Recovery of phosphorus and other minerals from greenhouse wastewater generated during soilless tomato cultivation by means of alkalizing agents.

The research was aimed at determining the possibility of recovering part of nutrients by precipitation from greenhouse wastewater (GW) from soilless tomato cultivation. Analyses included such elements as: P, S, N, Cl, Ca, Mg, K, Mo, Mn, Fe, Zn, Cu, and B. Three alkalizing agents were tested in a pH range of 6.5-12.0: Ca(OH)2, KOH, and NH4OH, which simultaneously enrich greenhouse wastewater in calcium, potassium, and nitrogen. It was determined what dose of the alkalizing agent should be used, how the composition of the treated GW will change, how much and what kind of sludge will be formed, what will be the stability and technical possibility of sediment separation, and whether the type of alkalizing agent affects the course of the process. Precipitation triggered by the alkalizing agents proved to be an effective method for the recovery of phosphorus, calcium, magnesium, manganese, and boron, while it turned out ineffective in the case of the other elements tested, including nitrogen and potassium. Phosphorus recovery depended mainly on GW pH and forms of phosphate ions corresponding to this pH, and not on the alkalizing agent type. The pH value adjustment to pH = 9 for KOH and NH4OH and to pH = 9.5 for Ca(OH)2 ensured <99 % phosphorus recovery, which corresponded to P concentration in GW below 1 mgP/L and to the applied Ca(OH)2, KOH, and NH4OH doses of 0.20 g/L, 0.28 g/L, and 0.08 g/L, respectively. The highest P contents in the sludge were determined at pH = 7 and reached 18.0 %, 16.8 %, and 16.3 % in the experimental series with Ca(OH)2, KOH, and NH4OH, respectively. The sludge volume index increase along with pH increase up to pH = 10.5 for KOH and to pH = 11 for Ca(OH)2 and NH4OH.

Investigation on the improved electrochemical and bio-electrochemical treatment processes of soilless cultivation drainage (SCD).

The soilless crop cultivation under cover generates wastewater called soilless cultivation drainage (SCD), being a nutrient-rich overflow. The average concentration of phosphorus- and nitrogen-based pollutants from soilless tomato cultivation usually ranges from 35.4 to 104.0 mg P/L and from 270.0 to 614.9 mg N/L, respectively. In bio-electrochemical reactors, nitrogen and phosphorus are removed via biological denitrification, electrochemical nitrate reduction, bio-electrochemical reduction, and electrocoagulation. The novelty of this study is due to the use of alternating current (AC), which can both mitigate the corrosion on the anode and solve the issue of insoluble oxide build-up on the cathode. Additionally, and crucially, it promotes bacterial growth and activity. The aim of the present study was to determine (1) the effectiveness of soilless cultivation drainage treatment methods that employ biological and electrochemical processes, with consideration given to (2) the quantity and quality of the produced sludge as a potential nutrient-rich product. The bio-electrochemical reactor proved more effective than the electrochemical one and ensured a high TP and TN removal efficiency exceeding 97% and 66%, respectively. The resulting sludge was rich in such elements as calcium, potassium, carbon, phosphorus, and nitrogen, and as such may serve as a viable alternative to conventional mineral fertilizers.

Potential toxicity of leachate from the municipal landfill in view of the possibility of their migration to the environment through infiltration into groundwater.

Leachate from landfills is a product of complex biological and physicochemical processes occurring during waste storage. In the present study, the toxicity of landfill leachate (LL) to human and bacterial cells was investigated for better understanding of LL environmental toxicity. Studies regarding LL physicochemical properties and cytotoxicity analysis were conducted. In Escherichia coli, Pseudomonas fluorescens, Bacillus subtilis, fibroblasts and melanoma A-375 cells, cell viability assays were applied. For the determination of LL antibacterial activity, twofold dilution series of LL were prepared in the range from 50% to 0.1% (50%, 25%, 12.5%, 6.25%, 3.13%, 1.56%, 0.78%, 0.39%, 0.2%, 0.1%). Human cells viability was examined at LL concentrations of 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 5%, 10%, 15%, 20% and 30%. ROS (reactive oxygen species) content and apoptosis level were also measured in bacterial and human cells under the influence of LL. Unexpectedly obtained results indicate stimulation of bacterial viability by LL. Fibroblasts under the influence of LL showed decrease in their viability and increase in apoptosis level and A-375 melanoma cells showed an increase in relative viability and decrease in apoptosis. ROS level in bacterial cells was elevated in higher LL concentrations and decreased in lower LL concentrations. In human cells, ROS content was rather high in both tested cell lines. Presented results indicate cytotoxic potential of analyzed LL and the necessity of LL monitoring because it may pose a health hazard for exposed human populations and the whole human environment.

