Flocculation and dewaterability of chemically enhanced primary treatment sludge by bioaugmentation with filamentous fungi

Combined high-rate contact stabilization and chemically enhanced primary treatment for enhanced recovery of organic matter and biogas from sewage

This study examined integrating high-rate contact stabilization (HRCS) and chemically enhanced primary treatment (CEPT) for wastewater to improve the carbon recovery rate (CRR). Enhancing chemical oxygen demand (COD) removal efficiency was hypothesized to improve the CRR. The evaluation covered serial HRCS-CEPT, serial CEPT-HRCS, and single-stage carbon recovery (Single-CR). The COD removal efficiencies for individual HRCS and CEPT were 50.3 % and 56.2 %, respectively. The serial CEPT-HRCS system failed in the HRCS process due to poor settling, resulting in microbial washout. However, the serial HRCS-CEPT system achieved the highest COD removal efficiency (84.5 %). The Single-CR system exhibited the highest CRR of 0.780 ± 0.083 g-CODCH4/g-CODinf, identifying it as the most promising process for energy-positive wastewater treatment. The selective pressure in the high-rate system resulted in a simplified and specialized bacterial community, mainly comprising microorganisms with high polyhydroxyalkanoate storage capacity, such as Lactococcus sp., Enterobacter sp., and Acinetobacter sp.

Enhanced recovery of waste-born nutrients from sewage sludge ash and fish meal through fungal treatment: Mechanistic insights and impact of heavy metals

This study investigates the potential of Talaromyces adpressus TCPF to enhance phosphate recovery and nutrient bioavailability from sewage sludge ash (SSA) and fish meal (FM) through co-fermentation. The fungal treatment was found to significantly increase phosphate recovery, achieving up to 16 % efficiency, especially at a 10 g/L waste concentration. The key mechanism behind this enhancement is the production of low molecular weight organic acids (LMWOAs), which played a crucial role in solubilizing nutrients while also mitigating the negative effects of heavy metals like lead and cadmium. Spectroscopic analyses confirmed substantial acid-based leaching and biomineralization processes, with over 70 % of phosphorus successfully bioleached from metal-treated waste. These findings underscore the effectiveness of fungal treatments in transforming waste substrates into valuable bio-organic fertilizers. Fungal treatment boosts phosphate recovery, even in the presence of heavy metals, by employing processes such as bioweathering, bioprecipitation, biocorrosion, and bioleaching.

Enhancing sludge dewaterability in sequential bioleaching: Degradation of dissolved organic matter (DOM) by filamentous fungus Mucor sp. ZG-3 and the influence of energy source

This study aimed to enhance sludge dewatering through sequential bioleaching, employing the filamentous fungus Mucor sp. ZG-3 and the iron-oxidizing bacterium Acidithiobacillus ferrooxidans LX5. The mechanism by which Mucor sp. ZG-3 alleviates sludge dissolved organic matter (DOM) inhibition of A. ferrooxidans LX5 was investigated, and the optimal addition of energy source for enhanced sludge dewaterability during sequential bioleaching was determined. Sludge dissolved organic carbon (DOC) decreased to 272 mg/L with a 65.2% reduction by Mucor sp. ZG-3 in 3 days, and the degraded fraction of sludge DOM was mainly low-molecular-weight DOM (L-DOM) which inhibited the oxidization of Fe2+ by A. ferrooxidans LX5. By degrading significant inhibitory low-molecular-weight organic acids, Mucor sp. ZG-3 alleviated DOM inhibition of A. ferrooxidans LX5. In the sequential bioleaching process, the optimal concentration of FeSO4·7H2O for A. ferrooxidans LX5 was 4 g/L, resulting in the minimum specific resistance to filtration (SRF) of 2.60×1011 m/kg, 40.0% lower than that in the conventional bioleaching process with 10 g/L energy source. Moreover, the sequential bioleaching process increased the sludge zeta potential (from -31.8 to -9.47 mV) and median particle size (d50) of the sludge particle (from 17.90 to 27.44 μm), contributing to enhanced sludge dewaterability. Inoculation of Mucor sp. ZG-3 during the bioleaching process reduced the demand for energy sources by A. ferrooxidans LX5 while improving sludge dewaterability performance.

