Biological Treatment Of Effluents Research Articles

Sulfadiazine degradation by hydroxyl radical and direct electron transfer pathways in the self-prepared boron doped diamond electrochemical process

Sulfonamide antibiotics are frequently detected in livestock wastewater, seriously harming the ecological environment and human health. Boron-doped diamond (BDD) electrochemical process has prominent potential in degrading organic pollutants from special industrial wastewater. In this work, the degradation efficiency and mechanism for sulfadiazine (SDZ) with the prepared BDD electrode were investigated. Scanning electron microscopy (SEM) and Raman spectroscopy revealed a 2 μm thick, compact, and crack-free BDD film on silicon. The BDD's oxygen evolution potential was 1.47 V. About 93.3 % of SDZ in the synthetic wastewater was removed under the conditions of a current density of 40 mA/cm2, electrode spacing of 20 mm, electrolyte concentration of 40 mM, and an initial pH of 8. Hydroxyl radical and direct electron transfer (DET) mainly contributed to SDZ degradation based on specific quencher tests and electrochemical analysis. The possible transformation pathways of SDZ were proposed according to the detected oxidation products and DFT calculation, mainly including amino hydroxylation, sulfur dioxide extrusion, and pyrimidine heterocyclic ring opening. Furthermore, the toxicity of intermediates products markedly weakened compared to that of SDZ. The presence of ion chloride could slightly improve the removal of SDZ, while bicarbonate and phosphate inhibited the SDZ degradation. In addition, the efficient removal of chemical oxygen demand and SDZ in the effluent of aerobic biological treatment effluent of actual livestock wastewater was confirmed. To sum up, BDD electrochemical oxidation is a viable approach for the advanced treatment of livestock wastewater.

Current and future perspectives of a microalgae based circular bioeconomy to manage industrial wastewater– A Systematic Review

AbstractPost technological advancements and industrialisation, the recovery of resources by treating wastewater is gaining momentum. As the global population continues to grow, the need for water is becoming increasingly urgent. Therefore, the re‐utilisation of water is becoming an increasingly important factor in the preservation of life on this planet. Wastewater is classified according to its source of origin. When left untreated, the effluent causes several environmental hazards and poses health issues as they have higher concentrations of nutrients and toxic heavy metals. Currently, several conventional methods exist to treat and handle wastewater, but they generate secondary waste post‐treatment and are not sustainable. Microalgae‐based treatment of wastewater is highly sustainable, cost‐efficient and aligns with the concept of circular bioeconomy. The biological treatment of effluents using microalgae has several advantages. Approximately 1.83 kg of CO2 is sequestered per kg of the dry biomass during microalgae cultivation. Among all the sustainable alternatives, microalgae offer better biomass productivity by utilising a higher concentration of nutrients in wastewater. The wastewater‐grown microalgae have higher efficiency in producing commercially important secondary metabolites. This systematic review highlights the competence of microalgae in different wastewater sources and their industrial perspectives. This also gives an overview of the biproducts produced from microalgae‐based wastewater treatment.

Different Fenton treatments on diverse landfill organics: Discover the underestimated effect of derived-DOM

Fenton is one of the most promising processes for the removal of dissolved organic matter (DOM). It has always been highly suspected that derived-DOM would be generated during Fenton reaction, but there is lack of direct evidence at the molecular level. The present study explored the molecular properties of the derived-DOM of five common Fenton technologies for degradation of nine landfill organics including leachates and concentrates based on UPLC Orbitrap MS/MS analysis. The comparative results confirmed that DOM derivation was essential for Fenton technologies, with the DOM derivation rate as high as 17.3%–70.3%. The derived-DOM are dominated by trace organic contaminants (CHON-DOM), and typical new contaminants (PPCPs, flavors, etc.). Heterogeneous Fenton had significantly lesser derived-DOM (35.1% ± 16.9%) than other Fenton technologies. Among all landfill organics, medium leachate was most likely to derive DOM (51.4% ± 13.9%), while unexpectedly old leachate had the lowest derivation rate (32.0% ± 5.3%). In the overall membrane treatment process, the secondary membrane concentrate is more susceptible to DOM derivation (43.4% ± 5.5%–49.6% ± 3.8%) than the primary membrane concentrate (40.7% ± 14.1%), and the elements and subcategories composition and molecular property indexes of the derived-DOM become more complex. On the contrary, the DOM derivatization rate of the biological treatment effluent after Fenton treatment was much lower than that of the various concentrates after Fenton treatment and the molecular property are simpler. Therefore, Fenton may replace the membrane process directly as a deep treatment process after biological treatment of landfill leachate. These information would help the selection and application of Fenton technologies.

