In this study, the role of Cyperus sp. was evaluated for removal of pollutants from swine wastewater. Vertical-flow pilot scale constructed wetlands (CWs) operating with a hydraulic retention time (HRT) of 72 h were monitored in a greenhouse, located in Viçosa, Brazil. Significant differences were observed for the following parameters: Kjeldahl nitrogen, total phosphorus, alkalinity and electric conductivity, with averages removals of 37.5 and 28.5%, 55.9 and 44.4%, 30.2 and 25.6 and 26.1% and 22.9% (for planted and unplanted CWs, respectively). The rate of dry matter yield from Cyperus sp. was 7.5 g m−2 day−1, and the nutrient uptake capacities were 21.8, 2.1, 14.0 and 0.9 g m−2 of N, P, K and Na, respectively. Evapotranspiration (2.7 mm day−1) was statistically higher in the planted CWs. Plants in the CWs are important for achieving high nutrient removal.

Groundwater drains used to manage saline watertables in the semi-arid zone of south-western Australia can discharge acidic saline water with high concentrations of metals to waterways. Mitigating the acidity impacts of the waters requires sulfate-reducing bioreactors capable of functioning under semi-arid conditions with limited source materials. Two simple pilot-scale bioreactor designs using straw and sheep manure mixtures were evaluated over several years. The bioreactors increased pH from <3.5 to >5.5 for 125–260 days, with concurrent evidence of sulfate reduction, >85% reductions in net acidity and >90% reductions in Al and most trace elements (e.g. Pb, Cu, Ni, Zn, Ce and La). When outflow pH < 5.5 (remaining greater than inflows), reduction in net acidity was 10–80% but concentrations of Pb, Cu and Ni remained >80% reduced over periods of 250 to >700 days. Rates of alkalinity generation initially exceeded 10 g CaCO3/m2/day in both bioreactors thereafter decreasing to >1–2 CaCO3/m2/day. Al and Fe retention was implicated in trace metal removal when pH < 5.5, mediated by biological alkalinity generation. High evaporation rates limited bioreactor function by restricting outflows with no benefits to alkalinity generation rates. This experiment showed that simple bioreactors can neutralise acidic waters and remove metals for short durations and show capacity for sustained reduction in acidity and metal concentrations over several years despite low alkalinity generation.

The Loxahatchee National Wildlife Refuge (Refuge) developed as a system with waters low in nutrients. Today, the Refuge wetlands are impacted by inflows containing elevated nutrient concentrations originating from agricultural sources flowing into canals surrounding the west side and from urban and horticultural areas flowing into canals surrounding the eastern side of the Refuge. We analyzed water quality sampled at 40 sites divided into eastern and western areas and four zones in the Refuge. We defined four zones as the canals surrounding the Refuge marsh, the perimeter zone, the transition zone, and the interior zone. The canal receiving agricultural inflows had greater alkalinity and conductivity (SpC), Si and SO4 but lower turbidity and total suspended solids than the canal receiving urban and horticultural inflows. Alkalinity, total dissolved solids (TDS), SpC, Ca, Cl, and SO4 concentrations were greater in the perimeter than in transition and interior zones. Alkalinity and SpC values and SO4 concentrations were greater in the transition than in interior zone. Alkalinity, SpC, and TDS values and Ca, SO4, and Cl concentrations correlated in negative curvilinear relationships with distance from the canal (r 2 = 0.78, 0.70, 0.61, 0.78, 0.64, 0.57, respectively). Analysis of multiple water quality parameters may reveal the complexity of interactions that might be overlooked in a simple single parameter analysis. These data show an impact of canal water containing high nutrient concentrations on water quality flowing from the canal towards the Refuge interior.

