Linking the use of reclaimed water to indicators of crop stress by metabolomic and transcriptomic analyses. A tool to compare water irrigation quality.

The occurrence of contaminants of emerging concern (CECs) or heavy metals in reclaimed water used for agricultural irrigation may affect crop morphology and physiology. Here, we analyzed lettuce (Lactuca sativa) grown in outdoor lysimeters and irrigated with either tap water, used as a control, or reclaimed water: CAS-reclaimed water, an effluent from a conventional activated sludge system (CAS) followed by chlorination and sand filtration, or MBR-reclaimed water, an effluent from a membrane biological reactor (MBR). Chemical analyses identified seven CECs in the reclaimed waters, but only two of them were detected in lettuce (carbamazepine and azithromycin). Metabolomic and transcriptomic analyses revealed that irrigation with reclaimed water increased the concentrations of several crop metabolites (5-oxoproline, leucine, isoleucine, and fumarate) and of transcripts codifying for the plant stress-related genes Heat-Shock Protein 70 (HSP70) and Manganese Superoxide Dismutase (MnSOD). In both cases, MBR-water elicited the strongest response in lettuce, perhaps related to its comparatively high sodium adsorption ratio (4.5), rather than to its content in CECs or heavy metals. Our study indicates that crop metabolomic and transcriptomic profiles depend on the composition of irrigating water and that they could be used for testing the impact of water quality in agriculture.

Pollution source identification of nitrogen and phosphorus in the lower West Main Canal, the Ganfu Plain irrigation district (South China).

The degradation of surface water quality has been a widespread concern around the world. However, irrigation canal water does not attract much attention although it is important to agriculture and population. In this study, a 5-year water quality monitoring of surface water was conducted in the lower West Main Canal of the Ganfu Plain irrigation district to identify the levels and pollution sources of nitrogen and phosphorus.Over 75% of samples had total phosphorus (TP) concentrations of > 0.02 mg/L, and all samples had total nitrogen (TN) concentrations of > 0.2 mg/L, indicating a risk of eutrophication. The concentrations of NO3--N and NH4+-N averagely occupied 57% and 18% of TN, respectively. PCA analysis showed that phosphorus and nitrogen in canal water were associated with meteorological factors, urban life and surface runoff, agricultural cultivation, livestock-poultry breeding, and water-sediment interaction in the wet season, whereas they were affected by meteorological factors, industrial effluent, urban domestic sewage, and livestock-poultry breeding in the dry season. Absolute principal component score-multiple linear regression (APCS-MLR) model results revealed that (1) agricultural cultivation plus livestock-poultry breeding contributed 43.2% of TP in canal water in the wet season, while livestock-poultry breeding contributed 52.9% in the dry season, and (2) domestic sewage plus surface runoff contributed 29.4% of TN in the wet season, while livestock-poultry breeding contributed 45.9% in the dry season. The unidentified sources had significant contributions of > 20% for almost all variables. So further investigations are required for determining unidentified sources, and anthropogenic pollution control is imperative for canal water quality protection.

Characteristics and risk assessment of sewage sludge from urban wastewater treatment plants in Shaanxi Province, China.

In this study, an investigation of important properties, including moisture content, pH, plant nutrients, organic matter, mineral oil, and the contents of heavy metals (HMs) in sewage sludge (SS) collected from 32 urban treatment plants in Shaanxi Province, China, was carried out. The test results showed that the pH and the moisture, organic matter, total nitrogen (TN), total phosphorus (TP), and mineral oil contents of the SS varied over different rainfall periods, and most of the indicators met the standard criteria for SS agricultural reuse in China. Principal component analysis (PCA) and correlation analysis indicated that the pollutant characteristics of the SS depended on time span and geographical distribution. The mean contents of Pb, Cd, Cu, Zn, Ni, Cr, Hg, and As in SS were 3.95, 16.38, 5.43, 7.70, 1.31, 1.53, 32.77, and 1.40 times higher than the soil background values, respectively. Speciation analysis showed that the forms of HMs in the SS were significantly different. Assessments based on the geoaccumulation index (Igeo), Nemerow integrated pollution index (NIPI), and potential ecological risk index (RI) suggested that HM pollution risk levels were either uncontaminated or moderately contaminated in some regions and that SS recycled for agricultural applications carried a low risk. In conclusion, certain potential ecological risks exist for SS agricultural utilization in Shaanxi Province, and it is necessary to reduce the HM content before SS resource utilization for land application.

