechnology may provide a microcosm view both of the introduction of technological innovations, more generally, and of emerging patterns of dominance of major agricultural firms in the worldwide economic arena. The analysis of that history suggests that a new paradigm for technological advancement is needed.

Development and optimization of a solid-phase extraction scheme for determination of the pesticides metribuzin, atrazine, metolachlor and esfenvalerate in agricultural runoff water

Concomitant determination of the pesticides metribuzin, atrazine, metolachlor and esfenvalerate in agricultural runoff water was developed utilizing solid-phase extraction (SPE). A 2 5 factorial experimental design compared relative importance for extraction efficiency of the five variables sample pH, elution solvent strength, ionic strength of the sample, addition of organic modifier to the sample, and elution by gravity or vacuum. The protocol was further optimized with respect to sorbent mass, sample volume, elution volume and concentration. The approach offers optimal recoveries, low detection limits, rapid extraction, and final determination by either gas or high-performance liquid chromatography.

Environmental Soil Testing for Phosphorus

Many soils in the USA have extremely high soil test P levels from long-term fertilization and manuring. Sediment-bound and soluble P in runoff from these soils may contribute to eutrophication of surface waters. A field rating system, the “P index,” has been developed to assess the potential for soil P to contribute to nonpoint source pollution. A critical component in this index is soil test P. The primary objective of this paper is to discuss the roles soil testing programs can play in the development of nutrient management strategies, such as the P index, that are needed to minimize nonpoint source pollution by soil P. A survey of soil testing labs participating in four regional soil testing committees (North Central, Northeast, Mid-Atlantic, Southeast) was conducted in 1991–1992 to determine current approaches to soil P testing, the percentage of soils testing in the high or excessive range, and major concerns with high P soils. Results indicated a need for more consistency in defining and identifying soils that are excessive in P, from an environmental standpoint, and that P management in animal waste-amended soils was the major environmental issue for most states. Soil P testing for environmental purposes will require a careful re-evaluation of the sampling, analytical, interpretive, and educational roles of soil testing programs. Alternatives considered in this paper include integration of soil testing databases with land-use planning information via geographic information systems, the use of special soil tests for biologically available P, or to estimate P sorption/desorption, and expanded educational efforts focused not only on farmers, but on advisory and regulatory agencies and the general public. Research Question Phosphorus in agricultural runoff and drainage waters can contribute to the eutrophication of surface waters. Many soils in the USA have extremely high soil test P levels as a result of long-term fertilization and manuring. Innovative approaches are needed to assess the potential bioavailability of P in soils and to develop nutrient management programs that reduce nonpoint source pollution by soil P. Soil testing for environmental purposes, rather than to identify situations where crop response to fertilizer P is likely, will require a careful reevaluation of the sampling, analytical, interpretive, and educational roles of soil testing programs. Literature Summary Previous research on nonpoint source pollution of surface waters has clearly identified the importance of soil P management. Many soil testing programs have extensive databases that can assist in prioritizing areas where most intensive soil P management practices are needed. Further, routine soil tests have been shown to be well-correlated with several parameters of importance to eutrophication, such as bioavailable P. Previous research also had identified other analytical procedures for soil P, such as ion exchange resins, iron oxide-impregnated gels, and single-point sorption isotherms, that may have to be adapted as special tests by soil testing labs to enhance existing nutrient management efforts. Study Description This paper reports the results of a survey of labs in four regional soil testing committees, discusses possible approaches to improve interpretation of soil testing results for high P soils, and describes means by which alternative analytical procedures can supplement existing soil testing methods. How extensive is the distribution of soils testing very high or excessive in P? Applied Questions Previous national soil test summaries indicate that, in many states, greater than 50% of commercial soil samples tested are rated as high, very high, or excessive. In the survey conducted for this paper, 86% of the states in the northeastern, north central, mid-Atlantic, and southeastern regional soil testing committees reported that more than 40% of the commercial soil test samples analyzed were high or excessive in P. How can soil testing labs assist in the development of improved, environmentally based nutrient management programs for soil P? More effective use of existing soil test databases can aid in effective allocation of resources to control nonpoint source polluton. Integration of soil testing results with land-use planning information via geographic information systems can contribute to long-term solutions. Development of a consistent approach to rate high P soils in terms of environmental impact is needed and can be accomplished best through the efforts of regional soil testing committees. Soil testing programs should re-evaluate the most appropriate sampling strategies and analytical methods for environmental soil testing for P. New soil testing procedures should be added to lab programs and educational efforts expanded to interpret the results of these tests for farmers, and for individuals in advisory and regulatory agencies.

Mineralization and Uptake of Triazine Pesticide in Soil‐Plant Systems

Deep-rooted trees planted as a buffer zone can intercept runoff and eroded sediments, thus reducing non–point-source pollution due to agricultural chemicals. In this study, \IPopulus\N sp. were grown in bioreactors with an agricultural soil (silt-loam) and in a silica-sand media; both were spiked with ¹\u4C uniformly ring-labeled atrazine. The plants took up over 11% of the ¹\u4C labeled atrazine applied to the silt-loam soil and over 91% of that applied to the silica sand media, with the majority of the ¹\u4C accumulating as non-phytotoxic metabolites in the leaves. Research suggests that, in addition to nutrient uptake, poplar tree buffer strips may be effective in removing atrazine from agricultural percolation and runoff water.

