Nutrient-rich Wastewater Research Articles

Transforming waste into wealth in sustainable shrimp aquaculture: Effective phosphate removal and recovery using shrimp shell-derived adsorbents

The growing global demand for shrimp has driven the intensification of shrimp aquaculture, leading to significant environmental challenges due to nutrient-rich wastewater and solid waste. This study developed shrimp shell-derived adsorbents (SSs) by pyrolysis and calcium hydroxide (Ca(OH)2) activation to remove phosphate (PO43−) from aqueous solutions. Ca(OH)2 activated adsorbent achieved higher PO43− removal than adsorbent obtained at higher pyrolysis temperature, with adsorption capacities up to 381.24 mg/g of PO43− at 20 °C. The primary mechanism driving PO43− removal was chemical precipitation between Ca and PO43−. SSs were found to release Ca2+ from hydroxylellestadite (HDL), Ca(OH)2, and calcium carbonate (Ca(CO)3). Additionally, ligand exchange of PO43− by Ca(CO)3 and π-π interactions from aromatic rings further enhanced the PO43− adsorption. SEM-EDS showed PO43− dispersed on the SSs surface. XPS revealed that Ca-O bond was shifted to Ca-P bond with a higher binding energy and a new π-π interaction peak appeared at 293.60 eV. FTIR confirmed ligand exchange between PO43− and CO32−, with the 1400 cm−1 band disappearing and a new 870 cm−1 band appearing. The XRD, FTIR, and XPS analyses confirmed the formation of various calcium-phosphate (Ca-P) groups, including calcium apatite (Ca-apatite), monocalcium phosphate (Ca(H2PO4)2), and dicalcium phosphate (CaHPO4), on the saturated SSs. Specifically, all XPS spectra of Ca-O moved to higher binding energy, reflecting Ca-P linkages. This study provides a sustainable alternative for handling shrimp shell waste and suggests a promising approach for PO43− recovery, thereby contributing to a circular system in shrimp aquaculture.

Molecular insights into the enhanced growth of cyanobacteria by adaptive laboratory evolution in wastewater environments

The expansion of population leads to an increase in nutrient-rich wastewater, posing a threat to the ecosystem. The cultivation of economically beneficial cyanobacteria consumes amounts of freshwater, exacerbating the depletion of freshwater resources. This study investigates the potential of utilizing adaptive laboratory evolution (ALE) to enhance the growth performance of Synechocystis sp. PCC 6803, a model cyanobacterium, in wastewater. After 374 days of ALE, a strain designated as WW was successfully evolved. When cultivated in wastewater, WW exhibited a specific growth rate of 0.317 per day and achieved a dry weight of 0.693 g/L by the 13th day, outperforming the wild type. WW achieved removal efficiencies of 35.55 % for total nitrogen and 60.95 % for total phosphorus in the wastewater. RNA sequencing and photosynthetic measurements revealed that enhanced photosynthetic capacity in the WW contributes to its superior growth performance. The lipid content in WW was 16.19 %, with a notable increase in the proportion of polyunsaturated fatty acids. The shift in fatty acid composition has a consequential impact on biodiesel index, including oxidation stability and saponification number. This study not only demonstrates the effectiveness of ALE in enhancing the growth of cyanobacteria in wastewater for biofuel production, but also offers significant insights into the molecular mechanisms that drive this improved performance.

Binding between Cu2+/Zn2+ and aged polyethylene and polyethylene terephthalate microplastics in swine wastewaters: Adsorption behavior, and mechanism insights

