Impact of blending for direct potable reuse on premise plumbing microbial ecology and regrowth of opportunistic pathogens and antibiotic resistant bacteria.

Little is known about how introducing recycled water intended for direct potable reuse (DPR) into distribution systems and premise plumbing will affect water quality at the point of use, particularly with respect to effects on microbial communities and regrowth. The examination of potential growth of opportunistic pathogens (OPs) and spread of antibiotic resistance genes (ARGs), each representing serious and growing public health concerns, by introducing DPR water has not previously been evaluated. In this study, the impact of blending purified DPR water with traditional drinking water sources was investigated with respect to treatment techniques, blending location, and blending ratio. Water from four U.S. utility partners was treated in bench- and pilot-scale treatment trains to simulate DPR with blending. Water was incubated in simulated premise plumbing rigs made of PVC pipe containing brass coupons to measure regrowth of total bacteria (16S rRNA genes, heterotrophic plate count), OPs (Legionella spp., Mycobacterium spp., Pseudomonas aeruginosa), ARGs (qnrA, vanA), and an indicator of horizontal gene transfer and multi-drug resistance (intI1). The microbial community composition was profiled and the resistome (i.e., all ARGs present) was characterized in select samples using next generation sequencing. While regrowth of total bacteria (16S rRNA genes) from the start of the incubation through week eight consistently occurred across tested scenarios (Wilcoxon, p ≤ 0.0001), total bacteria were not more abundant in the water or biofilm of any DPR scenario than in the corresponding conventional potable condition (p ≥ 0.0748). Regrowth of OP marker genes, qnrA, vanA, and intI1 were not significantly greater in water or biofilm for any DPR blends treated with advanced oxidation compared to corresponding potable water (p ≥ 0.1047). This study of initial bacteria colonizing pipes after introduction of blended DPR water revealed little evidence (i.e., one target in one water type) of exacerbated regrowth of total bacteria, OPs, or ARGs in premise plumbing.

The use of carbon adsorbents for the removal of perfluoroalkyl acids from potable reuse systems.

Bench- and pilot-scale sorption tests were used to probe the performance of several biochars at removing perfluoroalkyl acids (PFAA) from field waters, compared to granular activated carbon (GAC). Screening tests using organic matter-free water resulted in hardwood (HWC) (Kd = 41 L g-1) and pinewood (PWC) (Kd = 49 L g-1) biochars having the highest perfluorooctanoic acid (PFOA) removal performance that was comparable to bituminous coal GAC (Kd = 41 L g-1). PWC and HWC had a stronger affinity for PFOA sorbed in Lake Mead surface water (KF = 11 mg(1-n) Ln g-1) containing a lower (2 mg L-1) dissolved organic carbon (DOC) concentration than in a tertiary-filtered wastewater (KF = 8 mg(1-n) Ln g-1) with DOC of 4.9 mg L-1. A pilot-scale study was performed using three parallel adsorbers (GAC, anthracite, and HWC biochar) treating the same tertiary-filtered wastewater. Compared to HWC, and anthracite, GAC was the most effective in mitigating perfluoropentanoic acid (PFPnA), perfluorohexanoic acid (PHxA), PFOA, perfluorooctane sulfonic acid (PFOS), and DOC (45-67% removed at 4354 bed volumes) followed by HWC, and then anthracite. Based on bench- and pilot-scale results, shorter-chain PFAA [perfluorobutanoic acid (PFBA), PFPnA, or PFHxA] were more difficult to remove with both biochar and GAC than the longer-chain, PFOS and PFOA.

Ozone regeneration of granular activated carbon for trihalomethane control.