Assessment of manure-application effects upon the runoff water quality by algal assays and chemical analyses

The effects of manure-application mode, rate to soil, and rainfall characteristics on the quality of agricultural runoff water have been assessed by means of the algal-growth-potential test (AGPT) and chemical analyses. This study used two modes of manure application (i.e. surface mode and incorporation mode), three manure-application rates (0, 150, 300 kg N ha −1), and two rainfall intensities and times (i.e. 11 mm h −1 for 142 min and 22 mm h −1 for 71 min). The effects of the dilution of runoff water on algal growth were also examined. The algal yields obtained with runoff from soil with the incorporated manure mode are similar to those from soil without manure application and are lower than those with the surface mode of manure application. A higher manure-application rate increases the load of nutrients in the runoff and subsequently the algal yield. The dilution of runoff water can stimulate or limit the algal growth, depending on the concentration of toxicants, N (nitrogen) and P (phosphorus) from runoff and in the aquatic diluting medium. A lower rainfall intensity plus a longer rainfall time increases algal productivity. This study showed that N is the limiting factor to algal growth at low dilution but that, at high dilution or with the incorporation mode of manure application, P becomes the limiting factor to algal growth.

Nutrient trapping efficiency of a small sediment detention reservoir

Weekly measurements of water quality parameters were taken over a 5 year period from four sites in Morris Pond, a 1.09 ha reservoir in the loess hills of Mississippi's Goodwin Creek drainage basin. Catchment of the 30 year old reservoir, constructed for flood and sediment control, consisted of 17.8 ha of permanent pasture and 14.6 ha of cultivated and mixed-cover land. Inflow in winter and spring increased reservoir concentrations of phosphorus (from nondetectable to 1 mg/l), nitrate-nitrogen (from nondetectable to 1 mg/l), and suspended sediments (from 30 to > 300 mg/l). Storm-related inflow was the driving force behind short-term limnological and water quality cycles in Morris Pond. Multiple chlorophyll peaks indicated rapid phytoplankton response to runoff-related nutrient loading in this shallow (2.5 m normal max. depth) reservoir. Chlorophyll a ranged from < 10 mg/m 3 in winter to < 100 mg/m 3 in summer. Nutrient and suspended sediment concentrations in inflow were significantly correlated ( P < 0.001) with precipitation and storm runoff and were significantly ( P < 0.05) higher than normal seasonal pond concentrations. Nutrient trapping efficiency during storms averaged above 70% for phosphorus and nitrogen compounds flushed into the pond. This buffering capability of agricultural impoundments makes them excellent tools for managing intensive agricultural runoff and downstream water quality.

Soluble potassium transport in agricultural runoff water

Potassium transport in runoff from three agricultural soils was investigated in laboratory and field experiments using a kinetic equation describing soil K desorption. In the laboratory, this equation was used to study the effect of rainfall intensity and soil slope, cover, and residue incorporation on the effective depth of interaction between surface soil and runoff ( edi), an important parameter in the kinetic equation. Using simulated rainfall, edi increased linearly (from 1.6 to 22.0 mm) with an increase in rainfall intensity (50 to 160 mm h −1) and soil slope (2 to 20%). edi was reduced an average 82% following incorporation of 5.0 t ha −1 of wheat straw ( Triticum aestivum L. sp.) and 44% by a 0.5-mm 2 mesh screen, simulating crop cover, compared to the control (4.5 mm). This reduction was attributed to a decreased turbulent mixing of water at the soil surface brought about by an increased physical protection of soil. For all soils and treatments, edi was logarithmically related to soil loss ( r 2 = 0.80), allowing estimation of edi under variable rainfall intensity, soil slope, type, and cover conditions from measured or estimated soil loss. The values of edi, thus estimated were used in the kinetic equation to predict solution K transport in runoff from eight agricultural watersheds in Oklahoma, U.S.A. Measured and predicted mean annual flow-weighted concentrations of solution K were not significantly different and were strongly correlated ( r 2 = 0.92). These results improve our capability to predict K transport in runoff under field conditions. These methods could also be applied to other agricultural chemicals transported in runoff and results used to improve management of soil and water.

Capillary Column Gas Chromatographic Determination of Trace Residues of the Herbicide Chlorsulfuron in Agricultural Runoff Water

A capillary column gas chromatographic method is described for determining parts-per-trillion (ppt) levels of chlorsulfuron in agricultural runoff water. The water sample is acidified with acetic acid and extracted with methylene chloride. The chlorsulfuron in the extracts derivatized to its monomethyl derivative. After Florisil column cleanup, the methylated chlorsulfuron is determined by electron-capture gas chromatography. Recovery of chlorsulfuron from fortified water samples is greater than 80%. Detection limit of the method is 25 ng chlorsulfuron/L water (25 ppt). There are 2 reaction sites on the chlorsulfuron molecule, both of which are susceptible to methylation leading to monomethyl chlorsulfuron and dimethyl chlorsulfuron. A procedure is described to methylate selectively the sulfonamide nitrogen of chlorsulfuron.

