Discharge Standards Research Articles

Effect of macronutrients (carbon, nitrogen, and phosphorus) on the growth of Chlamydomonas reinhardtii and nutrient recovery under different trophic conditions.

More stringent discharge standards have led to the development of an alternative nutrient recovery system from wastewater. Microalgae cultivation in wastewater treatment works has presented considerable promise from the perspective of sustainable resource management. Growth kinetics models are useful tools to optimize nutrient recovery from wastewater by algal uptake. Therefore, this research aims to identify the growth kinetics of Chlamydomonas reinhardtii under both heterotrophic and phototrophic conditions with different nutrient concentrations that typify those found in wastewater treatment works. In addition, the effects of macronutrients (C, N, and P) on heterotrophic and phototrophic microalgae growth and nutrient recovery were studied. Greater specific growth rates were achieved under heterotrophic conditions than in phototrophic cultivation. The maximum specific growth rates and nutrient recovery efficiencies were achieved at 5 mg P L-1 under both heterotrophic and phototrophic growth conditions. Nitrate was the preferred form of nitrogen source under heterotrophic conditions, while nitrogen sources did not present any significant influences in the phototrophic cultivation. Specific growth rates reported for both heterotrophic and phototrophic microalgae at lower carbon concentrations (3.10 d-1 and 0.46 d-1, sequentially) were higher than those at higher carbon concentrations (1.95 d-1 and 0.22 d-1, respectively). C. reinhardtii presented an extreme capacity to adapt and grow at all experimental conditions tested in heterotrophic and phototrophic cultivations.

Nanoscale Zero-Valent Iron (nZVI) for Heavy Metal Wastewater Treatment: A Perspective

Industries such as non-ferrous metal smelting discharge billions of gallons of highly toxic heavy metal wastewater (HMW) worldwide annually, posing a severe challenge to conventional wastewater treatment plants and harming the environment. HMW is traditionally treated via chemical precipitation using lime, caustic, or sulfide, but the effluents do not meet the increasingly stringent discharge standards. This issue has spurred an increase in research and the development of innovative treatment technologies, among which those using nanoparticles receive particular interest. Among such initiatives, treatment using nanoscale zero-valent iron (nZVI) is one of the best developed. While nZVI is already well known for its site-remediation use, this perspective highlights its application in HMW treatment with metal recovery. We demonstrate several advantages of nZVI in this wastewater application, including its multifunctionality in sequestrating a wide array of metal(loid)s (> 30 species); its capability to capture and enrich metal(loid)s at low concentrations (with a removal capacity reaching 500 mg·g−1 nZVI); and its operational convenience due to its unique hydrodynamics. All these advantages are attributable to nZVI’s diminutive nanoparticle size and/or its unique iron chemistry. We also present the first engineering practice of this application, which has treated millions of cubic meters of HMW and recovered tons of valuable metals (e.g., Cu and Au). It is concluded that nZVI is a potent reagent for treating HMW and that nZVI technology provides an eco-solution to this toxic waste.

How to choose the best tertiary treatment for pulp and paper wastewater? Life cycle assessment and economic analysis as guidance tools

Pulp and paper wastewater (P&P WW) often requires tertiary treatment to remove refractory compounds not eliminated by conventional biological treatment, ensuring compliance with high-quality effluent discharge or reuse standards. This study employs a life cycle assessment (LCA) methodology to compare alternative tertiary treatment technologies for P&P WW and rank them accordingly. The evaluated technologies in the scenarios include inorganic (S1) and organic (S2) coagulation-flocculation, ozonation (O3) (S3), O3+granular activated carbon (GAC) (S4), and ultrafiltration (UF)+reverse osmosis (RO) (S5). The analysis focuses on a P&P wastewater treatment plant (WWTP) in Northeastern Italy. The LCA is complemented by an economic analysis considering each technology's capital and operating costs, as well as potential revenues from internal effluent reuse. Results indicate that S4 (O3+GAC) outranks all the other scenarios in terms of both environmental performance and economic viability, primarily due to the advantages associated with effluent reuse. S5 (UF+RO), which also involves reuse, is limited by the high energy consumption of UF+RO, resulting in increased environmental impacts and costs. The physicochemical scenario S2 (Chem Or), currently utilized in the WWTP under study, remains the best-performing technology in the absence of effluent reuse. In contrast, S3 (O3 alone) exhibits the poorest environmental and economic outcomes due to substantial energy requirements for O3 generation and the inability to reuse the treated effluent directly. Lastly, a sensitivity analysis underscores the strong influence of chemical dosages in S1 and S2 on environmental and economic impacts, which is more significant than the impact of water reuse percentages in S4 and S5. The high electricity cost observed during 2022 negatively affects the energy-intensive scenarios (S3-S5), making coagulation-flocculation (S1-S2) even more convenient.

