Coagulation as an effective method for cyanobacterial bloom control: A review.

Eutrophication, the over-enrichment with nutrients, for example, nitrogen and phosphorus, of ponds, reservoirs and lakes, is an urgent water quality issue. The most notorious symptom of eutrophication is a massive proliferation of cyanobacteria, which cause aquatic organism death, impair ecosystem and harm human health. The method considered to be most effective to counteract eutrophication is to reduce external nutrient inputs.

Surfactant-assisted air flotation: A novel approach for the removal of microplastics from municipal solid waste incineration bottom ash.

The potential for the presence of microplastics (MPs) in municipal solid waste incineration bottom ash (MSWI-BA) has not been fully explored. In this study, surfactant-assisted air flotation separation in aqueous media was used to examine the removal of MPs and other pollutants from different particle size fractions of MSWI-BA. The use of 1 mmol L sodium dodecylbenzene sulfonate (SDBS), at a liquid-solid ratio of 60:1, increased by 66 % the quantity of MPs floated from the MSWI-BA 0-0.

Pb contaminated soil from a lead-acid battery plant immobilized by municipal sludge and raw clay.

Soil heavy metal pollution poses a serious threat to the eco-environment. Municipal sludge-based passivators and clay minerals have been widely applied to immobilize heavy metal contamination in soils. However, little is known about the immobilization effect and mechanisms of raw municipal sludge and clay in reducing the mobility and bioavailability of heavy metals in soils.

Electric field-enhanced immobilization of Cd and Pb in contaminated river sediments.

The immobilization of heavy metal pollutants in river and lake sediments is critical for environmental health and safety. In this study, combined electrokinetic and chemical immobilization were used to remediate Cd and Pb polluted river sediments. The effect of the concentrations of the immobilization reagents and the applied voltage were investigated.

Microplastics contamination associated with low-value domestic source organic solid waste: A review.

Waste activated sludge and food waste are two typical important domestic low-value organic solid wastes (LOSW). LOSW contains significant organic matter and water content resulting in the transboundary transfer of liquid-solid-gas and other multi-mediums, such that the complexity of microplastics (MPs) migration should be of greater concern. This article provides a review of the literature focusing on the separation and extraction methods of MPs from LOSW.

Transfer of microplastics in sludge upon Fe(II)-persulfate conditioning and mechanical dewatering.

Sewage treatment plants act as both sinks and sources of microplastics with elevated concentrations of microplastics accumulating in the sludge. Consequently, the effects of sludge conditioning and dewatering processes on the fate of microplastics need to be clarified. Microplastic characteristics in sludge, before and after advanced oxidation Fe(II)-activated persulfate conditioning were studied using a microplastics dynamic flotation separator (MDFS).

Properties and heavy metal leaching characteristics of leachate sludge-derived biochar.

Heavy metals and metalloids, in sludge and sediments, are environmental pollutants of concern with long-term negative effects on human and ecological health. In this study, sludge from biological treatment of municipal waste leachate was pyrolyzed into leachate sludge-derived biochar (LSDB) at 300°C to 900°C, comprising complex organic and inorganic (particularly heavy metals) species formed from heterogeneous chemical reactions. Based on different advanced material analyses, that is, Thermogravimetric Analysis (TGA), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis, this study revealed that mass loss and microstructural changes of LSDBs occurred primarily due to decomposition of volatiles, aromatic rings, carbonates, and hydroxides.

Adaptability of organic matter and solid content to Fe/persulfate and skeleton builder conditioner for waste activated sludge dewatering.

Sludge conditioning is important for improved dewatering, with the sludge characteristics impacting the effect of conditioning. A composite conditioner, Fe-activated sodium persulfate (Fe/SPS) combined with phosphogypsum (PG), was used to examine its impact on sludges with different organic contents (34.6-43.

Examination of multiple sources of selenium release from coal wastes and strategies for remediation.