Isolation and identification of naturally occurring textile effluent-degrading bacteria and evaluation of their ability to inhibit potentially toxic elements

Untreated textile dye-contaminated wastewater contains potentially toxic elements (PTEs) and causes pollution when discharged. Herein, we attempted to isolate and identify naturally occurring effluent-degrading bacteria and investigate their resistance potentials against various PTEs. Wastewater samples were collected from the biological effluent treatment plant of a textile dyeing industry located at the Chattogram Export Processing Zone, Bangladesh. The effluent samples contained Pb and Cr, with 27 times higher Cr content than the regulatory limit. A total of 14 bacterial isolates were isolated from the effluent based on differences in their cultural properties. Based on morphological and biochemical features, isolates were identified as Staphylococcus xylosus, Bacillus korlensis, Pseudomonas fluorescens, Pseudomonas cichorii, Brevundimonus diminuta, and Enterococcus columbae. Isolates were primarily screened for their ability to reduce the content of PTEs, such as Cr, Pb, Mn, Cu, and Cd. Pre-incubation of effluents and isolates revealed that most bacteria reduced the PTEs in the effluent. Of the 14 isolates, six exhibited potential in reducing most of the PTEs—Cd (94–99%). Further, Cr was decreased by 68 and 61% in the presence of S. xylosus and P. fluorescens, respectively, after 72 h of incubation in a medium containing 400 mg L−1 salt. The findings of this study can provide insights into the efficient biological remediation of PTEs in industrial wastewater.

Cost-effective Application of Fenton Oxidation Process to the Biologically Treated Leachate Containing Refractory Organics and Nitrite

This paper presents an economic application of Fenton oxidation process to biological treatment effluent containing high-strength nitrite and refractory organics. To cope with two major drawbacks in applying Fenton oxidation process to the nitrite-rich effluent simultaneously, i.e. expensive reagent and excessive sludge production, we examined two pretreatment methodologies prior to the application of Fenton process in the following way. First, residual nitrite in the biologically treated leachate (BTL) was removed with iron-catalyzed air oxidation (ICAO) as a cost-effective pretreatment. The time necessary for ICAO reaction is approx. 5 hr. Secondly, to reduce organic loads iron sludge was regenerated for an alternative coagulant. With the regenerated iron sludge, the dose of Fenton’s regent can be reduced by half to remove residual COD in the BTL.

Potencialidades Biotecnológicas dos Fungos da Amazônia Brasileira: Uma Revisão Sistemática

The Amazon Biome is known as the greatest biological diversity and forest richness of the planet, constitutes a source of great value for the search of new enzymatic extracts to be explored for biotechnological application. In this context, fungi are used in food production, in the pharmaceutical industry, in the biodegradation process, in the biological treatment of effluents, they act in the enzymatic activity, of industrial interest and biotransformation, they are also of great agricultural and ecological importance. Thus, the present work aimed to perform a systematic review on fungal biotechnology in the Brazilian Amazon, presenting works developed in the region, noting the period of inclusion in the last 10 years (2010-2020). It was verified the publication of 31 works of bibliographic productions on biotechnological applications. The productions on the theme of fungal biotechnology were infrequently comprehensive in the year 2010 until the year 2013. It was found that there was a following growth of stability of the theme's incidence in publications in the subsequent years, especially in the year 2017 until the year 2020. Based on the study conducted, it was verified the importance of different works that address the study of Biotechnology to obtain various substances through the manipulation of fungi, in order to obtain new technologies for the benefit of society and importance to the environment.

