Showing 32 results for Sludge
M Mokhtari, A Salehi Vaziri, T Zareyi, M Jalili,
Volume 9, Issue 4 (3-2017)
Abstract
Background and Objective: Dewatered sewage sludge is a by-product of wastewater treatment process which can cause health and environmental problems if not properly managed. The aim of this study was to determine the feasibility of composting of Yazd WWT dewatered sludge with windrow method using different treatments.
Materials and Methods: In this study, the dewatered sewage sludge was mixed with two treatments of agricultural wastes (straw) and green waste (leaves), respectively. The mixture was done based on weight ratio of 20:1 and 10:1 (agricultural waste: dewatered sludge, and green waste: dewatered sludge) to achieve a ratio of C/N:20. The windrows were built with a length of 2 m, width of 75 cm and height of 1.5 m. Composting process was controlled by measuring the temperature, humidity, volatile solids, ash, pH, EC, organic carbon and estimating the C/N ratio. The results were compared with those of the Institute of Standards and Industrial Research of Iran.
Results: After 100 days of composting, C/N ratio was 13.08±6.25 in the treatment with green waste and reached to 15.46±5.35 in the treatment with agricultural waste. The amount of volatile solids decreased to 19.8±14.01% and 20.71±16.06% in the treatments with green waste and agricultural waste, respectively. The amount of EC had an increasing trend in both treatments.
Conclusion: composting with both treatments was led to an improvement in indicators of organic fertilizers in dewatered sewage. However, the windrow containing green waste reached to the mature compost standards sooner than the windrow containing agricultural waste.
R Barati Rashvanlou, M Farzadkia,
Volume 11, Issue 1 (6-2018)
Abstract
Background and Objective: Ultrasonic disintegration is a pretreatment process before stabilization and dewatering that degrades sludge and changes its physical and chemical characteristics. The aim of this study was to investigate the effectiveness of ultrasonic in enhancing hydrolyses, stabilization and dewatering of municipal raw activated sludge.
Materials and Methods: The samples were taken from returned activated sludge and then they were exposed to ultrasonic (Frequency: 20 and 40 kHz) in different times (0.5, 1, 3, 5, 10, 15, 30, and 60 min). The effectiveness of ultrasonic for hydrolysis, stabilization and dewatering processes were determined with measuring TS, TSS, CST, SRF, VS, nVS, VSss, and VSsol.
Results: VSsol was increased by 73% in 15 min and at frequency of 20 kHz, whereas VSsol increas was100% at 10 min and 40 kHz. The reduction of VS was observed at 15 min and 20 kHz. Then after, it was reached 18% after 60 min. For 40 kHz, VS reduction started at 10 min and reached 24% after 60 min. Specific resistance of sludge at two frequencies of 20 and 40 kHz and contact time of 1 min were decreased by 25 and 20% respectively. The capillary suction time at the frequencies of 20 and 40 kHz and contact time of 1 min was decreased 28 and 21%, respectively.
Conclusion: The optimum effectiveness of ultrasonic in hydrolysis of organic matter of raw biological sludge was at the contact time of 10 min and frequency of 40 kHz. The highest stabilization at the frequency of 40 kHz was observed at 60 min contact time. The best condition for sludge dewatering was at frequency of 20 kHz and contact time of 1 min.
Se Mahdavian, F Ostovar, H Mirbolooki,
Volume 11, Issue 3 (12-2018)
Abstract
Background and Objective: Coagulation, which is carried out by mixing coagulants such as alum, ferric chloride and poly aluminum chloride PAC with raw water, is one of the main processes in conventional water treatment plants. Sludge from this process contains high amounts of coagulants with high economic value. Therefore, if these coagulants are recovered, in addition to reducing the risks relate to sludge disposal, the expenses related to the supply of fresh coagulant in water or wastewater treatment plant may decrease.
Materials and Methods: To access related documentation, ScienceDirect, Google scholar and other databases were searched using keywords such as “coagulant recovery”, “water residuals management”, etc. More than one hundred fifty documents were investigated based on the content validity and thematic relation. Gathered contents were classified and summarized under the titles of “recovery methods”, “repeated recoveries”, “recovery regarding economic aspect” and “advantages and disadvantages of methods”.
Results: Use of new methods such as combination of membrane and chemical processes or ion exchange membrane processes leads to the recovery of coagulants with a similar quality to the commercial ones. In case of using conventional and less costly methods such as acid digestion, quality of recovered coagulants is not comparable with those of commercial ones, which are used in water treatment.
Conclusion: Different coagulants recovery methods were investigated to determine the reuse strategies. It is likely that using of recovered coagulants through conventional methods is in accordance with the related regulations of the wastewater treatment plants. Industrial use of novel processes for recovery of coagulants with higher quality needs precise technical and economical investigations.