Selenium (Se) has been mobilised by leaching from coal and associated waste rock exposed by mining activities in Western Canada, with deleterious impact on aquatic wildlife. Waste rock characterisation indicates that up to 7% of the Se, as Se(IV), may be associated with organic matter, with ≈9%, as Se(0), associated with euhedral pyrite. Small 1-2 µm mineral particles with average Se concentration of 1.

Passivation of pyrite for reduced rates of acid and metalliferous drainage using readily available mineralogic and organic carbon resources: A laboratory mine waste study.

Acid and metalliferous drainage (AMD) is a major environmental issue resulting largely from exposure to weathering of mine wastes containing pyrite (FeS). At-source strategies to reduce the rate of formation of AMD have potential to be more cost-effective and sustainable than post-generation downstream treatments. The objective of this study was to examine the efficacy of geochemical and microbial treatments for at-source control through pyrite surface passivation.

Oxidative Dissolution of Sulfide Minerals in Single and Mixed Sulfide Systems under Simulated Acid and Metalliferous Drainage Conditions.

Chalcopyrite, galena, and sphalerite commonly coexist with pyrite in sulfidic waste rocks. The aim of this work was to investigate their impact, potentially by galvanic interaction, on pyrite oxidation and acid generation rates under simulated acid and metalliferous drainage conditions. Kinetic leach column experiments using single-minerals and pyrite with one or two of the other sulfide minerals were carried out at realistic sulfide contents (total sulfide <5.

Synchronization of dehydration and phosphorous immobilization for river sediment by calcified polyferric sulfate pretreatment.

Disposal of dredged river sediment requires decreases in both water content for reduction in disposal area, and the amount of eutrophication pollutants at risking of leaching. The effects of CaCl, polyferric sulfate (PFS) and calcified polyferric sulfate (CaPFS) on dewatering and phosphorus immobilization were examined. Upon CaPFS dosage of 1.

Enhanced dewater efficiency for river sediment by top-to-bottom water transmitting channels with different materials.

Artificial top-to-bottom water transmitting channels made of threads of wool blend (WT), cotton (CT), flax (FT), and polyethylene (PET) were used to enhance the dewater efficiency for river sediment. In addition, the disordered channels composed of 3-mm-long WT segments mixed randomly into the river sediment were also employed. The most effective dewatering channels were found to be top-to-bottom WT channels with water absorption capacity of 8.

Leaching behaviors and speciation of cadmium from river sediment dewatered using contrasting conditioning.

Chemical conditioning is an effective strategy for improved river sediment dewatering affecting both the dewatering efficiency and subsequent resource utilization of the dewatered cake. Two types of conditioning agents, polyaluminium chloride (PAC)/cationic polyacrylamide (PAM) (coagulation precipitation conditioning agent, referred to as P-P conditioning) and ferrous activated sodium persulfate (advanced oxidation conditioning agent, referred to as F-S conditioning) were examined. With increasing leach liquid to solid (L/S) ratio the concentration of Cd for the real time leachates from the dewatered cakes decreased, but the leaching ratio of Cd in both P-P and F-S dewatered cakes increased.

Dewaterability and energy consumption model construction by comparison of electro-dewatering for industry sludges and river sediments.

Electro-dewatering (EDW) is an emerging technology for improved sludge/sediment dewatering enabling subsequent cost effective treatment for toxicity and pathogenic reduction if required and/or disposal, but the effects of sediment/sludge properties on the efficacy of EDW remain unclear. Here we investigate EDW in the absence of chemical conditioning which can result in secondary pollution. The influence of sediment/sludge volatile solids content (VS), electrical conductivity (EC), pH and zeta potential (ζ), on mechanical and electrical behaviors determining dewaterability and energy consumption (P) was investigated.

Role of microbial diversity for sustainable pyrite oxidation control in acid and metalliferous drainage prevention.