Treatment-based hospital wastewater characterization and fractionation of pollutants

This study investigated detailed characterization of hospital wastewater, size distribution of major organic pollutants and COD fractionation. In order to estimate the amount of wastewater, water consumption values and number of patients from 1156 hospitals were assessed statistically, and hourly water consumption data of a middle size hospital were recorded. Significant differences were observed in the total water consumption of the hospitals even among the ones having similar bed capacities. The average daily water consumption per hospital was about 140 m3, while the 1st and 3rd quartile were 25 m3 and 150 m3 respectively. Pollutant size distribution (PSD) analysis provided specific fingerprints for COD, BOD, colour and AOX parameters of hospital wastewater. Size distribution analyses resulted that about 20% of the AOX was in size range smaller than 1 kDa which might be attributed to adsorbable iodinated compounds (AOI) generated in iodinated X-ray process. According to the PSD results, it can be estimated that up to 85-90% of the total COD and 75-80% of the total AOX can be removed by direct filtration process using an ultrafiltration-sized membrane. COD fractionation experiments revealed that hospital wastewater has more soluble inert COD content than domestic wastewater with a similar COD concentration. Therefore, slightly higher COD concentrations can be expected at the biological treatment effluent of hospital wastewater compared to domestic wastewaters with similar COD concentrations. The difference may be attributed to the use of various chemicals and cleaning agents of inert properties.

Technical and Economic Aspects of Reusing Textile Effluent as Process Water: A Case Study of Denim Washing Factory

Textile and apparel industries are the major role-players in the fast-growing economy of Bangladesh. However, the textile sector consumes a large amount of water for various wet processing operations. Currently 98% of the water used by local textile factories is groundwater, which is causing depletion of ground water levels at a high rate. Considering the gravity of groundwater crisis in future, Bangladesh Government and international brands and retailers are advocating local textile factories to reuse textile effluents and implement ZLD (zero liquid discharge) option in the upcoming years. However, it is a new concept for Bangladesh textile sector, and there is limited understanding regarding technical and economic issues associated to advanced treatment and reusing textile effluent. In this paper, a case study is presented to analyse the application of advanced membrane treatment of conventional ETP (effluent treatment plant) treated water of a denim washing factory. The corresponding technical and economic issues of water recycling and reusing were also analyzed. The selected denim washing factory runs a conventional biological effluent treatment plant (ETP) which satisfies the basic requirements of national and international standards. For advanced treatment, a mobile setup of ultrafiltration (UF) and reverse osmosis (RO) unit was used at factory premises to further treat ETP treated water. The advanced treatment was carried out for three different permeate to reject ratios to observe changes in the permeate and reject water quality. Capital expenditure and operational costs were also assessed to see the economic feasibility of the approach. This study will help local textile factories with real time data to understand the technical and economic issues associated to reusing textile wastewater as process water.
 Chemical Engineering Research Bulletin 21(2020) 127-132

Treatment and valorization of municipal solid waste gasification effluent through a combined advanced oxidation – microalgal phytoremediation approach

Liquid effluents generated during the gasification process of municipal solid wastes (MSW) represent highly heterogenous and recalcitrant substrates, and thus require energy-intensive treatments prior to their discharge into the environment. However, these streams represent untapped carbon sources which can be converted, under the right conditions, to platform molecules, decreasing thus the elevated costs of current mitigation approaches. Thus, the present study describes a novel two-step chemical and biological effluent treatment process which co-generates microalgal biomass containing valuable functional components. The detoxification potential of ozone, ultrasonication and a combination of both of these advanced oxidation processes (AOPs) were initially evaluated using wastewater generated from scrubbing primary syngas produced from the gasification of MSW. The pretreated effluents were subsequently used to cultivate Chlorella vulgaris microalgae under various illumination (light/dark cycles of 24h/0h, 12h/12h and 0h/24h) and nutrient (supplementation of yeast extract) regimes, in order to assess their potential to further convert the remaining carbon into value-added functional biomolecules, such as photosynthetic pigments. The use of ozone, either individually or combined with ultrasounds, showed the best performances for the substrate detoxification prior to the biological treatment step. It was determined that 20 min of oxidative reaction using ozone coupled with ultrasounds was sufficient to degrade up to 70% of the total phenol compounds, 64% of the COD, and 75% of the color initially present in the gasification wastewater. The further microalgal phytoremediation and conversion experiments showed that 12 h of illumination per day, together with 0.5 g/L of yeast extract, generated the highest microalgae growth rate (0.29 d−1), biomass productivity (244 mg/L/d), photosynthetic pigment accumulation (12.0 and 4.5 mg/L of total chlorophyll and carotenoids, respectively) as well as total carbon removal (57 %). Therefore, the combination of AOPs with mixotrophic cultivation of C. vulgaris demonstrates for the first time an alternative to current treatment strategies of highly-recalcitrant industrial wastewaters, which includes the further valorization of the carbon available in these streams.