Spatial and temporal variations of trihalomethanes (THMs) in distribution systems have challenged water treatment facilities to comply with disinfection byproduct rules. In this study, granular activated carbon (GAC) and modified GAC (i.e., Ag-GAC and TiO2-GAC) were used to treat chlorinated tap water containing CHCl3 (15-21µg/L), CHBrCl2 (13-16µg/L), CHBr2Cl (13-14µg/L), and CHBr3 (3µg/L). Following breakthrough of dissolved organic carbon (DOC), GAC were regenerated using conventional and novel methods. GAC regeneration efficiency was assessed by measuring adsorptive (DOC, UV absorbance at 254nm, and THMs) and physical (surface area and pore volume) properties. Thermal regeneration resulted in a brief period of additional DOC adsorption (bed volume, BV, ∼6000), while ozone regeneration was ineffective regardless of the GAC type. THM adsorption was restored by either method (e.g., BV for ≥80% breakthrough, CHBr3 ∼44,000>CHBr2Cl ∼35,000>CHBrCl2 ∼31,000>CHCl3 ∼7000). Cellular and attached adenosine triphosphate measurements illustrated the antimicrobial effects of Ag-GAC, which may have allowed for the extended THM adsorption compared to the other GAC types. The results illustrate that ozone regeneration may be a viable in-situ alternative for the adsorption of THMs during localized treatment in drinking water distribution systems.

Biotransformation of trace organic compounds by activated sludge from a biological nutrient removal treatment system.

The removal of trace organic compounds (TOrCs) and their biotransformation rates, kb (LgSS(-)(1)h(-)(1)) was investigated across different redox zones in a biological nutrient removal (BNR) system using an OECD batch test. Biodegradation kinetics of fourteen TOrCs with initial concentration of 1-36µgL(-)(1) in activated sludge were monitored over the course of 24h. Degradation kinetic behavior for the TOrCs fell into four groupings: Group 1 (atenolol) was biotransformed (0.018-0.22LgSS(-)(1)h(-)(1)) under anaerobic, anoxic, and aerobic conditions. Group 2 (meprobamate and trimethoprim) biotransformed (0.01-0.21LgSS(-)(1)h(-)(1)) under anoxic and aerobic conditions, Group 3 (DEET, gemfibrozil and triclosan) only biotransformed (0.034-0.26LgSS(-)(1)h(-)(1)) under aerobic conditions, and Group 4 (carbamazepine, primidone, sucralose and TCEP) exhibited little to no biotransformation (<0.001LgSS(-)(1)h(-)(1)) under any redox conditions. BNR treatment did not provide a barrier against Group 4 compounds.

The potential role of biochar in the removal of organic and microbial contaminants from potable and reuse water: A review.

In this work, the potential benefits, economics, and challenges of applying biochar in water treatment operations to remove organic and microbial contaminants was reviewed. Minimizing the use of relatively more expensive traditional sorbents in water treatment is a motivating aspect of biochar production, e.g., $246/ton non-activated biochar to $1500/ton activated carbon. Biochar can remove organic contaminants in water, such as some pesticides (0.02-23 mg g(-1)), pharmaceutical and personal care products (0.001-59 mg g(-1)), dyes (2-104 mg g(-1)), humic acid (60 mg g(-1)), perfluorooctane sulfonate (164 mg g(-1)), and N-nitrosomodimethylamine (3 mg g(-1)). Including adsorption/filtration applications, biochar can potentially be used to inactivate Escherichia coli via disinfection, and transform 95% of 2-chlorobiphenyl via advanced oxidation processes. However, more sorption data using biochar especially at demonstration-scale, for treating potable and reuse water in adsorption/filtration applications will help establish the potential of biochars to serve as surrogates for activated carbons.

Sorption and cosorption of lead and sulfapyridine on carbon nanotube-modified biochars.

New, sustainable, and low-cost materials that can simultaneously remove a range of wastewater contaminants, such as heavy metals and pharmaceutical residues, are needed. In this work, modified biochars were produced by dip-coating hickory or bagasse biomass in carbon nanotube (CNT) suspensions with or without sodium dodecylbenzenesulfonate (SDBS)-aided dispersion prior to slow pyrolysis in a N2 environment at 600 °C. The sulfapyridine (SPY) and lead (Pb) sorption ability of pristine hickory (HC) and bagasse (BC) biochars and the modified biochars with (HC-SDBS-CNT and BC-SDBS-CNT, respectively) and without (HC-CNT and BC-CNT) SDBS was assessed in laboratory aqueous batch single- and binary-solute system. The greatest removal of SPY and Pb was observed for HC-SDBS-CNT (86 % SPY and 71 % Pb) and BC-SDBS-CNT (56 % SPY and 53 % Pb), whereas HC-CNT, BC-CNT, and the pristine biochars removed far less. This can be attributed to the fact that surfactant could prevent the aggregation of CNTs and thus promote the distribution and stabilization of individual CNT nanoparticle on the biochar surface to adsorb the contaminants. The observation of no significant change in Pb sorption capacities of the surfactant-dispersed CNT-modified biochars in the presence of SPY, or vice versa, was indicative of site-specific sorption interactions and a lack of significant competition for functional groups by the two sorbates. These results suggest that products of hybrid technologies, such as biochars modified with CNTs, can yield multi-sorbents and may hold excellent promise as a sustainable wastewater treatment alternative.