Capillary Column Gas Chromatographic Determination of Trace Residues of the Herbicide Chlorsulfuron in Agricultural Runoff Water

Abstract A capillary column gas chromatographic method is described for determining parts-per-trillion (ppt) levels of chlorsulfuron in agricultural runoff water. The water sample is acidified with acetic acid and extracted with methylene chloride. The chlorsulfuron in the extract is derivatized to its monomethyl derivative. After Florisil column cleanup, the methylated chlorsulfuron is determined by electron-capture gas chromatography. Recovery of chlorsulfuron from fortified water samples is greater than 80%. Detection limit of the method is 25 ng chlorsulfuron/L water (25 ppt). There are 2 reaction sites on the chlorsulfuron molecule, both of which are susceptible to methylation leading to monomethyl chlorsulfuron and dimethyl chlorsulfuron. A procedure is described to methylate selectively the sulfonamide nitrogen of chlorsulfuron.

RAINFALL AND WATER QUALITY IN THE SOUTHERN PLAINS

ABSTRACT The chemical composition of rainfall, agricultural runoff, groundwater, and pond water at several rural Oklahoma and north Texas locations was determined over a number of years (1972–1985). The inputs of acid, P, Cl, and cations in rainfall are not of major agronomic importance, although inputs of N (as NO3-N and NH4-N) and S (as SO4) in rainfall can contribute a significant proportion of the uptake of these elements by grasses or crops. The mean annual pH of rainfall was consistently greater than that of pure rainfall (5.6) averaging 6.5, while the average pH of two farm ponds (7.8) was even greater than that of rainfall. If a decrease in the pH of rainfall in the Southern Plains should occur in the future, the impact of the acidity on surface water will be reduced to a certain degree by the buffering capacity of the area soils. Appreciably more acid was added annually to the agricultural soils of the area via fertilizer P and N than in rainfall. Under present conditions it would take up to 1,500 years rainfall to add as much acid as added by fertilizer in one year. Even with a dramatic decrease in rainfall pH to 4.0, this period would be 10 years. Thus, rainfall acidity presents no immediate threat to agricultural soils, groundwater, or lakes in Oklahoma and north Texas under continuing management practices, although periodic monitoring is recommended due to an increasing number of coal-fired power stations located in this area.

The Contribution of Agricultural Loading to Eutrophication in Finnish Lakes

Agriculture accounts for 9 per cent of the total surface area of Finland and generates the greatest single nutrient input to Finnish watercourses. Since agricultural activity is scattered throughout the whole country its effects in lakes are less pronounced than those of domestic and industrial effluents. On the other hand, point source phosphorus loading of lakes and rivers decreased significantly during the nineteen-seventies. Phosphorus is the nutrient which primarily limits production in most Finnish lakes. The availability of phosphorus in agricultural runoff waters is therefore a crucial question in the evaluation of the eutrophicating effects of agriculture. Our results indicated that in runoff waters available phosphorus can be 60-70 per cent of the total phosphorus. However, the concentrations of available P were so low that they could be achieved in Finnish lakes of low ionic concentration through simple chemical desorption without the assistance of the algal uptake. The utilization of the spring maximum of runoff phosphorus in lakes would thus not depend on the concurrence of the maxima of loading and algal growth.

Constituent bioconcentration in rainbow trout exposed to a complex chemical mixture.

Classically, aquatic contaminant fate models predicting a chemical's bioconcentration factor (BCF) are based upon single-compound derived models, yet such BCF predictions may deviate from observed BCFs when physicochemical interactions or biological responses to complex chemical mixture exposures are not adequately considered in the predictive model. Rainbow trout were exposed to oil-shale retort waters. Such a study was designed to model the potential biological effects precluded by exposure to complex chemical mixtures such as solid waste leachates, agricultural runoff, and industrial process waste waters. Chromatographic analysis of aqueous and nonaqueous liquid-liquid reservoir components yielded differences in mixed extraction solvent HPLC profiles of whole fish exposed for 1 and 3 weeks to the highest dilution of the complex chemical mixture when compared to their corresponding control, yet subsequent whole fish extractions at 6, 9, 12, and 15 weeks into exposure demonstrated no qualitative differences between control and exposed fish. Liver extractions and deproteinized bile samples from exposed fish were qualitatively different than their corresponding controls. These findings support the projected NOEC of 0.0045% dilution, even though the differences in bioconcentration profiles suggest hazard assessment strategies may be useful in evaluating environmental fate processes associated with complex chemical mixtures. 12 references, 4 figures,more » 2 tables.« less