Low Organic Loading Research Articles

Real and Synthetic Greywater Treatment by a Combined Process of Ozonation, Granular Activated Carbon, and Ultrafiltration

Background: The water crisis in different parts of the world forces people to manage water resources. Greywater can be used to reduce water stress. The annual rainfall average in Iran is hardly one-third of the world. In this study, the treatment of synthetic greywater at low, medium, and high organic load and real greywater (RGW) by a combined process of ozonation/granular activated carbon (GAC)/ultrafiltration (UF) have been investigated. Objectives: This study aimed to find a greywater treatment method that is effective, new, environment-friendly, and cost-effective. Methods: Chemicals and commercial compounds were used to prepare synthetic greywater, and the research pilot was developed. After several preparation steps, the GAC was transferred to a GAC reactor. A continuous flow of synthetic greywater entered the treatment system with low: 6.1, medium: 12.2, and high: 18.3 gCOD/L.d organic loading rates for 6 months. Next, the RGW samples from a residential complex in Shiraz, Iran, entered the treatment system for two weeks. After chemical analysis, an analysis of variance was carried out to compare the removal efficiency of parameters: [chemical oxygen demand (COD), five-day biochemical oxygen demand (BOD5), turbidity, and linear alkylbenzene sulfonates (LAS)] at various organic loads (low, medium, and high) of synthetic greywater and RGW. Results: We found the average COD removal in low, medium, and high organic loads of synthetic greywater and RGW as approximately 79.3%, 86.1%, 77.3%, and 97.3%, respectively. Moreover, the average BOD5 removal in the mentioned groups was about 69.6%, 48.9%, 42.7%, and 86.8%, respectively. The average of turbidity removal was 95.6%, 98.3%, 97.4%, and 97.9%, and average LAS removal was 90.1%, 88.9%, 88.3%, and 91.9%, respectively. Conclusions: This treatment method is remarkable for real and synthetic greywater treatment. It can effectively remove COD, BOD5, turbidity, and LAS. In addition, it is a relatively low-cost and environment-friendly system. Therefore, it can be recommended as a greywater treatment method, especially in countries with inadequate water supplies, such as Iran.

The biotechnological potential of microbial communities from Antarctic soils and sediments: Application to low temperature biogenic methane production

Anaerobic digestion (AD) is an attractive bioprocess for waste treatment and energy recovery through methane-rich biogas production. Under temperate to cold climate, the implementation of AD for low-organic load wastewater treatment has been limited to date, due to the energetic and economic cost of maintaining optimal mesophilic temperature. Hence, we aim at (i) exploring the biotechnological potential of a microbial inoculum from Antarctic soils and sediments to run AD at low temperatures; and (ii) evaluating the effect of temperature over a psychrophilic-mesophilic range on both methane production rates and microbial community composition. Methane production stimulated by acetate amendment was detected from 5 to 37 °C, with a maximum at 25 °C, corresponding to the highest relative abundance of methanogenic archaea (c. 21.4% of the total community). From 5 to 25 °C, the predominant methanogen was Methanosaeta, while it shifted to Methanocorpusculum at 30 °C. Compared with an industrial mesophilic sludge, the relative methane production rate at 5 °C (compared to the maximum) was 40% greater in the Antarctic inoculum. Microbial communities from permanently cold Antarctic sediments efficiently produce methane at low temperatures revealing a biotechnological potential for the treatment of low-organic load residues in cold regions.

Whole process analysis on the efficiency of RBC+SBNR+[Fenton+BAF]<sup>2</sup> full-scale facilities for mature landfill leachate treatment

