Wastewater treatment, along with the simultaneous production of valuable chemical compounds, including lipids by microalgae is a challenging but attractive study. Towards this goal, the candidate ...microalgae were selected from culture collections or isolated from wastewater in this study. The initial screening test using microalgae revealed that various eukaryotic as well as prokaryotic microalgae showed steady growth in municipal wastewater samples. Among them, Tetraselmis sp. NKG400013 and Parachlorella kessleri NKG021201 from culture collections, and Chloroidium saccharophilum NKH13 from the wastewater sample exhibited high biomass productivity. Furthermore, P. kessleri NKG021201 and C. saccharophilum NKH13 showed high lipid productivity (56 ± 1 mg/L/day for NKG021201, 35 ± 10 mg/L/day for NKH13). During this cultivation, 99% of nitrogen and 82% of phosphorous compounds were removed from the wastewater sample by the strain NKG021201. Analysis of fatty acid compositions of P. kessleri NKG021201 and C. saccharophilum NKH13 revealed that lipids derived from these microalgae were suitable for the application of biodiesel fuels, indicating that these microalgae were promising for wastewater treatment and lipid production.
To cater to the increasing demand for secondary lithium-ion batteries, the recovery of valuable metal species in spent batteries is increasingly important, particularly for lithium, for which a few ...effective recovery techniques have been reported. This study investigated the behavior of lithium extraction from the reduction roasting residue (R–R–R) powder under hydrothermal conditions with and without CaCl
2
. The analysis results revealed that the hydrothermal treatment with CaCl
2
can effectively extract lithium from the R–R–R powder. Additionally, the optimal conditions were identified as powder treatment at 200 °C for more than 18 h with CaCl
2
(Ca/(P + F) = 4 (mol/mol)). This optimal condition did not rely on the volume scale of the pressure vessel; therefore, the proposed method can be practically effective. Furthermore, the separation of calcium and lithium cations in the extraction solution was investigated using sodium carbonate as a precipitator. The calcium cation was successfully separated as calcium carbonate from the extraction solution, and a pure lithium aqueous solution was collected. Based on our analysis, we propose a novel eco-friendly recycling process for extracting metals from spent lithium-ion batteries.
Production of biofuels and fine chemicals from biomass-derived carbohydrates through biorefinery attracts much attention because it is recognized as an environmentally friendly process. Microalgae ...can serve as promising carbohydrate producers for biorefinery rather than woody and crop biomass due to high biomass productivity, high CO2 fixation, and no competition with food production. However, microalgae with high carbohydrate productivity have not been well investigated despite intensive studies of microalgal lipid production. In this study, the carbohydrate production of Pseudoneochloris sp. strain NKY372003 isolated as a high carbohydrate producer, was investigated. Cultivation conditions with various combinations of nutrient contents and photon flux density were examined to maximize the biomass and carbohydrate productivities. At the optimal condition, the biomass and carbohydrate production of this strain reached 8.11 ± 0.37 g/L and 5.5 ± 0.2 g/L, respectively. As far as we know, this is the highest carbohydrate production by microalgae among ever reported. Cell staining with Lugol's solution visualized intracellular starch granules. Because algal starch can be converted to biofuels and building blocks of fine chemicals, Pseudoneochloris sp. NKY372003 will be a promising candidate for production of fermentable carbohydrates towards biofuels and fine chemicals production.
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•Acid-treated concrete sludge (A-CS) was used for phosphate (Pi) recovery.•The Pi removal efficiency of CS particles was improved by soaking them in HCl.•A-CS slurry served as a ...bifunctional adsorption-aggregation agent.•A-CS slurry effectively recovered Pi from anaerobic sludge digestion liquor.•The recovered product could be used as a slow-release Pi fertilizer.
A simple technology for phosphorus (P) recovery from aqueous solution has been developed using acid-treated concrete sludge (A-CS) as a bifunctional adsorption-aggregation agent. Dried particles of concrete sludge (CS), an alkaline waste containing hydrated cement and fine aggregates, were soaked in 1.3M HCl at a concentration of 0.1g/mL for 60min. The HCl-soaking treatment solubilized alkaline substances such as Ca(OH)2 and CaCO3, thereby releasing approximately 87% Ca2+ from the CS particles to the acid solution. When A-CS was added to 500-mL synthetic anaerobic sludge digestion liquor containing 273mg/L of phosphate (Pi) at the Ca/P molar ratio of 2.5, A-CS showed 20 times higher Pi removal efficiency than that of untreated CS particles. Although A-CS could precipitate 72% Pi in 5-min free sedimentation, the Ca2+-rich liquid fraction of A-CS alone led to the precipitation of only 48% Pi. This suggests that the solid fraction of A-CS can serve as an auxiliary aggregation agent. When Pi recovery was examined using anaerobic sludge digestion liquor from a full-scale wastewater treatment, A-CS could recover 96% Pi at the Ca/P molar ratio of 2.5. Citrate-soluble P2O5 accounted for 19% of the dry weight of the recovered Pi product. The levels of heavy metals such as As, Cd, Pb, Ni, and Cr in the recovered Pi product were much below their regulatory standards for fertilizers.