Microplastics (MPs) have aroused growing environmental concerns due to their biotoxicity and vital roles in accelerating the spread of toxic elements. Illuminating the interactions between MPs and heavy metals (HMs) is crucial for understanding the transport and fate of HM-loaded MPs in specific environmentally relevant scenarios. Herein, the adsorption of copper (Cu2+) and zinc (Zn2+) ions over polyethylene (PE) and polyethylene terephthalate (PET) particulates before and after heat persulfate oxidation (HPO) treatment was comprehensively evaluated in simulated and real swine wastewaters. The effects of intrinsic properties (i.e., degree of weathering, size, type) of MPs and environmental factors (i.e., pH, ionic strength, and co-occurring species) on adsorption were investigated thoroughly. It was observed that HPO treatment expedites the fragmentation of pristine MPs, and renders MPs with a variety of oxygen-rich functional groups, which are likely to act as new active sites for binding both HMs. The adsorption of both HMs is pH- and ionic strength-dependent at a pH of 4–6. Co-occurring species such as humic acid (HA) and tetracycline (TC) appear to enhance the affinity of both aged MPs for Cu2+ and Zn2+ ions via bridging complexation. However, co-occurring nutrient species (e.g., phosphate and ammonia) demonstrate different impacts on the adsorption, improving uptake of Cu2+ by precipitation while lowering affinity for Zn2+ owing to the formation of soluble zinc-ammonia complex. Spectroscopic analysis indicates that the dominant adsorption mechanism mainly involves electrostatic interactions and surface complexation. These findings provided fundamental insights into the interactions between aged MPs and HMs in swine wastewaters and might be extended to other nutrient-rich wastewaters.

Advanced electrochemical membrane technologies for near-complete resource recovery and zero-discharge of urine: Performance optimization and evaluation

The depletion of nutrient sources in fertilizers demands a paradigm shift in the treatment of nutrient-rich wastewater, such as urine, to enable efficient resource recovery and high-value conversion. This study presented an integrated bipolar membrane electrodialysis (BMED) and hollow fiber membrane (HFM) system for near-complete resource recovery and zero-discharge from urine treatment. Computational simulations and experimental validations demonstrated that a higher voltage (20 V) significantly enhanced energy utilization, while an optimal flow rate of 0.4 L/min effectively mitigated the negative effects of concentration polarization and electro-osmosis on system performance. Within 40 min, the process separated 90.13% of the salts in urine, with an energy consumption of only 8.45 kWh/kgbase. Utilizing a multi-chamber structure for selective separation, the system achieved recovery efficiencies of 89% for nitrogen, 96% for phosphorus, and 95% for potassium from fresh urine, converting them into high-value products such as 85 mM acid, 69.5 mM base, and liquid fertilizer. According to techno-economic analysis, the cost of treating urine using this system at the lab-scale was $6.29/kg of products (including acid, base, and (NH4)2SO4), which was significantly lower than the $20.44/kg cost for the precipitation method to produce struvite. Excluding fixed costs, a net profit of $18.24/m3 was achieved through the recovery of valuable products from urine using this system. The pilot-scale assessment showed that the net benefit amounts to $19.90/m3 of urine, demonstrating significant economic feasibility. This study presents an effective approach for the near-complete resource recovery and zero-discharge treatment of urine, offering a practical solution for sustainable nutrient recycling and wastewater management.

Re-Circulatory Aquaculture Systems: A Pathway to Sustainable Fish Farming

Recirculating Aquaculture Systems (RAS) represent a transformative approach to sustainable fish farming that offers a viable solution to meet the growing global demand for seafood while minimizing environmental impact. These closed-loop systems recirculate and reuse water, reducing water consumption by up to 99% compared to traditional aquaculture methods. RAS also mitigate the risk of disease transmission, escapement, and pollution by isolating farmed fish from natural populations and the surrounding environment. Technologically advanced RAS employ mechanical filtration, biological filtration, and disinfection processes to maintain optimal water quality for fish growth. This high level of control allows for the farming of a wide range of species, including predatory finfish, in locations far from coastal areas. Furthermore, the integration of aquaponics in RAS enables the production of high-quality vegetables and herbs using the nutrient-rich wastewater, creating a sustainable closed-loop system. Despite the higher initial investment required, RAS have demonstrated consistent profitability and the potential for significant returns. By promoting "in-sourcing" and creating local jobs, RAS can contribute to the economic development of communities while reducing the carbon footprint associated with international seafood trade. As the aquaculture industry continues to evolve, RAS are poised to play a crucial role in ensuring the long-term sustainability of fish farming. By combining technological advancements with environmental stewardship, RAS offer a promising pathway towards meeting the world's growing demand for seafood while preserving the health of our aquatic ecosystems.