Treatment of polluted river water using potential bioflocculant produced by Klebsiella pneumonia UKD24

Chemically enhanced primary treatment (CEPT) is a rapid wastewater treatment process involving treating wastewater with two chemical-aided processes, coagulation, and flocculation. In the present study, a natural extracellular polymeric substance flocculant (EPSBF) produced by Klebsiella pneumonia UKD24, a bacterium isolated from the sewage treatment plant, and a synthetic polyacrylamide anionic polymer flocculant (PAM) were evaluated to treat polluted river water. The synthetic PAM showed immediate turbidity reduction after agitation, while the EPSBF expressed a rapid decrease in optical density. After 20 min of the settling period, the EPSBF showed reduced rates of turbidity, optical density, and chemical oxygen demand at 74.14 ± 5.2%, 89.37 ± 0.76%, and 87.21 ± 0.73%, respectively, while PAM showed 67.08 ± 4%, 85.68 ± 2%, and 86.57 ± 2%, respectively. EPSBF treatment significantly improved the water quality parameters in terms of total dissolved solids, total suspended solids, conductivity, and oxidation-reduction potential than PAM treatment. However, the EPSBF has shown a more water-holding capacity and relatively weak flock formation, producing more sludge volume than PAM. Furthermore, though the sludge produced by the EPSBF treatment had a higher moisture content, it showed shorter capillary suction time (CST). In contrast, sludge formed in PAM treatment had lower moisture content, but it exhibited prolonged CST value indicating that PAM treatment sludge showed slow dewaterability.

Progress of improving waste activated sludge dewaterability: Influence factors, conditioning technologies and implications and perspectives

Large amounts of waste activated sludge (WAS) as a by-product generated from the biological treatment in wastewater treatment plants (WWTPs) is of high moisture content (MC), organic pollutants, heavy metals and pathogenic bacteria, it may cause serious environmental ecological risk without appropriate disposal. More than one half of the total operation cost is accounted for sludge disposal in a WWTP. Dewatering is an essential and important step during the sludge treatment and disposal process for it could efficiently reduce its volume, and be beneficial to the subsequent treatment and disposal of sludge. However, sludge should be conditioned before mechanical dewatering because of its high hydrophilicity. In this work, it presented a comprehensive review on sludge dewatering including summarizing the dewaterability measurement indexes, affecting factors, conditioning technologies, the improvement mechanisms. Finally, based on the eventual disposal and low carbon emission target, the implications and perspectives development of sludge conditioning were discussed. Based on the above discussion, there is no unified theoretical insight of the improvement mechanism of sludge dewaterability. In addition, the relationship between the microstructure of organic matters in sludge floc and the dewaterability should be deepened. Especially, how to choose the optimal conditioning technology for sludge dewatering lies in the physical and chemical properties of sludge, however, the carbon emission of the conditioning and dewatering process also needs to be considered. Accordingly, green, low-cost and organic conditioning agents are the direction of future research, and the establishment of automatic operating system and real-time evaluation index system is the key challenge.

Potential of bioaugmentation of heavy metal contaminated soils in the Zambian Copperbelt using autochthonous filamentous fungi

There is great potential to remediate heavy metal contaminated environments through bioaugmentation with filamentous fungi. However, these fungi have been poorly investigated in most developing countries, such as Zambia. Therefore, the present study aimed at isolating indigenous filamentous fungi from heavy metal contaminated soil and to explore their potential for use in bioaugmentation. The conventional streak plate method was used to isolate fungi from heavy metal-contaminated soil. Filamentous fungal isolates were identified using morphological and molecular techniques. The radial growth diameter technique was used to evaluate heavy metal tolerance of the fungi. The most abundant and highly tolerant fungi, identified as Aspergillus transmontanensis, Cladosporium cladosporioides, and Geotrichum candidum species, were used to bioremediate heavy metal contaminated soil samples with uncontaminated soil sample being employed as a control. A maximum tolerance index (TI) between 0.7 and 11.0 was observed for A. transmontanensis, and G. candidum while C. cladosporioides displayed the TI between 0.2 and 1.2 in the presence of 1,000 ppm of Cu, Co, Fe, Mn, and Zn. The interspecific interaction was analyzed to determine the compatibility among isolates. Our results showed mutual intermingling between the three evaluated fungal species, which confirms their common influence in biomineralization of heavy metals in contaminated soils. Maximum bio-removal capacities after 90 days were 72% for Cu, 99.8% for Co, 60.6% for Fe, 82.2% for Mn, and 100% for both Pb and Zn. This study has demonstrated the potential of highly resistant autochthonous fungal isolates to remediate the heavy metal contamination problem.