Analyzing factors driving of eutrophication of river-type urban landscape lakes.

The eutrophication of river-type urban landscape (RTUL) lakes is different from that of natural lakes. In this study, Xiaofu Lake, a typical RTUL lake with high anthropogenic interference, was used as the study area. Monitoring data from 2018 to 2020 were used to analyze the temporal and spatial distribution characteristics of chlorophyll a (Chl-a) concentrations with meteorological, hydrodynamic, and nutrient factors. Correlation and regression analyses were used to identify the relationship between the factors influencing eutrophication and the Chl-a. The MIKE21 model is used to simulate changes in water quality indicators. The study determined the relationship between river water quality and environmental factors and explored the causes of eutrophication in the water bodies of Xiaofu Lake. The results showed that from 2018 to 2020, the water quality showed seasonal variation and differences in spatial distribution. Except for total nitrogen, which remained at a high level (average 8.23 mg/L), other water qualities remained between classes II and IV. The proportions of mild, moderate, and severe eutrophication in the study area were 25%, 69%, and 6%, respectively. Indicators that were highly correlated with water eutrophication were turbidity, water temperature, total phosphorus, and permanganate index. The contribution of water temperature, ammonia nitrogen, and permanganate index to eutrophication was 30.5%, 22.6%, and 20.9%, respectively. The high proportion of sewage in the source of recharge water is one of the reasons for the deterioration of water quality. In addition, the change in water eutrophication was closely related to the gate operation in the region. PRACTITIONER POINTS: There are differences between river-type urban landscape (RTUL) lakes and natural lakes, and the conditions that cause eutrophication are different. RTUL are subject to strong human interference and rely on water transfer and gate scheduling to maintain water quantity. The high proportion of sewage treatment plant tailwater in upstream water is the main reason for the long-term pollution of RTUL. The indicators highly correlated with water eutrophication are turbidity, water temperature, total phosphorus, and permanganate index.

Seasonal distribution and dynamic evolution of antibiotics and evaluation of their resistance selection potential and ecotoxicological risk at a wastewater treatment plant in Jinan, China.

The seasonal distribution and dynamic evolution of antibiotics in wastewater from main treatment areas and in sludge and their resistance selection potential and ecotoxicological risk were studied at a municipal wastewater treatment plant in Jinan, East China. Ten antibiotics were selected, and all were detected in wastewater and sludge samples, with fluoroquinolones showing the highest detection concentrations and frequencies. Seasonal fluctuations in the antibiotic concentrations in the influent, effluent, and sludge were observed, with the highest values in winter in most cases. The dynamic evolution of antibiotics during the treatment process differed among the seasons. The antibiotic removal efficiencies were incomplete, ranging from - 40.47 to 100%. Mass balance analysis showed that sulfonamides, roxithromycin, and metronidazole were mainly removed through biological processing, whereas fluoroquinolones, doxycycline, and chloramphenicol were removed through sludge adsorption. Levofloxacin, as well as a mixture of the 10 antibiotics from the effluent, could pose a low ecotoxicological risk to Daphnia in the receiving waters. Additionally, levofloxacin and ciprofloxacin in the effluent and ciprofloxacin and metronidazole in the sludge may facilitate the selection of antibiotic-resistant bacteria in the environment.

Health risk assessment and metal contamination in fish, water and soil sediments in the East Kolkata Wetlands, India, Ramsar site.