Efficient recovery and treatment of actual electroplating wastewater using stable electrocatalyst-coupled super-stable mineralizer

Electroplating plays an indispensable and pivotal role in various aspects of industrial production, but its wastewater contains a large number of heavy metal ions, resulting in huge discharge pressure. The recovery of metals in wastewater, while meeting discharge standards, has become an urgent issue that requires a simple and efficient solution. In this work, a stable electrocatalyst-coupled with super-stable mineralizer structure has been developed for the recycling and treatment of wastewater. Using actual high-concentration copper electroplating wastewater (5330 mg/L) as a model, we successfully recovered 91.1 % copper by electrolysis process using a low-cost and stable lead dioxide electrode. Following the addition of a super-stable mineralization treatment utilizing layered double hydroxides (LDHs), the resultant pollution water successfully attained the prescribed threshold, specifically below 0.5 mg/L for Cu2+, with reduction of about 90 % of hazardous waste sludge. This new method of recycling heavy metals from wastewater is expected to be both environmentally friendly and sustainable, while also being cost-effective and efficient.

Enhanced biological wastewater treatment supplemented with anaerobic fermentation liquid of primary sludge

The wastewater treatment performance in an inverted A2/O reactor supplemented with fermentation liquid of primary sludge was explored comparing to commercial carbon sources sodium acetate and glucose. Similar COD removal rate was observed with the effluent COD stably reaching the discharge standard for those 3 carbon sources. However, the fermentation liquid distributed more carbon source in the anaerobic zone. Fermentation liquid and sodium acetate tests achieved better nitrogen removal rate than glucose test. The fermentation liquid test showed the best biological phosphorus removal performance with the effluent phosphorus barely reaching the discharge standard. The microbial community characterization revealed that the fermentation liquid test was dominated by phylum Proteobacter in all the anoxic, anaerobic and aerobic zones. Denitrifying phosphorus accumulating organisms (PAOs) (i.e., genera Dechloromonas and unclassified_f__Rhodocyclaceae) were selectively enriched with high abundances (over 20%), which resulted in improved phosphorus removal efficiency. Moreover, the predicted abundances of enzymes involved in nitrogen and phosphorus removal were also enhanced by the fermentation liquid.

Critical Assessment of 2-Methylpyridine: A Cause for Renewed Concern

2-Methylpyridine (2Mp) is a refractory xenotoxin naturally found in coal/crude oil reserves and used anthropogenically as a solvent/intermediate in agrochemical, pharmaceutical, and textile industries on a large scale. It has been classified as a hazardous pollutant (USEPA and EU) and a High Production Volume chemical (USEPA). Limits were set initially (1991) to curb the manufacture of 2Mp within the US, which indeed had led to a decrease in its usage volume from 1991 to 2008. However, no such limit was found on the import of 2Mp into the US, which has led to a hundred-fold increase in 2Mp usage in the last decade. This implies that 2Mp was now being imported from developing countries apart from being produced locally. This trend is directly related to the increased interest in the treatment of 2Mp in the last decade and a half (2007–2023) in developing countries like India, China, Jordan, Russia, Iran, and South Korea. Further, there is no availability of monitoring data in developing countries. There is thus an immediate need to highlight 2Mp as a pollutant of “re-emerging” concern. This review discusses historic and current literature on 2Mp, so that policy makers and researchers alike may focus their attention and update the official hazard standards to incorporate the new threat posed by 2Mp. This review summarizes the synthesis, usage trend, hazardous categorizations, toxicity, effluent discharge standards, incidence case-studies, contact mechanisms, quantification, remediation, and recovery techniques used for 2Mp.