H Niknejad, M Farzadkia, A Esrafili, M Kermani,
Volume 12, Issue 4 (2-2020)
Abstract
Background and Objective: 2,4 dinitrophenol is observed in sewage produced from chemical and petrochemical industries. Contamination of drinking water with these pollutants causes toxicity, health problems and change in taste and odor. The present study was developed to evaluate the efficiency of removal 2,4-DNP through dried sludge adsorbent and modified calcium chloride sludge adsorbent.
Materials and Methods: At first, sludge was dried at temperature of 60 °C. Next, CaCl2 was used to improve adsorption capacity. The removal efficiency of 2,4 dinitrophenol were determined by HPLC at wavelength of 360 nm. The effects of influencing factors including pH, initial pollutant concentration, contact time, and adsorbent dose were examined.
Results: The optimum pH of adsorption for both adsorbents was found to be 7. The optimum concentration of 2,4-DNP was 10 ppm. The results obtained from the present research showed that the removal of the contaminant using dried and modified sludge sorbent was increased from 72.6% to 86% at a dosage of 1.5 g. The adsorption kinetics were fitted with the pseudo second order kinetics model for both adsorbents. The isotherm data also showed that the adsorption of this pollutant on both adsorbents is fitted with the Freundlich model.
Conclusion: Results obtained from the present study indicated that the efficiency of the modified sludge ash is more than the non-modified sludge in 2,4 dinitrophenol removal. This can reduce adsorbent consumption in industrial treatment plants.
Bahareh Ghoreishi, Hassan Aslani, Mohammad Shaker Khatibi, Sepideh Nemati Mansur, Mohammad Mosaferi,
Volume 13, Issue 1 (4-2020)
Abstract
Background and Objective: Application of sewage sludge contaminated with heavy metals may cause health and ecological concern. Ecological risk and heavy metals content of sewage sludge from wastewater treatment plants of East Azerbaijan province were evaluated in the present study.
Materials and Methods: Nine composite samples were taken and analyzed for heavy metals. The geo-accumulation index (Igeo), contamination factor(CF) , and potential ecological risk index were calculated.
Results: Variation of the heavy metals concentrations were in the following order: Zn>Cu>Pb>Cr>Ni>As>Hg>Cd. The contents of some heavy metals were several order of magnitude higher than the crustal average (CA) values. Considering the Maximum Permissible Standards (MPS) and the Muller's index, the Cd, Cu, and Zn pollution were found to be in the moderate range, whereas As and Pb were in strongly polluted category; and Hg was in extremely polluted category. Considering MPS, the single-factor pollution index (PI) and the Nemerow’s synthetic pollution index (PN) were lower than 1 and 0.7 respectively. This indicated that the sludges were unpolluted with most heavy metals and could be safely applied for agricultural uses. However, a high potential ecological risk for As and Cd; very high risk for Pb; and extremely high risk for Hg were calculated when considering the CA values. There were significant differences between the levels of heavy metals and MPS (p <0.05).
Conclusion: Although the metal concentrations were below the MPS according to the US EPA regulations, sludge samples showed a high degree of potential ecological risk for the environment in comparision with the CA values,. Periodic monitoring of sludge quality are strongly recommended.
Mohsen Ansari, Mahdi Farzadkia,
Volume 14, Issue 2 (9-2021)
Abstract
Background and Objective: Wastewater treatment and stabilization always imposes costs and consequently a lot of energy on wastewater treatment plants. To achieve the purification and stabilization of as much sludge as possible, breaking complex components into simpler components is considered a critical step. Therefore, this study aimed to evaluate the feasibility of treating the produced sludge in the municipal wastewater treatment plant using ozonation method.
Materials and Methods: In this study, sludge was obtained from the return line of activated sludge from the wastewater treatment plant in the south of Tehran. An ozonation generator with a discharge rate of 3 L/min and an ozone concentration of 40-35 mg/L was discharged to the reactor and the residual ozone concentration was measured by iodometric method. Finally, the total suspended solids and volatile, soluble chemical oxygen demand, total organic carbon, and biochemical oxygen demand during ozonation processes were measured using the Standard Method.
Results: The results of this study showed that the amount of TSS and VSS in the activated return sludge decreased from 4060 to 2100 mg/L and from 3300 to 1850 mg/L during the ozonation process, respectively. However, SCOD, TOC, and SBOD had an upward trend of about 18, 11.7, and 14 times in the same reaction time, respectively.
Conclusion: According to the results of this study, it can be concluded that the ozonation system can be proposed as a suitable process for the decomposition of sludge produced in wastewater treatment plants and increasing the biodegradability of these sludges.