East Kolkata Wetlands (EKW) is an important site for fish culture in sewage-fed areas, which are major receivers of pollutants and wastages from Kolkata. EKW is internationally important as the Ramsar site was declared on Aug 2002 with an area of 125 km2. EKW is a natural water body where wastewater-fed natural aquaculture has been practiced for more than 70 years. It is ecologically vulnerable due to the discharge of toxic waste through sewage canals from cities. Assessing the EKW to understand the inflow and load of the toxic metal (s) in fish, water, and sediments samples is essential. The field (samples collection from 13 sites) and lab (determination of toxic level of metals) based research were carried out to assess metal toxicity and health risk assessment in EKW. The levels of eighteen metals (18), namely Chromium, Vanadium, Cobalt, Manganese, Copper, Nickel, Zinc, Silver, Molybdenum, Arsenic, Selenium, Tin, Gallium, Germanium, Strontium, Cadmium, Mercury, and Lead, were determined using Inductively coupled plasma mass spectrometry (ICP-MS) in five fish tissues viz. muscle, liver, kidney, gill and brain, along with the water samples and soil sediments in 13 sampling sites. The bioaccumulation and concentration of metals in fish tissues, soil sediments, and water samples were well within the safe level concerning the recommendation of different national and international agencies except for a few metals in a few sampling sites like Cd, As, and Pb. The geoaccumulation index (Igeo) was also determined in the soil sediments, indicating moderate arsenic, selenium, and mercury contamination in a few sites. The contamination index in water was also determined in 13 sampling sites. The estimated daily intake (EDI), reference dose (RfD), target hazard quotient (THQ), slope factor and cancer risk of Cr, Mn, Co, Ni, Cu, Zn, As, Se, Cd, Pb and Hg from fish muscle were determined. Based on the results of the present investigation, it is concluded that fish consumption in the East Kolkata Wetland (EKW) is safe. The effects of bioaccumulation of metals in muscle tissue were well within the safe level for consumption as recommended by WHO/FAO.

Pyrometallurgy treatment of electroplating sludge, emulsion mud and coal ash: ZnAlFeO4 spinel separation and stabilization in calcium metasilicate glass.

Electroplating sludge was a hazardous waste comprised of heavy metals and other Fe/Al/Ca/Si impurities, and produced massively in surface treatment industry. In the past, it was commonly purified via hydrometallurgy, chlorination and reduction calcination routes, but also blended as additive in rotary kiln, to stabilize the heavy metals in geopolymer. Herein, an alternative strategy was developed to treat a real electroplating sludge for recycling magnetic Zn-rich spinel and stabilizing Zn in calcium metasilicate glass via a facile pyrometallurgy route with the blending of emulsion mud and coal ash. The sludge contained 35.6% Zn and 0.54% Cr and then was blended with 50% emulsion mud. After calcination at 1200 °C, the product was highly dispersed, whilst octahedral ZnAlFeO4 spinel with Zn content of 40.0% were formed and separated by using magnet, in accordance with the recycling efficiency of 51.2% Zn from the electroplating sludge. But after calcination at 1400 °C, the gypsum in emulsion mud was decomposed as CaO and accelerated the dissolution of Si-bearing substance as calcium metasilicate glass for covering ZnAlFeO4 spinel, resulting in the Zn leaching of 1568 mg/L. By adding 50% Si-rich coal ash in the calcination system, more calcium metasilicate glass were generated, and then the Zn concentration in the toxic leaching test was only 12.09 mg/L. During the calcination, Cr showed similar performance to Al/Fe and involved in the spinel formation. This provided a new route to recycle Zn from Zn-rich electroplating sludge and to solidify heavy metals via calcium metasilicate glass route.

Radiochemical signature of radium-isotopes and some radiological hazard parameters in TENORM waste associated with petroleum production: A review study.