Advanced treatment using an agent synthesized from amorphous silica and hydrated lime (M-CSH-lime) was developed and applied to swine wastewater treatment. Biologically treated wastewater and ...M-CSH-lime (approximately 6 w/v% slurry) were fed continuously into a column-shaped reactor from its bottom. Accumulated M-CSH-lime gradually formed a bed layer. The influent permeated this layer and contacted the M-CSH-lime, and the treatment reaction progressed. Treated liquid overflowing from the top of the reactor was neutralized with CO ₂ gas bubbling. The colour removal rate approximately exceeded 50% with M-CSH-lime addition rates of>0.15 w/v%. The removal rate of exceeded 80% with the addition of>0.03 w/v% of M-CSH-lime. The removal rates of coliform bacteria and Escherichia coli exceeded 99.9% with>0.1 w/v%. Accumulated M-CSH-lime in the reactor was periodically withdrawn from the upper part of the bed layer. The content of citric-acid-soluble P ₂O ₅ in the recovered matter was>15% when the weight ratio of influent to added M-CSH-lime was>0.15. This content was comparable with commercial phosphorus fertilizer. The inhibitory effect of recovered M-CSH-lime on germination and growth of leafy vegetable komatsuna (Brassica rapa var. perviridis) was evaluated by an experiment using the Neubauer's pot. The recovered M-CSH-lime had no negative effect on germination and growth. These results suggest that advanced water treatment with M-CSH-lime was effective for simultaneous removal of colour, and coliform bacteria at an addition rate of 0.03–0.15 w/v%, and that the recovered M-CSH-lime would be suitable as phosphorus fertilizer.
A novel technique for phosphorus (P) recovery from aqueous solutions was developed using amorphous calcium silicate hydrates (A-CSHs). A-CSHs, which have a high Ca/Si molar ratio of 2.0 or greater, ...could be synthesized using unlimitedly available, inexpensive materials such as siliceous shale and calcium hydroxide. A-CSHs showed high performance for P recovery from an anaerobic sludge digestion liquor (ASDL) and the synthetic model liquor (s-ASDL) containing 89 mg PO4–P/L. After 20 min mixing, 1.5 g/L A-CSHs could remove approximately 69 and 73% PO4–P from ASDL and s-ASDL, respectively. By contrast, autoclaved lightweight concrete particles, which contained crystalline calcium silicate hydrates as a principal component, removed only 10 and 6% PO4–P from ASDL and s-ASDL, respectively, under the same experimental conditions. When A-CSHs were washed with deionized water to remove free Ca(OH)2, P removability was significantly improved (up to 82%) despite the reduction in the amount of Ca2+ released. Unlike in the case of Ca(OH)2, no significant carbonate inhibition was observed with P removal by A-CSHs. Moreover, P removed by A-CSHs showed better settleability, filterability, and dewaterability than P precipitated with conventional CaCl2 and Ca(OH)2. The present study demonstrated that A-CSHs have great potential as a novel, beneficial material for P recovery and recycling.
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► Amorphous calcium silicate hydrates (A-CSHs) were used for phosphorus (P) recovery. ► A-CSHs were synthesized using unlimitedly available, inexpensive materials. ► A-CSHs had a high P recovery potential without being inhibited by carbonate. ► P removed by A-CSHs showed high settleability, filterability, and dewaterability. ► P recovered by A-CSHs could be directly used as a by-product phosphate fertilizer.
The cement industry utilizes many wastes and by-products. In particular, the utilization of waste plastics in cement manufacturing processes is a method that can properly treat them while making ...effective use of their thermal energy. The use of waste plastics, which are conventionally incinerated due to the mixing of inorganic components or multiple resins, as a substitute for coal for high-temperature firing cement clinker is considered to have a decarbonizing effect. This paper introduces a case study where CO2 emission reductions by energy recovery from waste plastics in the cement manufacturing process were calculated based on LCA methods. The results of the calculations using an actual plant as a model showed that replacing 32% of the required thermal energy with waste plastics could reduce CO2 emissions by 75 kg per ton of cement, equivalent to about 10% of the emissions intensity of the entire cement manufacturing process. It is expected that a technology will be developed to allow more waste plastics to be used in the cement manufacturing process, and that this will be utilized as one of the treatment methods of waste plastics which have become an international issue.
Algal biomass production by phosphorus recovery and recycling from wastewater using amorphous calcium silicate hydrates.
