Agricultural Effluents Research Articles

Estimating oxygen consumption of rainbow trout (Oncorhynchus mykiss) in a raceway: A Precision Fish Farming approach

The Precision Fish Farming (PFF) approach was applied to the estimation of fish oxygen consumption of rainbow trout in a raceway farm. A dynamic model, simulating the evolution of Dissolved Oxygen concentration, was identified: the daily oscillation of fish oxygen consumption rate was simulated by means of a sinusoidal function. The model was applied to the data set collected during a four-week field study, which was carried out in July 2019. Water temperature and Dissolved Oxygen concentration were measured with an hourly frequency in farm influent and effluent. Fish biomass was monitored on a daily basis by combining the data provided by a state-of-the art system for non-invasive estimation of fish weight distribution with mortality counting. The monitoring period was partitioned into two time-windows, as fish was not fed during the first two weeks. These windows were further partitioned into a calibration and validation set. Three model parameters, i.e. the average daily respiration rate, the amplitude of its daily oscillation, and its phase were estimated by fitting the model output to the time series of DO concentration in the effluent. The results of the calibration show that: 1) the daily average oxygen consumption rate is consistent with the literature; 2) the amplitude of the daily oscillation when fish is regularly fed is more than twice that estimated for fasting fish. The results of the validation suggest that the model could be used to implement a cost-effective automatic control of oxygen supply, based on the short-term prediction of oxygen demand.

Pineapple Peel Waste Adsorbent for Adsorption of Fe(III)

The current study discovers the capability of pineapple peel, which is an agricultural effluent, to be converted into adsorbent to be used in the removal of Fe(III). The adsorbent was prepared from pineapple peel waste using a chemical activation method impregnated with zinc chloride (ZnCl2), and the morphological and functional characterisation of the adsorbent was performed using FTIR and SEM. SEM images show rough surfaces of raw pineapple peel with creases. After the chemical treatment, substances in the pineapple peel waste such as pigments and acid-soluble oligosaccharides were removed, leading to the porous structure. Raw pineapple peel contained more functional groups, including the O–H stretching vibration at 3300 cm−1 and the C–H vibration at 2917 cm−1, compared to the adsorbent with the fading of some characteristic peaks. The ability of the adsorbent to remove Fe(III) ions at different contact times and adsorbent dosages was studied. As the contact time and adsorbent dosage were increased, the adsorption capacity also increased. The results show the potential use of pineapple peel waste as an effective adsorbent for the treatment of wastewater in removing of Fe(III) ions

Potential of Echinodorus Cordifolius and Vallisneria Natans in Constructed Wetlands for the Removal of Water Pollution from Shrimp Farm Effluent

Management of shrimp aquaculture wastewater is still the major problems in fisheries. Objectives of this study are to set up laboratory-scale wetlands to evaluate the phytoremediator performance of Echinodorus Cordifolius and Vallisneria Natans in improving aquaculture wastewater as a treatment technology from the first day, 3 days, 7 days, 10 days, 14 days, 17 days and 21 days. The controlled and experimental design setup describes both constructed wetland by glass tank sizes with a circulation system. The controlled wetland dones’t have plants and an experimental wetland have plants with details as follows: Echinodorus Cordifolius had fresh weight 193.05±13.502 g, length of plant 55.5±2.081 cm, length of root 30.25 ±6.344 cm. Vallisneria Natans had fresh weight 57.58±0.05 g, length of plant 15cm, length of root 4cm. The results showed that the survival rate (SVR) of both aquatic plants in the experiment was 100% for Echinodorus Cordifolius and 16.7% for Vallisneria Natan in the 21-day experiment. Furthermore, the experimental wetland can be considered as an effective solution in reducing 95.68% of ammonium-nitrogen, 98.86% of nitrate-nitrogen, 60.02% of phosphate, 46,72% of chemical oxygen demand, 100% of iron, 97,4% of copper when compared with the concentration at the beginning of the experiment. To be concluded, the growth and development of Echinodorus Cordifolius and Vallisneria Natans in this wetland has a positive effect on reducing pollutants of shrimp aquaculture effluents in all the 21day experiment.

