Around the world, the eutrophication of freshwater lakes and streams by the excess loading of phosphorus (P) has become one of the most important water quality issues. In Vermont, P pollution from urban and agricultural non-point sources has led to severe blooms of toxic cyanobacteria in Lake Champlain, and the degradation of the lake’s value as a drinking water source and its recreation potential. Electric arc furnace (EAF) steel slag has been identified as an effective material for use as a filter media for the removal of P from both point and non-point sources of pollution. In order to further assess the feasibility of this technology for use in Vermont, several investigations were carried out starting in the winter of 2006. Three objectives for research were identified: 1) to construct 2 EAF steel slag filters in-series at the Constructed Wetlands Research Center (CWRC) and investigate their efficiency in P, TSS and metals reduction from dairy waste water in a cold climate; 2) investigate the potential for reuse of P saturated EAF steel slag as a soil amendment and plant fertilizer by testing bioavailability of sorbed P and quantities of P released to surface runoff; 3) To elucidate the principal mechanisms responsible for the removal of P in EAF slag filters when used for the treatment of dairy effluent. The results indicated that 2 EAF steel slag filters constructed in-series are an effective method to increase the treatment efficiency and longevity of a filter system. Additionally, parameters for the concentrations of total suspended solids (TSS) and biological oxygen demand (BOD) were developed, both important factors for design of filter systems. In greenhouse trials, Medicago sativa plants achieved greater above ground biomass growth with P fertilization by triple super phosphate (TSP) than EAF steel slag at the shorter growth period (5 weeks). However, by the end of the longer growth period (10 weeks) except at the highest amendment rate, the plants treated with EAF steel slag had a higher growth rate than the TSP, suggesting that EAF steel slag is an effective slow release P source. Using a rain simulator, the amount of P lost to surface runoff from both a saturated and a semi-saturated EAF steel slag was found to be negligible, and except for total P in the saturated slag, to be below 1 mg L-1. Voltammetric analysis and geochemical modeling were used to identify possible mechanisms for the removal of P from waste effluent. The Ca mineral hydroxyapaptite and the Fe(II) mineral vivianite were both shown to be likely mechanisms given the chemical conditions in EAF steel slag filters. This research represents the first investigation of cold weather performance of EAF steel slag filters for the treatment of dairy parlor and milk house waste effluent. Additionally, it was also the first research on the bioavailability of P sorbed to EAF steel slag, and of the possibility of its reuse as a soil amendment, and of the mechanisms involved in P removal from dairy waste effluent.

Due to the fact that the mechanism of acquisition of phosphorus (P) by roots, is mainly by interception, sufficient P uptake is only ensured by maximal root development ("exploitation"). Pot and field trials were conducted to determine the percentage exploitation of the soil volume by roots. The influence of P on root growth of Zea Mays was also studied. Previously, roots were described in terms of root density (cm cm-2, cm cm-3, gram cm-2 and gram cm-3). In this study roots are described in terms of exploitation which combines length, mass and the rhizosphere. The Gompertz function was used to model exploitation by roots as influenced by P application. P along with nitrogen and potassium, had a highly significant (P < 0.001) effect on root growth in the pot experiments. The root systems' function changed after 14 days from nutrient acquisition to shoot supportive. P had no significant effect on root growth in the field trial. Growth was governed by soil moisture, as dryer positions exhibited higher growth. The high P plot had much less root growth in the subsoil than the low P plot. Gompertz functions revealed subtle differences between different treatments. During the first two weeks (when most P uptake occur) roots exploited at the most 1 % of the top soil volume. This implies that any soil analysis (Bray-1 value), should be divided by ≈ 100 to render the "exploitable" P. When considering the total P uptake of a maize crop (5 kg P ton-I), this means that the crop acquires only ≈ 6% of its P from the "plant available" pool (that is represented by the Bray-1 value). This suggests that roots are indeed able to extract the P from "plant unavailable" pools. Therefore, the term "plant available" is misleading and not descriptive concerning P uptake, and its use should be discontinued. / Dissertation (MSc (Soil Science))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