An experimental study on Bio-gas production by anaerobic digestion of RiceMill Wastewater (RMW)

<p>With the rising interest for sustainable power source and ecological security, anaerobic digestion of biogas technology has attracted considerable attention within the scientific researchers. This paper proposes a new research achievement on biogas production from Rice Mill Wastewater (RMW) with the utilization of anaerobic digester. An anaerobic digester is maintained with RMW and distillery anaerobic sludge at mesophilic temperature condition for 15 days as stabilization mode. After attaining stabilization stage, studies continued to examine the effect of Organic Loading Rate (OLR) and Hydraulic Retention Time (HRT) on the mesophilic anaerobic digestion of RMW. The OLR of the anaerobic reactor increased stepwise from 0.25 to 3.91 Kg COD/m3/dayand HRT ranged from 1 to 32.0 days. The total chemical oxygen demand (TCOD) utilized was higher than 75% and the CH4 percentage of the biogas was 62.00-63.00% for the OLRs studied. The efficient working volume of the digester is preserved as 25% of distillery anaerobic sludge and 75% of rice mill wastewater, loaded at Mesophilic temperature conditions for study purpose. By changing the conditions of OLR and HRT, biogas production, methane yield and percentage of COD reduction is examined. An anaerobic sludge is utilized as a seeding material to biodegrade the organic pollutants present in the wastewater. It will enhance the biological treatment of effluent with anaerobic sludge in a continuous mode of activity.The result showed that the proposed analysis obtains more biogas production with reduced COD when compared with existing approaches.</p>

Algal and cyanobacterial biomass as potential dye biodecolorizing material: a review.

The considerable demand for dyes worldwide has triggered a surge in their production globally. The extensive application of dyes and inefficient dyeing processes has elevated the risk of environmental pollution. The effluents from dying industries contain toxic compounds that are dreadful to both the environment and living beings. Besides, conventional effluent treatment processes have proved ineffective in clearing the dye from the effluent. The sole way of tackling this problem would be by applying a more rational approach that would be sustainable and efficient. After a thorough study of the literature, we are convinced to say that cyanophyceae and algae could serve as one of the promising biodecolorizing agents substituting most other biosorbents used in conventional biological effluent treatment technology. To evidence this we compiled data from the literature, wherein, various algal biomasses capable of decolorizing dye effluents have been examined. This paper also gives comprehensive facts on the mechanism of decolorization, pretreatment, influencing factors, and toxicity of treated products.

Disinfection by-products formation and acute toxicity variation of hospital wastewater under different disinfection processes