<p indent="0mm">Although the “biological treatment + advanced oxidation technology” method can avoid the concentration difficulties generated by the widely used “membrane biological reactor + membrane separation” process, a complete full-scale assessment of this type of combined process is lacking. The study used three parallel treatment facilities as the research object, evaluating the transformation efficiency and contribution rate of pollutants in each treatment unit using “rotating biological contactor (RBC) + shortcut biological nitrogen removal (SBNR) + two stages of [Fenton + biological aerated filter (BAF)]” process. The results show that RBC does not contribute to nitrogen removal, and the entire process relies on multistage tandem aeration tanks to remove nitrogen in the mature landfill leachate via SBNR. The SBNR unit in two of the three facilities contributed more than 100% to the removal of dissolved nitrogen (DN). The backend BAF unit is primarily responsible for controlling dissolved organic nitrogen and ammonia. An abundant combination of biological treatment can keep DN and ammonia in the effluent below 40 and <sc>25 mg/L,</sc> respectively. Meanwhile, SBNR removes the majority of organic matter, with a contribution to dissolved organic carbon of 48.7%–75.3% and RBC, 9.49%–48.1%. However, the effluent of “RBC + SBNR” is more fragrant. Nevertheless, the first level Fenton can remove the dissolved organic matter formed from “RBC + SBNR” as well as the high aromatic humus compounds in raw leachate, thereby boosting biodegradability and assuring that BAF is in low toxicity and low organic loading operating state. The second level BAF, in contrast, did not show a stable operation impact for eliminating organic materials. The type of external carbon supply and its mixing mechanism in RBC can be optimized in the future to improve nitrogen elimination. The process can be simplified by reducing terminal nitrogen removal units (e.g., the second level BAF) while ensuring that nitrogen in the effluent is up to standard.

Anaerobic treatment of sugarcane vinasse pretreated with a calcium-based biopolymer

This study investigated the influence of a previous sugarcane vinasse coagulation, by using a calcium-based biopolymer, on anaerobic treatment in a lab-scale reactor. Two anaerobic reactors (R1 and R2) were operated for 155 days. R1 was fed only with raw sugarcane vinasse and R2 was fed with pretreated effluent. The operation was divided into three stages: E1 (inoculation and adaptation); E2; and E3. The major difference between E2 and E3 was the fact that R2 failed at the end of E2. Thus, R2 was recovered by applying a low organic loading rate (OLR) of raw vinasse for 29 days. In E2 and E3, for both reactors, pH, alkalinity, COD (influent and effluent samples), and methane production were monitored. During E1, an OLR of 2.0 kgCOD. m-3.d-1 1 was applied, and R1 and R2 sludges showed good adaptation to the wastewater in this condition. Then, the OLR was progressively increased to 7.0 kgCOD.m-3.d-1 in both systems. The average COD removal efficiencies were 82.9 ± 4.4% and 72.2 ± 18.1% for R1 and R2, respectively. R2, operated with pretreated vinasse, showed a decrease in the COD removal and methane production, which could be caused by the biopolymer presence. The average COD removal efficiencies in E3 were 77.5 ± 9.4% and 79.2 ± 9.7% for R1 and R2, respectively. After 155 days of operation, a decrease in the COD removal and methane production was identified again in R2, indicating a new failure. The quality of sludge granules from the inoculum and also from the granules developed at the end of R1 and R2 operation was analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). These analyses indicated a rise in the rugosity of R1 and R2 granules, possibly due to the deposition of sedimentable compounds present in both raw and pretreated vinasse. The EDS analyses indicated a high presence of calcium in R2 granules, indicating that this compound acted in the reduction of mass transfer between organic load from vinasse and the granules’ microbiota.

Clean Technologies for Production of Valuable Fractions from Sardine Cooking Wastewaters: An Integrated Process of Flocculation and Reverse Osmosis

The increase in environmental consciousness and stricter regulations has motivated industries to seek sustainable technologies that allow valorising wastewaters, contributing to the profitability of overall processes. Canning industry effluents, namely sardine cooking wastewater, have a high organic matter load, containing proteins and lipids. Their untreated discharge has a negative environmental impact and an economic cost. This work aims to design an integrated process that creates value with the costly sardine cooking wastewater effluent. The research strategy followed evaluates coagulation/flocculation technologies as pre-treatment of the sardine cooking wastewater followed by reverse osmosis. Two different added-value products were obtained: a solid fraction rich in proteins, lipids (above 20%), and aromas that might be used for feed/pet/aquaculture applications and, from the processing of the resultant aqueous stream by reverse osmosis, a natural flavouring additive, which can be applied in food/feed. Additionally, the permeate from reverse osmosis presents a much lower organic load than the original raw material, which may be reused in the overall process (e.g., as water for washings) or discharged at a lower cost, with environmental benefits and economic savings.