The role of effluent water irrigation in the mineral absorption of aerobic rice varieties (Oryza sativa L.)

Quality and quantity of different irrigation water types from conventional and alternative sources have a significant role on the productive parameters and chemical composition of crop plants. Appropriate alternative water sources and the reutilization of agricultural effluents can reduce the impact of rice production and animal husbandry on the natural water bodies. In the present study, influence of four different types of irrigation water was analyzed on the nutrient uptake (P, K, Ca, Mg, Na) of aerobic rice (Oryza sativa L.) in a complex lysimeter experiment in two consecutive years. Early maturing Hungarian rice varieties (M 488 and Janka) were irrigated with traditional river water (RW) and different alternative irrigation sources to evaluate the feasibility of a sodium containing intensive fish farm effluent with (EWG) or without (EW) gypsum supplementation and with the addition of natural river water (EWGR). Significant effects on the mineral content of the aboveground biomass were measured. P uptake by M 488 and Janka decreased after the irrigation with EW in 2017. In case of EW, EWG and EWGR, the Na content increased significantly (p ≤ 0.05) in both varieties; however, pre-treatment of salt containing effluent waters can moderate the stress level. As a consequence, the ability of both rice varieties to absorb Na suggests that rice production could be conditionally part of bioremediation of salt-affected soils and water bodies.

Water quality impact from shrimp farming effluents in a tropical estuary.

Shrimp farms cause environmental impacts in coastal ecosystems, compromising water quality by discharging effluents rich in nutrients and organic matter. The impacts of shrimp farming are often investigated by the unit effect of a farm. In this study, a harvest time series generator is used to analyze the impact of the synergistic effect of several shrimp farm harvests in a tropical estuary. Two other scenarios with harvests concentrated during spring and neap tides were also analyzed, showing waste management techniques that can reduce the impact of shrimp aquaculture on coastal areas. A hydrodynamic circulation and water quality model were implemented to evaluate the dispersion of pollutants using different discharge combinations. The harvesting scenarios were compared to a scenario without the activity. Results indicate that shrimp farming is not the main anthropogenic source of pollution in the estuary studied. There were no significant differences in the average and maximum variations in nutrient and organic matter concentrations between the different management techniques.

WASTEWATER TREATMENT WITH BIOCONVERSION FOR MOTOR FUEL PRODUCTION

The object of research: the process of wastewater treatment using bioconversion for subsequent motor fuel production. Investigated problem: improving the efficiency of bioconversion process for biofuel production with simultaneous wastewater treatment by removing nitrogen and phosphorous compounds. The main scientific results: providing the possibility of biofuel production with energy and economic inefficiency. It is done by combining the process of motor biofuel production with the process of treating wastewater from biogenic elements makes it perspective for commercial use. Traditional technology for the production of motor biofuels from microalgae includes cultivation, harvesting, dehydration and drying of biomass, extraction of oils from them and subsequent production of methyl esters and glycerol. Such technology is often not economically effective. It requires significant amount of energy for carrying out all necessary processes. In addition, it requires significant expenditures of water and nutrients. The use of nutrient-rich wastewater as a culture medium for the cultivation of microalgae allows not only to reduce costs, but also to purify wastewater from nitrogen and phosphorus compounds, which makes this process economically effective. The area of practical use of the research results: Sewage and gray water treatment plants. Industrial and agricultural effluents treatment plants. Different types of enterprises, which have wastewater enriched with nitrogen and phosphorous compounds. Innovative technological product: The technology of microalgae cultivation using wastewater as a culture medium. The technology allows effectively purifying used wastewaters from nitrogen and phosphorous compounds with no waste at the end. Scope of the innovative technological product: Improved technology of motor biofuel production with simultaneous wastewater purification, which is economically effective and environmentally safe.