Possible Protective Effects of TA on the Cancerous Effect of Mesotrione.

The interaction of different food ingredients is now a very important and often emerging topic of research. Pesticides and their breakdown products, which may be carcinogenic, are one of the frequently occurring food contaminants. Compounds like traumatic acid (TA), which originates from plants, are beneficial, antioxidant, and anticancer food ingredients. Previously obtained results from our research group indicated antioxidative in normal human fibroblasts and prooxidative in cancer cells activity of TA. Since the literature data show an undoubted connection between the presence of pesticides in food and the increased incidence of different types of cancers, we attempted to clarify whether TA can abolish the effect of mesotrione stimulating the growth of cancer cells. In order to study the influence of mesotrione on breast cancer cells, we decided to carry out cytotoxicity studies of environmentally significant herbicide concentrations. We also analyzed the cytotoxicity of TA and mixtures of these two compounds. After selecting the most effective concentrations of both components tested, we conducted analyses of oxidative stress parameters and apoptosis in ZR-75-1 cells. The obtained results allow us to conclude that traumatic acid by stimulating oxidative stress and apoptosis contributes to inhibiting the growth and development of cells of the ZR-75-1 line strengthened by mesotrione. This may mean that TA is a compound with pro-oxidative and proapoptotic effects in cancer cells whose development and proliferation are stimulated by the presence of mesotrione. The presented results may be helpful in answering the question of whether herbicides and their residues in edibles may constitute potential threat for people diagnosed with cancer and whether compounds with proven pro-oxidative effects on cancer cells can have potential cytoprotective functions.

The impact of biodegradable carbon sources on nutrients removal in post-denitrification biofilm reactors.

Wastewater from households wastewater treatment plants (HWWTP) is discharged to the ground or to the surface waters. Special consideration should be given to the improvement of HWWTP effectiveness, particularly in relation to nutrients. The addition of biodegradable carbon sources to biofilm reactor, can enhance microbial activity but may also lead to filling clogging. The study aimed to compare 3 different organic substrates: acetic acid (commonly applied)and two untypical - citric acid and waste beer, under the same operational conditions in a post-denitrification biofilm reactor. The study investigated the impact of a type of organic substrate, low pH and time on: (1) biofilm growth, (2) the characteristics of extracellular polymeric substances (EPS), (3) the kinetics of nutrients removal and (4) reactor clogging. Results were referred to (5) the effectiveness of nutrients removal. The study demonstrated that low pH assured the development of a thinbiofilm. Citric acid ensured the lowest biomass volume, being by 53% lower than in the reactor with acetic acid and by as much as 61% lower than in the reactor with waste beer. The soluble EPS fraction prevailed in the total EPS in all reactors. The content of the tightly bound EPS fraction ranged from 26.93% (citric acid) to 36.32% (waste beer). Investigations showed also a high ratio of exoproteins to polysaccharide in all fractions, which indicated a significant role of proteins in developing a highly-proliferating biofilm. The treated wastewater met requirements of Polish regulations concerning COD and nitrogen concentrations.

The share of electrochemical reduction, hydrogenotrophic and heterotrophic denitrification in nitrogen removal in rotating electrobiological contactor (REBC) treating wastewater from soilless cultivation systems.