Large amounts of TENORM waste (produced water, scale, and sludge) are created in oilfields around the world, presenting radiological risks to employees, the public, and the environment since activity concentrations of radioactive substances were above the exemption levels accredited by several authorities. Using the activity concentration of the radium-isotopes (226Ra and 228Ra) in the waste, we determined the 'fingerprint' as a radiochemical signature and some relevant 'radiological hazard parameters' in this review. The majority of the reported residues take the form of radio-contaminated (produced water, scale, and sludge) generated in Egypt's oilfields or elsewhere include radium isotope activity concentrations (226,228Ra) that exceed the international exemption limit. The activity concentrations of 226Ra(238U-series) in produced water, scale, and sludge waste were 0.04-1,480 Bq/L, 1.1-2,015,000 Bq/kg, and 1-120,800 Bq/kg, respectively, whereas 228Ra (232Th-series) was 0.34-250 Bq/L, 1.8-1,428,000 Bq/kg, and 10-122,830 Bq/kg, respectively. The radioactivities of radium isotopes were found to be above the exemption values recognized by WHO, IAEA, IOGP, EC, and ICRP in 95, 82, and 58% of produced water, scale, and sludge waste, respectively. The 226Ra(238U)/228Ra(232Th) ratio, from the other hand, was estimated to be utilised as a 'radiochemical fingerprint', or signature in the reported TENORM residues. The radium isotopes ratio in produced water, scale, and sludge waste in Egypt's oilfields is 0.41-4.45 (av. 1.98 ± 1.37, coefficient of variation, COV %: ∼69%), 0.2-21.4 (av. 4.3 ± 4.7, ∼109%), and 1.4-52.2 (av. 9.6 ± 15.3, ∼159%), respectively. For produced water, scale, and sludge waste, the 226Ra/228Ra ratios are 0.12-9.1 (av. 1.43 ± 1.72, ∼120%), 0.2-159 (av. 7.78 ± 23.5, ∼302%), and 0.8-223.5 (av. 14.1 ± 45.4, ∼322%) in global oilfields. The radiological hazard parameters (Ig, Ia, E◦, EG, and ELCR) owing to radium isotopes or 222Rn in most scale and sludge residues, as well as a small percentage of produced water, are all over the allowed safe limits. Substantial differences in the radium isotopes ratio in the reported waste can be attributed to thier geological, chemical, physical, and/or operational constraints. However, from the different perspectives of remediation and/or radiation protection programs, these values can be employed as a guidance for organizations investing in oil and gas production.

Characteristics analysis of water pollutants in Cihu Lake, China, based on a multivariate statistical analysis method.

In order to understand the sources of pollutants and the temporal and spatial distribution characteristics of the water quality in Cihu Lake, China, the monitoring data of seven water quality indicators from 12 sampling sites from 2015 to 2019 were selected, and the temporal and spatial variation laws of the water quality and pollution sources were analyzed by the use of the multivariate statistical analysis method. The results show that nitrogen and phosphorus pollution in the lake is dominant. The average concentrations of total nitrogen (TN) and total phosphorus (TP) exceed the surface water quality Class III standards by 1.6 and 2.2 times, respectively. Spatially, the results of the cluster analysis showed that the water quality in Cihu Lake can be categorized into three regions: the northern half of the lake, the southern half of the lake, and the canal entering the lake. Temporally, the water quality in these three regions can be classified into three categories: March to May (the northern half of Cihu Lake), September to November (the southern half of Cihu Lake), and September (the canal entering Cihu Lake). The discriminant analysis results showed that NH3-N, TN, CODCr, and BOD5 are the main factors that affect the uneven spatial distribution of the water quality of Cihu Lake, while TN, DO, and CODMn are the main factors that affect the temporal difference in the northern half of Cihu Lake, and NH3-N, TP, CODCr, DO, CODMn, TN, and TP are the main factors affecting the temporal difference in the southern half of Cihu Lake and the canal entering Cihu Lake. It was found that the water pollution in the study area can be mainly attributed to the incoming water and urban domestic pollution. The main pollution sources for the canal entering Cihu Lake and the southern half of Cihu Lake are the water from the sewage treatment plant and the domestic sewage that has not been intercepted, while the northern half of Cihu Lake is mainly affected by surface runoff, mixed rainwater and sewage, and internal pollution.

Distribution Characteristics and Source Analysis of Nitrogen and Phosphorus in Different Rivers in Two Water Period: A Case Study of Pi River and Shiting River in the Upper Reaches of Tuo River in China.

In this paper, the distribution characteristics of total nitrogen (TN), total phosphorus (TP) and fractions of nitrogen and phosphorus in water and surface sediments of the Pi and Shiting rivers in the dry and wet seasons were studied by molybdenum blue/ascorbic acid spectrophotometry and Standard Measurements and Testing (SMT). Correlation analysis, cluster analysis and principal component analysis were used to identified nitrogen and phosphorus pollution sources. The results showed that: (1) nitrogen and phosphorus in water and surface sediments in the study area were at different levels. (2) In the Pi river, the decomposition of animal and plant residues, the leachate from the accumulation of aquaculture wastewater and urban domestic sewage were the main sources of nitrogen and phosphorus pollution, while in the Shiting river, the unreasonable application of pesticides and fertilizers, the degradation of animal and plant residues, agricultural wastewater from agricultural drainage channels, industrial production wastewater and the weathering of agricultural wastes had a great impact on the nitrogen and phosphorus pollution. The results in this study provide reliable experimental data and a reference to local relevant departments for the implementation of effective control measures for the reduction of the nitrogen and phosphorus pollution load in the river basin.