Reduction of antibiotic resistome in influent of a wastewater treatment plant (WWTP) via a chemically enhanced primary treatment (CEPT) process

Chemically enhanced primary treatment (CEPT) has been considered for maximizing wastewater energy recovery by enhancing the carbon captured through the primary treatment. However, evaluating the potential of CEPT as a primary treatment process for removing antibiotic resistance genes (ARGs) in the influent from a wastewater treatment plant (WWTP) has seldom been investigated. In this study, CEPT was conducted to assess simultaneous reduction of 13 major targeted ARGs and common pollutants in wastewater compared with primary sedimentation alone (non-CEPT). CEPT processes using three types of coagulants (PACl, FeCl₃ and alum) effectively reduced absolute abundance of ARGs and intI1 in the influent from municipal WWTP. Average log-removal of absolute abundance of ARGs was achieved up to 1.77 ± 0.41 along with 90% turbidity reduction compared to non-CEPT. Through the simultaneous reduction of ARGs and intI1 genes during a CEPT process, ARGs proliferation may be limited directly through reduction of antibiotic resistant bacteria or indirectly through decreasing the possibility of horizontal gene transfer by intI1 removal. Reduction of ARGs and intI1 was improved by increasing coagulants' doses: abundances of residual ARGs under optimal dose conditions were similar, regardless of the different characteristics of coagulant types. The strongly positive correlation between reduction of turbidity/total phosphorus (T-P) and ARGs was explored, identifying that turbidity or T-P might be suitable indicators linked with variations in the abundance of ARGs during CEPT. As a result, CEPT may prove promising in efforts to control ARGs flowing into a WWTP.

Enhancement of sewage sludge dewaterability by fungal conditioning with Penicillium simplicissimum NJ12: from bench- to pilot-scale consecutive multi-batch investigations

Bench- and pilot-scale successive multi-batch trials were conducted to investigate the performance and sustainability of fungal conditioning with Penicillium simplicissimum NJ12 for improving sludge dewatering. The dominant factors affecting the sludge dewaterability improvement by P. simplicissimum NJ12 were also identified. Fungal treatment with P. simplicissimum NJ12 at a volume fraction of 5% of the inoculum greatly improved the sludge dewaterability. This improvement was characterized by sharp decreases in the specific resistance to filtration from 1.97 × 10¹³ to 3.52 × 10¹¹ m/kg and capillary suction time from 32 to 12 s within 3 days. Stepwise multiple linear regression analysis showed that a marked decrease (58.8%) in the protein content in slime extracellular polymeric substances and an increase in the zeta potential of the sludge (from -35 to -10 mV) were the most important factors that improved the dewaterability of sludge after fungal treatment. Consecutive processes of fungal treatment could be realized by recirculating the fungal-treated sludge with a recycling rate of 1:2 (V_{biotreated sludge}/V_{total sludge}). The treatment effectiveness was maintained only over three successive cycles, but replenishment with fresh P. simplicissimum NJ12 would be provided periodically at set batch intervals. These findings demonstrate the possibility of P. simplicissimum NJ12-assisted fungal treatment for enhancing sludge dewatering.

Preparation of ultrahigh-surface-area sludge biopolymers-based carbon using alkali treatment for organic matters recovery coupled to catalytic pyrolysis

In this work, we employed waste activated sludge (WAS) as carbon source to prepare ultrahigh specific surface area (SSA) biopolymers-based carbons (BBCs) through alkali (KOH) treatment coupled to pyrolysis strategy. Before the pyrolysis process, the involvement of KOH made a great recovery of soluble biopolymers from WAS, resulting in highly-efficient catalytic pyrolysis. The Brunner-Emmett-Teller and pore volume of BBCs prepared at 800°C (BBC₈₀₀) reached the maximum at 2633.89 m²·g^-1 and 2.919 m³·g^-1, respectively. X-ray photoelectron spectroscopy suggested that aromatic carbon in the form of C=C was the dominant fraction of C element in BBCs. The N element in BBCs were composed of pyrrolic nitrogen and pyridinic nitrogen at 700°C, while a new graphitic nitrogen appeared over 800°C. As a refractory pollutant of wastewater treatment plants, tetracycline (TC) was selected to evaluate adsorption performance of BBCs. The adsorption behavior of BBCs towards TC was conformed to the pseudo-second-order kinetic and the Langmuir models, signifying that chemisorption of monolayers was dominant in TC adsorption. The adsorption capacity of BBC₈₀₀ reached the maximum at 877.19 mg·g^-1 for 90 min at 298 K. Thermodynamic analysis indicated that the adsorption process was endothermic and spontaneous. Hydrogen bonding and π-π stacking interaction were mainly responsible for TC adsorption, and interfacial diffusion was the main rate-control step in adsorption process. The presence of soluble microbial products (SMPs) enhanced TC removal. This work provided a novel strategy to prepare bio-carbon with ultrahigh SSA using WAS for highly-efficient removal of organic pollutants.