No abstract provided / Dissertation (MSc (Agric) Nutrition)--University of Pretoria, 2005. / Animal and Wildlife Sciences / unrestricted

While treating domestic wastewater, algae can be grown and harvested for biofuel production. Water is a vital resource and it is imperative to conserve and reuse as much as possible. Several pilot and lab scale experiments were conducted to further research into a full scale wastewater treatment and biofuel production facility. This thesis will include these topics: nitrogen and phosphorus concentrations of clarified wastewater pond feed, nitrogen and phosphorus transformations by algae, and the potential of algae cell disruption technologies to increase nutrient solubilization. The pilot scale experiments were conducted using nine 33 m2, 0.3 m deep multi-culture raceway algae ponds being continuously mixed. These ponds were setup in triplicates and fed municipal wastewater in the form of primary clarifier effluent. The three experiments conducted using these pilot scale ponds were: grab and 24-hour composite influent comparison, nitrogen and phosphorus of various hydraulic residence times (HRTs), and nitrogen and phosphorus nutrient depletion with water recycle. The grab and 24-hour composite comparison was conducted from July 30 to December 3, 2014 and compared the dissolved reactive phosphorus (DRP) and total ammonia nitrogen (TAN) concentrations of the two sample types. Equations were made to convert from grab to 24-hour concentrations. The sample types for both DRP and TAN were on average within 10% and essentially the same. A comparison of data from ponds operating at different HRTs was collected from October 30 and November 6, 2013 and October 29 and November 5, 2014. There were linear correlations between different HRTs and both soluble nitrogen and DRP. Equations were made to calculate the expected removal of ponds using the HRT. The nutrient depletion with water recycle experiment was conducted during October 15-29, 2015. Soluble nitrogen removal was linear with a rate of 1.5 mg-N/L-day and required 14 days to drop below 5 mg-N/L in the ponds. DRP removal was also linear with a rate of 0.18 mg-P/L-day. The algae cell disruption solubilization experiments were conducted using homogenization, sonication, autoclaving, and boiling pretreatment technologies. Algae harvested from the pilot ponds was anaerobically digested and then aerobically digested in an attempt to reuse nutrients for continued growth. It was found that there was no significant difference between the pretreated and non-pretreated digested samples. Keywords: algae, raceway pond, nutrient transformation, anaerobic digestion, aerobic digestion, assimilation, volatilization, nitrogen, phosphorus, pretreatment of algae, nutrient resolubilization, nutrient solubilization

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A incorporação de fósforo (P) foi avaliada através da técnica de marcador enzimático fluorescente a fim de determinar a atividade da fosfatase alcalina (PA) em dois clones de Phaeodactylum tricornutum (Bohlin), Ub3 e Ub7, isolados de Ubatuba (SP), em Tetraselmis aff. chui (Butcher) e Prorocentrum minimum (Pavillard) J. Schiller, isoladas da Baía de Guanabara (RJ) e na Comunidade Natural da Baía de Guanabara (RJ). A fosfatase alcalina (PA) é uma enzima extracelular associada à membrana que catalisa a hidrólise de compostos orgânicos de fósforo em resposta à limitação de fosfato. Sua análise, a partir do marcador ELF-97, proporciona uma avaliação individual e, portanto, determina as condições nutricionais de fósforo inorgânico em células fitoplanctônicas. Os clones de P. tricornutum apresentaram diferenças no desenvolvimento quando incubados no tratamento P-repleto. O clone