Treatment of heavy metal-polluted sewage sludge using biochar amendments and vermistabilization.

Heavy metal contamination of sewage sludge hampers its recycling. Contaminated sewage sludge was amended with different proportions of biochar and vermistabilized. Biochar produced from wheat straw was added at four proportions (0%, 2%, 4%, and 6%). Ten earthworms Eisenia fetida were added, and the sludge was vermistabilized for 60 days. Heavy metal and nutrient concentrations and the accumulation of metals to E. fetida were measured. The treatment with 4% biochar was the most efficient in reducing the concentrations of heavy metals. The concentration of Cd decreased 55%, Cr 28%, Cu 30%, and Pb 21%. The concentrations of plant nutrients increased: total N 43%, total P 92%, and total K 60%. E. fetida accumulated all heavy metals in their internal tissues. The survival and reproductive rate of E. fetida improved during the vermistabilization process. We interpret that the biochar alone did not improve the decomposition process, but the main actors were the earthworms E. fetida. The most efficient proportion of biochar was 4%, not the highest tested (6%). We recommend 4% biochar to be used in the vermistabilization of heavy metal-contaminated municipal sewage sludge. The study benefits both the management of heavy metal-contaminated sewage sludge and agriculture where the final vermistabilization product can be used to improve crop production.

Chlorhexidine residues in sludge from municipal wastewater treatment plants: analytical determination and toxicity evaluation.

In this work, a procedure for the sensitive and selective determination of chlorhexidine in sludge from municipal sewage treatment plants (STPs) based on matrix solid-phase dispersion (MSPD) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was optimized and validated. Analysis of sewage sludge samples, obtained from different STPs in Northwest Spain from 2018 to 2021, showed that chlorhexidine was ubiquitous in this environmental compartment with concentrations between 0.3 and 16 µg g-1. The toxicity of this pollutant was assessed in in vitro assays considering three different model organisms: Candida albicans, Escherichia coli, and Staphylococcus aureus. C. albicans was the most sensitive of the tested microorganisms to chlorhexidine with a lethal threshold concentration of 0.1 mg L-1. Thus, the lowest observed sludge residue was 3 times higher than the acute toxicity threshold measured for C. albicans. Moreover, E. coli and S. aureus were also affected at chlorhexidine concentrations around 1.8 mg L-1 and 0.5 mg L-1, respectively. So, chlorhexidine residues might affect the population of microorganisms existing in STPs. In addition, the potential phytotoxicity of the compound was evaluated with germination experiments using different model seeds. At the evaluated dose (10 µg g-1 dried soil), chlorhexidine did not affect the germination of Sorghum saccharatum, Lepidium sativum, or Sinapis alba seeds. Thus, amending agriculture soils with chlorhexidine containing sludge is unlikely to affect the germination of plants.

Characteristics of overflow pollution from combined sewer sediment: Formation, contribution and regulation.

Sewer sediments contain high concentrations of carbon, nitrogen, and phosphorus pollutants, which can be the main source of overflow pollution due to high-velocity scouring. To elucidate the scouring overflow pollution characteristics and regulation mechanism of sewer sediment under different precipitation intensities, a sewer-storage tank linkage control experimental device was established to simulate the practical sewer overflow under different precipitation intensities and the control process of storage tank overflow pollutants. Based on the division of flow from small to large, the pollution characteristics of overflow pollutants and the contribution rate of sewer sediments to overflow pollutants were analysed. The results showed that the total load of overflow pollutants increased with an increase in rainfall intensity and were 7.58 kg, 16.54 kg, 27.42 kg, respectively. The concentration of particulate pollutants increased sharply in a short time, and the concentration of dissolved pollutants decreased at a certain dilution. Sewer sediment was the main source of overflow pollutants, contributing up to 70%. After the overflow pollutants entered the regulation and storage tank, a certain stratification phenomenon was discovered at different sedimentation times. The concentration of large particle pollutants gradually increased from top to bottom in the regulation and storage tank, and the concentration of dissolved pollutants showed no obvious difference between the layers. With an increase in rainfall intensity, the recommended regulation and storage times of overflow pollutants were within 15 min, 45-60 min, and 60 min, respectively. Finally, based on the relationship among rainfall intensity, sediment scouring thickness, regulation and storage time, a prediction formula for the regulation and storage time of overflow pollutants was obtained, which provided a basis for the regulation and treatment of subsequent overflow pollutants.

