On-Site Pilot-Scale Microalgae Cultivation Using Industrial Wastewater for Bioenergy Production: A Case Study towards Circular Bioeconomy.

This case study assesses the valorization of industrial wastewater streams for bioenergy generation in an industrial munition facility. On-site pilot-scale demonstrations were performed to investigate the feasibility of algal growth in the target wastewater on a larger outdoor scale. An exploratory field study followed by an optimized one were carried out using two 1000 L open raceway ponds deployed within a greenhouse at an industrial munition facility. An online system allowed for constant monitoring of operational parameters such as temperature, pH, light intensity, and dissolved oxygen within the ponds. The original algal seed evolved into an open-air resilient consortium of green microalgae and cyanobacteria that were identified and characterized successfully. Weekly measurements of the level of nutrients in pond liquors were performed along with the determination of the algal biomass to quantitatively evaluate growth yields. After harvesting algae from the ponds, the biomass was concentrated and evaluated for oil content and biochemical methane potential (BMP) to provide an estimate of the algae-based energy production. Additionally, the correlation among biomass, culturing conditions, oil content, and BMP was evaluated. The higher average areal biomass productivity achieved during the summer months was 23.9 ± 0.9 g/m2d, with a BMP of 350 scc/gVS. An oil content of 22 wt.% was observed during operation under low nitrogen loads. Furthermore, a technoeconomic analysis and life cycle assessment demonstrated the viability of the proposed wastewater valorization scenario and aided in optimizing process performance towards further scale-up.

Oxidative degradation of nitroguanidine (NQ) by UV-C and oxidants: Hydrogen peroxide, persulfate and peroxymonosulfate.

Nitroguanidine (NQ), a component used in insensitive munitions formulations, has high solubility which often leads to highly contaminated wastewater streams. In this work, batch experiments were conducted to investigate and compare the NQ degradation by UV-based advanced oxidation processes (AOPs); hydrogen peroxide (H2O2), persulfate (PS) and peroxymonosulfate (PMS) were selected as oxidants. A preliminary evaluation of AOPs kinetics, byproducts, and potential degradation pathways were carried out and compared to NQ degradation by direct UV-C photolysis. The effects of oxidant dosage, NQ concentrations and pH were evaluated by determining the respective kinetic constants of degradation. Among the treatments applied, UV/PS showed to be a promising and effective alternative leading to faster rates of degradation respect to both oxidant dosage (25 mM) and initial NQ concentrations (≤24 mM). Nevertheless, the degradation rate of NQ by UV/PS appeared to be affected strongly by the initial pH compared to UV/H2O2 and UV/PMS, with the lowest rate overall at pH ≥ 8.0. In addition, the main byproducts from NQ degradation, guanidine and cyanamide, showed to be involved in further degradation steps only with UV/PS and UV/PMS suggesting higher degradation effectiveness of these oxidants compared UV/H2O2 and UV alone.

Load-bearing biodegradable PCL-PGA-beta TCP scaffolds for bone tissue regeneration.

A biocompatible and biodegradable scaffold with load-bearing ability is required to enhance the repair of bone defects by facilitating the attachment, and proliferation of cells, and vascularization during new bone formation. However, it is challenging to maintain the porosity and biodegradability, as well as mechanical properties (especially compressive strength), at the same time. Therefore, in the present work, a biodegradable composite structure of poly(caprolactone) (PCL) was designed using compression molding with varying amounts of poly(glycolic acid) (PGA) (25, 50, 75 wt%) and fixed amount (20 wt%) of beta tricalcium phosphate (beta TCP). It was hypothesized that the fabricated composite structure will develop porosity during the degradation of the PGA and that the corresponding decrease in mechanical properties will be compensated by new bone formation and ingrowth, in vivo. Accordingly, we have systematically studied the effects of sample composition on time-dependent dissolution and mechanical properties of the PGA/beta TCP scaffolds. The compressive strength increased up to ~92 MPa at 50% compression of the designed PCL-PGA samples. Furthermore, the dissolution rate, as well as weight loss, was observed to increase with an increase in the PGA amount in PCL. Based on the mechanical properties and dissolution data, it is concluded that the PCL-PGA scaffolds with beta TCP can be suitable candidates for bone tissue engineering applications, specifically for the reconstruction of bone defects, where strength and biodegradation are both important characteristics.

Challenges of arsenic removal from municipal wastewater by coagulation with ferric chloride and alum.

Discharge of treated municipal wastewater containing arsenic (As) may cause adverse effects on the environment and drinking water sources. Arsenic concentrations were measured throughout the treatment systems at two municipal wastewater plants in New Jersey, USA. The efficiency of As removal by ferric chloride and alum coagulants were evaluated. Besides, the effects of suspended solids in the mixed liquor, pH, and orthophosphate (PO43-) on As removal were investigated. The total recoverable As (TAs) concentrations in the influent and effluent of Plant A were in the ranges of 2.00-3.00 and 1.50-2.30 µg/L, respectively. The results indicated that <30% of the As was removed by the conventional biological wastewater treatment processes. The influent and effluent TAs concentrations at Plant B was below 1.00 µg/L. The bench-scale coagulation results demonstrated for the first time that the coagulation treatment could not effectively remove As from the municipal wastewater to <2.00 µg/L. Very high doses of the coagulants (8 and 40 mg/L of Fe(III) or Al(III)) were required to reduce the TAs from 2.84 and 8.61 µg/L in the primary clarifier effluent and arsenate-spiked effluent samples to <2.00 µg/L, respectively, which could be attributed to the high concentrations of PO43- and dissolved organic matters (DOM) in the wastewater. The protein DOM in wastewater may negatively impact removal efficiencies more than the DOM in natural water, which mainly consists of humic substances. Furthermore, an artificial neural network was constructed to determine the relative importance of different parameters for As removal. Under the experimental conditions, the importance followed the order: coagulant dose>dissolved PO43- > initial As concentration > pH. The findings of this study will help develop effective treatment processes to remove As from municipal wastewater.

