A feasible, novel, and natural coagulant extracted from G. ulmifolia stem bark was characterized and used in experiments of coagulation/dissolved air flotation (C/DAF) to treat synthetic dairy ...wastewater (SDW). The performance of G. ulmifolia to remove turbidity, chemical oxygen demand (COD), and UV254 was evaluated by using response surface methodology (Doehlert matrix). G. ulmifolia dosage and pH were evaluated and optimized in the C/DAF process and its characterization was performed by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and also zeta potential. Results showed that G. ulmifolia stem bark is composed of large quantities of condensed tannins represented by the groups C=C-C and CO of pyran (flavonoid C-rings), which serve as bridges during coagulation. Moreover, the presence of porous cavities in surface of G. ulmifolia, shown by SEM, indicated capacity for adsorption. G. ulmifolia dosage and pH were significant (p ≤ 0.05) for pollutant removal from the SDW. Jar test results revealed that 95.8% of turbidity, 76.0% of COD, 81.2% of BOD, and 85.6% of UV254 were removed from SDW by using G. ulmifolia stem bark at a dose of 775.8 mg L−1 and pH 5.00. Finally, our results showed promising use of G. ulmifolia as a coagulating agent due to its novelty, efficiency, low-cost, and eco-friendly properties as an alternative for the treatment of dairy wastewaters.
Display omitted
•G. ulmifolia is an efficient coagulant for removing pollutants from dairy wastewater.•95.8% of turbidity and 81.2% of BOD were removed by G. ulmifolia extract.•775.8 mg L−1 of G. ulmifolia at pH 5.00 was found to be optimal for coagulation.•Condensed tannins present in G. ulmifolia extract act on the coagulation mechanisms.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The banana tree circle (BTC) is a low-cost system for local greywater management, using a natural treatment and disposal process, providing additional resource recovery benefits. However, there are ...no standard design criteria for BTC that would allow for quality control of its efficiency and sustainability, and little is currently known about the full-scale performance of BTC. Based on the scoping literature review of 31 documents in the scientific database and eight documents from grey literature, a standard design model was proposed for the BTC technology based on the concept of water balance, greywater flows, rain, infiltration, and evapotranspiration. The first two steps of the BTC design were determining the areas required for infiltration and evapotranspiration. A cylindrical form trench, the soil percolation rate, and the hydraulic loading rate were considered for the infiltration area. The banana trees' evapotranspiration rate was taken into consideration for the evapotranspiration area. The proposed model was applied in a case study where we used a trench with 0.8 m depth and 1.5 m diameter. This study proposes a standard design criterion for the BTC based on environmental factors, and the scoping of the literature provides the basis for future studies to evaluate its environmental sustainability.
There are several techniques for sizing horizontal subsurface-flow constructed wetlands systems (CWs), and mathematical models have been frequently used for this purpose because they more accurately ...represent the liquid behaviour in these reactors. The P-k-C* model has already been used in the prediction of organic matter removal in CWs, but it has been little explored in the literature. On other hand, the model proposed by Chan and Chu Modeling the reaction kinetics of Fenton's process on the removal of atrazine. Chemosphere. 2003;51(4):305-311 was not known for prediction of organic matter removal in CW systems. In the present work, the kinetic data for chemical oxygen demand (COD) removal of 28 horizontal subsurface-flow constructed wetlands were used to compare the performance of two pseudo-first-order kinetic models (P-k-C* model and model from Chan and Chu. The comparisons of nonlinear regressions were performed considering Akaike information criterion (AIC), root-mean-square error (RMSE), and adjusted coefficient of determination (
). In general, both models were able to provide good predictions of relative remaining concentration (C/C
0
). However, the Chan and Chu model produced higher adjustment coefficients, showing the potential to be used in modelling and simulation of the degradation kinetics of organic matter in wetlands.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
A comparison of chromium abatement from irrigation water, by the use of two selected plant species,
Phragmites australis
and
Helianthus annuus
, planted in chromium-contaminated soil, was studied in ...the present work. The above plant species were irrigated, in a continuous mode, with 10 mg Cr
VI
/L contaminated tap water. More than 90 % of hexavalent chromium was reduced to trivalent chromium, from both plant species, as measured in the drainage water. Moreover, total chromium removal ranged from 54 % (
Phragmites
) to 70 % (
Helianthus
). After 90 days, the total chromium content of the contaminated soil dropped from 70 to 32 and 34 mg Cr/kg
dry soil
, for
Helianthus
and
Phragmites
, respectively.