Phosphorus removal from municipal wastewater through a novel Trichosporon asahii BZ: Performance and mechanism.

A yeast BZ was screened from a laboratory-scale anaerobic/aerobic reactor and designated as Trichosporon asahii through 26S rDNA gene sequence analysis. The screened BZ abated over 70% of phosphorus in municipal sewage with 2-10 mg/L phosphorus in the appropriate conditions. The yeast BZ had strong adaptability to pH and the dissolved oxygen, but the cultivation temperature, carbon source, the ratio of C/P and the ratio of N/P had a critical influence on the phosphorus abatement performance of yeast BZ. The analysis of phosphorus concentration in the wastewater, cells, and extracellular polymeric substances (EPS) suggested that about 55%-66% of the removed phosphorus was in the yeast cells and 34%-45% in the EPS. The proposed probable metabolic mechanism of phosphorus in yeast BZ showed that EPS acted as a dynamic phosphorous transfer station, and most of phosphorus was transferred into yeast cells through EPS transfer station. These findings have crucial implications for the development of a promising stable and easy-operation biological phosphorus abatement process for municipal wastewater treatment.

Evaluation and analysis of perlite and municipal wastewater sludge (biosolids) from three wastewater treatment plants in East Texas, USA.

Municipal wastewater sludge (also known as biosolids) is produced in large quantities from wastewater treatment plants (WWTPs). Traditionally, analyses of biosolids revealed the presence of inorganic (including metals) and organic contaminants which pose health concerns to man and the environment. This study investigated physical-chemical parameters and comparative element concentrations (Ag, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Ni, P, Pb, S, Se, Zn, V, Na, S, and P) in biosolids and composted wastewater sludge (CWS) from Nacogdoches Wastewater Treatment Plant (NWWTP), Lufkin Wastewater Treatment Plant (LWWTP), and Angelina-Neches Compost Facility (NCF) in East Texas (USA). In addition, concentrations in perlite, a hydroponic material, were determined via Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy/energy dispersive X-ray diffraction (SEM/EDX), inductively coupled plasma-optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD)), and thermogravimetric (TGA) analysis. Via ICP-OES analysis, metal concentrations in biosolid samples were similar. Macroelement amounts followed the order: NWWS ≈ LWWS > NCS > perlite. Notably, concentrations in biosolids, CWS, and perlite are below recommended USEPA and WHO maximum ceiling levels. The pH of biosolid samples was determined between 5.33 and 6.74. The weight loses of 6-19% wt at ~ 300-700 ℃ are attributed to volatile compounds and inorganic metal oxides. From environmental and circular economy perspectives, this study shows biosolids to be safe, and potential recycling can be encouraged for use in soil amendments. This finding could find impetus to design of much better WWTPs which improve removal efficiencies and encourage recycling of biosolids.

Reuse of waste sludge from water treatment plants and fly ash for manufacturing of adobe bricks.

Reuse of sludge from a water treatment plant and fly ash for the manufacturing of adobe brick is a feasible approach for practical applications due to the numerous benefits from the cost savings of construction materials and the reduction of environmental pollution. In this study, sludge from a groundwater treatment plant and fly ash from a thermal power plant were used as alternative aggregates to replace clay, a traditional component for brick making. The main objective of this study is to produce adobe bricks by using hydraulic press technology. The optimum aggregate composition was investigated by determining the compressive strength according to Vietnam national standard TCVN 6355:1-2009. Other supplementary materials, including cement, liquid glass, and polypropylene fibers, were used as additives and adhesives. Results showed that a 2-hole brick product (8 × 4 × 8 cm) with strength M 4.0 satisfied the national quality standard, TCVN 6477-2016. In addition, the aggregate composition (wt%) as sludge: cement: fly ash: polypropylene fibers of 50 : 35: 15 : 0.5%/m3 aggregates was found to be the optimum ratio. This product shows a medium compressive strength that is appropriate in the construction of walls or fences in industrial factories or households. The results obtained in this study show a promising approach for the brick-making industry in Vietnam. A large amount of sludge can be reused as an alternative material to reduce the product price and achieve natural resource conservation.