A Bioaugmentation Approach for Efficient Total Nitrogen Reduction in Landfill Leachate

In this study, the focus was on assessing the efficacy of Bioaugmentation in addressing Total Nitrogen (TN) levels in leachate from one of South Korea’s largest waste landfills. The utilization of proprietary bioaugmentation technology led to a remarkable 89% reduction in Total Nitrogen levels within a mere three weeks of implementation at the site. The significant outcome of this reduction not only ensured compliance with stringent Total Nitrogen discharge standards but also brought about the added advantage of eliminating the need for certain chemicals in the leachate treatment process. This dual benefit highlights the practical and sustainable nature of Bioaugmentation as a solution for Total Nitrogen reduction in Landfill Leachate. The findings from this study contribute valuable insights into the potential of Bioaugmentation as a cost-effective and efficient strategy. The ability to expedite the reduction of Total Nitrogen levels in landfill leachate not only addresses environmental concerns but also holds promise for streamlining waste management practices on a larger scale. As we move forward, such innovative approaches could play a crucial role in shaping more sustainable and eco-friendly solutions for waste treatment in landfills.

A Self‐Powered Power Management Circuit for Triboelectric Nanogenerators Utilizing Gas Discharge Tube

AbstractSpark discharge is essential for extracting energy from triboelectric nanogenerators (TENGs). However, the lack of universal technical standards for most discharge switches limits their widespread application. Herein, a buck circuit utilizing gas discharge tube (GDT) as discharge switches is presented. The GDT switch significantly enhances the instantaneous power to 30 mW, 15 times higher than the direct method. When VGDT (the breakdown voltage of GDT) ≤1000 V, it can be integrated with an LC converter, forming the GDTx‐Buck circuit with a maximum energy conversion efficiency of 92.2%. When VGDT >1000 V, GDT can combine with a transformer, forming the GDT‐nT circuit, which enables higher voltage power management. The results demonstrate GDT's universal applicability, reducing circuit complexity during design. In practical applications, the circuit can illuminate 1250 LEDs at an ultra‐low operating frequency of 0.6 Hz, generating electromagnetic waves during GDT breakover, which proves valuable for self‐powered wireless applications. Additionally, the circuit drives parallel calculators and thermometers at 2 Hz in micro‐nano energy applications and provides continuous power to high‐power fire sensors. Its high integration and simple design render it highly promising for large‐scale energy management applications based on TENGs.

A Comparative Analysis of Rural Domestic Wastewater Discharge Standards in the Yangtze River Delta Region, China

With the deepening of comprehensive improvement of rural living environments in China, various regions have issued rural domestic wastewater discharge standards based on their economic foundations, management levels, and characteristics of rural wastewater discharge. The Yangtze River Delta region, in particular, has been at the forefront of exploring these standards nationwide. By analyzing the local standards for rural domestic wastewater discharge in Shanghai, Jiangsu, Zhejiang, and Anhui provinces within the Yangtze River Delta region, along with the "Discharge standard of pollutants for municipal wastewater treatment plant" and the "Standard for irrigation water quality", it was found that the standards in each region primarily consider the classification based on the water environmental grade of the receiving water body. The pollutant concentration control requirements are generally consistent with the pollutant concentration limits for urban wastewater treatment plant discharge, but the total nitrogen and total phosphorus limits are more lenient than those for urban wastewater treatment plants. This paper can guide the transformation of rural domestic wastewater discharge from high standards to resource utilization, and provide references for the selection of wastewater treatment technologies, models, and governance strategies in the Yangtze River Delta region.

Evaluation of carbon emission efficiency based on urbanscaling law: take 308 cities in China as an example.

The development of urban low carbonization is an important foundation for achieving the goal of "dual carbon." The differences in spatial differences based on scientific methods revealing the characteristics of urban carbon emissions and its efficiency are of great significance for shaping the green low-carbon land space pattern. This article uses urban standard models and scale adjustments to the urban index (SAMIs) identification in 2006-2017 308 Chinese urban carbon discharge standards and efficiency time and space evolution pattern and their characteristics. The results of the study show that there is a stable secondary relationship between carbon emissions and urban population scale, which means that the growth rate of urban carbon emissions is significantly lagging behind the growth of urban systems. The analysis of urban carbon emission efficiency based on SAMI values shows significant spatial heterogeneity: the carbon emission efficiency of cities in North China, East China, and Northeast China is lower than that of other regions. In terms of temporal changes, there was a phenomenon of SAMI high-value cities moving north and low-value cities moving south between 2006 and 2017, and △SAMIs showed a pattern of hot in the west and cold in the east. This study broadens the applicability of urban scaling law models in urban environmental research, providing a new perspective for evaluating urban carbon emission efficiency and China's energy conservation and emission reduction work.