Ub7 de P. tricornutum apresentou a maior atividade enzimática quando comparado às demais espécies testadas, em condições P-repletas. Enquanto P. minimum apresentou a maior atividade da fosfatase alcalina em condições P-limitadas. Entre as espécies T. aff. chui e P. minimum, a maior atividade enzimática ocorreu durante a fase estacionária de desenvolvimento, entretanto diferenças foram observadas somente nas menores concentrações de fosfato. P. tricornutum, T. aff. chui e P. minimum, ao longo dos experimentos, utilizaram duas estratégias para incorporação de fosfato, aumentando a atividade da fosfatase alcalina, assim como alterando o biovolume ou a máxima dimensão linear para manter a relação S/V estável. Em P. tricornutum os sítios da atividade enzimática ocorreram na membrana celular, em T. aff. chui encontrados intracelularmente, enquanto em P. minimum observados tanto nas membranas, quanto no interior das células. No experimento realizado com a comunidade natural, houve predomínio das diatomáceas entre todos os grupos e tratamentos; as espécies foram agrupadas nas estratégias adaptativas C e R e classificadas principalmente como R-estrategistas. Os dinoflagelados da Ordem Prorocentrales utilizaram a incorporação do fósforo orgânico como estratégia para obtenção de fósforo em condições limitantes. Entretanto, as diatomáceas apresentaram tal estratégia de forma mais variável. Quanto às prasinofíceas, embora Tetraselmis sp. tenha apresentado baixa atividade enzimática nos experimentos unialgais, as concentrações de fosfato ao longo do experimento não resultaram na utilização de P orgânico para o grupo. Os resultados destacaram as diferenças intra e interespecíficas na atividade da fosfatase alcalina, e, consequentemente, na incorporação de fósforo orgânico, uma vez que as espécies testadas regularam a atividade enzimática de acordo com as diferentes concentrações externas de fosfato. / The incorporation of phosphorus (P) was evaluated by the activity of alkaline phosphatase (AP) as a marker, using a fluorescent probe technique, in order to ascertain the activity of this enzyme in two clones of Phaeodactylum tricornutum (Bohlin), Ub3 and Ub7, isolated from Ubatuba (SP), as well as in Tetraselmis aff. chui (Butcher), Prorocentrum minimum (Pavillard) J. Schiller, originally isolated from the Guanabara Bay (RJ) and Natural community of Guanabara Bay (RJ). Alkaline phosphatase (AP) is an extracellular membrane-associated enzyme that catalyzes the hydrolysis of organic phosphorus compounds in response to the phosphate limitation. Its analysis, from ELF-97 probe, provides an individual evaluation, and therefore determines the nutritional status of inorganic phosphorus in phytoplanktonic cells. Bioassays were performed in triplicate comparing the control treatment Guillard F/2 to both phosphate-enriched and phosphate-depleted conditions by varying only the phosphate concentration in the media for Phaeodactylum tricornutum, Tetraselmis aff. chui, Prorocentrum minimum and Natural community of Guanabara Bay. The P. tricornutum clones showed differences in its development when incubated in the phosphate-enriched media. In this condition, the Ub7 clone presented a different development. The alkaline phosphatase analysis indicated limitations of this clone under such conditions. T. aff. chui and P. minimum showed higher enzymatic activity during the stationary phase, although differences were observed only in the phosphate-depleted treatments. P. tricornutum Ub7 clone showed higher PA activity when compared to the other species, in P-enriched condition. While P. minimum showed higher enzimatic activity in P-depleted conditions. P. tricornutum, T. aff. chui and P. minimum, presented both increases in AP activity and low variation in the S/V ratio, by increasing biovolume and maximum linear dimension, as estrategies for phosphate incorporation. In P. tricornutum the AP sites were observed on the cell membrane, in T. aff. chui the sites were located within the cells, while in P. minimum were found both in membranes as inside the cells. In the experiment carried out with Natural community of Guanabara Bay, there was a predominance of diatoms among all groups and treatments; species were grouped into adaptive strategies C and R. The dinoflagellates of Prorocentrales Order uses the incorporation of organic phosphorus as strategy for obtaining phosphorus in P-depleted conditions. However, wen we consider the diatoms, this strategy is more inconstant. Regarding the Prasinophyceae, the phosphate concentrations throughout the experiment did not result in the use of organic phosphorus in this group. Our results highlighted the differences intra and interspecific in alkaline phosphatase activity and hence in the incorporation of organic phosphorus as the tested species regulated the enzymatic activity under different external phosphate concentrations.