Revisiting Chemically Enhanced Primary Treatment of Wastewater: A Review

Chemically enhanced primary treatment (CEPT) is a process that uses coagulant and/or flocculant chemicals to remove suspended solids, organic carbon, and nutrients from wastewater. Although it is not a new technology, it has received much attention in recent years due to its increased treatment capacity and related benefits compared to the conventional primary treatment process. CEPT involves both physical and chemical processes. Alum and iron salts are the commonly used coagulants in CEPT. Several types of anionic, cationic, and uncharged polymers are used as flocculants, where poly aluminum chloride (PACL) and polyacrylamide (PAM) are the widely used ones. Some of the coagulants and flocculants used may have inhibitory and/or toxicity effects on downstream treatment and recovery processes. There has been an increasing amount of work on the treatment of wastewaters from various sources using CEPT. These wastewaters can range from municipal/domestic wastewater, combined sewer overflow, landfill leachate, cattle manure digestate to wastewaters from textile industry, pulp and paper mill, slaughterhouse, milk processing plant, tannery and others. In recent cases, CEPT is employed to enhance carbon redirection for recovery and substantially reduce the organic load to secondary treatment processes. CEPTs can remove between 43.1–95.6% of COD, 70.0–99.5% suspended solids, and 40.0–99.3% of phosphate depending on the characteristics of wastewater treated and type of coagulants and/or flocculants used. This article reviews the application, chemicals used so far, removal efficiencies, challenges, and environmental impacts of CEPT.

Dewaterability enhancement and sulfide mitigation of CEPT sludge by electrochemical pretreatment

Dewatering and sulfide control are the key challenges in treating chemically enhanced primary treatment (CEPT) sludge. In this study, an electrochemical pretreatment (EPT) approach with the input of 10 V/800 mA was explored for simultaneously improving the dewaterability of CEPT sludge and eliminating its sulfide production. The effects of different electrode materials (carbon and titanium) and EPT durations (from 5 to 15 min) were documented to reveal the underlying EPT mechanism. EPT with titanium electrodes (titanium-EPT) led to limited improvement in dewaterability and sulfide control. EPT with carbon electrodes (carbon-EPT) for 15 min, however, led to decreases in capillary suction time and specific resistance in filtration of over 80% and the suppression of about 99% of hydrogen sulfide (H₂S_(g)) production over 5 days of anaerobic storage. Analysis of the characteristics of treated CEPT sludge revealed that carbon-EPT disintegrated sludge flocs with ∼70% reduction in sludge particle sizes and release of aromatic and tyrosine protein-like substances, thus enhancing sludge dewaterability. The sulfur balance in the liquid and gaseous phases showed that most of the sulfur-containing compounds remained in the solid phase as aliphatic sulfur and sulfonic acid after carbon-EPT, thereby mitigating sulfide emission. While the pattern of sulfur distribution in sludge with titanium-EPT was dominated by sulfide, it was similar to the control sample. Reduction in bacteria associated with sulfide production (i.e., Lachnospiraceae) in CEPT sludge after carbon-EPT also contributed to sulfide elimination. This study demonstrates that EPT can be a superior option for simultaneously enhancing the dewaterability of CEPT sludge and mitigating its sulfide production.

Characterization of changes in extracellular polymeric substances and heavy metal speciation of waste activated sludge during typical oxidation solubilization processes

Biopolymer solubilization is considered to be the rate-limiting stage of anaerobic digestion of waste activated sludge (WAS). Oxidation processes have been proven to be effective in disrupting sludge flocs and causing solubilization of the solid biopolymers. In this study, WAS was treated by NaNO₂ or H₂O₂ oxidation at pH of 2. The changes in extracellular polymeric substances properties and the speciation of heavy metals were investigated. The results revealed that both NaNO₂ and H₂O₂ treatments were effective in solubilizing organics in WAS, while the conversion of biopolymers in the two treatment processes was different. Free nitrous acid destroyed the gel network structure of EPS, and organic materials were released from the solid phase to the supernatant. Indigenous peroxidase catalyzed H₂O₂ to produce hydroxyl radicals which caused significant solubilization of biopolymers, and the protein-like substances were further degraded into micro-molecule polypeptides or amino acids at high dosages of H₂O₂. During the oxidation processes, Zn, Cd and Cu, with excellent mobility, tended to migrate to the supernatant, and thus were easy to remove through the liquid-solid separation process. Ni and As showed moderate migration ability, of which the residual fraction tended to transform into reducible and soluble fractions. With poor mobility, Cr and Pb mainly existed in the forms of residual and oxidizable fractions, which were difficult to dissolve and remove from WAS. Both NaNO₂ and H₂O₂ treatment resulted in the enhancement of sludge solubilization efficiency and heavy metal mobility in WAS, but different heavy metals showed distinct migration and transformation behaviors.