There is a growing global environmental problem of agricultural wastewater from soilless plant cultivation systems. In most countries dominate open fertilization systems, in which excess of nutrient solution is discharged in an uncontrolled way into the ground inside greenhouses or adjacent areas. Wastewater from such systems is characterized by a very high concentration of nitrogen and phosphorus compounds and their discharge into the environment causes significant pollution of the water and soil environment. The goal of the research was to determine the contribution of electrochemical reduction of nitrogen, hydrogenotrophic and heterotrophic denitrification in the process of nitrogen removal in a rotating electrobiological contactor (REBC) depending on hydraulic retention time (HRT) and electric current density (J). Synthetic sewage with characteristics corresponding to wastewater from soilless cultivation of tomatoes was the subject of the research. The first part of the experiment included determination of the effect of HRT on the effectiveness of bio-processes of nutrients removal in a rotating biological contactor (RBC). The second concerned the effect of HRT and J on the effectiveness of nutrients removal in a rotating electrochemical contactor (RECC), while the third part - the effect of HRT and J on the effectiveness of nutrients removal in REBC. RBC was characterized by low efficiency of denitrification (6.2 to 9.2%). The effectiveness of nitrogen removal in RECC was determined by both electric current density and hydraulic retention time. The highest efficiency was 53.4%. REBC nitrogen removal effectiveness was higher than in RBC and in RECC. The nitrogen removal efficiency increased along with increasing values of HRT, reaching the maximum value of 68.6% for J=10.0A/m2 and HRT=24h. The contribution of hydrogenotrophic denitrification in total nitrogen removal increased with the increase of electric current density.

Hydrogel chitosan sorbent application for nutrient removal from soilless plant cultivation wastewater.

In this study, we determined the effectiveness of removal of nutrients (nitrates and orthophosphates) from greenhouse wastewaters (GW) using non-cross-linked chitosan (CHs) and chitosan cross-linked with epichlorohydrin (CHs-ECH) in the form of hydrogel beads. GW used in the study had the following parameters: N-NO3 621.1 mg/L, P-PO4 60.8 mg/L, SO42- 605.0 mg/L, Cl- 0.9 mg/L, Ca2+ 545.0 mg/L, Mg2+ 178.0 mg/L, K+ 482.0 mg/L, hardness 113° dH, and pH 6.2. The scope of the study included determination of the effect of pH on wastewater composition and effectiveness of nutrient sorption, analyses of nutrient sorption kinetics, and analyses of the effect of sorbent dose on percentage removal of nutrients from GW. CHs-ECH was able to sorb 79.4% of P-PO4 and 76.7% of N-NO3 from GW, whereas CHs to remove 92.8% of P-PO4 and 53.2% of N-NO3.

Citric acid application for denitrification process support in biofilm reactor.

The study demonstrated that citric acid, as an organic carbon source, can improve denitrification in Anaerobic Sequencing Batch Biofilm Reactor (AnSBBR). The consumption rate of the organic substrate and the denitrification rate were lower during the period of the reactor's acclimatization (cycles 1-60; 71.5 mgCOD L-1 h-1 and 17.81 mgN L-1 h-1, respectively) than under the steady state conditions (cycles 61-180; 143.8 mgCOD L-1 h-1 and 24.38 mgN L-1 h-1). The biomass yield coefficient reached 0.04 ± 0.02 mgTSS· mgCODre-1 (0.22 ± 0.09 mgTSS mgNre-1). Observations revealed the diversified microbiological ecology of the denitrifying bacteria. Citric acid was used mainly by bacteria representing the Trichoccocus genus, which represented above 40% of the sample during the first phase of the process (cycles 1-60). In the second phase (cycles 61-180) the microorganisms the genera that consumed the acetate and formate, as the result of citric acid decomposition were Propionibacterium (5.74%), Agrobacterium (5.23%), Flavobacterium (1.32%), Sphaerotilus (1.35%), Erysipelothrix (1.08%).

Effect of dairy wastewater on changes in COD fractions in technical-scale SBR type reactors.