Controlling factors and involved mechanisms on forming alginate like extracellular polymers in flocculent sludge

Alginate like extracellular polymers (ALE) recovered from excess sludge have been evaluated as an eco-friendly, cost effective and sustainable alternative to highly valued materials. However, the ALE extraction from flocculent sludge ranges normally from 90 to 190 mg/g VSS, which is only equivalent to the lowest edge of the ALE production from aerobic granular sludge (AGS). But flocculent sludge is much higher in production than AGS and thus a further investigation was expected on key factors and associated mechanisms controlling ALE formation of flocculent sludge. The investigation was conducted by lab-scale sequencing batch bioreactors. The experiments revealed that flocculent sludge with starch used as an influent substrate contained the highest ALE production (220.3 ± 8.0 mg/g VSS). Low temperature was favorable to enriching ALE, up to 303.3 ± 21.5 mg/g VSS at 12 °C. Moreover, ALE reached up to 137.8 ± 13.2 mg/g VSS at C:N = 5:1 and slightly declined with increased or decreased the C/N ratio. The specific ALE yield was 63.7 mg ALE/(g BOD5) at a low organic load, which was twice as high as that with high organic loads. However, SRT had a minor effect on ALE formation. Obviously, such scenarios as starch-rich and low temperature could promote the ALE production. Furthermore, the characteristic analysis including alginate equivalent, different fractions and hydrogel forming property among different ALE, confirmed that the ALE extracted from flocculent sludge had a potential in substituting for commercial alginates. However, different working conditions would exert a significant influence on the composition and chemical properties of ALE, which implies that the controlling some parameters could be an approach to directionally cultivating ALE for their unique structures and potential applications.

Enhanced primary treatment for net energy production from sewage – The genetic clarification of substrate-acetate-methane pathway in anaerobic digestion

• Substrate-acetate-methane pathway in AD fed with CEPT sewage sludge was elucidated. • Net energy increased from −0.36 kWh to 0.06 kWh per m 3 sewage treated. • Total COD degradation achieved with 7.44 g/day with methane yield at 0.42 m 3 /kg VSS in . • Bio-analysis confirmed high cellulolytic bacteria/methanogens and low syntrophs. • Cellulosome related genes were identified in a methanogen Methanosarcina . Organic matters such as cellulose are key components in municipal sewage, and its degradation consume significant aeration energy in biological process. Pre-harvesting organic particles by chemical enhanced primary treatment (CEPT) could prevent energy consumption while increase bioenergy potential in anaerobic digestion (AD). This study provides biological proof of an “substrate-acetate-methane pathway” that may result in energy positive practice in sewage treatment. When applying CEPT sludge in AD, a stable methane yield at 0.42 m 3 /kg VSS in was achieved. Meanwhile, the results of mass balance suggested that for biogas conversion of CEPT sewage sludge, cellulose and protein degradation played a key factor at low organic loading operation (2 gVSS/L-day, SRT = 15 days), while lipid degradation was more significant at high loading operation (3 gVSS/L-day, SRT = 20 days). Microbial analysis revealed high abundance of cellulolytic bacteria, cellulosome related genes, and methanogens; and low abundance of syntrophs, suggesting effective degradation and uptake of amorphous cellulose to acetate. An unexpected result showed that cellulosome genes were identified from two high abundance species of Methanosarcina . In line with the reduced total volatile fatty acids and propionate (to 1,200 and 600 mg/L, respectively), such cellulolytic and methanogenic synergy implies unique syntrophs bypass for bioenergy production. With the combination of CEPT sludge and AD, the net energy of sewage treatment could increase from −0.36 kWh to 0.06 kWh per cubic meter wastewater treated, including reduced energy consumption in aeration process.