Indigenous Knowledge and Acceptability of Treated Effluent in Agriculture

The twin challenges of lack of access to improved sanitation and food insecurity remain critical, particularly in the global south. With cognizance of the nutrient potential of human excreta, there has been increasing interest in linking sanitation innovations with agriculture by using nutrients recovered from human excreta for crop production, thus, closing the nutrient loop. While studies and field trials have explored and validated the technical feasibility of reusing nutrients recovered from human excreta in agriculture, there is still limited knowledge of its social acceptability. This study examined whether indigenous knowledge can be leveraged to increase the acceptability of human-excreta-derived plant nutrient sources such as treated effluent in agriculture. A qualitative research design comprising seven focus group interviews (five in rural areas and two in peri-urban areas) was conducted in KwaZulu Natal, South Africa. Findings from the focus groups reveal a willingness to grow and consume food using treated effluent. Additionally, participants made references to indigenous practices that encourage recycling and reuse of human excreta. Given the potential to simultaneously address issues of food insecurity and sanitation that characterize many peri-urban and rural areas in South Africa, we recommend further studies in this area.

Clogging rate of pressure compensating emitters in irrigation with rainbow trout fish farm effluent

One of the most fertilizing effluents for irrigation are those from fish farms. In drip irrigation systems, emitter clogging is the biggest problem of the effluent application. Therefore, the aim of this paper was to assess the clogging rate of a drip irrigation system using the effluent of a rainbow trout farm. A control treatment with the input fish farm freshwater and two more using fish farm effluent, with and without irrigation lateral drainage, were tested. Pressure compensating emitters Microflapper with nominal discharges of 4 and 8 L/h (M4, M8) and Netafim with discharges of 4, 8, and 12 L/h (N4, N8, and N12) were used. For each treatment, 42 irrigations events were carried out with a total of 336 h over a 4-month period. Each irrigation event lasted 8 h every 3 days. Clogging rate, Christiansen uniformity (CU) and emission uniformity (EU) coefficients were utilized for assessing the hydraulic performance of emitters. There was no emitter completely clogged during the experiment. However, as the clogging rate gradually increased, lateral discharges during the irrigation season decreased to a maximum of 57% of the initial value in some laterals. Evolution of the clogging rate was unstable, especially in the control treatment. N4 emitter show the best performance regardless of the quality of irrigation water. The clogging rates of M4 and N8 emitters were significantly (p < 0.05) higher when effluent was used. The N12 and M8 emitters had the highest sensitivity to clogging, without differences between treatments. Results show the dependence of clogging rate on emitter type and its discharge. The CU as well as EU for all emitters and treatments were higher than the allowable minimum. Lateral drainage had the greatest impact on the N12 and M8 emitters, which had the highest discharge. Moreover, some relationships between CU and clogging rate were obtained. It is generally possible to use the rainbow trout effluent in a drip irrigation system with pressure compensating emitters.

Fate, transport and ecological risk of antibiotics from pig farms along the bang pakong River, Thailand

This study was conducted to investigate the impact of different seasons (dry and rainy seasons) in 2018 on the fate, transport, and ecological risk of antibiotics drained from pig farms along the Bang Pakong River, Thailand. Twenty-one residual antibiotics were detected in pig farm effluents, drainages, and the river in both seasons. Amoxicillin, tetracycline, chlortetracycline, and tiamulin were found dominantly in the pig farm effluents, showing high detection frequencies of 83–100 % in the total number of the effluent samples. Maximum concentrations of these four dominant antibiotics in the drainage and the river were 0.12–5.20 μg L−1 in the dry season and 0.12–16.1 μg L−1 in the rainy season. Tetracycline (15.1 μg L−1) and chlortetracycline (16.1 μg L−1) were found at the highest concentrations in the rainy season. The multiple linear regression and random forest analyses between residual antibiotics in the farm effluents and the river in both seasons were performed to model dilution and removal processes of the antibiotics. The antibiotic removal processes were determined by their partition coefficients, solubility, biodegradability, and volatility. Compared to multiple linear regression, random forest models better identified the removal processes of pig farm antibiotics drained into the river. The risk quotient (RQ) of tiamulin determined based on its actual concentration in the river (0.0016 and 0.0017 in dry and rainy seasons) and its modeled concentration in river as predicted by random forest model (0.0029 and 0.001 in dry and rainy seasons) presented its potential ecological risk to fish, daphnia and green algae.