Helianthus
accumulated higher amount of chromium in the roots (2,730 mg Cr/kg
dry tissue
) as compared to 1,800 mg Cr/kg
dry tissue
for
Phragmites
. Most of Cr
VI
was reduced to Cr
III
in all plant tissues, with
Phragmites
showing lower affinity for Cr
VI
reduction in the root tissues but higher chromium translocation potential from roots to stems, while
Helianthus
showed higher chromium translocation from roots to leaves. Toxicity effects, expressed as root growth rate inhibition, indicated that
Phragmites
were the most tolerant specie to chromium effects. Both plant species showed high potentialities to be used in phytoremediation installations for chromium removal.
Full text
Available for:
CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Given the increasing demand, there is a constant need to identify ways to optimize water use without imposing drought risks and conflicts for its use. The water availability, represented by low ...flows, is used as a criterion to grant water use by regulators. Therefore, the objective here was to investigate the effects on water availability considering annual and monthly estimates of two low flows: the low flow observed for 7 consecutive days with a return period of 10 years (Q
7,10
) and the permanent flow present 95% of the time (Q
95
). Streamflow regionalization techniques were used to transfer information from the stream gauges to the rest of the basin, so it was possible to compute the relative difference between the estimates (RD%) of all hydrographic segments. The results show that the annual Q
95
is 31% higher than the Q
7,10
, whereas the monthly values were statistically equal. The annual Q
7,10
was the most restrictive estimate, however, there is potential to increase from 50% (January) to about 5% (October) when seasonality is considered. Conversely, monthly Q
95
can only increase by 20% (February) and has to decrease during dry seasons, i.e. 20% reduction in September, in relation to the annual estimate. The findings show that the consideration of seasonality can optimize water use and, thus, watershed management and planning.
Dairy operations generate large volumes of polluted wastewater that require treatment prior to discharge. Chemically enhanced primary treatment (CEPT) is a widely utilized wastewater treatment ...strategy; but it requires the use of non-biodegradable coagulants that can lead to toxic-byproducts. In this study, chitin from shrimp shell waste is extracted and converted into chitosan. Chitosan was demonstrated to be a natural, low-cost alternative coagulant compatible with the CEPT. Following treatment, dissolved air flotation allowed for the removal of turbidity, COD, and UV
254
from the synthetic dairy effluent (SDE). Doehlert matrix was used to optimize the chitosan dosage and pH of the CEPT; as well as to model the process. The mechanisms behind the coagulation-flocculation were revealed using zeta potential analysis. FTIR spectroscopy was utilized to confirm the functional groups present on the chitosan. Chitosan with a degree of deacetylation equal to 81% was obtained. A chitosan dose of 73.34 mg/L at pH 5.00 was found to be optimal for the removal of pollutants. Removals of COD, turbidity and UV
254
were 77.5%, 97.6%, and 88.8%, respectively. The amount of dry sludge generated to treat 1 m³ of SDE was 0.041 kg. Coagulation-flocculation mechanisms involved in chitosan-mediated treatment of SDE involve the neutralization of electrostatic charges carried on the amine groups present in cationic chitosan at pH 5.00. Doehlert matrix proved to be a useful tool in optimizing parameters throughout the coagulation-flocculation process. Chitosan from shrimp waste is a low-cost, eco-friendly coagulant alternative for the removal pollutants from dairy effluent using the CEPT.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
To investigate the feasibility of implementing decentralized sewage treatment systems aiming to meet environmental standards, the performance of three decentralized wastewater treatment plants ...(WWTPs) comprising septic tanks and anaerobic filters (ST+AF) was evaluated. The ability of the WWTPs to comply with the provisions of the legislation and the technical literature was investigated by monitoring physical and chemical parameters at the entrance and exit of the WWTPs, from May 2017 to August 2018. Considering that factors such as operational routine, design of treatment systems, and the existence of pluvial contributions to the sewage network can influence the performance of WWTPs, an investigation of these factors was conducted. The results show that the ST+AF systems can meet the requirements of the legislation. The hypothesis raised in this study is that factors such as cleaning routine and dimensioning of the treatment units can influence the performance of the systems. The best performance was found in the WWTP submitted to frequent cleaning and whose ST dimensions were closest to those recommended by technical standards. The average annual efficiencies of removal of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in this WWTP assumed values of 93 and 89%, while its solid effluents presented concentrations 82% below the limit established in legislation. Finally, no rainwater contributions were found in the WWTPs, which may be associated with the use of short collection networks in decentralized systems.