INTRODUCTION: This study focused on the assessment of the geochemistry and hydrology of the Imgok Creek–Young Dong tributary for the design of a field coal mine drainage treatment system. METHODS AND RESULTS: Examination of this site showed that the pH was greatly lowered by the addition of the Young Dong water, except in the month of March. The alkalinity was also affected; the concentrations of iron, aluminum, and sulfate were elevated at sites below the confluence; of these, iron was particularly problematic. High iron concentrations were primarily restricted to the acid rock drainage (ARD) (YD-9) water sources, whereas high aluminum concentrations were seen in both the ARD and in some of the upstream water sources. The acidity was primarily due to ferrous and ferric iron with a lesser amount of aluminum acidity. Except for the sampling in March, the flow was dominated by the ARD. This hydrologic condition resulted from the loads of iron, aluminum, sulfate, and acidity, among other constituents, that were dominated by the ARD. CONCLUSION: Finally, treatment activities should primarily focus on the ARD and specifically seek to remove ferrous and ferric iron from the treatment system.

PURPOSE: To examine (1) the effect of organic (poultry manure) and inorganic (residue mud and phosphogypsum) amendments on nutrient leaching losses from residue sand and (2) whether amendments improve the growth of plants in residue sand. METHODS: Leaching columns were established using residue sand. The phosphogypsum-treated surface layer (0–15 cm) was amended with poultry manure and/or bauxite residue mud and the subsurface layer (15–45 cm) was either left untreated or amended with phosphogypsum. RESULTS: Much of the Na+, K+, Cl− and SO 4 2− was lost during the first four leachings. Additions of phosphogypsum to both surface and subsurface layers resulted in partial neutralization of soluble alkalinity. Mean pH of leachates ranged from 8.0 to 8.4, the major cation leached was Na+ and the major balancing anion was SO 4 2− . Where gypsum was not applied to the subsurface, mean pH of leachates was 10.0–10.9, the main cation leached was still Na+ and the main balancing anions were a combination of SO 4 2− and HCO 3 − /CO 3 2− . At the end of the experiment, concentrations of exchangeable Na+ in the subsurface layers were similar regardless of whether gypsum had been applied to that layer or not. Yields of Acacia saligna were promoted by additions of poultry manure to the surface layer but unaffected by gypsum incorporation into the subsurface layer. CONCLUSIONS: Lack of reaction of phosphogypsum with the subsurface layer is unlikely to be a major factor limiting revegetation of residue sand since in the absence of phosphogypsum the excess Na+ leaches with the residual alkalinity (HCO 3 − /CO 3 2− ) rather than SO 4 2− .

INTRODUCTION: Flowing of the acid mine drainage may contaminate the adjacent water bodies causing substantial changes in the aquatic ecosystem. This aspect is the most relevant problem in the southern of Santa Catarina once the contaminated areas are inserted in the watershed of the Araranguá, Urussanga, and Tubarão rivers, increasing the need for recovery studies. These areas are between Criciúma, Içara, Urussanga, Siderópolis, Lauro Müller, Orleans, and Alfredo Wagner towns where a conservation unit exist called the Environmental Preservation Area of Baleia Franca. Aiming to compare the kinetics of the ash derived from burning coal and to neutralize acid mine drainage, different neutralizer, limestone, fly, and bottom ash, was mounted on a pilot scale experiment. DISCUSSION: The transport parameters showed the same order of infiltration and dispersion: fly ash < bottom ash < limestone. The order of measured alkalinity was: limestone < fly ash < bottom ash, with pH values of 9.34, 12.07, and 12.25, respectively. The limestone kinetics of acidic drainage neutralization was first order with reaction rate constant k = 0.0963 min−1, bottom ash was 3/4 with k = 0.0723 mol1/4 L−1/4 min−1, and the fly ash had higher order kinetics, 4/3, with reaction rate constant k = 27.122 L1/3 mol−1/3 min−1. However, by mathematical modeling, it was found that due to a combination of transport and kinetics, only limestone treatment reached a pH above 6 within 5 years, corresponding to the ideal as planned.