Fish isotopic niches associated with environmental indicators and human disturbance along a disturbed large subtropical river in China

Stable isotopes are increasingly used to detect and understand the impacts of environmental changes on riverine ecological properties. The δ13C and δ15N signatures of fish with different feeding habits were measured in a large subtropical river to evaluate how fish isotopic niches respond to environmental gradients and human disturbance. From basal resources to fish consumers, the high values of epilithic periphyton (biofilm) δ13C and suspended particulate organic matter δ15N concurrently determined the niche ranges and space (e.g., convex hull area) of fish communities. Along a longitudinal gradient (except in the industrial zone), the number of fish trophic guilds identified by Bayesian ellipses continuously increased; meanwhile, higher trophic diversity and less redundancy were observed near the lower reaches and estuary. Variance inflation factors were estimated to detect the multicollinearity of 40 environmental variables, 14 of which were selected as indicators. Relative importance (RI) analysis was used to evaluate the explanatory power of these indicators for the spatial variation in isotopic niche metrics; the results showed that riffle habitat area, water nitrate concentration, gravel-cobble substrate, and riparian buffer width were the 4 key environmental indicators (average RI > 12%) that determined the longitudinal pattern of fish isotopic niches. These findings suggested that community-level δ13C signatures are more responsive to changes in habitats (e.g., riffle) and substrates (e.g., gravel-cobble) supporting the productivity of autochthonous diatoms while δ15N signatures respond to water quality altered by nitrogen pollution from manure-fertilized farming and poultry livestock effluent. Furthermore, δ15N may be more robust and interpretable than δ13C as an isotopic indicator of ecosystem change in rivers exposed to multiple or complex anthropogenic stressors.

Biological reconditioning of sodium enriched zeolite by halophytes: case study of dairy farm effluent treatment

Constructed wetlands (CW) containing clinoptilolite zeolite and planted with five halophytes (Sesvium portulacastrum, Juncus effusus, Suaeda monoica, Inula crithmoides and Sarcocornia fruticosa) were irrigated with treated dairy farm effluent. The CW were operated for two years with retention time ranging from 2 to 7 d. Plant species did not affect SAR which was reduced in all treatments from 4.85 to 2.59 (mmol/L)0.5 due to ion exchange in zeolite. Halophytes increased evapotranspiration to 30 mm d−1 which countered sodium removal. Zeolite planted with Sesuvium portulacastrum had 15% lower sodium percentage (ESP, F1,118 = 12.53, p = 0.0006) and 5% higher calcium percentage (F1,118 = 7.44, p = 0.007) compared to non-planted zeolite, indicating reconditioning of zeolite with respect to sodium. Enhancement of SAR removal capability by reconditioned zeolite was demonstrated in 24 h batch experiments on excavated zeolite (n = 6) with saline water (SAR = 0, 17.6, 62.8, and 122.8 (mmol/L)0.5). Zeolite from Sesuvium planted CW reduced SAR to a greater extent than non-planted zeolite and was significant for inlet SAR 17.6 which was reduced to 3.33 ± 0.3 (mmol/L)0.5 compared to 3.68 ± 0.12 by non-planted zeolite (p < 0.05). In-situ biological reconditioning of active matrix in CW by tailored macrophytes is a novel strategy that may be applicable to other pollutants.

Nutrient removal from aquaculture effluent using settling ponds and filter-feeding species (Amphibalanus amphitrite and Saccostrea cucullata): an in-situ study