Hospital wastewater (HWW) contains a large number of pathogenic microorganisms; therefore disinfection is an indispensable unit for its treatment. This study compared the formation and formation potential of disinfection by-products (DBPs) and assessed the variations of acute toxicity for both of first physical treatment effluent (FPTE) and second biological treatment effluent (SBTE) of HWW under five different disinfection processes, including free chlorine (Cl2), chlorine dioxide (ClO2), ozone (O3), ultraviolet (UV) and ultraviolet/chlorine (UV/Cl2). Firstly, the optimal parameters of each disinfection process for FPTE and SBTE were determined respectively based on the required disinfection efficiency (i.e., controlling the concentration of fecal coliforms). The amounts of total DBPs in different disinfection processes under the optimal disinfectants dosage followed the order of Cl2 > UV/Cl2 > ClO2 > UV ≈ O3, which demonstrated that the amount of DBPs formation was closely related to the dosage of chlorine. Meanwhile, the amounts of total disinfection by-products formation potential (DBPFP) under the optimal disinfectants dosage followed the order of UV/Cl2 > UV ≈ Cl2 > O3 > ClO2. Besides, it was found that with the reduction of chlorine dosage, the formed DBPs in UV/Cl2 disinfection process decreased. However, UV/Cl2 disinfection process might degrade organic compounds into more DBPs precursors, leading to higher DBPFP than that in Cl2 disinfection process. Significantly, some specific DBPFPs such as haloketones-FP (HKFP), chloral hydrate-FP (CHFP) and trichloronitromethane-FP (TCNMFP) in O3 disinfection process were found higher than that in Cl2 disinfection process, which could be attributed to the formation of O3 oxidation by-products, for instance aldehydes, methyl ketones and trivalent nitrogen compounds. Additionally, apart from O3, the growth inhibition rate of Chlorella vulgaris increased in all the other disinfection processes and the order of the acute toxicity in each disinfected effluent was consistent with that of DBPs formation.

Minimization of energy demand in slaughterhouses: Estimated production of biogas generated from the effluent

Many studies have evaluated agroindustrial effluent treatment systems. However, the use of quality control tools in this area is still not widespread, while reports of the use of such tools to monitor slaughterhouse waste treatment systems are practically non-existent. Investigation of exploitation of the energy potential of waste produced within these industries is a strategically important issue, considering the current drive to minimize environmental impacts and to generate power from renewable sources. Therefore, the purpose of this study was to monitor the biological treatment of effluents, using control charts, as well as to estimate the potential production of methane and biogas in a slaughterhouse in southern Brazil. Wastewater samples were collected weekly and measurements were made of ambient and liquid temperatures, pH, solids (total and volatile), chemical oxygen demand (COD), oils and greases (OG), nitrogen, and phosphorus. The potential for methane and biogas production was estimated using the average daily effluent flow rate and the average organic load removal in the anaerobic pond. The effluent treatment system was evaluated by means of the construction of control charts, using the measured variables. This enabled the identification of factors that influenced the effluent treatment process, such as changes in the affluent load, environmental conditions, waste characteristics, and mechanical and human parameters. In terms of energy potential, the use of a covered pond (biodigester) would partially meet the energy demand of the industry, which consumed approximately 66 m3 of firewood per month, hence requiring 42969 m3 of biogas per month to supply all its needs. According to theoretical data, the waste could generate around 6790 m3 of biogas, which would supply 16% of the energy demand, besides providing environmental advantages such as improved efficiency of the treatment system and reduced emissions of greenhouse gases.

Effects of electrostatic precipitators ash leachate (EPAL) from recovery boilers on the biological treatment of effluent of kraft pulp mills

The electrostatic precipitators ash leachate (EPAL) from recovery boilers of kraft pulp mills is generated in processes dedicated to the removal of potassium and chloride salts seeking to avoid fouling and corrosion in pipes and equipment. However, the EPAL is rich in salts and has high electrical conductivity. Whenever it is sent to the effluent treatment plant (ETP), it can cause negative impacts to the biological process. It may jeopardize particularly the microbial community and the sludge bio-flocculation, causing sludge losses in the secondary clarifiers, reducing the overall efficiency of the effluent treatment plant. The objective of this research was to evaluate the influence of EPAL from the recovery boilers added to a typical effluent from a bleached eucalyptus kraft pulp mill in gradually increased doses and in sudden doses (shock loads) in the efficiency of the biological treatment. Three biological sequential batch reactors (R1, R2, R3) with a volume of 1000 ml each were tested. The Reactor R1 was operated as a reference and fed only with typical effluent from the pulp mill; Reactor R2 was fed with mill effluent with gradually increased doses of EPAL in fixed proportions until reaching a real industrial condition; Reactor R3 was fed with mill effluent and with sudden doses of EPAL. The reactors were operated in similar conditions, i.e., the concentration of dissolved oxygen (DO) was always kept higher than 2 mg L−1, COD:N:P ratio equal to 250:5:1 and hydraulic retention time of 12 h. Depending on the dose which was applied, the EPAL inhibited microbiological activity, reduced the efficiency of COD removal of the biological treatment (10% when EPAL was gradually applied and 15% in sudden doses) and increased the sludge carryover in the sedimentation phase (148% when EPAL was gradually applied and 170% in sudden dosages). Furthermore, the reduced efficiency and suspended solid carryover were more significant when sudden doses were applied compared to the application of gradual doses of the EPAL.