Advanced treatment of landfill leachate through combined Anammox-based biotreatment, O3/H2O2 oxidation, and activated carbon adsorption: technical performance, surrogate-based control strategy, and operational cost analysis

The complexity of landfill leachate makes it difficult to treat it with a single biological/ physical/chemical process. Moreover, the dynamic leachate characteristics pose a challenge for effective process control. Therefore, a combined treatment, consisting of a one-stage partial nitrification-Anammox process, an O3/H2O2 process, and a granular activated carbon filtration (GAC) process, was investigated. Meanwhile, a novel surrogate-based ozone dose control strategy for O3/H2O2 process was evaluated. Results show that this three-stage process offers high removal of total nitrogen (> 90%), COD (chemical oxygen demand, 60–82%), and micropollutants (atrazine, alachlor, carbamazepine, and bisphenol A, > 96%), satisfying discharge requirements. In the combined post-treatment, ozone dosing for COD removal can be real-time controlled by UVA254 reduction monitoring, based on a specific correlation between COD and UVA254 changes. On the other hand, O3/H2O2 pre-treatment controlled at a 50% UVA254 reduction shows to be the optimal point, when adsorption is designed as the main step for COD removal. Cost analysis shows that post-treatment with low (high) organic load i.e., COD ≤ (≥)540 mg/L, a combination with O3/H2O2 (GAC) as the main step appears to be more cost-effective. Therefore, a dynamic operation strategy in response to the leachate change is recommended.

Micronutrients and COD/N ratio as factors influencing granular size and SND in aerobic granular sequencing batch reactors operated at low organic loading

Simultaneous nitrification-denitrification (SND) depends on dissolved oxygen, granule size and COD/N ratio. Slow-growing nitrifying bacteria at low COD/N ratio lead to the formation of small-size granule. Anoxic denitrification is encouraged at higher granule size. In the present study, the effect of different COD/N ratios and addition of micronutrients (Fe, Zn, Mn, Cu, Co, Mo, B) on granule size and SND was studied in a laboratory-scale aerobic SBR at low organic loading (358.4–1075.2 mg COD.(L·day)−1). Synthetic cheese whey wastewater and ammonia was used. Small-size granules (0.28–0.7 mm) were developed at COD/TKN ratio of 8.6–13.7 with micronutrients and long famine phase (83–92% of the cycle). COD/TKN ratio of 13.7 achieved the best removal of inorganic nitrogen Ni (62%). At COD/TKN ratio of 8.6, without micronutrients, the low COD uptake rate caused shortening of the famine phase to 66%. Large-size granules (3.0 mm) with limitation of substrates diffusion showed low Ni removal and dominant slow-growing rhizobia (Bradyrhizobium) as detected by 16S rRNA gene amplicon sequencing. In small granules, without diffusion limitations and higher ammonia exposition, the energetically unfavorable heterotrophic nitrification occurred. Heterotrophic nitrifiers Lysobacter and Dyadobacter were found. Hydrogenophaga was a potential aerobic denitrifier. SND process was probably performed by AOB, heterotrophic nitrifiers, and anoxic and aerobic denitrifiers.

Simultaneous aerobic-anaerobic biodegradation of an industrial effluent of polymeric resins with high phenol concentration at different organic loading rates in a non-conventional UASB type reactor

The presence of phenol in the environment is a consequence of both natural actions and anthropogenic contributions, mainly of an agricultural and industrial nature. Its concentration in wastewater ranges from 0.1 to 3,900 mg/L and in some cases from 30,000 to 80,000 mg/L. Among the technologies used for its elimination, are the physicochemical, biological, adsorption, and chemical oxidation processes. For its recovery, there is adsorption, ion exchange, extraction, volatilization, polymerization, electrocoagulation, advanced oxidation and ion exchange. In this research, a new configuration Upflow Anaerobic Sludge Blanket reactor (UASB) was studied to biodegrade the phenol present in an industrial effluent of polymeric resins by varying the organic load rate in 3.2 ± 0.6, 13.9 ± 0.8, 33.5 ± 1.1 and 34.6 ± 0.9 kg COD/m3.d, at two rates of Dissolved Oxygen (DO): 0.78 ± 0.18 mg/L (experiments 1–3) and 1.23 ± 0.02 mg/L (experiment 4), with a Hydraulic Retention Time (HRT) of 0.5 days at 30 ± 0.5 °C. The results showed the best Chemical Oxygen Demand (COD) removal rate and phenol biodegradation (64 and 74%, respectively) at a lower organic load (experiment 1). With a gradual increase in this, during experiments 2 and 3, it decreased by 55.6 and 17%, respectively. However, by increasing the dissolved oxygen rate to 1.23 ± 0.02 mg/L during experiment 4, the phenol biodegradation rate was slightly improved, but not the COD removal rate.