The potential application of settling ponds and two fouling filter-feeder species Amphibalanus amphitrite and Saccostrea cucullata to bioremediate semi-intensive shrimp farm effluent through 6 hours residence time was investigated. Settling pond reduced total nitrogen, total phosphorus and chlorophyll a to 80.5%, 77.8% and 94.3% of the initial concentrations (2.47 ± 0.07 mg L-1, 0.154 ± 0.006 mg L-1, and 24.44 ± 2.02 µg L-1), respectively. Amongst S. cucullata, A. amphitrite and combination of both species, oysters showed the highest efficiency in nutrient removal. Total nitrogen, total phosphorus and chlorophyll a diminished respectively to 70.6%, 67.7% and 40.9% of the initial concentrations in oyster treatments. These proportions were respectively 81.5%, 63.2% and 72.4% for ponds contacting barnacles, and 69.3%, 71.2% and 44.9% of the initial amounts in the combination of the two species treatment. Among three different densities used for treatments, medium density of oysters (0.54 oyster per liter) showed comparable effectiveness in nutrients and phytoplankton removal to the high density. Lower ammonia production along with imposing less costs and effort, as well as relatively equal ability; suggest the medium density of S. cucullata as the most suitable choice. Our results suggest that applying settlement ponds, and particularly with filter-feeder species such as S. cucullata, might mitigate the adverse impacts of shrimp wastewater, including coastal eutrophication, on adjacent ecosystems.

Rainbow trout farm effluent as a potential source of feed and medium for mass culture of Artemia parthenogenetica

This study was conducted to evaluate the effects of the trout farm effluent (TFE) co-feeding with microalgae Dunaliella tertiolecta (MA) on Artemia parthenogenetica biomass production. The feeding regimes were 95% TFE+5% MA, 85% TFE+15% MA, and 75% TFE+25% MA, with different Artemia densities of 250, 500, 1000 and 1500 individuals L−1 in 1-L tanks and 1000 individuals L−1 in 800-L tanks in three replicates in two distinct experiments, comprising 48 experimental units in 1-L tank stage (including four controls fed 0%TFE+100% MA in four densities) and 9 experimental units in 800-L stage. The growth performance and nutritional value of animals were measured on days 8, 11, 14, 17, 20 and 23. The highest growth and survival performance was observed in the treatment containing 75% TFE+25% MA at a density of 250 individuals L−1 (1-L tanks) and 85% TFE+15% MA at a density of 1000 individuals L−1 (800-L tanks). Furthermore, higher protein, carbohydrate, and lipid contents were obtained in the treatment feed 75% TFE+25% MA for both 1-L and 800-L tanks. In the same treatment, significantly higher contents of fatty acids were obtained too. However, the maximum amount for each fatty acids was different based on the different densities. Based on the present result, Artemia parthenogenetica can be cultured successfully using trout farm effluent even with high substitution ratio instead of microalgae as the main feed for Artemia biomass production.

Utilisation of an aquatic plant (Scirpus grossus) for phytoremediation of real sago mill effluent

Abstract Phytoremediation technology is one of the most promising treatment methods for wastewater, especially from food and agricultural effluent. In this experiment, sago mill effluent (SME) was treated through phytoremediation. The present study aimed to explore the potential of a native aquatic plant, Scirpus grossus, to reduce the concentrations of total suspended solids (TSS), chemical oxygen demand (COD), and biological oxygen demand (BOD) in SME before installing a full-scale system, to ensure the effectiveness of the remedy. Two systems, subsurface batch (SS) and free-surface batch (FS), were applied to select a better system to treat SME using S. grossus. After 80 days of experimentation, the findings indicate that the plant can better survive in the SS batch system compared to the FS batch system. Furthermore, the plant can reduce TSS, COD, and BOD by 98, 88, and 93%, respectively. Therefore, it can be concluded that S. grossus has remarkable potential in the removal of pollutants in the phytoremediation of SME.

Shrimp farming influence on carbon and nutrient accumulation within Peruvian mangroves sediments

In order to investigate the influence of shrimp farming activities on carbon and nutrient accumulation, sediment cores were collected from two areas at different distances from shrimp farms within a Peruvian mangrove ecosystem. In both areas two sediment cores were collected in a transect, one from a mangrove-covered site and one from a mudflat site. At both study sites, the isotopic values of carbon and nitrogen as well as the C:N molar ratios suggest that the highest carbon accumulation rates were linked to terrestrial-derived organic matter, with higher carbon stocks and fluxes within mangrove-covered zones. The historical records indicate that since the mid-1970′s, the areas nearest to the shrimp farming activity have been accumulating higher proportions of algal derived organic matter, which were likely triggered by the high nutrient influx derived from shrimp farming effluents. The carbon and nutrient fluxes were up to threefold higher within the area nearest to the shrimp farms, whereas the geochronologies showed that the carbon and nutrient stocks in this area increased by up to twofold. The results showed that mangrove-covered zones are more capable to keep pace with sea level rise (SLR) as compared to the mudflat zones, indicating the importance of mangrove vegetation in terms of the vulnerability of this region to SLR and an ongoing capacity to continue accumulating sediments. This study highlights the role that mangrove vegetation plays in mitigating the impact of shrimp farming activities, accumulating carbon and nutrients in pace with SLR.