Production of lipolytic enzymes by bacteria isolated from biological effluent treatment systems.

This work aimed to evaluate the production of lipolytic complexes, produced by microorganisms isolated from a biological treatment system of effluents from a hotel. To select the best lipolytic microorganism for use in biotechnological processes, we tested 45 bacterial isolates recovered from the raw effluent of the hotel's restaurant waste tank. Lipase production was assayed in culture medium supplemented with olive oil and rhodamine B, incubated at 25 °C and 30 °C for 24 h - 48 h. Results showed 22 isolates lipase producers. All isolates were inoculated on medium without yeast extract to select the ones with highest enzyme yields. Out of these, nine isolates showed high lipase activity. The strain with the larger halo was assayed in submerged culture using an orbital shaker and a bioreactor, with three different substrates (olive oil, grape seed oil, and canola oil). Isolate G40 identified as Acinetobacter baylyi was selected to run the production assays because it showed the best result in the solid medium. In the bioreactor, maximum lipase production was obtained after 12 h of culture with the three substrates evaluated: 0,358 U/mL.min-1 in olive oil, 0,352 U/mL.min-1 with grapeseed oil, and 0,348 U/mL.min-1 with canola oil.

Bacterial community dynamics involved in Reactive Orange M2R dye degradation using a real time quantitative PCR and scale up studies using sequence batch reactor

ABSTRACTBacterial consortium volatile suspended soil (VSS) (Vatva soil sample) with a capability of azo dye Reactive Orange M2R (ROM2R) decolorization and degradation (shown in our earlier studies using Fourier transform infrared spectroscopy (FTIR) and phytotoxicity studies) was isolated from industrial wastewaters by enrichment culture technique. The present study was carried out to study bacterial population dynamics in consortium Vatva soil sample (VSS) during azo dye ROM2R degradation and to identify the consortium members that were actively involved in the degradation process. To achieve this goal, a real-time Polymerase chain reaction (PCR) assay targeting species-specific region of 16S rDNA of each consortial bacteria was developed to provide quantitative information about the bacterial abundance during azo dye degradation. The real-time PCR assay indicated that Pseudomonas aeruginosa (VSS-6) dominated consortium bacterial community during the active continuous bioremediation process. Attempt has been made to scale up from 100 ml volume to 10 L operation volume with intermittent additions (batch fed loadings) in a Sequence batch reactor (SBR). The development of VSS consortium biomass (MLVSS), changes in COD and biochemical oxygen demand, and the dye degradation were studied under conditions simulating the operations of biological effluent treatment in an attempt to develop a commercially applicable dye effluent treatment process unit.

Assessment of Ozone or Not-Treated Wastewater Ecotoxicity Using Mechanism-Based and Zebrafish Embryo Bioassays

Toxicity of wastewater treatment plant (WWTP) effluents is usually assessed with standardized bioassays, as e.g. the Fish Embryo Toxicity test (FET), but assessment of sub-lethal toxic effects requires to develop more adapted tests. The present work aimed to add the recording of several sub-lethal endpoints in exposed zebrafish embryo-larval stages in order to increase the sensitivity of residual toxicity evaluation of WWTP effluents using a semi-quantitative method (iFET score). This approach was complemented with the genotoxicity assessment on the exposed embryos, a sub-acute hazard particularly relevant to evaluate a potential chronic toxicity risk of low and multi-contaminated environmental matrices. Additionally, endocrine activities of effluents were quantified using human reporter cell lines. This test battery was applied to the assessment of the residual toxicity of five biological treatment effluents, further treated or not using various ozonation treatments intended to improve pharmaceutical compounds removal. Acute toxicity towards zebrafish embryos was very low. However, iFET score approach proposed was able to reveal residual toxicity through the presence of developmental abnormalities in all samples tested. Additionally, a low residual genotoxicity was measured in embryos exposed to two of the WWTP effluents when all excepted one exhibited a residual endocrine activity potential in the ng/L range providing complementary information on the occurrence of endocrine active chemicals and their reduction by different processes. To sum up, such a simplified and ecologically relevant test battery was found sensitive enough to characterize and differentiate various residual effluent’s ecotoxicity at contaminant levels of environmental concern.