Pyrolytic temperatures impact lead sorption mechanisms by bagasse biochars.

The characteristics and mechanisms of Pb sorption by biochars produced from sugarcane bagasse at 250, 400, 500, and 600 °C were examined. The Pb sorption isotherms, kinetics and desorption were investigated. All biochars were effective in Pb sorption and were well described by Langmuir isotherm model and pseudo-second-order kinetic model. The maximum sorption capacity decreased from 21 to 6.1 mg g(-1) as temperature increased from 250 to 600 °C. The Pb sorption was rapid initially, probably controlled by cation exchange and complexation and then slowed down, which might be due to intraparticle diffusions. FTIR data and kinetic models suggested that oxygen functional groups were probably responsible for the high Pb sorption onto low temperature biochars (250 and 400 °C) whereas intraparticle diffusion was mainly responsible for low Pb sorption onto high temperature biochars (500 and 600 °C). Decreased phosphorus concentration indicated that P-induced Pb precipitation was also responsible for Pb sorption. Pyrolysis temperature significantly affected biochar properties and played an important role in Pb sorption capacity and mechanisms by biochars.

Engineered carbon (biochar) prepared by direct pyrolysis of Mg-accumulated tomato tissues: characterization and phosphate removal potential.

An innovative method was developed to produce engineered biochar from magnesium (Mg) enriched tomato tissues through slow pyrolysis in a N2 environment. Tomato plants treated with 25mM Mg accumulated much higher level of Mg in tissue, indicating Mg can be substantially enriched in tomato plants, and pyrolysis process further concentrated Mg in the engineered biochar (8.8% Mg). The resulting Mg-biochar composites (MgEC) showed better sorption ability to phosphate (P) in aqueous solutions compared to the other four tomato leaves biochars. Statistical analysis showed a strong and significant correlation between P removal rate and biochar Mg content (R(2)=0.78, and p<0.001), indicating the enriched Mg in the engineered biochar is the main factor controlling its P removal ability. SEM-EDX, XRD and XPS analyses showed that nanoscale Mg(OH)2 and MgO particles were presented on the surface of MgEC, which serve as the main adsorption sites for aqueous P.

Phosphate removal ability of biochar/MgAl-LDH ultra-fine composites prepared by liquid-phase deposition.

Morphological structures and adsorption properties of biochar/MgAl-LDH ultra-fine composites prepared by liquid-phase deposition have been determined in laboratory. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), and Fourier transform infrared (FTIR) were used to characterize the biochar based ultra-composites. The XRD and FTIR data indicated that the biochar/MgAl-LDHs ultra-fine composites can successfully be obtained by liquid-phase deposition. The SEM images showed the dispersion of colloidal and nanosized LDH flakes on the carbon surfaces within the biochar matrix. The thickness and size of single LDH platelet are 20-40 nm and 100-300 nm. Batch sorption experiments were also conducted and the results indicated that the biochar/MgAl-LDHs ultra-fine composites is an effective sorbent for the removal of phosphate from aqueous solutions.

Preparation and characterization of a novel magnetic biochar for arsenic removal.

A magnetic biochar based adsorbent with colloidal or nanosized γ-Fe(2)O(3) particles embedded in porous biochar matrix was fabricated via thermal pyrolysis of FeCl(3) treated biomass. The synthesized samples were studied systematically by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, selected-area electron diffraction pattern, scanning electron microscopy, energy-dispersive X-ray analysis, superconducting quantum interference device, and batch sorption measurements. The characterization analyses showed that large quantity of γ-Fe(2)O(3) particles with size between hundreds of nanometers and several micrometers tightly grow within the porous biochar matrix. Biochar/γ-Fe(2)O(3) composite exhibited excellent ferromagnetic property with a saturation magnetization of 69.2emu/g. Batch sorption experimental results showed that the composite has strong sorption ability to aqueous arsenic. Because of its excellent ferromagnetic properties, the arsenic-laden biochar/γ-Fe(2)O(3) composite could be easily separated from the solution by a magnet at the end of the sorption experiment.