Heavy Metals Accumulation in Surface Waters, Bottom Sediments and Aquatic Organisms in Lake Mainit, Philippines

Lake Mainit is one of the largest lakes recognized as Key Biodiversity Areas (KBA) in the Philippines with rich fishery resources. However, the lake is at risk from heavy metal contamination due to inputs of industrial, agricultural effluents and small-scale mining activities. The present work evaluated levels of heavy metals namely cadmium, lead, and mercury from key aquatic fauna and sediments from seven strategic sections of the lake in 2018. Muscle samples of all seven fish species assessed were below detections limits (BDL) for tHg and Cd. Trace concentrations of Pb in the muscles were detected in Oreochromis niloticus, Glossogobius giuris, Channa striata and Vivipara angularis but values were within safe ranges. Trace concentrations of Pb in the riverine crab (Sundathelpusa sp) exceeded safe limits. Both Cd and tHg were below detection limits in the three invertebrates assessed. Traces of Pb were detected in S4 (Magtiaco) and S5 (Jaliobong) below standard limits (0.05 ppm) only during the southwest (SW) monsoon but Pb were not detected across all stations during the NE monsoon of 2018. For Cd, however, trace concentrations were detected only during the NE monsoon wherein Cd in S2 (Mayag), S3 (Magpayang), S4 (Magtiaco), S5 (Jaliobong), S6 (Dinarawan) and S7 (Kalinawan) exceeded standard limits for Cd in waters (0.01 ppm). Concentrations of tHg in the water were not detected across the two sampling seasons in all seven tributary stations. In sediments, Pb were all detected during the southwest monsoon with highest Pb concentrations in S6 (Dinarawan) and S7 (Kalinawan) which exceeded safe limits. Trace Cd in sediments were mostly below detectable limits. Concentrations of tHg in sediments exceeded safe limits during the SE monsoon in S4 (Magtiaco) and S7 (Kalinawan) areas. These findings recommended that continuous heavy metal monitoring must be conducted. It is also strongly suggested to evaluate the presence of heavy metals in other aquatic organisms and assess the ecological risk posed by these heavy metals though heavy metal speciation analysis.

Heavy Metals Accumulation in Surface Waters, Bottom Sediments and Aquatic Organisms in Lake Mainit, Philippines

Lake Mainit is one of the largest lakes recognized as Key Biodiversity Areas (KBA) in the Philippines with rich fishery resources. However, the lake is at risk from heavy metal contamination due to inputs of industrial, agricultural effluents and small-scale mining activities. The present work evaluated levels of heavy metals namely cadmium, lead, and mercury from key aquatic fauna and sediments from seven strategic sections of the lake in 2018. Muscle samples of all seven fish species assessed were below detections limits (BDL) for tHg and Cd. Trace concentrations of Pb in the muscles were detected in Oreochromis niloticus, Glossogobius giuris, Channa striata and Vivipara angularis but values were within safe ranges. Trace concentrations of Pb in the riverine crab (Sundathelpusa sp) exceeded safe limits. Both Cd and tHg were below detection limits in the three invertebrates assessed. Traces of Pb were detected in S4 (Magtiaco) and S5 (Jaliobong) below standard limits (0.05 ppm) only during the southwest (SW) monsoon but Pb were not detected across all stations during the NE monsoon of 2018. For Cd, however, trace concentrations were detected only during the NE monsoon wherein Cd in S2 (Mayag), S3 (Magpayang), S4 (Magtiaco), S5 (Jaliobong), S6 (Dinarawan) and S7 (Kalinawan) exceeded standard limits for Cd in waters (0.01 ppm). Concentrations of tHg in the water were not detected across the two sampling seasons in all seven tributary stations. In sediments, Pb were all detected during the southwest monsoon with highest Pb concentrations in S6 (Dinarawan) and S7 (Kalinawan) which exceeded safe limits. Trace Cd in sediments were mostly below detectable limits. Concentrations of tHg in sediments exceeded safe limits during the SE monsoon in S4 (Magtiaco) and S7 (Kalinawan) areas. These findings recommended that continuous heavy metal monitoring must be conducted. It is also strongly suggested to evaluate the presence of heavy metals in other aquatic organisms and assess the ecological risk posed by these heavy metals though heavy metal speciation analysis.