Adsorption of phosphate in water by defective UiO-66/Ce2(CO3)3 composite: Adsorption characteristics and mechanisms

In this study, the defect-rich UiO-66 is first synthesized by a two-step strategy, and then a new T-UiO-66/Ce2(CO3)3 (TUC) adsorbent has been successfully synthesized for phosphate removal from water using a simple co-precipitation method. The pseudo-secondary kinetic model and the Langmuir model, respectively, fit the adsorption kinetics and isotherms. The combined thermodynamic analysis shows the spontaneous and heat-absorbing nature of the adsorption process. TUC has a maximum adsorption capacity of 138.9 mg/g at 298 K, and its adsorption capacity is stable throughout a large pH range (4–9). Electrostatic attraction, defect-induced ligand compensation groups and CO32-active groups with phosphate in ligand exchange make up the majority of the adsorption mechanism. Meanwhile, TUC shows excellent adsorption performance for low concentration phosphorus-containing solution. By applying adsorption for 120 min while treating actual water samples, the phosphate concentration can be reduced from 1.68 mg/L to 0.2 mg/L, which is much less than the primary A phosphorus discharge standard of urban wastewater treatment plants. Moreover, the adsorbent shows good stability after five cycles, and the phosphate may still be adsorbed with an efficiency of up to 81% and desorbed with an efficiency of over 85%.

Efficiency and effectiveness of systems for the treatment of domestic wastewater based on subsurface flow constructed wetlands in Jarabacoa, Dominican Republic

Constructed wetlands (CW) are well known nature-based systems for water treatment. This study evaluated the efficiency and effectiveness of seven domestic wastewater treatment systems based on horizontal flow CWs in Jarabacoa, the Dominican Republic. The results showed that the CWs were efficient in reducing the degree of contamination of wastewater to levels below the Dominican wastewater discharge standards for parameters such as the 5-day biochemical oxygen demand (BOD5) and chemical oxygen demand, but not for the removal of phosphorus and fecal coliforms. In addition, a horizontal flow subsurface wetland in the peri-urban area El Dorado was evaluated in terms of the performance of wastewater treatment in tropical climatic conditions. The concentrations of heavy metals, such as zinc, copper, chromium, and iron, were found to decrease in the effluent of the wetland, and the concentrations for nickel and manganese tended to increase. The levels of heavy metals in the effluent were lower than the limit values of the Dominican wastewater discharge standards. The construction cost of these facilities was around 200 USD per population equivalent, similar to the cost in other countries in the same region. This study suggested some solutions to the improved performance of CWs: selection of a microbial flora that guarantees the reduction of nitrates and nitrites to molecular nitrogen, use of endemic plants that bioaccumulate heavy metals, combination of constructed wetlands with filtration on activated carbon, and inclusion of water purification processes that allow to evaluate the reuse of treated water.

Achieved advanced wastewater phosphate removal via improved ionic interference resistance in a migration-electric-field assisted electrocoagulation (MEAEC) system with modified-biochar pseudocapacitor electrode

The capacitive deionization-assisted electrocoagulation system has promising application potential in advanced phosphate removal of its low electricity consumption and sacrificial anode material. Phosphate removal in wastewater is crucial since excess phosphate might lead to eutrophication. However, the complex ion composition in raw wastewater can influence the effective phosphate removal by competing with the precipitable metal ions during electrocoagulation. In this study, a novel migration electric-field assisted electrocoagulation (MEAEC) with an assisted capacitive electrode made of N-doped and Fe-La co-modified biochar (LFNB) to achieve specific phosphate electro-adsorption for effective advanced phosphate removal. The LFNB-MEAEC achieved ultrahigh phosphate removal with the effluent of 0.1 mg/L in synthetic and raw municipal wastewater and met the first Grade A standard of total phosphate in the discharge standard of pollutants for municipal wastewater treatment plant (DSPMWTP) in China. The commonly observed coexisting ions in wastewater and a pH range of 2–12 did not significantly fluctuate the phosphate removal of LFNB-MEAEC. Cyclic voltammetry and charging-discharging tests confirmed the high phosphate affinity and excellent durability of LFNB in ion-interference circumstances. The MEAEC assisted with selective-adsorption capacitive electrodes and provided an effective and practical method for advanced phosphate removal from low-phosphorus-contaminated wastewater. The MEAEC with a selective-adsorbed capacitive electrode improved phosphate removal by 21 % (from 74 ± 1.7% to 95 ± 1.0%), reduced the energy consumption by 65.7% (0.012 kWh m−3-wastewater), and saved the sacrificial anode material by 67.5% (from 200 to 65 g m−3-wastewater) than those of MEAEC without phosphate-selective electrode in the same period (Sacrificial anode working time 200 s).