Synthesis, characterization, and environmental implications of graphene-coated biochar.

Biochar has attracted much research attention recently because of its potential applications in many environmental areas. In this work, the biochar technology was combined with the emerging graphene technology to create a new engineered graphene-coated biochar from cotton wood. The biomass feedstock was first treated with graphene/pyrene-derivative and was then annealed at 600°C in a quartz tube furnace under N(2) environment. Laboratory characterization with different microscopy and spectrometry tools showed that the graphene sheets were "soldered" by the pyrene molecules on the biochar surface during the annealing process. Thermogravimetric analysis showed that the graphene "skin" could improve the thermal stability of the biochar, making the engineered biochar a better carbon sequester for large scale land applications. Batch sorption experimental results indicated that the graphene-coated biochar has excellent adsorption ability of polycyclic aromatic hydrocarbons (PAHs) with a maximum methylene blue adsorption capacity of 174 mg g(-1), which is more than 20 times higher than that of the unmodified cotton wood biochar and comparable to those of some physically or chemically activated carbons. The enhanced adsorption of methylene blue on the graphene-coated biochar is mainly controlled by the strong π-π interactions between aromatic molecules and the graphene sheets on biochar surface. It is anticipated that this novel, facile, and low-cost method can be expanded to other carbon-rich materials to create engineered biochar for various environmental applications.

Effect of biochar amendment on sorption and leaching of nitrate, ammonium, and phosphate in a sandy soil.

When applied to soils, it is unclear whether and how biochar can affect soil nutrients. This has implications both to the availability of nutrients to plants or microbes, as well as to the question of whether biochar soil amendment may enhance or reduce the leaching of nutrients. In this work, a range of laboratory experiments were conducted to determine the effect of biochar amendment on sorption and leaching of nitrate, ammonium, and phosphate in a sandy soil. A total of thirteen biochars were tested in laboratory sorption experiments and most of them showed little/no ability to sorb nitrate or phosphate. However, nine biochars could remove ammonium from aqueous solution. Biochars made from Brazilian pepperwood and peanut hull at 600°C (PH600 and BP600, respectively) were used in a column leaching experiment to assess their ability to hold nutrients in a sandy soil. The BP600 biochar effectively reduced the total amount of nitrate, ammonium, and phosphate in the leachates by 34.0%, 34.7%, and 20.6%, respectively, relative to the soil alone. The PH600 biochar also reduced the leaching of nitrate and ammonium by 34% and 14%, respectively, but caused additional phosphate release from the soil columns. These results indicate that the effect of biochar on the leaching of agricultural nutrients in soils is not uniform and varies by biochar and nutrient type. Therefore, the nutrient sorption characteristics of a biochar should be studied prior to its use in a particular soil amendment project.

Removal of heavy metals from aqueous solution by biochars derived from anaerobically digested biomass.

This study examined the ability of two biochars converted from anaerobically digested biomass to sorb heavy metals using a range of laboratory sorption and characterization experiments. Initial evaluation of DAWC (digested dairy waste biochar) and DWSBC (digested whole sugar beet biochar) showed that both biochars were effective in removing a mixture of four heavy metals (Pb(2 +), Cu(2+), Ni(2+), and Cd(2+)) from aqueous solutions. Compared to DAWC, DWSBC demonstrated a better ability to remove Ni and Cd. Further investigations of lead sorption by the two biochars indicated that the removal was mainly through a surface precipitation mechanism, which was confirmed by batch sorption experiments, mathematical modeling, and examinations of lead-laden biochars samples using SEM-EDS, XRD, and FTIR. The lead sorption capacity of the two biochars was close to or higher than 200mmol/kg, which is comparable to that of commercial activated carbons.

Adsorption of sulfamethoxazole on biochar and its impact on reclaimed water irrigation.