The annual global production of milk is approximately 630,000 million litres and the volume of generated dairy wastewater accounts for 3.2 m3·m-3 product. Dairy wastewater is characterized by a high load of chemical oxygen demand (COD). In many wastewater plants dairy wastewater and municipal wastewater are co-treated. The effect of dairy wastewater contribution on COD fraction changes in municipal sewage which has been treated with a sequencing batch reactor (SBR) in three wastewater treatment plants in north-east Poland is presented. In these plants the real contribution of dairy wastewater was 10, 13 and 17%. In raw wastewater, SS fraction (readily biodegradable dissolved organic matter) was dominant and ranged from 38.3 to 62.6%. In the effluent, SS fraction was not noted, which is indicative of consumption by microorganisms. The presence of dairy wastewater in municipal sewage does not cause changes in the content of the XI fraction (insoluble fractions of non-biodegradable organic matter). SBR effluents were dominated by non-biodegradable dissolved organic matter SI, which from 57.7 to 61.7%. In raw wastewater SI ranged from 1.0 to 4.6%. Xs fraction (slowly biodegradable non-soluble organic matter) in raw wastewater ranged from 24.6 to 45.5% while in treated wastewater it ranged from 28.6 to 30.8%. In the control object (fourth wastewater plant) which does not process dairy wastewater, the SS, SI, Xs and XI fraction in inflow was 28.7, 2.4, 51.7 and 17.2% respectively. In the effluent the SS, SI, Xs and XI fraction was below 0.1, 33.6, 50.0 and 16.4% respectively.

Ammonia Nitrogen Transformations in a Reactor with Aggregate made of Sewage Sludge Combustion Fly Ash.

The influence of light weight aggregate made of fly ash from sewage sludge thermal treatment (FASSTT LWA) on ammonia nitrogen metabolism, and on quantitative and qualitative changes of microorganisms colonizing the filling, was investigated. Two reactors were used in the experiment. The first was filled with gravel, the other with FASSTT LWA. The reactors were operated with a wastewater hydraulic loading rate of 5 mm(3) mm(-2) d(-1). During the eleven-week experiment, high efficiency of ammonia removal was observed. The lower concentrations of nitrites and nitrates in the effluent indicate that ammonia nitrogen removal resulted not just from nitrification. Nitrate concentration increase was reflected in a decrease in nitrogen removal efficiency. One possible explanation for this phenomenon is that in the period when ammonia nitrogen and nitrites were present in the reactor's FASSTT LWA filling, facilitating conditions occurred for the deammonification process.

Hydrogenotrophic denitrification process efficiency and the number of denitrifying bacteria (MPN) in the sequencing batch biofilm reactor (SBBR) with platinum and carbon anodes.

This work reports on the effect of electric current density and anode material (platinum, carbon) on the concentration of oxidized and mineral forms of nitrogen, on physical parameters (pH, redox potential, electrical conductivity) and the number of denitrifying bacteria in the biofilm (MPN). Experiments were conducted under anaerobic conditions without and with the flow of electric current (with density of 79 mA · m(-2) and 132 mA · m(-2)). Results obtained in the study enabled concluding that increasing density of electric current caused a decreasing concentration of nitrate in the reactor with platinum anode (R1) and carbon anode (R2). Its concentration depended on anode material. The highest hydrogenotrophic denitrification efficiency was achieved in R2 in which the process was aided by inorganic carbon (CO2) that originated from carbon anode oxidation and the electrical conductivity of wastewater increased as a result of the presence of HCO3(-) and CO3(2-) ions. Strong oxidizing properties of the platinum anode (R1) prevented the accumulation of adverse forms of nitrogen, including nitrite and ammonia. The increase in electric current density affected also a lower number of denitrifying bacteria (MPN) in the biofilm in both reactors (R1 and R2). Metal oxides accumulated on the surface of the cathode had a toxic effect upon microorganisms and impaired the production of a hydrogen donor.

Effect of the C:N:P ratio on the denitrifying dephosphatation in a sequencing batch biofilm reactor (SBBR).