Effect of floating plant growth rate on water quality performance of wetland in treating domestic sewage

A man-made system that mimics the function and structures of natural wetlands is called constructed wetlands. It is able to treat sewage water with low technology, low energy requirements, affordable and easy to maintain. However, how it works in tropical climates is still unknown and there is a need to figure out the sustainability of floating plants in treating domestic sewage. This study aims to investigate the pollutant removal efficiency of two selected floating plant species, water hyacinth and water lettuce, in treating domestic sewage. The growth rate of both plants will be examined for the best-recommended plants in the constructed wetland systems for domestic sewage treatment. The data was collected through a pilot-constructed wetland in the USM, Engineering Campus that is integrated with two species of floating plants: water hyacinth and water lettuce. The parameters studied were chemical oxygen demand (COD), total suspended solids (TSS), and ammoniacal nitrogen (AN). The findings reveal that the removal efficiency of water hyacinth is higher for COD and TSS at 40.96 % and 43.94 % respectively compared to Water Lettuce with 26.86 % for COD and 17.79 % for TSS. However, Water Lettuce has a slightly higher removal efficiency of NH3-N at 26.52 % compared to Water Hyacinth at 24.35 %. In terms of growth rate, Water Hyacinth is lost to water lettuce, but they have higher biomass to uptake nutrients with just a small increment of area coverage. Therefore, water hyacinth is favourable to implement in floating plant-constructed wetlands as it needs less maintenance than water lettuce to achieve discharge with standard A for TSS and COD and standard B for NH3-N based on Malaysia Wastewater Effluent Discharge Standards.

Model-based comparison of biological wastewater and sludge treatment combinations for nutrient removal, sludge and biogas production

One of the strategies for reducing the potential environmental and health-related risks associated with wastewater treatment sludge is to select treatment options that would minimize its production while using its beneficial products and meeting effluent discharge standards. In this regard, simulation models can aid in estimating treatment performance, sludge production, and biogas formation. This study evaluates effluent concentrations focusing on nutrients, sludge production, and biogas generation rates for various combinations of wastewater and sludge treatment alternatives for varying strengths of domestic wastewater. Overall, 105 scenarios were simulated for three different wastewater strengths for 35 treatment schemes. Bardenpho-5 (B5) was superior over A2O (A2) in removing nitrogen and phosphorous. Adding primary sedimentation to A2 and B5 models improved sludge and in turn biogas production. Effluent total phosphorus (TP) was usually higher in scenarios with anaerobic sludge digestion. However, struvite precipitation following anaerobic digestion helped reduce total nitrogen (TN) and TP effluent concentrations for all wastewater treatment technologies. Sludge production amounts ranged between 2865 kg/day to 38,709 kg/day (total solids) for an influent flow rate of 100,000 m3/day. Sludge production rates were relatively insensitive to sludge treatment alternatives for extended aeration (EA) compared to conventional activated sludge (AS), A2, A/O (AO), and B5. Generally, the impact of a sludge treatment option was significant for wastewater treatment technologies with higher waste sludge production. Thermal hydrolysis followed by anaerobic digestion provided the lowest sludge production and significantly improved the biogas production.