Mystery of the high chlorine consumption in disinfecting a chemically enhanced primary saline sewage

Stonecutters Island Sewage Treatment Works is one of the largest sewage treatment plants in the world and consists mainly of a chemically enhanced primary treatment (CEPT) unit and a disinfection unit. It has long been realized that most of the dosed chlorine (15 mg/L) is lost at the beginning part of the disinfection unit during disinfection of the CEPT effluent. Lab-scale tests were therefore conducted in this study to determine the causes. Because ferric chloride is used in CEPT, ferrous iron in the CEPT effluent (from the reduction of ferric iron) was initially thought to be the main chlorine consumer. However, the chlorine consumption by ferrous iron was found to be 1.2 mg/L at most. Suspended solids and sulfide also did not contribute significantly to the chlorine consumption. Batch tests were therefore conducted to evaluate the effects of mixing condition and chlorine stock solution concentration on the chlorine consumption. Less chlorine was consumed upon increased mixing. Using a high-concentration chlorine stock solution (25000 mg/L) resulted in a 3-times-higher chlorine consumption in the absence of mixing than using a low-concentration chlorine stock solution (2500 mg/L). By correlating the losses of ammonia and total nitrogen with the chlorine consumption, we hypothesized that the use of a high-concentration chlorine stock solution under poor mixing leads to a localized high ratio of chlorine to ammonia, resulting in breakpoint chlorination and an unusually excessive chlorine consumption. A novel apparatus was developed to quantify the nitrogen gas generated during chlorination of a simulated wastewater, and the mass balance of nitrogen-containing species (i.e., ammonia, nitrogen gas, nitrite and nitrate) during the chlorination was inspected. The good fit between the measured chlorine consumption and that back-calculated from nitrogen-containing species verified our hypothesis. Finally, it needs mentioning that the high chlorine consumption and the breakpoint chlorination may occur during chlorine disinfection of any sewage effluents with relatively high ammonia levels; thus it is suggested that either not-too-high concentrations of chlorine stock solutions or sufficient mixing should be applied during disinfection of the sewage effluents.

Coagulation/flocculation in dewatering of sludge: A review

Sludge disposal is an integral part of wastewater treatment systems, and its cost usually accounts for more than half of the total operation cost. Sludge disposal technology is facing challenges and opportunities simultaneously and can still be improved. Sludge dewatering is an essential process in sludge disposal, and it is important for the effective reduction of the final processing cost. Coagulation/flocculation is a relatively mature, cost-effective, user-friendly sludge dewatering technology. In this work, coagulation/flocculation and their combinations with other pretreatments, including dewatering mechanisms, are reviewed. Various coagulants/flocculants used in sludge dewatering, including inorganic coagulants, organic synthetic and natural polymeric flocculants, and bioflocculants, are introduced in detail because coagulants/flocculants are the key in coagulation/flocculation. The different factors that influence the dewatering performance of these coagulants/flocculants are also presented briefly. Moreover, aiming at the complicated composition of sludge and its treatment difficulty, the prospects and technical developments of coagulation/flocculation in sludge dewatering are discussed.

Highly effective enhancement of waste activated sludge dewaterability by altering proteins properties using methanol solution coupled with inorganic coagulants

Proteins are the dominant organic component of extracellular polymeric substances (EPS) in waste activated sludge (WAS), and play an important role during sludge dewatering processes. Methanol is a polar hydrophilic reagent and can denature proteins, which suggested to us that the modification of protein configurations with methanol could improve sludge dewatering performance. In this study, methanol was used to precondition WAS prior to adding inorganic coagulants for dewatering enhancement. The morphology and EPS properties (especially of proteins) were investigated to analyze and explain the effects of methanol in the sludge conditioning process. The results show that methanol performed much better than traditional inorganic coagulants in improving sludge dewaterability in term of specific resistance to filtration (SRF) and cake solid content (CSC). Extractable proteins in EPS increased to a maximum when the concentration of methanol reached 40% (w/w) because cell membranes were destroyed and intracellular substances and water were released. Floc protein content was reduced with the further increase in methanol concentration due to protein precipitation. Confocal laser scanning microscopy analysis indicated that proteins precipitated and formed larger aggregates because methanol destroyed both the hydration shell and the hydrophobic clusters of proteins and expanded the protein tertiary structure to release interstitial water and bound water. The combination treatment of methanol and inorganic coagulants (PAC or FeCl₃) showed significant synergetic effects on enhancing sludge dewatering and cake drying. In practical applications, methanol from the dewatering sludge can be returned to the biochemical pool and used as the carbon source for nitrogen removal in the denitrification process. This integrated process is appropriate for sludge final disposal technologies that have high energy demands, such as incineration and pyrolysis. This paper describes a novel approach to improving sludge dewaterability through the alteration of protein properties by use of physiochemical techniques.