A series of investigations were conducted using sequencing batch biofilm reactor (SBBR) to explore the influence of C:N:P ratio on biological dephosphatation including the denitrifying dephosphatation and the denitrification process. Biomass in the reactor occurred mainly in the form of a biofilm attached to completely submerged disks. Acetic acid was used as the source of organic carbon. C:N:P ratios have had a significant effect on the profiles of phosphate release and phosphate uptake and nitrogen removal. The highest rates of phosphate release and phosphate uptake were recorded at the C:N:P ratio of 140:70:7. The C:N ratio of 2.5:1 ensured complete denitrification. The highest rate of denitrification was achieved at the C:N:P ratio of 140:35:7. The increase of nitrogen load caused an increase in phosphates removal until a ratio C:N:P of 140:140:7. Bacteria of the biofilm exposed to alternate conditions of mixing and aeration exhibited enhanced intracellular accumulation of polyphosphates. Also, the structure of the biofilm encouraged anaerobic-aerobic as well as anoxic-anaerobic and absolutely anaerobic conditions in a SBBR. These heterogeneous conditions in the presence of nitrates may be a significant factor determining the promotion of denitrifying polyphosphate accumulating organism (DNPAO) development.

Anaerobic rotating disc batch reactor nutrient removal process enhanced by volatile fatty acid addition.

RBC effluent needs further treatment because of water-quality standards requiring low nitrogen and phosphorus concentrations. It may be achieved by using reactors with biomass immobilized on the filling's surface as post-denitrification biofilm reactors. Due to the lack of organic matter in treated wastewater, the introduction of external carbon sources becomes necessary. The new attached growth bioreactor--anaerobic rotating disc batch reactor (ARDBR)--was examined as a post-denitrification reactor. The impact of selected volatile fatty acids on nutrient removal efficiency in an ARDBR was studied. The biofilm was developing on totally submerged discs mounted coaxially on a vertical shaft. Acetic, propionic, butyric and caproic acids were applied. Wastewaters were removed from the reactors after 24-h treatment, together with the excess solids. In the ARDBR tank, there was no biomass in the suspended form at the beginning of the treatment process. Acids with a higher number of carbon atoms (butyric and caproic) were the most efficient in denitrification process. The highest phosphorus removal efficiency was noted in the ARDBR with butyric and propionic acids. The lowest unitary consumption of the external source of carbon in denitrification was recorded for acetic acid, whereas the highest one for caproic acid.

Recycling potential of air pollution control residue from sewage sludge thermal treatment as artificial lightweight aggregates.

Thermal treatment of sewage sludge produces fly ash, also known as the air pollution control residue (APCR), which may be recycled as a component of artificial lightweight aggregates (ALWA). Properties of APCR are typical: high content of Ca, Mg, P2O5, as well as potential to induce alkaline reactions. These properties indicate that ALWA prepared with a high content of APCR may remove heavy metals, phosphorus, and ammonium nitrogen from wastewater with high efficiency. The aim of this preliminary study was to determine the optimal composition of ALWA for potential use as a filter media in wastewater treatment systems. Five kinds of ALWA were produced, with different proportions of ash (shown as percentages in subscripts) in mixture with bentonite: ALWA0 (reference), ALWA12.5, ALWA25, ALWA50, and ALWA100. The following parameters of ALWA were determined: density, bulk density, compressive strength, hydraulic conductivity, and removal efficiency of ions Zn(2+), NH4 (+), and PO4 (3-). Tests showed that ALWA had good mechanical and hydraulic properties, and might be used in wastewater filtering systems. Phosphates and zinc ions were removed with high efficiency (80-96%) by ALWA25-100 in static (batch) conditions. The efficiency of ammonium nitrogen removal was low, <18%. Artificial wastewater treatment performance in dynamic conditions (through-flow), showed increasing removal efficiency of Zn(2+), PO4 (3-) with a decrease in flow rate.

The effect of volatile fatty acids (VFAs) on nutrient removal in SBR with biomass adapted to dairy wastewater.