Granular sludge characterization and microbial response in a hydroxyapatite (HAP)- anammox coupled process at different nitrogen loading rates

To enhance the treatment capacity and operational stability of the anammox process for nutrient-rich wastewater disposal, a hydroxyapatite (HAP)-anammox coupled process was developed in a granular sludge-based upflow bioreactor. The impact of nitrogen loading rate (NLR) on process performance was investigated by gradually increasing the NLR from 1 to 1.5, 3, and 5 kgN/m3/d for 264 days continuous operation. TN and TP removal rates of 82.51 ± 3.58 % and 60.49 ± 2.82 % were achieved at the NLR of 5 kgN/m3/d. The precipitation of Ca and phosphorus resulted in HAP crystals formation evidenced by sludge morphology and component analysis, which enhanced sludge settling properties and facilitated biomass enrichment. The HAP-anammox granular sludge was characterized by the outer layer HAP crystals formed on inner anammox granules, while highly mineralized granular sludge with higher density distributed at the bottom of the reactor is conducive to HAP-based phosphorus recovery. After a long-term accumulation, the abundance of Planctomycetota phylum gradually increased (from 7.7 % to 14.1 %), consisting of three species of anammox bacteria, namely Candidatus_Brocadia_sapporoensis, Candidatus_Brocadia_sinica and Candidatus_Kuenenia_stuttgartiensis. Nitrogen metabolic pathway analysis illustrated that denitrification was also present except the anammox reaction, synergistically contributing to superior nitrogen removal in the HAP-anammox process.

Mixotrophic Chlorella pyrenoidosa biofilm with enhanced biomass production, microalgal activity, and nutrient removal from nutrient-rich wastewater

Microalgae possess significant advantages in nitrogen and phosphorus removal from nutrient-rich wastewater that are highly efficient and independent of the C/N ratio. However, challenges such as low biomass productivity, high variability in nutrient removal under different trophic types, and difficulty in harvesting biomass limits the large-scale application of microalgae wastewater treatment. This study attempted to employ mixotrophic microalgae biofilm to address these issues. The biomass production, microalgal activity, and nutrient removal of Chlorella pyrenoidosa biofilms with different trophic types were compared for nutrient-rich wastewater treatment. The results showed that the biomass productivity of the mixotrophic microalgal biofilm (0.215 g/(L·d)) was 2.3, 8.6, and 6.0 times higher than that of photoautotrophic microalgal biofilm, heterotrophic microalgal biofilm, and photoautotrophic suspended microalga, respectively. Additionally, the dehydrogenase activity (DHA), indicating microalgal activity, of the mixotrophic biofilm was 2.3 and 16.5 times higher than that of photoautotrophic and heterotrophic biofilms, respectively. Meanwhile, the mixotrophic biofilm removed 96.0 % of NH4+-N and 99.2 % of PO43–-P, more efficient than that with other types of biofilms and suspended microalgae. In an open-ended air-lift photobioreactor, the mixotrophic microalgal biofilm produced biomass at 0.12 g/(L·d) and removed 90.0 % of NH4+-N and 97.6 % of PO43–-P. This study suggests that the mixotrophic microalgal biofilm shows promise in treating nutrient-rich wastewater and producing microalgal biomass for value-added products.

Hydrothermal liquefaction aqueous phase mycoremediation to increase inorganic nitrogen availability

Hydrothermal liquefaction aqueous phase (HTL-AP) is a waste product from a thermochemical process where wet biomass is converted into biocrude oil. This nutrient-rich wastewater may be repurposed to benefit society by assisting crop growth after adequate treatment to increase inorganic nitrogen, especially NO3−. This study aims to increase HTL-AP inorganic nitrogen, specifically NH3/NH4+ and NO3−, through fungal remediation for further use in hydroponic systems. Trametes versicolor, a white-rot fungus known for degrading a range of organic pollutants, was used to treat a diluted (5 %) HTL-AP for 9 days. No fungal growth was observed, but T. versicolor activity was suspected by laccase activity throughout cultivation time. NO3−-N and NH3/NH4+-N increased by 17 and 8 times after three days of fungal treatment, which was chosen as the appropriate time for HTL-AP fungal treatment as it resulted in the highest concentration of NO3−-N. The addition of nitrifying bacteria to the fungal treatment resulted in a twofold increase in NO3−-N concentration compared to the fungal treatment alone, indicating an enhancement in treatment efficacy. COD decreased by 51.33 % after 24 h, which may be related to the fungus’ capacity to reduce the concentration of organics in the wastewater; nonetheless, COD increased in the following days, which may be related to the release of fungal byproducts. T. versicolor shows promise as a potential candidate for increasing inorganic nitrogen in HTL-AP. However, future studies should primarily address HTL-AP toxicity, reducing NH3/NH4+-N while increasing NO3−-N, and hydroponics crop production after fungal treatment.