Justification of parameters of electric activator applicable to reduce mineralization of collector-drainage water

The article substantiates the relevance of the problem of using collector-drainage water and the advisability of using electroactivators for this purpose. It is of scientific and practical interest to use diaphragm electroactivators for demineralization of collector-drainage water, using the principle of electrochemical activation due to unipolar treatment of agricultural effluents. Unipolar treatment reduces the degree of mineralization, changes the chemical composition, increases the electrodynamic properties, and makes it possible to treat water to the required degree. Prior to the experiments, the main factors and optimization parameters were identified, and a planning matrix of the experiment was drawn up. The experimental results allow us to identify the degree of correlation of the optimization parameter with the main factors. Using the Box-Benken method, the optimal parameters of the electroactivator are found.

The use of Chlorella vulgaris beijer in bioremediation activities

The article focuses on the possibility of applying the green alga Chlorella vulgaris Beijer. culture to bioremediation activities. Two types of wastewater were simulated, agricultural (ACW) and domestic (DW). The experiment was conducted under laboratory conditions in 500-ml Erlenmeyer flasks. The ratio of the amount of the algal culture and the wastewater volume was 1:10. The content of NO3-, NO2-and NH4+ in the composition of the wastewater was tested before and after cultivating the alga; during cultivation, the pH of the culture medium and the optical density of the Ch. vulgaris culture were monitored. The indicators of the amount of various forms of nitrogen and the pH level show that simulated domestic and agricultural wastewater can serve as an alternative nutrient medium for growing green algae. The use of Ch. vulgaris for the treatment of domestic and agricultural effluents allows avoiding almost completely their nitrate and ammonia pollution. The amount of biomass obtained within 25 days of cultivating Ch. vulgaris on agricultural sewage was two times higher than in the control Tamiya medium. Resulting Ch. vulgaris algal mass with the proteins content of 55% and lipids reaching 30% can match various needs being used a source of protein or lipids.

Nitrogen mineralization and eutrophication risks in mangroves receiving shrimp farming effluents

Nitrogen (N) inputs originated from shrimp farming effluents were evaluated for potential changes in the net N mineralization for mangrove soils from Northeastern Brazil. Our study provides notable information and assessment for the potential enhancement of N mineralization in preserved and shrimp-impacted semi-arid mangrove soils of the Jaguaribe River estuary, which is one of the largest shrimp producers of Brazil, using an analytical and daily tidal variation experimental approach. Nitrogen-rich effluents promoted a significant (p value < 0.001) increase of the total soil N content (1998 ± 201mgkg-1 on average) compared with the preserved sites (average: 1446 ± 295mgkg-1). The effluents also increased the N mineralization in the shrimp-impacted sites (N-min: 86.6 ± 37.5mgkg-1), when compared with preserved mangroves (N-min: 56.5 ± 23.8mgkg-1). Over a daily tidal variation experiment, we found that just 30% (36.2 ± 20.6mgkg-1) of mineralized N remains stored in the soil, whereas 70% (102.9 ± 38.8mgkg-1) was solubilized in tidal waters. Therefore, the N mineralization process may trigger eutrophication by increasing N inorganic bioavailability in mangrove soils receiving N-rich effluents from shrimp ponds, which in turn might increase primary producers' activity. This approach has not been studied so far in semi-arid mangroves, where the shrimp farming activity is one of the most important economic activities.