Enhanced sludge solubilization and dewaterability by synergistic effects of nitrite and freezing

In this study, nitrite was added into sludge during freezing process to evaluate its role in waste activated sludge (WAS) solubilization and effect on sludge dewatering characteristics. The results showed that the introduction of 100 mg L^-1 of nitrite could increase dissolved organic carbon (DOC) concentration from 29.5 to 48.8 mg DOC g^-1 VSS under freezing conditions. More DOC was released with the increase of nitrite concentration. Freezing temperature, or freezing speed, also played a role in sludge solubilization. It was found that some readily-biodegradable low molecular weight (LMW) compounds, e.g. LMW protein, LMW polysaccharide, LMW neutrals, building blocks and LMW acids, were mainly released during the freezing process with the presence of nitrite. Interestingly, nitrite could also improve the sludge filterability at the lower nitrite concentration as a result of the increased sludge particle size. However, electrolytes (sodium nitrite) addition effects may mask such enhancement when nitrite concentration was high (800 mg L^-1). The rheological characteristics of sludge could be well modeled by Herchel-Bulkley model and the introduction of nitrite into freezing process further increased sludge flowability and decreased sludge viscosity. These results indicated that freezing with the presence of suitable concentration of nitrite could promote sludge solubilization and dewaterability. As such, good liquid and solid separation can be achieved with the recovery of liquid stream as carbon source.

Acidogenic fermentation of iron-enhanced primary sedimentation sludge under different pH conditions for production of volatile fatty acids

Iron-based chemically enhanced primary sedimentation (CEPS) is increasingly adopted for wastewater treatment in mega cities, producing a large amount of sludge (Fe-sludge) with a high content of organics for potential organic resource recovery. In this experimental study, acidogenic fermentation was applied treat FeCl₃-based CEPS sludge for production of volatile fatty acids (VFAs) at different pHs. Batch fermentation tests on the Fe-sludge with an organic content of 10 g-COD/L showed that the maximum VFAs production reached 2782.2 mg-COD/L in the reactor without pH control, and it reached 688.4, 3095.3, and 2603.7 mg-COD/L in reactors with pHs kept at 5.0, 6.0 and 8.0, respectively. Analysis of the acidogenesis kinetics and enzymatic activity indicated that the alkaline pH could accelerate the rate of organic hydrolysis but inhibited the further organic conversion to VFAs. In semi-continuous sludge fermentation tests, the VFAs yield in the pH6 reactor was 20% higher than that in the control reactor without pH regulation, while the VFAs yield in the pH8 reactor was 10% lower than the control. Illumina MiSeq sequencing revealed that key functional microorganisms known for effective sludge fermentation, including Bacteroidia and Erysipelotrichi, were enriched in the pH6 reactor with an enhanced VFAs production, while Clostridia became more abundant in the pH8 reactor to stand the unfavorable pH condition. The research presented acidogenic fermentation as an effective process for CEPS sludge treatment and organic resource recovery and provided the first insight into the related microbial community dynamics.

Enhancement of sludge dewaterability with filamentous fungi Talaromyces flavus S1 by depletion of extracellular polymeric substances or mycelium entrapment

This study was conducted to explore the mechanism of dewaterability improvement of waste activated sludge by the filamentous fungus Talaromyces flavus S1. When the fungal spores were inoculated to the sterilized sludge, the sludge dewaterability was significantly improved by 48.1% and the reasons can be attributed to sludge pellet formation and degradation of extracellular polymeric substances, in particular the slime-EPS and loosely-bound EPS (LB-EPS). With the addition of fungal mycelium into the either sterilized sludge or non-sterilized sludge, the values of CST decreased by 74.0% and 43.7%, respectively, suggesting the fungal mycelium can improve the sludge dewaterability. After conditioned by the mycelium, the sludge cake by the diaphragm filter press was thicker and showed less water content than the control sludge. The results in this study demonstrated that the Talaromyces flavus S1 can serve as an environmentally friendly biological dewatering agent and has a promising application potential in the future.