Phosphorus removal from fermented dairy manure concurrent with polyhydroxybutyrate-co-valerate synthesis under aerobic conditions

Wastewater phosphorus removal achieved biologically is associated with the process known as enhanced biological phosphorus removal (EBPR). In contrast with canonical EBPR operations that employ alternating anaerobic–aerobic conditions and achieve asynchronous carbon and phosphorus storage, research herein focused on phosphorus removal achieved under aerobic conditions synchronously with volatile fatty acid (VFA) storage as polyhydroxybutyrate-co-valerate (PHBV). 90.3 ± 3.4 % soluble phosphorus removal was achieved from dairy manure fermenter liquor; influent and effluent concentrations were 38.6 ± 9.5 and 3.7 ± 0.8 mgP/L, respectively. Concurrently, PHBV yield ranged from 0.17 to 0.64 mgCOD/mgCOD, yielding 147–535 mgCODPHBV/L. No evidence of EBPR mechanisms was observed, nor were canonical phosphorus accumulating organisms present; additionally, the polyphosphate kinase gene was not present in the microbial biomass. Phosphorus removal was primarily associated with biomass growth and secondarily with biomass complexation. Results demonstrate that concurrent PHBV synthesis and phosphorus recovery can be achieved microbially under aerobic dynamic feeding conditions when fed nutrient rich wastewater.

EFFECT OF DAIRY AND MEAT WASTEWATER IRRIGATION ON SEEDLING GROWTH

Milk and meat processing industries release large quantities of nutrient-rich wastewater with organic compounds (proteins, fats, carbohydrates) in high concentrations. Reusing and recycling this biodegradable wastewater for crop irrigation could be a sustainable solution once the phytotoxic effects of wastewater on crops have been investigated. Therefore, the aim of this study was to evaluate the effects of milk and meat processing wastewaters on germination percentage, seed vigour indices, the seedling tolerance index and the phytotoxicity index of pea (Pisum sativum L.), sugar maize (Zea mays saccharata), purslane (Portulaca oleracea), wheat (Triticum aestivum) and red spinach (Amaranthus dubius). The two wastewater types were collected at the inlet of the city’s sewage system and analysed to determine their physicochemical and microbiological characteristics. The seeds of all five plant species were irrigated with untreated wastewater effluents. The highest - germination percentages were obtained for wheat (92%) and the lowest for red spinach (2.5%). Wheat, purslane, pea and red spinach samples irrigated with meat processing wastewater had higher germination percentages than samples irrigated with dairy wastewater. A higher phytotoxicity was observed for sugar maize, followed by red spinach irrigated with both types of wastewater. Future investigation into the effects of effluent dilution on these types of plants is recommended.

Mechanisms of copper and zinc bioremoval by microalgae and bacteria grown in nutrient rich wastewaters

Swine farming produces large quantities of nutrient-rich wastewater, which often contains metals such as Cu and Zn, used as feed additives for pigs. These metals must be removed from the wastewater before discharge but their retention in the biomass can limit its subsequent utilization. Photobioreactors are a very promising alternative for swine wastewater treatment, as the consortium of microalgae and bacteria growing symbiotically in these reactors allows high nutrient and metal removal efficiency at moderate costs. This work studies the mechanisms of removal of Cu(II) and Zn(II) by the two types of microorganisms growing in these photobioreactors. A microalga commonly used in wastewater treatment (Scenedesmus almeriensis) and an activated sludge were kept in contact with synthetic wastewater containing 100 mg/L of Cu and Zn. After 72 h, Scenedesmus almeriensis removed 43% of Cu and 45% of Zn, while activated sludge removed 78% of Cu and 96% of Zn. Single and sequential extractions of the biomasses using different extracting reagents revealed that biosorption on protonable groups is the dominant removal mechanisms. Mild reagents solubilized 69% of Cu and 94% of Zn from the microalgae and 76% of Cu and 93% of Zn from the activated sludge. Low metal concentrations in the oxidizable and residual fractions evidenced minimal bioaccumulation inside the cells. FTIR and ESEM-EDX analysis confirmed biosorption by ion exchange and complexation as the main metal remediation mechanisms. The weak bonds of the biosorbed Cu and Zn ions are beneficial for the valorization of biomass and the obtaining of safe bioproducts.

