Nutrient removal efficiency using microalgae in different photoperiod cycles, combined with constructed wetland in a wastewater treatment plant

This research evaluates the removal of nutrients by microalgae in different photoperiod cycles, combined with constructed wetland in the wastewater treatment plant of the University of Santa Cruz do Sul, RS, Brazil. The treatment used took place between July and December 2018 and consisted of the following steps: preliminary treatment, secondary treatment with an anaerobic reactor, microalgae tank (MT), sand filter and constructed wetland, using the macrophyte Chrysopogon zizanioides. In the microalgae tank, three light cycles were considered: 12h/12h, 24h and 18h/06h, whose lighting was powered by a white LED lamp of 9 Watts and 6000 Kelvin, regulated by a light controller. The results indicated that there were no significant differences (p>0.05) between the values of soluble phosphorus, ammoniacal nitrogen, COD and BOD for MT comparing the three photoperiod cycles (12h/12h, 24h and 18h/06h). However, the system setup removed 100% of total coliforms, E. coli and TSS in the three light cycles. Regarding the removal of nutrients and organic matter, the light cycle with the best performance was the 24-hour cycle, considering a removal of 67.6% for soluble phosphorus, 94.0% for ammoniacal nitrogen, 63.7% for COD and 42, 7% for BOD, at the end of the treatment process. These results demonstrate that the use of microalgae in combination with constructed wetland has greater efficiency in the removal of nutrients, mainly phosphorus and nitrogen, in addition to reducing physical-chemical parameters and eliminating effluent toxicity. Keywords: light cycles, microalgae tank, wastewater treatment plant.

Nutrient removal efficiency using microalgae in different photoperiod cycles, combined with constructed wetland in a wastewater treatment plant

This research evaluates the removal of nutrients by microalgae in different photoperiod cycles, combined with constructed wetland in the wastewater treatment plant of the University of Santa Cruz do Sul, RS, Brazil. The treatment used took place between July and December 2018 and consisted of the following steps: preliminary treatment, secondary treatment with an anaerobic reactor, microalgae tank (MT), sand filter and constructed wetland, using the macrophyte Chrysopogon zizanioides. In the microalgae tank, three light cycles were considered: 12h/12h, 24h and 18h/06h, whose lighting was powered by a white LED lamp of 9 Watts and 6000 Kelvin, regulated by a light controller. The results indicated that there were no significant differences (p>0.05) between the values of soluble phosphorus, ammoniacal nitrogen, COD and BOD for MT comparing the three photoperiod cycles (12h/12h, 24h and 18h/06h). However, the system setup removed 100% of total coliforms, E. coli and TSS in the three light cycles. Regarding the removal of nutrients and organic matter, the light cycle with the best performance was the 24-hour cycle, considering a removal of 67.6% for soluble phosphorus, 94.0% for ammoniacal nitrogen, 63.7% for COD and 42, 7% for BOD, at the end of the treatment process. These results demonstrate that the use of microalgae in combination with constructed wetland has greater efficiency in the removal of nutrients, mainly phosphorus and nitrogen, in addition to reducing physical-chemical parameters and eliminating effluent toxicity. Keywords: light cycles, microalgae tank, wastewater treatment plant.

Influence of addition of calcium salts on extraction of potassium from phosphorus- potassium associated mineral

In this article, calcium salts were added into the hydrofluoric acid-sulfuric acid (HF-H2SO4) leaching system, and their effects on the extraction of potassium from phosphorus-potassium associated mineral (mineral deposits containing Ca5(PO4)3F (fluorapatite) and KAlSi3O8 (potassium feldspar)) were investigated. KAlSi3O8 was converted into water-soluble potassium fertilizers, and important factors affecting the extraction, including dosages of H2SO4, types and dosages of calcium salts were studied. The results showed that the maximum extraction of 75.3 wt.% was obtained with H2SO4 (70 wt.%) dosage of 5 mL. When the reaction was added with 0.15 g CaSO4, the extraction rate of K of 95 wt.% was achieved, which was an increase by 19.7 wt.% compared with that without calcium salts. Moreover, the Eh-pH diagrams for K-Si-(P)-(F)-(Ca)-H2O systems were plotted and applied to analyze the mechanism of potassium extraction in the HF-H2SO4 reaction system. The analysis demonstrated that with the presence of F-, the formation of fluoro-complexes enlarged the stable regions of soluble phosphorus (KPF6) and silicon (K2SiF6). However, when calcium salts were added, such region decreased with the increase of [Ca2 +]; and such trends suggested that [K+] could be enhanced by adding [Ca2 +] during the leaching process.