Incorporation of colonization pressure into the propagule pressure‐based global ballast water standard

AbstractAimIn 2024, cargo vessels must meet the International Maritime Organization's global ballast water discharge standards (IMO D‐2) that limit the concentration of living organisms. D‐2 focuses on reducing invasion risk by reducing ‘community propagule pressure (CPP)’, though it does not consider colonization pressure (CP).LocationGlobal.MethodsWe modelled risk differences in IMO D‐2‐compliant discharges (10 ind. m−3) for communities that had inverse patterns of CP and species' individual propagule pressures (IPP). Secondly, we determined the effect on risk of varying CPP and CP. As part of this, we tested whether the IMO D‐2 standard for zooplankton‐sized organisms of <10 individuals m−3 was an optimal choice. Risk was defined as probability of at least one species invading using four risk–release models.ResultsRisk differed strongly at the D‐2 limit based on community composition. At low CPP (<25 ind. m−3), risk was strongly affected by CP for hyperbolic and linear risk–release models and weakly for exponential and logistic models, while CPP affected only the former two model types. Across a much wider range of CPP values, risk was affected by CP, CPP and by their interaction for all models.Main ConclusionThe IMO D‐2 standard for zooplankton‐sized organisms requires very low CPP and even lower IPPs in mixed‐species releases, which will impede successful colonization. Species‐abundance theory predicts that discharges meeting the D‐2 standard (low CPP) will also have low CP. Much more empirical data are required to determine whether vessels can consistently reduce CP as it lowers CPP in order to meet these requirements.

Removal of Phosphorus from Domestic Sewage in Rural Areas Using Oyster Shell-Modified Agricultural Waste–Rice Husk Biochar

In order to promote the improvement of rural living environments, the treatment of rural domestic sewage has attracted much attention in China. Meanwhile, the rural regions’ sewage discharge standards are becoming increasingly stringent. However, the standard compliance rate of the total phosphorus (TP) is very low, and the TP has become the main limiting pollutant for the water pollutant discharge standards of rural domestic sewage treatment facilities. In this study, oyster shell waste was employed as a calcium source, and agricultural waste–rice husk was used as a carbon source to synthesize calcium-modified biochar adsorbent materials (Ca-BC) by a simple one-step pyrolysis method. The resultant Ca-BC adsorbent materials demonstrated efficient phosphate (P) adsorption from aqueous solutions over a wide pH range (3–11) and adsorption selectivity. Ca-BC’s adsorption capacity for P increased with the pyrolysis temperature, increasing from 700 °C to 900 °C, which was attributed to the higher specific surface area and calcium oxide content at higher pyrolysis temperatures. The Ca-BC sample, which was made from oyster shells and rice husks with a mass ratio of 2:1 and a pyrolysis temperature of 900 °C, had a maximum adsorption capacity of 196.2 mg/g. The Langmuir model and pseudo-second-order model were the best at describing the adsorption process, and the predominant sorption mechanism for P is the precipitation of calcium oxide or calcium hydroxide with phosphate to create hydroxyapatite. Ca-BC can effectively remove P from rural domestic sewage. The removal rate of the total phosphorus (TP) in rural domestic sewage is 93.9–99.4%. After the adsorption treatment, the discharge of the TP in the rural sewage met the second-grade (TP < 3 mg/L) or even the first-grade (TP < 2 mg/L) Discharge Standard of Water Pollutants for Centralized Rural Sewage Treatment Facilities (DB33/973-2021). This study provides an experimental basis for efficient P removal by Ca-BC adsorbent materials and suggests possible applications in rural domestic sewage.

Adsorption Removal of Phosphate from Rural Domestic Sewage by Ca-Modified Biochar Derived from Waste Eggshell and Sawdust

In recent years, in order to improve the rural living environment, rural domestic sewage treatment has received more and more attention in China. However, the standard compliance rate of total phosphorus (TP) in rural domestic sewage after treatment is very low, and TP has become the main pollutant that prevents rural domestic sewage treatment facilities from meeting water pollutants discharge standards. In this study, to prepare calcium-modified biochar composites (E-BC) by one-step pyrolysis, waste eggshell (E) was employed as a calcium source and waste pine sawdust (BC) was employed as a carbon source. The E-BC composites produced were effective in adsorbing phosphate (P) from aqueous solutions in a broad pH range of 3–11, with good adsorption selectivity. E-BC’s adsorption capacity for P increased as the pyrolysis temperature increased from 700 °C to 900 °C, which was attributed to the higher specific surface area and calcium oxide content at higher pyrolysis temperatures. The E-BC sample, which was made from eggshell (filtered through 100 mesh sieves) and pine sawdust (filtered through 100 mesh sieves) with a mass ratio of 2:1 and a pyrolysis temperature of 900 °C, had a maximum adsorption capacity of 301 mg/g. The Langmuir model and pseudo second-order model were the best at describing the adsorption process, and the predominant sorption mechanism for P is the chemisorption reaction of calcium oxide or calcium hydroxide with phosphate to create hydroxyapatite. E-BC can effectively remove P from rural domestic sewage. The total phosphorus (TP) removal rate in rural domestic sewage ranges from 95.3 to 99.5%. After adsorption treatment, the discharge of TP in rural sewage meets the second-grade (TP < 3 mg/L) or even the first-grade (TP < 2 mg/L). This study provides an experimental basis for efficient P removal using E-BC adsorbent materials and suggests possible applications in rural domestic sewage.