Acid and metalliferous drainage (AMD) remains a challenging issue for the mining sector. AMD management strategies have attempted to shift from treatment of acid leachates post-generation to more sustainable at-source prevention. Here, the efficacy of microbial-geochemical at-source control approach was investigated over a period of 84 weeks.

The Combined Effects of Galvanic Interaction and Silicate Addition on the Oxidative Dissolution of Pyrite: Implications for Acid and Metalliferous Drainage Control.

The aim of this study was to determine the combined effect of galvanic interaction and silicate addition on the dissolution of pyrite, the major contributor to acid and metalliferous drainage (AMD). Single (pyrite, sphalerite, and galena)- and bi-sulfide (pyrite-sphalerite and pyrite-galena) batch dissolution experiments were carried out with addition of 0.8 mM dissolved silicate for comparison to previously published data.

Unexpected Non-acid Drainage from Sulfidic Rock Waste.

Most rock extraction sites, including mine sites and building construction sites, require a plan to assess, and mitigate if present, the risk of acid mine drainage (AMD). AMD is typically the major environmental concern where sulfide minerals are present in the excavated material and AMD prediction and remediation is based on internationally-accepted acid-base accounting (ABA) tests of representative field samples. This paper demonstrates that standardized ABA tests may not always be provide the correct AMD classification for commonly occurring waste rocks containing low-pyrite and -carbonate due to mineralogic assumptions inherent in their design.

Formation of Aluminum Hydroxide-Doped Surface Passivating Layers on Pyrite for Acid Rock Drainage Control.

The aim of this study was to test the performance of a novel method for acid rock drainage (ARD) control through the formation of Al(OH)-doped passivating surface layers on pyrite. At pH 2.0 and 4.

Effect of electric field strength on electro-dewatering efficiency for river sediments by horizontal electric field.

A series of electro-dewatering experiments were conducted to explore the effect of sediment cake thickness (1-5 cm) and electric field strength (2-50 V cm). The final dry solids content, energy consumption and dewatering productivity were modeled and the validity of the model was tested. It was demonstrated that the electric field strength determines final dry solids content and the power utilization is an exponential function of electric field strength.

The fundamental roles of monovalent and divalent cations with sulfates on molybdenite flotation in the absence of flotation reagents.

Due to regional shortage of freshwater, the use of saline/seawater for Cu-Mo sulfide ore flotation has received considerable attention. However, the effects of various salts, especially the cations present in seawater, on molybdenite flotation and the mechanisms involved remain unclear due to the complexity of the solutions applied. In this work, the influence of some common cations (, Na, K, Ca and Mg) with sulfate (SO ) anions on molybdenite flotability was investigated in the absence of flotation reagents (, frothers and collectors) at pH 10.

The Effects of Galvanic Interactions with Pyrite on the Generation of Acid and Metalliferous Drainage.

Although the acid generating properties of pyrite (FeS) have been studied extensively, the impact of galvanic interaction on pyrite oxidation, and the implications for acid and metalliferous drainage, remain largely unexplored. The relative galvanic effects on pyrite dissolution were found to be consistent with relative sulfide mineral surface area ratios with sphalerite (ZnS) having greater negative impact in batch leach tests (sulfide minerals only, controlled pH) and galena (PbS) having greater negative impact in kinetic leach column tests (KLCs, uncontrolled pH, >85 wt% silicate minerals). In contrast the presence of pyrite resulted consistently in greater increase in galena than sphalerite leaching suggesting that increased anodic leaching is dependent on the difference in anodic and cathodic sulfide mineral rest potentials.

The Formation of Silicate-Stabilized Passivating Layers on Pyrite for Reduced Acid Rock Drainage.

Acid and metalliferous release occurring when sulfide (principally pyrite)-containing rock from mining activities and from natural environments is exposed to the elements is acknowledged as a major environmental problem. Acid rock drainage (ARD) management is both challenging and costly for operating and legacy mine sites. Current technological solutions are expensive and focused on treating ARD on release rather than preventing it at source.