Struvite recovery from microbial fuel cells treating different nutrient-rich wastewaters

Wastewater is an abundant renewable source of nutrients such as nitrogen and phosphorus. However, current recovery methods require substantial amounts of energy and chemicals, which pose various economic and environmental burdens. Microbial fuel cells (MFCs) represent a feasible alternative for nutrient recovery from wastewater as they reduce the cost of chemicals and energy input while producing electricity from treated organics. Despite the promising benefits of MFCs, there is limited knowledge of the effect of substrate type on their operation and nutrient recovery. Therefore, this study investigates the efficiency of struvite formation for nutrient recovery in 700-ml-volume dual-chamber MFCs using various wastewaters: urine, centrate, and greywater (laundry and dishwasher wastewater). The performance was assessed based on electricity output, organics removal in terms of soluble chemical oxygen demand (SCOD), and struvite recovery. The highest SCOD removal efficiency of over 95 % was achieved with the centrate-fed cell. Moreover, the highest maximum power densities generated from the urine, centrate, and greywater-fed MFCs were 1.7, 1.5, and 0.95 mW/cm2, respectively. In terms of struvite recovery, the urine-fed cell produced the highest struvite precipitate quantity (2.1 g/l), followed by the centrate (1.8 g/l) and the greywater (0.4 g/l). The phosphate recovery efficiencies were 55, 36, and 48 % for the MFCs treating urine, centrate, and greywater, respectively. Morphological and chemical analyses of the formed precipitates confirmed that the nutrients were recovered primarily as struvite. Overall, the results and conclusions of the present study support the potential for utilizing MFCs for nutrient recovery and energy generation.

Comparison of plant biostimulating properties of Chlorella sorokiniana biomass produced in batch and semi-continuous systems supplemented with pig manure or acetate

Microalgae-derived biostimulants provide an eco-friendly biotechnology for improving crop productivity. The strategy of circular economy includes reducing biomass production costs of new and robust microalgae strains grown in nutrient-rich wastewater and mixotrophic culture where media is enriched with organic carbon. In this study, Chlorella sorokiniana was grown in 100 l bioreactors under sub-optimal conditions in a greenhouse. A combination of batch and semi-continuous cultivation was used to investigate the growth, plant hormone and biostimulating effect of biomass grown in diluted pig manure and in nutrient medium supplemented with Na-acetate. C. sorokiniana tolerated the low light (sum of PAR 0.99 ± 0.18 mol/photons/(m2/day)) and temperature (3.7–23.7° C) conditions to maintain a positive growth rate and daily biomass productivity (up to 149 mg/l/day and 69 mg/l/day dry matter production in pig manure and Na-acetate supplemented cultures respectively). The protein and lipid content was significantly higher in the biomass generated in batch culture and dilute pig manure (1.4x higher protein and 2x higher lipid) compared to the Na-acetate enriched culture. Auxins indole-3-acetic acid (IAA) and 2-oxindole-3-acetic acid (oxIAA) and salicylic acid (SA) were present in the biomass with significantly higher auxin content in the biomass generated using pig manure (> 350 pmol/g DW IAA and > 84 pmol/g DW oxIAA) compared to cultures enriched with Na-acetate and batch cultures (< 200 pmol/g DW IAA and < 27 pmol/g DW oxIAA). No abscisic acid and jasmonates were detected. All samples had plant biostimulating activity measured in the mungbean rooting bioassay with the Na-acetate supplemented biomass eliciting higher rooting activity (equivalent to 1–2 mg/l IBA) compared to the pig manure (equivalent to 0.5–1 mg/l IBA) and batch culture (equivalent to water control) generated biomass. Thus C. sorokiniana MACC-728 is a robust new strain for biotechnology, tolerating low light and temperature conditions. The strain can adapt to alternative nutrient (pig manure) and carbon (acetate) sources with the generated biomass having a high auxin concentration and plant biostimulating activity detected with the mungbean rooting bioassay.