A comparison between exogenous carriers enhanced aerobic granulation under low organic loading in the aspect of sludge characteristics, extracellular polymeric substances and microbial communities

In this study, polymeric ferric sulfate (PFS), aluminum sulfate (AS) and diatomite were added to enhance the aerobic granulation under low organic loading rate (OLR) of 0.6 kg·COD/(m3·d), and their effects of aerobic granule formation, extracellular polymeric substances (EPS) secretion and microbial community were investigated. The results showed that adding carriers could facilitated the growth of aerobic granules and improve the sludge settleability and biomass retention. Nutrient removal efficiencies were also enhanced. Compared with diatomite, adding PFS and AS resulted in more significant increase in EPS production, especially for the extracellular proteins. For microbial community, the dominated bacteria (Zoogloea, 18.47–23.95%) in the mature granular consortia were similar. Moreover, the introduction of PFS and diatomite contributed to the enrichment of Paracoccus, which was responsible for denitrification. Adding carriers potentially activated the functional genes related to metabolism and genetic information processing, and PFS had the most significant effects.

Olive mill wastewater phytoremediation employing economically important woody plants

In this study two plant species, Punica granatum L. and Myrtus communis L., have been tested as candidates for phytoremediation of olive mill wastewater (OMW) through recirculation in soil pilot units, according to the proposed patented technology by Santori and Cicalini [EP1216963 A. 26 Jun 2002]. Wastewater was treated in batches of low to high organics strength (COD: 2 700–45 700 mg/L) during summer months of two consecutive years. Dynamics of the most important wastewater parameters were investigated, and corresponding removal rates were estimated. During treatment of low organic load OMW, average removal rate of organics, phenolics, total nitrogen and total phosphorus were 0.68 g-COD/kg-soil d, 0.073 g-TPh/kg-soil d, 0.033 g-TN/kg-soil d and 0.0074 g-TP/kg-soil d respectively and plants proved to be tolerant to the OMW. During treatment of high organic load OMW removal rates were roughly 10-fold higher although phytotoxic symptoms were observed. Plants were found to contribute greatly to the OMW treatment process since organics removal rates in pilot units were found to be at least 10-fold higher than in wastewater treatment in non-vegetated soil.Plant species with high added value products such as pomegranate and myrtle trees were used in this study, improving the circular economy potential of the aforementioned technology. Moreover, its efficiency has been demonstrated by quantification of the overall removal rates of key constituents as well as the contribution of the plants in the OMW treatment.

Removal of denatured protein particles enhanced UASB treatment of oxytetracycline production wastewater

Enhanced hydrolysis, which can selectively destroy antibiotic potency, has been previously demonstrated to be an effective pretreatment technology for the biological treatment of antibiotic production wastewater. However, full-scale application of enhanced hydrolysis to the treatment of real oxytetracycline production wastewater showed that the up-flow anaerobic sludge blanket (UASB) reactors treating the pretreated wastewater could only be stable under a low organic loading rate (OLR) of 1.8 ± 0.4 g·COD/L/d. Deterioration of UASB was also confirmed in treating the same wastewater using a bench-scale reactor (R1) at an OLR of 4.4 ± 0.3 g·COD/L/d. Assuming that the particles formed due to the denaturation of soluble proteins under the hydrolysis temperature (110 °C), resulting in the significant increase of suspended solids (SS) in oxytetracycline production wastewater from less than 200 mg/L to 1200 ± 500 mg/L, were responsible for the deterioration of UASB, the pretreated wastewater was filtered using polypropylene cotton fiber and ultrafiltration membrane, and then fed into two parallel bench-scale UASB reactors (R2 and R3). Both reactors maintained a stable COD removal (53.2% ~ 61.1%) even at an OLR as high as 8.0 g·COD/L/d. When the feed of R3 was switched to unfiltered wastewater, however, deterioration of the reactor occurred again. Microscopic observation showed that the granules in R3 were fully covered by protein particles after the switch of the feed. It was possible that the tight layer of the denatured protein particles blocked the inner pores of the granules, resulting in the obstruction of substrate transfer and biogas emission, while removing the protein particles could abate such blockage problem. This study provides a scientific basis for the efficient treatment of antibiotic production wastewater.