Pharmacopollution and Household Waste Medicine (HWM): how reverse logistics is environmentally important to Brazil

Pharmacopollution is a public health and environmental outcome of some active pharmaceutical ingredients (API) and endocrine-disrupting compounds (EDC) dispersed through water and/or soil. Its most important sources are the pharmaceutical industry, healthcare facilities (e.g., hospitals), livestock, aquaculture, and households (patients' excretion and littering). The last source is the focus of this article. Research questions are "What is the Household Waste Medicine (HWM) phenomenon?", "How HWM and pharmacopollution are related?", and "Why is a reverse logistic system necessary for HWM in Brazil?" This article followed the seven steps proposed by Rother (2007) for a systematic review based on the Cochrane Handbook and the National Health Service (NHS) Center for Reviews Dissemination (CDR) Report. The HWM phenomenon brings many environmental, public health, and, social challenges. The insufficient data is a real challenge to assessing potential human health risks and API concentrations. Therefore, the hazard of long-term exposure to low concentrations of pharmacopollutants and the combined effects of API mixtures is still uncertain. HWM are strongly related to pharmacopollution, as this review shows. The Brazilian HWM case is remarkable because it is the fourth pharmaceutical market (US$ 65,971 billion), with a wide number of private pharmacies and drugstores (3.3: 10,000 pharmacy/inhabitants), self-medication habits, and no national take-back program. The HWM generation is estimated in 56.6 g/per capita, or 10,800 t/year. The absence of a reverse logistics for HWM can lead to serious environmental and public health challenges. The sector agreement for HWM is currently under public consultation.

Sludge conditioning using biogenic flocculant produced by Acidithiobacillus ferrooxidans for enhancement in dewaterability

Biogenic flocculant produced by Acidithiobacillus ferrooxidans was used for sludge conditioning to improve the dewaterability of anaerobically-digested sludge, and its efficiency was compared with commercial cationic polyacrylamide (PAM). Biogenic flocculant rapidly reduced the pH and increased the oxidation-reduction potential of sludge. Capillary suction time (CST) and specific resistant to filtration (SRF) of sludge was decreased by 74% and 89%, respectively, compared with control; and the reductions were 58% CST and 67% SRF higher when compared with commercial polymer. Biogenic treatment improved the sludge calorific value by 13%, and also reduced the unpleasant odor. The small-scale mechanical filter press study showed that the biogenic flocculant can reduce the moisture content of sludge to 70%, and improve the clarity of the filtrate in terms of removal of total suspended solids and total dissolved solids when compared with synthetic polymer treatment.

Fate of extracellular polymeric substances of anaerobically digested sewage sludge during pre-dewatering conditioning with Acidithiobacillus ferrooxidans culture

This study investigated the fate of extracellular polymeric substances (EPS) of anaerobically digested saline sewage sludge during its preconditioning. Sludge was conditioned with Acidithiobacillus ferrooxidans (AF) culture for 24h in the presence and absence of Fe(2+) as an energy substrate. pH decreased from 7.24 to 3.12 during sludge conditioning process. The capillary suction time (CST) of conditioned sludge significantly decreased to <10s, and specific resistance to filtration (SRF) was reduced by >94% as compared with control within 4h of conditioning with or without Fe(2+), indicating a significant (P<0.001) improvement in sludge dewaterability. A noticeable decrease in extractable EPS was observed in conditioned sludge. The EPS contents showed a significant negative correlation with dewaterability of sludge (P<0.05). The results suggest that bioacidification treatment using A. ferrooxidans effectively improved sludge dewaterability through modification of sludge EPS.

Bacterial community analysis of an industrial wastewater treatment plant in Colombia with screening for lipid-degrading microorganisms

The operation of wastewater treatment technologies depends on a combination of physical, chemical and biological factors. Microorganisms present in wastewater treatment plants play essential roles in the degradation and removal of organic waste and xenobiotic pollutants. Several microorganisms have been used in complementary treatments to process effluents rich in fats and oils. Microbial lipases have received significant industrial attention because of their stability, broad substrate specificity, high yields, and regular supply, as well as the fact that the microorganisms producing them grow rapidly on inexpensive media. In Colombia, bacterial community studies have focused on populations of cultivable nitrifying, heterotrophic and nitrogen-fixing bacteria present in constructed wetlands. In this study, culture-dependent methods, culture-independent methods (TTGE, RISA) and enzymatic methods were used to estimate bacterial diversity, to monitor temporal and spatial changes in bacterial communities, and to screen microorganisms that presented lipolytic activity. The dominant microorganisms in the Wastewater Treatment Plant (WWTP) examined in this study belonged to the phyla Firmicutes, Proteobacteria and Bacteroidetes. The enzymatic studies performed indicated that five bacterial isolates and three fungal isolates possessed the ability to degrade lipids; additionally, the Serratia, Kosakonia and Mucor genera presented lipase-mediated transesterification activity. The implications of these findings in regard to possible applications are discussed later in this paper. Our results indicate that there is a wide diversity of aerobic Gram-negative bacteria inhabiting the different sections of the WWTP, which could indicate its ecological condition, functioning and general efficiency.