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•Phosphorous recovery facility was constructed in sewage ...wastewater treatment plant.•Phosphorous was recovered from wastewater using amorphous calcium silicate hydrate.•Amorphous calcium silicate hydrate eluted phosphate in IMK medium within 1 day.•Pseudoneochloris sp. NKY372003 was cultivable with the recovered phosphate.•Phosphorous recovery and recycling were demonstrated with algal biomass production.
The phosphorous supply crisis is a major challenge for a sustainable society, and the algal industry is not unrelated to this crisis. Recycling phosphorus from sewage wastewater is a potential way to address this issue. We previously developed amorphous calcium silicate hydrates (aCSH) as excellent phosphorus recovery materials. In this study, we designed a phosphorus recovery process using aCSH in a pilot-scale facility connected to a sewage wastewater treatment plant, and demonstrated the production of microalgal biomass using phosphorous-containing aCSH (P_aCSH). As a result, high phosphorous recovery rates (>80%) were obtained throughout the year. The carbohydrate-rich microalga Pseudoneochloris sp. NKY372003 was cultivable with P_aCSH. The biomass and carbohydrate productivity of this microalga with P_aCSH was comparable to that with conventional media. Approximately 94% of the phosphorus in P_aCSH was recycled into the biomass. This study successfully demonstrated the recycling the phosphorus recovered from wastewater for microalgal cultivation by aCSH.
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•The structure of amorphous calcium silicate hydrates (A-CSHs) was examined.•A-CSHs consisted of silicate polymers having an average chain length of 3.5.•Silicate polymers in A-CSHs ...are linked to each other through ion binding with Ca2+.•A-CSHs could recover phosphate (Pi) with high reactivity and settleability.•Pi was likely removed by the formation of Ca–Pi–silicates ion aggregates.
Amorphous calcium silicate hydrates (A-CSHs) were synthesized using soluble silicates extracted from a natural siliceous shale (M-rite) and Ca(OH)2. Simultaneous thermogravimetry and differential thermal analysis confirmed that the synthesized A-CSHs contained no detectable amount of free Ca(OH)2. Their performance on phosphate (Pi) recovery from aqueous solutions was examined using a 3.0-L bacth reactor. A-CSHs possessed a greater ability to recover Pi from a synthetic anaerobic sludge digestion liquor than did CaCl2 and Ca(OH)2. 29Si magic-angle-spinning NMR analysis suggested that wet A-CSHs consisted of silicate polymers (average chain length of 3.5) that are linked to each other through ion binding with Ca2+. Based on Ca2+ release and settleability experiments, it was speculated that Ca–Pi–silicates aggregates were formed by the ionic association of Pi, Ca2+, and negatively charged silicates. This hypothesis could reasonably explain the high settleability of Pi removed by A-CSHs. Powder X-ray diffraction analysis showed that recovered products had an amorphous structure similar to that of A-CSHs. In this study, we suggest that A-CSHs have a unique mechanism for recovering Pi, thereby enabling their high reactivity and settleability.
•The growth rates of Sargassum macrocarpum in bio-filtered wastewater (BFW) treatment were significantly higher than those in the control.•The total phosphorus contents in 5.0% (v/v) BFW and SNM were ...significantly higher than those of the initial values.•BFW fertilization could be suitable for enhancing growth of seaweed and contribute to phosphorus accumulation in their tissues.•The maximum uptake rate (Vmax) for phosphate at a temperature range between 15 °C to 25 °C maintained same level, and increased at 30 °C.
The specific growth rate of a brown alga, Sargassum macrocarpum, was evaluated by supplying bio-filtered wastewater (BFW) and synthetic nutrient medium (SNM) adjusted to the same nutrient concentration as BFW. The nutrient uptake characteristics were examined under various temperature conditions. The growth rates in the 0.5% and 5.0% (v/v) BFW treatments (0.015–0.025 wet weight day−1) were approximately the same as those in the 0.5% and 5.0% (v/v) SNM treatments (0.016–0.023 wet weight day−1), and were significantly higher (p < 0.05) than those in the non-enriched treatment (control) (0.006 day−1). The total phosphorus contents in 5.0% (v/v) BFW and SNM were significantly higher than those of the initial values (p < 0.01) because of excess phosphorus supplied above their demand. These results suggested that BFW can be utilized for seaweed growth and contribute to phosphorus accumulation in seaweed tissues. The maximum uptake rate (Vmax) for phosphate at a temperature ranging from 15 °C to 25 °C was constant (0.40–0.45 μmol g−1(dry weight) hrs−1), and increased at 30 °C (0.69 μmol g−1-(dry weight) hrs−1) probably because of their high phosphate demand induced by high respiration rate. The ratio of Vmax to Km for phosphate generally increased with increasing temperature (0.09 ± 0.02–0.27 ± 0.09), which was characterized as demand-driven uptake. These results indicated that fertilization effects based on the physiological response of seaweeds in response to temperature changes need to be considered when providing wastewater-derived nutrients.