[Characteristics of Sludge and Associated Risk Assessment of Urban Sewage Treatment Plants].

In urban solid waste management, the scientific and reasonable disposal and utilization of sewage sludge is becoming more and more important. It can be said that the pollution status and chemical properties of sewage sludge in urban sewage treatment plants can provide a basis for the scientific disposal and utilization of sludge. In this study, the characteristics of pH, moisture content, Cd, Cr, Cu, Zn, Pb, As, Hg, Ni, mineral oil, volatile phenol, PAHs, organic matter, nitrogen, phosphorus, and potassium were evaluated in sewage sludge collected from 49 sewage treatment plants in a certain city. The pollution status of heavy metals and organic pollutants, the frequency distribution of pollutant concentrations, and changes in the nutrient content were analyzed. The Nemero index and Hakanson potential ecological hazard index were used to assess the potential ecological risks of heavy metals in the agricultural utilization process of sludge. The results showed that under the condition of neutral pH values and high moisture content, the order of heavy metal content was Zn > Cu > Cr > Pb > Ni > As > Hg > Cd. The principal component analysis (PCA) results indicated that Cd, Pb, Hg, Ni, and As constituted the main load factors of the first main component of heavy metal sources. The most concentrated contents of 8 heavy metal frequency distributions among the 49 samples were 38.9-1380.0, 62.6-182.7, 63.6-181.3, 0.0-97.8, 19.3-68.4, 0.8-29.2, 0.3-8.7, and 0.01-0.96 mg·kg-1. In addition, the most concentrated frequency distribution of mineral oil, volatile phenol, and PAH concentration were 87.0%, 87.9%, and 77.6%, respectively. Moreover, the nutrient content of sludge was higher than the average level in China, and the organic matter content was 67.4%, 75.9%, and 92.5% of that of pig manure, cow dung, and chicken manure, while the content of nitrogen, phosphorus, and potassium was not very different. The Nemero index and Hakanson ecological hazard index results showed that the sludge of urban sewage treatment plant in the city has certain ecological risks. However, four sewage treatment plants were heavily polluted or highly ecologically hazardous among the 44 plants in this study, which were in line with the Standards for pollutant control of agricultural sludge. In summary, there are certain potential ecological risks for the agricultural utilization of sludge in the city, and it is necessary to reduce the heavy metal content before resourcing. More importantly, on the premise that the sludge meets the agricultural standards, a comprehensive ecological risk assessment is required to select a reasonable sludge recycling method.

An efficient strategy of phosphorus recovery: Electrochemical pretreatment enhanced the anaerobic fermentation of waste activated sludge.

The anaerobic fermentation (AF) of waste activated sludge (WAS) with an electrochemical pretreatment (EPT) was investigated to determine its correlation with the release of phosphorus and the disintegration of WAS. The sludge was pretreated by holding under 4.5 V for 60 min, followed by AF for 9 days. Untreated sludge was used as the control group (no-EPT). Results showed that, with pretreatment, the total dissolved P (TDP), orthophosphate (PO43--P) and organic P (OP) reached the maximum values of 7.30 mg/L, 4.77 mg/L and 2.35 mg/L on day 8, respectively, which were approximately 5.3, 9.2 and 2.7 times greater than that in the control group. The analysis of soluble chemical oxygen demand (SCOD), protein and polysaccharides showed that the EPT promoted the disintegration of sludge, thereby enhancing the P release. The SCOD reached 1625 mg/L on day 6 in pretreatment experiment, which was about 9.8 times greater than that in control group. Additionally, the EPT contributed to fewer metal ions in sludge supernatant. This mechanism might have been due to the anions accumulating in the supernatant from the greater degree of sludge collapse after EPT, which caused the released metal ions to combine with anions to form insoluble compounds. In conclusion, EPT could be a promising method for the dissolution of sludge and the recovery of phosphorus from WAS under AF. Besides, the economic benefit evaluation showed the potential value of EPT for P recovery.