Isolation and study of cyanobacterial cultures from oil refinery wastewaters

Wastewater from oil refineries, as well as other chemical industries, has specific features. Phototrophic microorganisms are commonly used to treat wastewater containing toxic components, such as oil and petroleum products. Cultivating microalgae and cyanobacteria in nutrient-rich wastewater can yield high biomass for simultaneous biotreatment, making it a more cost-effective and environmentally friendly approach. This study investigated the species composition of microalgae in wastewater from oil refineries in the Atyrau region. The results showed that Cyanophyta representatives dominated the microalgae composition in the enrichment culture. The presence of cyanobacteria in the wastewater was attributed to the high nutrient and calcium content of the organic matter. An axenic culture of the cyanobacterium Anabaena sp. was isolated to study its ability to grow and degrade different concentrations of motor oil. The results indicate the potential of Anabaena sp. strain in remediating aquatic environments contaminated with petroleum products.

Narrow host range phages infect essential bacteria for water purification reactions in groundwater-fed rapid sand filters

Biofiltration is used worldwide to provide safe potable water due to its low energy demand and excellent treatment performance. For instance, in Denmark, over 95% of drinking water is supplied through groundwater-fed rapid sand filters (RSF). Bacteriophages, viruses that infect bacteria, have been shown to shape the taxonomic and functional composition of microbial communities across a range of natural and engineering systems. However, phages in the biofiltration systems are rarely studied, despite the central role microbes play in water purification. To probe this, metagenomic data from surface water, groundwater and mixed source water biofiltration units (n = 26 from China, Europe and USA) for drinking water production were analysed to characterize prokaryotic viruses and to identify their potential microbial hosts. The source water type and geographical location are found to exert influence on the composition of the phageome in biofilters. Although the viral abundance (71,676 ± 17,841 RPKM) in biofilters is only 14.4% and 17.0% lower than those of the nutrient-rich wastewater treatment plants and fresh surface waters, the richness (1,441 ± 1,046) and diversity (Inverse Simpson: 91 ± 61) in biofiltration units are significantly less by a factor of 2–5 and 3–4, respectively. In depth analysis of data from 24 groundwater-fed RSFs in Denmark revealed a core phageome shared by most RSFs, which was consistently linked to dominant microbial hosts involved in key biological reactions for water purification. Finally, the high number of specific links detected between phages and bacterial species and the large proportion of lytic phages (77%) led to the conjecture that phages regulate bacterial populations through predation, preventing the proliferation of dominant species and contributing to the established functional redundancy among the dominant microbial groups. In conclusion, bacteriophages are likely to play a significant role in water treatment within biofilters, particularly through interactions with key bacterial species.

Phosphorus adsorption using chemical and metal chloride activated biochars: Isotherms, kinetics and mechanism study

Efficient treatment of nutrient-rich wastewater is of paramount importance for protecting the ecosystem. In this work, an efficient, abundant, and eco-friendly adsorbent was derived from biochar and employed for phosphorus (P) adsorption. The key factors influencing the P removal efficiency of the activated biochar, including P concentration, pH, dosage, temperature, adsorption time, and influence of co-existing ion type, were investigated. Maximum P adsorption percentage (100%) was obtained with 10 mg/L and zinc chloride activated biochar (BC–Zn) compared to the other activated biochars. Results show that by increasing the P concentration from 5 to 200 mg/L, the phosphorus adsorption capacity increases from 0.13 to 10.4 mg/g biochar. Isotherms and kinetic studies further show that the P adsorption follows the Langmuir and quasi-second-order kinetic models. The mechanistic investigation demonstrated that P adsorption occurred by precipitation reaction. Furthermore, P desorption has been studied at different time intervals to understand the P release rate after adsorption.