Nitrogen enrichment of animal bone-derived biochars as an agricultural NP-fertilizer

<p>Food processing creates many by-products, and not all of them are used efficiently. Especially animal-based side products are frequently considered as waste with costly disposal requirements. For recycling of the nutrients contained in these residues, also under consideration of the hygienic specifications, pyrolysis can be used to create animal bone-based biochars. A lab-scale pyrolysis reactor (Pyreka 3.0) was used to produce biochars from different bone fractions of cattle and pigs after these bones had originated as waste from abbatoir operations. This study had the objective to investigate the potential of the bone chars to serve as a phosphorus (P) supply for agricultural purposes and to study the ammonium sorption potential of these chars.</p><p>The total phosphorus content of bones reached up to 140 mg/g. The water-soluble phosphorus content was in the range of 0.16 – 0.93 mg/g, an increase in pyrolysis temperature from 350 °C to 500 °C or 650 °C increased the water-soluble content by 13.3 or 12.2 % respectively. The citric acid soluble phosphorus content was between 1.75 – 2.19 mg/g. After pyrolysis temperatures of 350 °C, slightly more phosphorus dissolved in the coal products than at 500 °C (+2.7 %) and at 650 °C (+5.5 %).</p><p>The ammonium sorption capacity of biochars produced by varying pyrolytic processes was investigated by a series of sorption experiments. The removal of ammonium by the biochars from an aqueous ammonium solution was measured by using colorimetric determination of the ammonium content. The maximum ammonium sorption results were achieved by biochars produced from bovine heads and feet respectively at a temperature of 900°C and activated with H<sub>2</sub>O.</p><p>When exposed to a solution containing 50 mg/L of ammonium, these biochars adsorbed 1.23 and 1.14 mg ammonium/g biochar, respectively. The possibility to enrich abattoir waste biochars, which are depleted in nitrogen because of the pyrolysis process, with ammonium gained from a nitrogen-enriched biogas slurry produced from animal residues of the meat production process was tested using a substitute slurry made with ammonium sulfate. The highest absorbance rate using the substitute slurry containing 10 g/L ammonium was achieved by biochar made from bovine heads and resulted in 43.1 mg ammonium/g biochar.</p><p>This study shows that bone-based biochars enriched with nitrogen from e.g. biogas digestates have significant potential as an NP-fertilizer that supports the strategies of circular economy.</p>

PHOSPHATE-MOBILIZING MICROORGANISMS: 1. BIODIVERSITY, INFLUENCE ON PLANTS MINERAL NUTRITION AND PRODUCTIVITY

Phosphorus is an essential plant nutrient involved in plants’ growth and development, accelerated formation of reproductive organs and other important factors for obtaining high and stable crop yields and, therefore, high-quality products. Easily absorbed phosphorus compounds obtained from soil or fertilizers are the most valuable for plants. One of the promising directions for improving the phosphorus nutrition of agricultural crops is biological phosphate mobilization that is carried out by soil microorganisms – bacteria and filamentous fungi (micromycetes). They contribute to the conversion of poorly soluble phosphorus compounds into forms accessible to higher plants. The effect of microorganisms on plants in terms of improving their mineral nutrition, in particular phosphorus, was reviewed in this article. We analysed domestic and foreign literature sources (over the last 15 years) focused on the biodiversity of soil phosphate-mobilizing microorganisms and their influence on converting insoluble phosphate to soluble forms. The features of the mechanisms of biotransformation of organic and mineral phosphates by soil microorganisms and the main criteria for screening effective isolates able to convert poorly soluble phosphorus compounds into forms available for plants were described in detail. This review also demonstrates that several microorganisms belonging to different taxonomic groups (bacteria and micromycetes) are recognized as powerful phosphate solubilizers or bioconverters of poorly soluble phosphorus compounds into water-soluble forms. We also surveyed scientific works, in which the practical application of effective strains of microorganisms that transform unavailable phosphorus compounds into available for plants was studied; and those, in which the role of microorganisms in increasing the availability of phosphorus for agricultural plants and their productivity improvement was demonstrated. A comprehensive description of microbial preparations “Agrofil”, “Biovays”, “Ekophosphorin”, “Ekovital”, “Biophosphorin”, “Albobacterin”, “Polymiksobacterin”, “Agrobacterin”, “Phosphostim”, “Fitostimophos”, “Agromik”, “Baktopin” based on phosphate-mobilizing microorganisms, developed and used in various countries to optimize mineral nutrition of cultivated plants, is given.