Load-bearing biodegradable polycaprolactone-poly (lactic-co-glycolic acid)- beta tri-calcium phosphate scaffolds for bone tissue regeneration.

A biodegradable scaffold with tissue ingrowth and load-bearing capabilities is required to accelerate the healing of bone defects. However, it is difficult to maintain the mechanical properties as well as biodegradability and porosity (necessary for bone ingrowth) at the same time. Therefore, in the present study, polycaprolactone (PCL) and poly(lactic-co-glycolic acid) (PLGA5050) were mixed in varying ratio and incorporated with 20 wt.% ßTCP. The mixture was shaped under pressure into originally non-porous cylindrical constructs. It is envisioned that the fabricated constructs will develop porosity with the time-dependent biodegradation of the polymer blend. The mechanical properties will be sustained since the decrease in mechanical properties associated with the dissolution of the PLGA and the formation of the porous structure will be compensated with the new bone formation and ingrowth. To prove the hypothesis, we have systematically studied the effects of samples composition on the time-dependent dissolution behavior, pore formation, and mechanical properties of the engineered samples, in vitro. The highest initial (of as-prepared samples) values of the yield strength (0.021±0.002 GPa) and the Young's modulus (0.829±0.096 GPa) were exhibited by the samples containing 75 wt.% of PLGA. Increase of the PLGA concentration from 25 wt.% to 75 wt.% increased the rate of biodegradation by a factor of 3 upon 2 weeks in phosphate buffered saline (1× PBS). The overall porosity and the pore sizes increased with the dissolution time indicating that the formation of in-situ pores can indeed enable the migration of cells followed by vascularization and bone growth.

Plasma-activated water: antibacterial activity and artifacts?

Broad biological activities of "plasma-activated water" (PAW) have drawn great attentions recently. Treatment of water using gas discharge plasma led to acidic solutions with excellent and broad antibacterial activity. Because PAW caused severe membrane damages in bacteria and diffused freely in extracellular matrix, PAW also demonstrated good anti-biofilm activity. However, further studies revealed that trace amounts of metal ions (mainly copper and zinc) in PAW brought by plasma treatment played key roles in bacteria inactivation. The contribution of metal ions to the antibacterial activity varied among PAWs from different working gases. However, solution acidification caused by reactive species in plasma was essential. The experimental results demonstrated that potential artifacts in reported biological activities of PAWs should be considered.

Self-Polymerization of Dopamine in Acidic Environments without Oxygen.

An alkaline environment and the presence of oxygen are essential requirements for dopamine polymerization. In this study, we are the first to demonstrate the self-polymerization of dopamine through plasma-activated water (PAW) under acidic environments (pH < 5.5). Resulting poly(dopamine) (PDA) was characterized using Nanosizer, SEM, FTIR, UV-vis, 1H NMR, and fluorescence spectrophotometers and proved to have similar physical and chemical properties to those polymerized under a basic condition, except that the PDA particles formed in PAW were more stable and hardly aggregated at varied pHs. The PAW polymerization method avoids alkaline solutions and the presence of oxygen and thus extends the applications of dopamine polymerization, particularly in biomedical and pharmaceutical sciences.

SERS detection of arsenic in water: A review.

Arsenic (As) is one of the most toxic contaminants found in the environment. Development of novel detection methods for As species in water with the potential for field use has been an urgent need in recent years. In past decades, surface-enhanced Raman scattering (SERS) has gained a reputation as one of the most sensitive spectroscopic methods for chemical and biomolecular sensing. The SERS technique has emerged as an extremely promising solution for in-situ detection of arsenic species in the field, particularly when coupled with portable/handheld Raman spectrometers. In this article, the recent advances in SERS analysis of arsenic species in water media are reviewed, and the potential of this technique for fast screening and field testing of arsenic-contaminated environmental water samples is discussed. The problems that remain in the field are also discussed and an outlook for the future is featured at the end of the article.

Symbolic regression of upstream, stormwater, and tributary E. coli concentrations using river flows.

Symbolic regression was used to model E. coli concentrations of upstream boundary, tributaries, and stormwater in the lower Passaic River at Paterson, New Jersey. These models were used to simulate boundary concentrations for a water quality analysis simulation program to model the river. River flows from upstream and downstream boundaries of the study area were used as predictors. The symbolic regression technique developed a variety of candidate models to choose from due to multiple transformations and model structures considered. The resulting models had advantages such as better goodness-of-fit statistics, reasonable bounds to outputs, and smooth behavior. The major disadvantages of the technique are model complexity, difficulty to interpret, and overfitting. The Nash-Sutcliffe efficiencies of the models ranged from 0.61 to 0.88, and they adequately captured the upstream boundary, tributary, and stormwater concentrations. The results suggest symbolic regression can have significant applications in the areas of hydrologic, hydrodynamic, and water quality modeling.