Changes in rearing water microbiomes in RAS induced by membrane filtration alters the hindgut microbiomes of Atlantic salmon (Salmo salar) parr

An important step in water treatment in recirculating aquaculture systems (RAS) is the removal of particulate organic matter. While commonly applied treatment technologies remove most of the particles, fine particulate organic matter typically accumulate in RAS, and serve as substrate for heterotrophic bacteria in the system. Membrane ultrafiltration has been shown to reduce the concentrations of total organic carbon and to counteract blooms of opportunistic bacteria in periods with high organic loading. The potential influence of such opportunistic bacteria on the fish microbiomes and fish welfare is poorly understood. In this study, we investigated the effects of high organic loading on the water and hindgut microbiomes in RAS with Atlantic salmon parr. Two pilot-scale RAS, one with membrane ultrafiltration of a 10–15% side-stream (mRAS), and one without (cRAS), were operated in periods with low and high organic loadings, and the water and hindgut microbiomes were characterized by Illumina sequencing of 16S rDNA amplicons. At the end of the experiment, after a period of high organic loading, two OTUs representing Mycobacterium and Spartobacteria dominated the water microbiomes in cRAS, with relative abundances as high as 24 and 17%, respectively. In the mRAS water they were rare (relative abundances of 1.9 and 0.1%). The membrane ultrafiltration stabilized the water microbiota and efficiently prevented the growth of these bacterial populations in RAS. The parr hindgut microbiomes were generally highly distinct from the RAS water microbiomes and were dominated by the bacterial phyla Bacilli and Firmicutes. Furthermore, an OTU probably representing Carnobacterium inhibens, originally isolated from the gut of adult salmon, was highly abundant in the gut microbiomes, with relative abundances reaching over 30%. However, for the cRAS fish after a period with high organic loading, the relative abundance of this Carnobacterium OTU was reduced, and an increased similarity between the gut and the water microbiomes was observed. The Mycobacterium and Spartobacteria OTUs that were abundant in the cRAS water were also abundant in the cRAS hindgut samples. This indicates a direct influence of the water microbiomes on the gut microbiomes, and that high organic loading in the cRAS resulted in growth of opportunistic bacteria that were able to colonize the fish gut. The present study shows that membrane filtration is an applicable strategy to counteract growth of opportunistic bacteria in RAS and to promote positive fish – microbe interactions.

Calcium hypochlorite pretreatment improves thermophilic digestion of waste activated sludge in an upflow anaerobic sludge blanket reactor

Anaerobic wasted activated sludge (WAS) digestion has been widely applied to reduce sludge volume and generate bioenergy in the form of methane. However, anaerobic WAS digestion performance is often challenged with poor hydrolysis of biomass cellular structures. In the present study, the feasibility of using calcium hypochlorite (Ca(ClO)2) to improve the thermophilic digestion of WAS was studied. Two thermophilic upflow anaerobic sludge bed (UASB) reactors (one with and one without Ca(ClO)2 pretreatment) were operated for 120 days under low and high organic loading rate (OLR) conditions, corresponding hydraulic retention time (HRT) of 10 days and 6 days, respectively. Both reactors achieved satisfied performance during the studied period. Under the low OLR condition, Ca(ClO)2 pretreatment significantly improved WAS total volatile solids (VS) removal efficiency (from 48.06 ± 2.63% to 57.34 ± 3.54%) and methane yield (from 289.2 ± 27.6 to 362.2 ± 36.7 N mL/g VS). However, no significant improvement was observed under the high OLR condition. g_S1 and g_Fervidobacterium were predominant bacteria in the thermophilic UASB reactor fed with Ca(ClO)2 pretreated WAS. Methanosarcina was dominant archaea in both reactors. The treatment mechanism and application potential of using Ca(ClO)2 to enhance the WAS digestibility were further discussed.