This study aims to determine the effect of volatile fatty acids on nitrates and orthophosphate removal in a sequencing batch reactor (SBR) with activated sludge biomass adapted to process dairy wastewater. The research also determine whether it is the type of fatty acid applied that is responsible for the effectiveness of denitrification and dephosphatation at varying nitrate:orthophosphate ratios, or whether these processes are additionally affected by the presence of microorganisms that have adapted to the specific carbon composition of the wastewater being treated. At the beginning of an operating cycle SBRs were dosed with VFAs to provide a source of carbon. A comparative analysis was performed of nitrate and orthophosphate removal at initial nitrate concentrations of 1.22, 7.3 and 15.2 mgN(NO3)L⁻¹. Doses of fatty acids were approximately 10.5 mg⁻¹COD·mgP(PO4). They consisted of acetic, propionic, butyric, isobutyric, valeric, isovaleric and caproic acids. Increases of nitrate concentration from 1.22 to 15.2 mg N(NO3)L⁻¹ were observed to reduce the quantity of removed orthophosphate depending on the fatty acid applied, from 7.2-9.2 mgP(PO4)L to 4.5 - 6.7 mgP(PO4)L. Every increase in the removed nitrates by 5.0 mgN(NO3)L⁻¹ was accompanied by a decrease in the removed orthophosphate of around 1 mgP(PO4)L⁻¹. The reactor containing acetic acid was found to remove the highest amount of orthophosphate irrespective of the nitrates concentration. Acids present in significant amount in dairy wastewaters (i.e. acetic, propionic and butyric) were more effective source of carbon in the denitrification process compared to low concentration acids.

Effect of fermented wastewaters from butter production on phosphates removal in a sequencing batch reactor.

This study determined the potential for fermented wastewaters from butter production plant to act as a carbon source to facilitate phosphates removal. Synthetic dairy wastewaters were treated using SBR, with doses of fermented wastewaters. An increase in the fermented wastewater doses were found to improve the effluent quality in respect of phosphates and nitrates. The lowest concentrations of phosphate and nitrates, respectively 0.10 ± 0.04 mg PO(4)-PL(-1) and 1.03 ± 0.22 mg NO(3)-NL(-1), were noted in the effluent from the reactor fed with fermented wastewaters in a dose of 0.25 L d(-1) per 0.45 L d(-1) of wastewaters fed to the reactor. In the case of the two highest doses, an increase in effluent COD was stated. The higher effectiveness resulted from the fact that the introduction of fermented wastewaters caused an increase in the easily-available carbon compounds content and the predominance of acetic acid amongst VFAs available to dephosphatating and denitrifying bacteria.

Effect of electric current on adsorption effectiveness on chitin and chitosan.

The objective of this study was to determine the effect of an electric current on the effectiveness of reactive dye Reactive Black 5 (RB 5) adsorption onto two adsorbents: chitin and chitosan. The current density applied in the experiment was 50 A/m2. The experiment was carried out using electrodes made of stainless steel. At the first stage of the experiment - without the flow of electric current - the effectiveness of RB 5 dye adsorption onto chitin was determined at pH 3.0 and 5.0, whereas onto chitosan it was at pH 5.0. In the second stage, the effectiveness of RB 5 dye adsorption was determined onto chitin and chitosan with a simultaneous flow of direct current. In the case of both adsorbents, the pH value of the solution was 5.0. Results achieved in the study proved that the electric current had a positive effect on adsorption effectiveness onto chitin, as it contributed to an increase in the quantity of removed RB 5 dye to 440 mg/g d.m. from the initial 270 mg/g d.m. when assayed at the optimal pH 3.0 and from 135 mg/g d.m. when assayed at pH 5.0.

Electrolytically aided denitrification on a rotating biological contactor.

The study was conducted at a bench scale on a rotating biological contactor under both conventional conditions (without the flow of electric current) and with the passage of an electric current having the following densities: 0.2 A m(-2), 0.8 A m(-)2 and 1.5 A m(-2). Stainless-steel discs covered with an immobilized biofilm served as a cathode, whereas an electrode made of stainless steel immersed in the wastewater of the flow tank of the contactor served as an anode. Experiments were carried out on municipal wastewater containing nitrogen in the organic and ammonium forms. The highest efficiency of nitrogen removal was observed with the passage of electric current at the density of 0.2 A m(-2). The efficiency of the denitrification process was over 64% and the nitrification efficiency was 93.4%.