Full text
Available for:
CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Heavy metal pollution creates environmental health concerns. Among these, iron (Fe), copper (Cu) and manganese (Mn) are commonly found in aquatic environments due to the release of wastewaters. ...Phytoremediation in hydroponics uses macrophytes to treat contaminated environments, and this is influenced by environmental factors. However, the relationship between these factors and the removal of Fe, Cu and Mn by macrophytes is not known. Therefore, a meta-analysis serves to determine the correlations between environmental factors and the removal of these metals in real wastewater by macrophytes, as well as to identify the role of different aquatic forms of macrophytes in phytoremediation. Emergent macrophytes had higher concentrations of manganese in their tissues, and higher bioconcentrations factor of iron and manganese than floating plants. Regardless of the biotope, higher concentrations of Fe and Cu decreased the ability of plants to bioconcentrate them. The correlations among exposure time, pH, dissolved oxygen, nitrogen, phosphorus, photoperiod and metal phytoremediation by plants were also found. It can be concluded that the emergent macrophytes showed better performance in terms of the removal of Fe, Cu and Mn, and that the significant correlations between environmental factors and removal vary with the type of metal and the environmental factor analyzed.
The evapotranspiration tank (TEvap) is a 'zero-discharge' ecotechnology for toilet water disposal. This work refers to a preliminary study to evaluate the influence of forages and the addition of a ...vertical soil strip on evapotranspiration (ET), electrical conductivity (EC) and pH in TEvap receiving fresh water. The factors studied were the forages and the soil strip, resulting in four treatments with three replications. Two plant growing seasons, cycle 1 and cycle 2, were monitored, during which the variables were measured every three and seven days, respectively. Weather variables were used to estimate the reference evapotranspiration and determine the TEvap coefficient (K
TEvap
). The accumulated ET for TEvap with Capiaçu was 27.93% and 45.89% greater than for TEvap cultivated with Tifton-85 during the first and second cycles, respectively. There were no significant differences in ET for TEvap with and without the soil strip. BRS Capiaçu also showed lower values for EC and pH. High values were obtained for K
TEvap
: 2.37 and 1.76 for TEvap cultivated with BRS Capiaçu and Tifton-85 grass, respectively. Considering the period of this study, the minimum area for 'zero-discharge' would be 5.70 m
2
inhab
−1
and 7.77 m
2
inhab
−1
by TEvap planted with BRS Capiaçu and Tifton-85 grass, respectively. Due to its greater capacity for evapotranspiration, it can be concluded that the BRS Capiaçu forage is suitable for a 'zero-discharge' constructed wetland systems. It is suggested that further, more-thorough studies be carried out to design a 'zero-discharge' TEvap, considering different weather conditions, crops and inlet toilet water.
HIGHLIGHTS
Evapotranspiration tank (TEvap) is a 'zero discharge' ecotechnology for disposing toilet water;
A preliminary study was conducted to simulate the evapotranspiration in TEvap receiving fresh water;
Two forages - Cynodon spp. (Tifton-85 grass) and Pennisetum spp. (BRS Capiaçu) - were cultivated in the tanks;
5.70 m
2
inhab
−1
were estimated for evapotranspiration with BRS Capiaçu and 7.77 m
2
inhab
−1
with Tifton-85 grass.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Optimization of coagulant dosage and pH to reduce the turbidity and chemical oxygen demand (COD) of synthetic dairy wastewater (SDW) was investigated using a full factorial design (FFD) and full ...factorial design with center point (FFDCP). Two organic coagulants, polyacrylamide (PAM) and Tanfloc were used. The optimal values of coagulant dosage and pH were determined using a multiple response optimization tool and desirability function. The results obtained revealed that the optimum condition for removing turbidity and COD were at pH 5.0 using 50 mg L−1 of coagulant. The same optimum point was obtained in both experimental designs, indicating a good agreement between them. In optimum conditions, the expected removal of turbidity was above 98% with PAM and above 95% with Tanfloc. The estimated COD removal was above 72% with PAM and above 65% with Tanfloc. The addition of center points with replicates in the factorial design allowed to obtain the estimate of the experimental error with a smaller number of runs, allowing to save time and cost of the experimental tests. Moreover, the addition of center points did not affect the estimates of the factorial effects and it was possible to verify the effect of curvature, allowing obtaining information about the factors at intermediate levels.
PDF