A novel Electrolysis-integrated anammox system for intensified nitrogen removal and simultaneous phosphorus recovery as vivianite

A novel electrolysis-integrated anammox (Ele-anammox) process was developed for intensified nitrogen removal and concomitant phosphorus recovery from nutrient-rich wastewater. By conducting a parallel experiment, average removal efficiencies of total nitrogen (TN) and total phosphorus (TP) in Ele-anammox reactor reached 90.69% and 95.02% respectively, showing increases of 7.76% and 79.08%, as compared to the traditional anammox process. Anammox reaction and synergetic denitrification were mainly responsible for the reinforced N-removal. Successions of microbial communities revealed that Candidatus Kuenenia declined markedly while Candidatus Brocadia was enriched in Ele-anammox system, suggesting that electrical environment provided Candidatus Brocadia with a competitive advantage over other anammox bacteria. Based on the proposed current control strategy (the applied current was calculated to match the influent P loading), precise release of soluble Fe2+ could be achieved by anodic oxidation. Various elemental analysis methods, including the standards, measurements and testing (SMT) protocol, energy dispersive X-ray spectroscopy (eSEM-EDX), X-ray fluorescence spectrometry (XRF) and inductively coupled plasma emission spectroscopy (ICP-OES), jointly indicated that the solid phase of Ele-anammox was primarily Fe-P precipitation, which showed a similar Fe:P ratio with vivianite (Fe3(PO4)2·8H2O, 1.5). X-ray diffraction (XRD) analysis further validated the in-situ crystallization of vivianite, and semi-quantification implied a vivianite content of 85%. Mössbauer spectroscopy showed at least 51.48% ∼ 59.11% of iron was bound in vivianite, while impurity occupation and potential oxidization may impair the purity of P-recovery products, which should be concerned in future practice.

Sweet Fuel: A Political and Environmental History of Brazilian Ethanol

Sweet Fuel: A Political and Environmental History of Brazilian Ethanol

Recent advances in the biological treatment of wastewater rich in emerging pollutants produced by pharmaceutical industrial discharges.

Pharmaceuticals and personal care products present potential risks to human health and the environment. In particular, wastewater treatment plants often detect emerging pollutants that disrupt biological treatment. The activated sludge process is a traditional biological method with a lower capital cost and limited operating requirements than more advanced treatment methods. In addition, the membrane bioreactor combines a membrane module and a bioreactor, widely used as an advanced method for treating pharmaceutical wastewater with good pollution performance. Indeed, the fouling of the membrane remains a major problem in this process. In addition, anaerobic membrane bioreactors can treat complex pharmaceutical waste while recovering energy and producing nutrient-rich wastewater for irrigation. Wastewater characterizations have shown that wastewater's high organic matter content facilitates the selection of low-cost, low-nutrient, low-surface-area, and effective anaerobic methods for drug degradation and reduces pollution. However, to improve the biological treatment, researchers have turned to hybrid processes in which all physical, chemical, and biological treatment methods are integrated to remove various emerging contaminants effectively. Hybrid systems can generate bioenergy, which helps reduce the operating costs of the pharmaceutical waste treatment system. To find the most effective treatment technique for our research, this work lists the different biological treatment techniques cited in the literature, such as activated sludge, membrane bioreactor, anaerobic treatment, and hybrid treatment, combining physicochemical and biological techniques.

Controlling Nitrogen Removal Processes in Improved Vertical Flow Constructed Wetland with Hydroponic Materials: Effect of Influent COD/N Ratios

Discharge of nitrogen (N) with wastewater causes eutrophication in surface water. On the other hand, nutrient-rich wastewater can be valuable for agriculture. Tailoring N removal or conservation is important to meet the requirements of different water end uses. Improved vertical flow constructed wetlands with hydroponic materials (CWH) as substrata were developed at lab scale in a greenhouse and studied to optimize N removal in CWH. This study investigated the effect of influent COD/N ratios of 5/1 and 15/1 on the removal or conservation of N in CWHs with Syngonium as vegetation and three substrata, pumice, cocopeat, and mineral wool. CWH with pumice showed the highest TN removal at both COD/N ratios. The Syngonium plant significantly contributed to the additional 50% TN removal in CWH. Nitrification of above 90% was observed at both studied COD/N ratios, indicating sufficient oxygenation due to the vertical pulse flow operated CWH. The denitrification process was enhanced at a higher COD/N ratio of 15/1 compared to 5/1 by around 10–40%. The occurring nitrification and denitrification indicate the coexistence of aerobic and anaerobic conditions in CWH, and balancing these conditions is necessary for future applications to remove N for its specific end use, i.e., irrigation water (high standards) or discharge to surface water (low standards).