Levels, Sources, and Health Risk Assessments of Heavy Metals in Indoor Dust in a College in the Pearl River Delta

Thirty indoor dust samples were collected from staff and study areas in a college in Foshan, and the As, Hg, Cd, Cu, Zn, Ni, Pb, and Cr contents were measured. The Spearman correlation coefficient, principal component analysis, and US EPA health risk assessment model were used to determine the sources and degree of pollution and the health risks. The results showed that the levels of the eight heavy metals were higher than the background values in Guangdong Province and the reported values in other Chinese cities, excluding Hg. The levels of the eight heavy metals were higher in the staff area than in the study area, but the difference was not significant. The eight heavy metals were derived from similar sources; Hg was mainly derived from outdoor anthropogenic sources, while the others were mainly derived from indoor anthropogenic sources. The daily non-carcinogenic exposure dose was in the following order:ingestion > dermal exposure > inhalation. Ingestion was the major pathway of heavy metal exposure from indoor dust. Except for Cr, the non-carcinogenic hazard indexes of ingestion and dermal exposure were taken from partial sample points > 1. All of the health risks were lower than the average risk thresholds of the heavy metals, and would not cause health risks to humans. Printers, copiers, instruments, and equipment were important sources of indoor pollution and risk sources of heavy metals. Thus, protective measures should be taken to reduce the risk of exposure.

Relationship between COD particle size distribution, COD fractionation and biodegradation characteristics in domestic sewage

AbstractBACKGROUNDThe study rationale was to explore the potential of particle size distribution (PSD) to support COD fractionation of sewage. Accordingly, the main aim focused on establishing the experimental relation between COD fractionation and PSD on two samples of a selected source, one representing the average character of the sewage and the other a weaker sample. PSD analyses were also conducted on effluent samples.RESULTSPSD profiles of COD yielded the typical bimodal distribution, one major peak representing 65% of COD, higher than 1600 nm and the second peak of 10% lower than 2 nm. Results were evaluated to underline the potential of PSD in complementing COD fractionation as related to biodegradation. PSD exhibited a close relationship with COD fractions with different biodegradation characteristics and defined all major COD fractions except the initial soluble and particulate inert COD fractions.CONCLUSIONSelection of appropriate values for inert COD fractions together with default kinetic information available for sewage would enable modelling and designing of various biological treatment alternatives without the need for time consuming experiments on COD fractionation. Furthermore, PSD of biological treatment effluent provided concrete evidence for the generation of soluble residual products, which should be part of all modelling evaluations. © 2017 Society of Chemical Industry

Review of Molecular Techniques for the Identification of Bacterial Communities in Biological Effluent Treatment Facilities at Pulp and Paper Mills

One of the processes most used in biotechnology today for handling industrial liquid wastes is biological wastewater treatment. The efficiency and quality of its operation depends on the composition and activity of the microbial community that is present. The application of traditional and molecular techniques has provided a glimpse into the “black box” and has given information to improve the wastewater treatment process. However, bleach pulp and paper mill effluents require a better understanding of the active bacterial population. For the study of these microorganisms, molecular techniques have been used for more than 15 years. However, there has been a lack of knowledge of the physiological requirements and relations with the environment, which seems to be very difficult to obtain involving profile on the diversity. Nowadays, high-throughput sequencing technology is a promising method that makes it possible to identify the entire profile of microbial communities. In combination with fingerprint methods, this approach allows the identification and analysis of the whole biodiversity of microbial communities. In this review, several identification techniques will be discussed.