Reclaimed water irrigation can satisfy increasing water demand, but it may also introduce pharmaceutical contaminants into the soil and groundwater environment. In this work, a range of laboratory experiments were conducted to test whether biochar can be amended in soils to enhance removal of sulfamethoxazole (SMX) from reclaimed water. Eight types of biochar were tested in laboratory sorption experiments yielding solid-water distribution coefficients (K(d)) of 2-104 L/kg. Two types of biochar with relatively high K(d) were used in column leaching experiments to assess their effect on reclaimed water SMX transport through soils. Only about 2-14% of the SMX was transported through biochar-amended soils, while 60% was found in the leachate of the unamended soils. Toxicity characteristic leaching experiments confirmed that the mobility and bioavailability of SMX in biochar-amended soils were lower than that of unamended soils. However, biochar with high accumulations of SMX was still found to inhibit the growth of the bacteria compared to biochar with less SMX which showed no effects. Thus, biochar with very high pharmaceutical sorption abilities may find use as a low-cost alternative sorbent for treating wastewater plant effluent, but should be used with caution as an amendment to soils irrigated with reclaimed water or waste water.

Removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings.

Biochar converted from agricultural residues or other carbon-rich wastes may provide new methods and materials for environmental management, particularly with respect to carbon sequestration and contaminant remediation. In this study, laboratory experiments were conducted to investigate the removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings (DSTC). Batch adsorption kinetic and equilibrium isotherm experiments and post-adsorption characterizations using SEM-EDS, XRD, and FTIR suggested that colloidal and nano-sized MgO (periclase) particles on the biochar surface were the main adsorption sites for aqueous phosphate. Batch adsorption experiments also showed that both initial solution pH and coexisting anions could affect the adsorption of phosphate onto the DSTC biochar. Of the mathematical models used to describe the adsorption kinetics of phosphate removal by the biochar, the Ritchie N_th-order (N=1.14) model showed the best fit. Two heterogeneous isotherm models (Freundlich and Langmuir-Freundlich) fitted the experimental isotherm of phosphate adsorption onto the biochar better than the Langmuir adsorption model. Our results suggest that biochar converted from anaerobically digested sugar beet tailings is a promising alternative adsorbent, which can be used to reclaim phosphate from water or reduce phosphate leaching from fertilized soils. In addition, there is no need to regenerate the exhausted biochar because the phosphate-laden biochar contains abundance of valuable nutrients, which may be used as a slow-release fertilizer to enhance soil fertility and to sequester carbon.

Biochar derived from anaerobically digested sugar beet tailings: characterization and phosphate removal potential.

Two biochars were produced from anaerobically digested and undigested sugar beet tailings through slow-pyrolysis at 600°C. The digested sugar beet tailing biochar (DSTC) and raw sugar beet tailing biochar (STC) yields were around 45.5% and 36.3% of initial dry weight, respectively. Compared to STC, DSTC had similar pH and surface functional groups, but higher surface area, and its surface was less negatively charged. SEM-EDS and XRD analyses showed that colloidal and nano-sized periclase (MgO) was presented on the surface of DSTC. Laboratory adsorption experiments were conducted to assess the phosphate removal ability of the two biochars, an activated carbon (AC), and three Fe-modified biochar/AC adsorbents. The DSTC showed the highest phosphate removal ability with a removal rate around 73%. Our results suggest that anaerobically digested sugar beet tailings can be used as feedstock materials to produce high quality biochars, which could be used as adsorbents to reclaim phosphate.

Biochar from anaerobically digested sugarcane bagasse.

This study was designed to investigate the effect of anaerobic digestion on biochar produced from sugarcane bagasse. Sugarcane bagasse was anaerobically digested to produce methane. The digested residue and fresh bagasse was pyrolyzed separately into biochar at 600 degrees C in nitrogen environment. The digested bagasse biochar (DBC) and undigested bagasse biochar (BC) were characterized to determine their physicochemical properties. Although biochar was produced from the digested residue (18% by weight) and the raw bagasse (23%) at a similar rate, there were many physiochemical differences between them. Compared to BC, DBC had higher pH, surface area, cation exchange capacity (CEC), anion exchange capacity (AEC), hydrophobicity and more negative surface charge, all properties that are generally desirable for soil amelioration, contaminant remediation or wastewater treatment. Thus, these results suggest that the pyrolysis of anaerobic digestion residues to produce biochar may be an economically and environmentally beneficial use of agricultural wastes.