Efficient Adsorption Removal of Phosphate from Rural Domestic Sewage by Waste Eggshell-Modified Peanut Shell Biochar Adsorbent Materials.

In order to promote the improvement of the rural living environment, the treatment of rural domestic sewage has attracted much attention in China. Meanwhile, the rural regions' sewage discharge standards are becoming increasingly stringent. However, the standard compliance rate of total phosphorus (TP) is very low, and TP has become the main limiting pollutant for the water pollutants discharge standards of rural domestic sewage treatment facilities. In this study, waste eggshell (E) was employed as a calcium source, and waste peanut shell (C) was employed as a carbon source to prepare calcium-modified biochar adsorbent materials (E-C). The resulting E-C adsorbent materials demonstrated efficient phosphate (P) adsorption from aqueous solutions over the initial pH range of 6-9 and had adsorption selectivity. At an eggshell and peanut shell mass ratio of 1:1 and a pyrolysis temperature of 800 °C, the experimental maximum adsorption capacity was 191.1 mg/g. The pseudo second-order model and Langmuir model were best at describing the adsorption process. The dominant sorption mechanism for P is that Ca(OH)2 is loaded on biochar with P to form Ca5(PO4)3OH precipitate. E-C was found to be very effective for the treatment of rural domestic sewage. The removal rate of TP in rural domestic sewage was 91-95.9%. After adsorption treatment, the discharge of TP in rural sewage met the second-grade (TP < 3 mg/L) and even first-grade (TP < 2 mg/L). This study provides an experimental basis for efficient P removal by E-C adsorbent materials and suggests possible applications in rural domestic sewage.

CuFe2O4/penicillin residue biochar heterogeneous Fenton-like catalyst used in the treatment of antibiotic wastewater: Synthesis, performance and working mechanism

A heterogeneous Fenton-like catalyst, CuFe2O4/penicillin residue biochar (CuFe2O4/PRBC), was synthesized and used to treat antibiotic wastewater. The physicochemical properties of PR, PRBC, and CuFe2O4/PRBC were characterized by a series of methods. CuFe2O4/PRBC showed better performance (removal rate constant of tetracycline = 0.0599 min−1) than those of CuFe2O4 (0.0458 min−1), PRBC (0.0244 min−1), and a direct physical mixing of CuFe2O4 with PRBC (0.0285 min−1). Under the optimal conditions (fresh CuFe2O4/PRBC loading = 0.4 g·L−1, H2O2 dosage = 30 mmol·L−1, the range of initial pH was 3–9), the removal rate of tetracycline was >95 % within 90 min, and the removal rate slightly decreased to 90.7 % in the fifth use of CuFe2O4/PRBC. Besides tetracycline, CuFe2O4/PRBC catalyzed Fenton-like process can effectively oxidize sulfamethoxazole, oxytetracycline, and ciprofloxacin with the corresponding removal rates of 99.4 %, 97.1 %, and 88.8 %, and effectively remove COD from oxytetracycline and cephalosporin real production wastewaters, respectively, satisfying the discharge standard of GB 21903–2008. The main oxidative free radicals were ·OH and ·O2−/HO2·, and the working mechanism of CuFe2O4/PRBC was the synergy process between adsorption and catalytic oxidation, where the separate redox recycles of ≡Fe(III)/≡Fe(II) and ≡Cu(II)/≡Cu(I) and the redox reaction between ≡Fe(III) and ≡Cu(I) were critical steps.