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A incorporação de fósforo (P) foi avaliada através da técnica de marcador enzimático fluorescente a fim de determinar a atividade da fosfatase alcalina (PA) em dois clones de Phaeodactylum tricornutum (Bohlin), Ub3 e Ub7, isolados de Ubatuba (SP), em Tetraselmis aff. chui (Butcher) e Prorocentrum minimum (Pavillard) J. Schiller, isoladas da Baía de Guanabara (RJ) e na Comunidade Natural da Baía de Guanabara (RJ). A fosfatase alcalina (PA) é uma enzima extracelular associada à membrana que catalisa a hidrólise de compostos orgânicos de fósforo em resposta à limitação de fosfato. Sua análise, a partir do marcador ELF-97, proporciona uma avaliação individual e, portanto, determina as condições nutricionais de fósforo inorgânico em células fitoplanctônicas. Os clones de P. tricornutum apresentaram diferenças no desenvolvimento quando incubados no tratamento P-repleto. O clone Ub7 de P. tricornutum apresentou a maior atividade enzimática quando comparado às demais espécies testadas, em condições P-repletas. Enquanto P. minimum apresentou a maior atividade da fosfatase alcalina em condições P-limitadas. Entre as espécies T. aff. chui e P. minimum, a maior atividade enzimática ocorreu durante a fase estacionária de desenvolvimento, entretanto diferenças foram observadas somente nas menores concentrações de fosfato. P. tricornutum, T. aff. chui e P. minimum, ao longo dos experimentos, utilizaram duas estratégias para incorporação de fosfato, aumentando a atividade da fosfatase alcalina, assim como alterando o biovolume ou a máxima dimensão linear para manter a relação S/V estável. Em P. tricornutum os sítios da atividade enzimática ocorreram na membrana celular, em T. aff. chui encontrados intracelularmente, enquanto em P. minimum observados tanto nas membranas, quanto no interior das células. No experimento realizado com a comunidade natural, houve predomínio das diatomáceas entre todos os grupos e tratamentos; as espécies foram agrupadas nas estratégias adaptativas C e R e classificadas principalmente como R-estrategistas. Os dinoflagelados da Ordem Prorocentrales utilizaram a incorporação do fósforo orgânico como estratégia para obtenção de fósforo em condições limitantes. Entretanto, as diatomáceas apresentaram tal estratégia de forma mais variável. Quanto às prasinofíceas, embora Tetraselmis sp. tenha apresentado baixa atividade enzimática nos experimentos unialgais, as concentrações de fosfato ao longo do experimento não resultaram na utilização de P orgânico para o grupo. Os resultados destacaram as diferenças intra e interespecíficas na atividade da fosfatase alcalina, e, consequentemente, na incorporação de fósforo orgânico, uma vez que as espécies testadas regularam a atividade enzimática de acordo com as diferentes concentrações externas de fosfato. / The incorporation of phosphorus (P) was evaluated by the activity of alkaline phosphatase (AP) as a marker, using a fluorescent probe technique, in order to ascertain the activity of this enzyme in two clones of Phaeodactylum tricornutum (Bohlin), Ub3 and Ub7, isolated from Ubatuba (SP), as well as in Tetraselmis aff. chui (Butcher), Prorocentrum minimum (Pavillard) J. Schiller, originally isolated from the Guanabara Bay (RJ) and Natural community of Guanabara Bay (RJ). Alkaline phosphatase (AP) is an extracellular membrane-associated enzyme that catalyzes the hydrolysis of organic phosphorus compounds in response to the phosphate limitation. Its analysis, from ELF-97 probe, provides an individual evaluation, and therefore determines the nutritional status of inorganic phosphorus in phytoplanktonic cells. Bioassays were performed in triplicate comparing the control treatment Guillard F/2 to both phosphate-enriched