Reducing fat, oil, and grease (FOG) deposits formation and adhesion on sewer collection system structures through the use of fly ash replaced cement-based materials.

The accumulation of fat, oil, and grease (FOG) deposits in sewer pipes reduces their conveyance and results in Sanitary Sewer Overflows (SSOs). Previous research has shown that concrete used in sewer lines is a significant source for calcium ion, which participates in the FOG deposit formation mechanism. However, no research has been conducted to understand the effect of calcium leaching from cement on FOG deposits formation and adhesion. This study quantifies the reduction in FOG deposit formation when Fly Ash (FA), a Supplementary Cementitious Material (SCM), is used to replace cement in the production of High Volume Fly Ash (HVFA) concrete materials. Results show that after 90 days of leaching test under controlled pH conditions, 75% and 86% reduction in calcium release were achieved from 50% and 75% FA replacement, respectively. After 30 days of FOG deposits formation tests on HVFA samples, 58% and 81% reduction in FOG deposit formation was found for 50% and 75% FA replacement, respectively. FTIR analyses of FOG deposits formed on concrete samples without FA replacement exhibited high calcium soap content (48%), while, FOG deposit formed on HVFA concrete materials showed low calcium soap percentage (22~29%). Furthermore, FTIR analyses report the first spatial variation found in FOG deposits that includes a surface layer of hard FOG deposits with high calcium soap absorbance and an outer layer of soft FOG deposits consisting of a low calcium absorbance. FTIR analyses revealed that the FOG deposit formation mechanism is affected by the availability of calcium and pH near the concrete surface. Finally, HVFA concrete materials were tested for compressive strength and durability against microbially induced concrete corrosion (MICC). After 180 days of sealed curing, HVFA concrete exhibited adequate compressive strength necessary for the sewer line construction and 50% FA replacement revealed satisfactory durability against MICC.

Rhizodegradation of Petroleum Oily Sludge-contaminated Soil Using Cajanus cajan Increases the Diversity of Soil Microbial Community.

Most components of petroleum oily sludge (POS) are toxic, mutagenic and cancer-causing. Often bioremediation using microorganisms is hindered by the toxicity of POS. Under this circumstance, phytoremediation is the main option as it can overcome the toxicity of POS. Cajanus cajan a legume plant, was evaluated as a phyto-remediating agent for petroleum oily sludge-spiked soil. Culture dependent and independent methods were used to determine the rhizosphere microorganisms' composition. Degradation rates were estimated gravimetrically. The population of total heterotrophic bacteria (THRB) was significantly higher in the uncontaminated soil compared to the contaminated rhizosphere soil with C. cajan, but the population of hydrocarbon-utilizing bacteria (HUB) was higher in the contaminated rhizosphere soil. The results show that for 1 to 3% oily sludge concentrations, an increase in microbial counts for all treatments from day 0 to 90 d was observed with the contaminated rhizosphere CR showing the highest significant increase (p < 0.05) in microbial counts compared to other treatments. The metagenomic study focused on the POS of 3% (w/w) and based on the calculated bacterial community abundance indices showed an increase in the values for Ace, Cho, Shannon (Shannon-Weaver) and the Simpson's (measured as InvSimpson) indices in CR3 compared to CN3. Both the Simpson's and the Shannon values for CR3 were higher than CN3 indicating an increase in diversity upon the introduction of C. cajan into the contaminated soil. The PCoA plot revealed community-level differences between the contaminated non-rhizosphere control and contaminated rhizosphere microbiota. The PCoA differentiated the two treatments based on the presence or absence of plant. The composition and taxonomic analysis of microbiota-amplified sequences were categorized into eight phyla for the contaminated non-rhizosphere and ten phyla for the contaminated rhizosphere. The overall bacterial composition of the two treatments varied, as the distribution shows a similar variation between the two treatments in the phylum distribution. The percentage removal of total petroleum hydrocarbon (TPH) after 90 days of treatments with 1, 2, 3, 4, and 5% (w/w) of POS were 92, 90, 89, 68.3 and 47.3%, respectively, indicating removal inhibition at higher POS concentrations. As the search for more eco-friendly and sustainable remediating green plant continues, C. cajan shows great potential in reclaiming POS contaminated soil. Our findings will provide solutions to POS polluted soils and subsequent re-vegetation.