Validation of a Modified Procedure for the determination of Chemical Oxygen Demand using standard dichromate method in industrial wastewater samples with high calcium chloride content

Background/ Objectives: Chemical Oxygen Demand (COD) is a widely used aggregate organic pollutant index in national discharge standards and is one of the critical parameters for water quality assessment. The conventional COD determination by wet oxidative method encounters the problem of chloride interference in water samples with high chloride content. The dichromate reflux method oxidizes 85-95% of organic matter and also 100% of chloride ions in the samples, without an appropriate chloride masking strategy. The standard method cannot measure COD accurately in samples containing more than 2000 mg L-1 chloride. The present study demonstrates and validates a modified procedure for the determination of COD in industrial sample with high calcium chloride content and low organic load. Method: Petrochemical industries manufacturing Propylene Oxide and Propylene Glycol via chlorohydrin route generate wastewater with high calcium chloride content. Due to high chloride content, the standard analysis method could not produce reliable data for COD values with known precision and accuracy. The standard method based on dichromate was modified, with an additional mixing step for a specified time to enhance the chloride masking by mercuric sulphate. Undiluted sample (20 mL) was mixed with the required amount of mercuric sulpahte to maintain 10:1 ratio to chloride content and 10 mL of sulphuric acid at 150-175 RPM for 20 minutes at room temperature to increase the contact time/ chloride masking. Method validation attributes of the modified procedure were assessed and found to be complying with the acceptance criteria. Findings: We developed a modified procedure for the standard dichromate based chemical oxygen demand (COD) determination in industrial wastewater samples rich in calcium chloride. An additional mixing step is introduced in the standard procedure to enhance the chloride masking with mercuric sulphate in samples containing high chloride. The amended procedure resulted in accurate COD values in samples with low organic load, rich in calcium chloride and the modifiedmethod was successfully validated. Novelty: The modified procedure with mixing step to enhance chloride masking was found to be satisfactory for determining COD in calcium chloride-rich industrial effluent. Keywords: Chemical Oxygen Demand (COD); Chloride interference; Modification of standard method; Wastewater analysis; Calcium chloride; Validation

Organic loading on biochemical fractions degradation pattern during food waste bioevaporation.

More food waste (FW) is desired to be treated in a certain processing period, while the degradation pattern of biochemical fractions during FW bioevaporation was significantly influenced by the organic loading (OL). Lower OL facilitated the lipids degradation, while higher OL favored the protein degradation. It was the more porous structure and abundant oxygen accelerated the lipids degradation, and the rapid proliferation of aerobic microorganisms compensated for the low protein degradation in lower OL. Detailly, 76.8% of the lipids was degraded in the trial with OL of 1.04kg VSFW/kg TSBS (Trial A), but in the trial with OL of 3.16kg VSFW/kg TSBS (Trial C) it was only 0.5%. For protein, the degradation was different that 17.5% of the protein was degraded in Trial A, whereas 69.1% was degraded in Trial C. Lipids degradation contributed 63.0% to the metabolic heat in Trial A, but its contribution in Trial C was only 0.5%. For protein, it contributed 4.1% to the metabolic heat in Trial A, but in Trial C it accounted for 53.6%. In addition, the degradation of carbohydrates (71.6-80.8%) and their contribution to metabolic heat (32.8-45.9%) were comparable in all trials, thus OL had little effect on carbohydrates degradation. Results from this study could provide important guideline for FW practical disposal during their biological treatment.