Improved dewatering of CEPT sludge by biogenic flocculant from Acidithiobacillus ferrooxidans

Bioleaching using an iron-oxidizing bacterium, Acidithiobacillus ferrooxidans, and its biogenic flocculants was evaluated to improve the dewaterability of chemically enhanced primary treatment (CEPT) sewage sludge. CEPT sludge in flasks was inoculated with A. ferrooxidans culture, medium-free cells and the cell-free culture filtrate with and without the energy substance Fe(2+), and periodically the sludge samples were analysed for the dewaterability. This investigation proves that bioleaching effectively improved the sludge dewaterability as evidenced from drastic reduction in capillary suction time (≤20 seconds) and specific resistance to filtration (≥90%); however, it requires an adaptability period of 1-2 days. On the other hand, the biogenic flocculant produced by A. ferrooxidans greatly decreased the time-to-filtration and facilitated the dewaterability within 4 h. Results indicate that rapid dewatering of CEPT sludge by biogenic flocculants provides an opportunity to replace the synthetic organic polymer for dewatering.

Decolorization and biodegradation of the Congo red by Acinetobacter baumannii YNWH 226 and its polymer production's flocculation and dewatering potential

The strain Acinetobacter baumannii YNWH 226 was utilized to degrade Congo red (CR) under aerobic conditions. CR was employed as the sole carbon source to produce extracellular polymeric substances (EPS) used as potent bioflocculants in this strain. A total of 98.62% CR was removed during the 48-h decoloration experiments using CR (100 mg/L). A total of 83% bioadsorption and 65% biodegradation were responsible for the decoloration and degradation of CR through the strain. The bioflocculant showed high flocculation activity and dewaterability on textile dyeing sludge. A maximum flocculation of 78.62% with a minimum SBF of 3.07×10(9) s(2)/g and a CST of 58.4 s were achieved. We investigated the internal relationship between the decolorization efficiency of YNWH 226 and the flocculation activity and dewatering capacity of its EPS. The components and structure of the EPS highly influenced the decolorization efficiency of CR and the flocculation activity and dewatering capacity on sludge.

Degradation of slime extracellular polymeric substances and inhibited sludge flocs destruction contribute to sludge dewaterability enhancement during fungal treatment of sludge using filamentous fungus Mucor sp. GY-1

Mechanisms responsible for the sludge dewaterability enhanced by filamentous fungi during fungal treatment of sludge were investigated in the present study. The filamentous fungus Mucor sp. GY-1, isolated from waste activated sludge, enhanced sludge dewaterability by 82.1% to achieve the lowest value of normalized sludge specific resistance to filtration (SRF), 8.18 × 10(10) m · L/kg · g-TSS. During the fungal treatment of sludge, 57.8% of slime extracellular polymeric substances (EPS) and 51.1% of polysaccharide in slime EPS were degraded, respectively, by Mucor sp. GY-1, contributing to the improvement of sludge dewaterability. Slime EPS is much more available for Mucor sp. GY-1 than either LB-EPS or TB-EPS that bound with microbial cells. In addition, filamentous fungus Mucor sp. GY-1 entrapped small sludge particles and inhibited the destruction of sludge flocs larger than 100 μm, thus enhancing sludge dewaterability, during fungal treatment of sludge using Mucor sp. GY-1.

Treatment of African catfish, Clarias gariepinus wastewater utilizing phytoremediation of microalgae, Chlorella sp. with Aspergillus niger bio-harvesting

This study focuses on the evaluation of the performance of Chlorella sp. in removing nutrient in aquaculture wastewater and its correlation with the kinetic growth of Chlorella sp. The treatment was applied with various Chlorella sp. inoculation dosage ranging from 0% to 60% (v/v) of wastewater. The optimum inoculation dosage was recorded at 30% (v/v) with effluent concentration of ammonia and orthophosphate recording at 0.012mgL(-1) and 0.647mgL(-1), respectively on Day 11. The optimum dosage for bio-flocculation process was obtained at 30mgL(-1) of Aspergillus niger with a harvesting efficiency of 97%. This type of development of phytoremediation with continuous bio-harvesting could promote the use of sustainable green technology for effective wastewater treatment.