and phosphate-depleted conditions by varying only the phosphate concentration in the media for Phaeodactylum tricornutum, Tetraselmis aff. chui, Prorocentrum minimum and Natural community of Guanabara Bay. The P. tricornutum clones showed differences in its development when incubated in the phosphate-enriched media. In this condition, the Ub7 clone presented a different development. The alkaline phosphatase analysis indicated limitations of this clone under such conditions. T. aff. chui and P. minimum showed higher enzymatic activity during the stationary phase, although differences were observed only in the phosphate-depleted treatments. P. tricornutum Ub7 clone showed higher PA activity when compared to the other species, in P-enriched condition. While P. minimum showed higher enzimatic activity in P-depleted conditions. P. tricornutum, T. aff. chui and P. minimum, presented both increases in AP activity and low variation in the S/V ratio, by increasing biovolume and maximum linear dimension, as estrategies for phosphate incorporation. In P. tricornutum the AP sites were observed on the cell membrane, in T. aff. chui the sites were located within the cells, while in P. minimum were found both in membranes as inside the cells. In the experiment carried out with Natural community of Guanabara Bay, there was a predominance of diatoms among all groups and treatments; species were grouped into adaptive strategies C and R. The dinoflagellates of Prorocentrales Order uses the incorporation of organic phosphorus as strategy for obtaining phosphorus in P-depleted conditions. However, wen we consider the diatoms, this strategy is more inconstant. Regarding the Prasinophyceae, the phosphate concentrations throughout the experiment did not result in the use of organic phosphorus in this group. Our results highlighted the differences intra and interspecific in alkaline phosphatase activity and hence in the incorporation of organic phosphorus as the tested species regulated the enzymatic activity under different external phosphate concentrations.

In the tobacco production area of Nelspruit, a problem is experienced in increasing the phosphorus content of tobacco leaves to above0.25% despite of the high phosphorus content of the soil (higher than 30 mg/kg Bray 1). The aim of this study was to investigate the reasons for the low P content in tobacco leaves and how P and Ca content in the soil and soil compaction influence it. During the 1998/99 season, field tests were conducted at 3 different localities in the Nelspruit area to investigate the influence of soil compaction, phosphorus and calcium supply on P uptake. Treatment consisted of 2 calcium treatments, 2 soil treatment actions and 5 phosphorus levels. Leaf samples were taken for chemical analysis, 115 to 120 days after planting and the different treatments were harvested as they ripened physiologically and cured in a tobacco drying oven. This was used to calculate the yield, quality and income per hectare. A pot experiment were done under controlled conditions at the experimental farm of the University of Pretoria with soil from one of the field plots. With the pot experiment different bulk densities were simulated with 3 phosphorus and 2 calcium levels, to evaluate the effect thereof on P uptake. As the leaves ripened physiologically they were picked and dried for chemical analysis. On all the data an analysis of variance was performed. A final conclusion can be made that, high levels of P fertilization are unnecessary and attention must be paid to soil compaction, and that gypsum must be applied with care. Although not investigated in this study the low P content of leaves can be due to the genetic characteristics of the tobacco cultivars used in the Nelspruit area and the high levels of zinc in the soil which can cause P precipitation in roots that could restrict the P transport to the leaves. With the pot experiment it is proved that high P applications lead to a decline of the percentage zinc in the leaves. The conclusion is made in this study that when soil compaction were overcome, high and low dosages of phosphorus and the increase of calcium levels in the soil did not show a constant increase in P values above 0.25%. / Dissertation (MSc)--University of Pretoria, 2005. / Plant Production and Soil Science / unrestricted