Combined fluorescence imaging and LA-ICP-MS trace element mapping of stalagmites: Microfabric identification and interpretation

Here, we map a series of stalagmites from Asturias, Spain, by laser ablation inductively-coupled-plasma mass spectrometry and confocal laser scanning (fluorescence) microscopy and discuss the origins of trace element and fluorescence variations. Seasonal banding is evident with both methods and may be attributed to lignins/humic acids based on fluorescence absorption and emission characteristics. Some lateral variations in fluorescence present as saw-tooth fluorescent “spires” and demonstrate disruptions of seasonal banding, corroborated by trace element variations (most prominently Mg and Na). Such features likely reflect the differential partitioning of trace elements by sectoral zoning as a result of low supersaturation and/or high organic matter load, combined with the effects of dissolved organic matter on the calcite growth surface and the association of each element with colloidal organic matter. The lateral variability of trace elements demonstrates the pitfalls of obtaining trace element information from one-dimensional transects without prior reconnaissance mapping. It is, however, possible that traditional drilling with ~1 mm holes homogenizes these features and provides reliable trace element estimates.

Aerobic granular sludge treating low-strength municipal wastewater: Efficient carbon, nitrogen and phosphorus removal with hydrolysis-acidification pretreatment

Low organic load while high fraction of particulates still challenging the application of aerobic granular sludge process in low-strength municipal wastewater treatment. The feasibility of adopting short cycle length to increase organic load and hydrolysis-acidification pretreatment to enhance anaerobic COD uptake was evaluated. As the cycle length decreased from 4 h to 2 h, the organic loading rate increased from 0.98 to 1.3 g L−1 d−1 and granulation appeared after two weeks. Moreover, with the hydrolysis-acidification pretreatment, the average effluent TN and TP concentrations decreased respectively from 17.8 to 13.7 mg L−1 and 0.76 to 0.41 mg L−1, meeting the Grade IA of the effluent standards in China. Furthermore, cycle tests were conducted to reveal the underlying mechanism of the pretreatment effects. The results showed that the hydrolysis-acidification pretreatment enhanced the COD storage and phosphorus release in anaerobic phase, and improved the simultaneous nitrification-denitrification process, as well as the phosphorus uptake in aeration phase.

The underlying mechanism of enhanced methane production using microbial electrolysis cell assisted anaerobic digestion (MEC-AD) of proteins

Anaerobic digestion (AD) is a promising technology capable of converting waste matter into bio-energy. Recent studies have reported that microbial electrolysis cell assisted anaerobic digestion (MEC-AD) is an effective system for methane production from organic waste, via enhanced electron transfer. However, little is known about the effects of applied voltage on the AD of proteins. Herein, the mechanism of MEC-AD on protein digestion was investigated using varying concentrations of bovine serum albumin (BSA) as the protein substrate (500 mg/L, 4 g/L, and 20 g/L BSA). Experimental results showed that the applied voltage can not only enhance the methane production rate from 23.8% to 45.6% at low and medium organic loading (BSA concentration of 500 mg/L and 4 g/L), but also improve the methanogenesis efficiency increased by 225.4% at high BSA concentration (20 g/L) with the applied voltage of 0.6 V compared to that with open circuit. Mechanism explorations revealed that the applied voltage significantly enhanced the acidogenesis and methanogenesis processes in the AD of proteins. Microbial community characterization showed that with the applied voltage, the abundance of fermentative bacteria increased by 46.7 % at the anode, while, the abundance of Methanobacterium at the cathode increased from 10.4 to 84.3%, indicating the methanogenesis pathway transformed from acetoclastic to hydrogenotrophic. External circuit electron transfer calculations demonstrated that only 10% of the produced methane could be attributed to direct interspecies electron transfer (DIET). From a thermodynamic perspective, the applied external voltage led to a reduction in the cathodic potential to -0.9 V, which is beneficial for enhanced methane production via mediated interspecies electron transfer (MIET) by enrichment of hydrogenotrophic methanogens. The findings reported here reveal the previously unrecognized contribution of proteins to MEC-AD, while also furthering our understanding of the role of applied voltage in the MEC-AD process.