Mohsen Ansari, Mehdi Farzadkia,
Volume 15, Issue 2 (8-2022)
Abstract
Background and Objective: The high concentration of petroleum hydrocarbons, along with some other parameters such as aromatics, paraffin, naphthene, and heavy metals, has led to the sludge of oil sludge listed as hazardous materials with a specific source by the US Environmental Protection Agency. Therefore, the purpose of this study is to investigate the potential of oil-contaminated soil in changing the biodegradability indices of oil sludge.
Materials and Methods: Moisture, pH, total organic carbon, total nitrogen, total phosphorus, elemental analysis, and amount and type of TPH of oil sludge samples were identified. The microbial consortium was isolated from contaminated oil soil around the oil refinery and poultry manure. Finally, biodegradability indices of oil sludge were examined.
Results: The results showed that the amount of organic carbon and nitrogen in oil sludge samples were 32.65 and 0.21%, respectively. Also, iron, calcium, and potassium with 5862, 2921, and 524 mg/kg, respectively, were the most elemental components in petroleum sludge. According to the SARA analysis, the highest TPH compounds in oil sludge samples included saturated compounds, aromatics, resins, and asphaltene with 70.45%, 15.2%, 10.9%, and 3.45%, respectively.
Conclusion: According to the results of biodegradability indicators of oil sludge, it can be concluded that the isolated consortium can be proposed as a suitable tool for the treatment of petroleum sludge at the bottom of crude oil storage tanks.
Arezoo Mahmoudi, Seyyed Alireza Mousavi, Danial Nayeri, Parastoo Darvishi,
Volume 15, Issue 3 (12-2022)
Abstract
Background and Objective: The consequence of using coagulant materials such as aluminum sulfate and ferric chloride in the coagulation unit of conventional water treatment plants can generate plenty of sludge that contains large amounts of coagulant, which in addition to environmental risks, will also possess disposal costs. Today, intending to preserve the environment and reduce treatment costs, researchers emphasize the recovery and reuse of coagulants from sludge. In this regard, the present study was proposed and implemented to recover and reuse water treatment plant sludge as a low-cost coagulant in wastewater treatment.
Materials and Methods: This research is an experimental-laboratory study. In order to recover the coagulant from the collected sludge, acid hydrolysis method was used. The physicochemical characteristics of the recovered sludge were also determined using FTIR, FE-SEM, and BET analysis. Moreover, the efficiency of recovered sludge in different doses (50 to 300 mg/L) on wastewater treatability in terms of COD, TSS, VSS, turbidity, phosphorus, and coliform indices was compared with aluminum sulfate, ferric chloride coagulants, also the results of the study were analyzed and presented using Excel software (version, 2016).
Results: According to the results, the prepared sludge had no crystalline structure with amorphous morphology. In addition, recovered coagulant from water treatment sludge has demonstrated high efficiency for wastewater treatment, so 66.6%, 82.49%, 79.66%, 80%, 65 %, 99.18% of COD, turbidity, TSS, VSS, phosphorus, total coliform were removed at the highest dosage of recovered coagulant (300 mg/L), respectively. Furthermore, the recovered coagulant dosage had a significant effect on the performance of the coagulation and flocculation process in wastewater treatment.
Conclusion: The results showed that recovered coagulant from the sludge of the water treatment plant can be considered an acceptable option with appropriate effectiveness in the wastewater treatment processes.
Hamid Kariab, Mohammad Mehdi Emamjomeh, Sheida Zakariaie,
Volume 15, Issue 4 (3-2023)
Abstract
Background and Objective: Due to the presence of heavy metals (HMs), sludge produced in industrial wastewater treatment plants (WWPT) is classified as special waste and can cause adverse health effects. The present study aimed to identify special wastes and assess the risk associated with the presence of HMs in the sludge of WWTP from an Industrial City.
Materials and Methods: Identifying the special wastes was conducted using a checklist, and classification was performed in accordance with the Basel Convention. Ecological risk assessment was done by determining the geo-accumulation and ecological indexes. The estimation of health risk was done by determining HQ and ELCR indexes.
Results: The highest amount of special waste was allocated to sludge with a value of 3900.0 kg/month. Chromium was detected in the highest concentration (95.89 ± 52.15 mg/kg). The level of chromium and nickel pollution was evaluated in the low range, and cadmium was very severe. The ecological risk of lead was estimated in a significant range and was very high for cadmium. The HQ was less than 1, and the ELCR for inhalation and dermal exposure was estimated to be lower than the acceptable risk level of WHO.
Conclusion: The present study showed that the largest amount of special waste is dedicated to sludge. Although the concentration of HMs was lower than the acceptable limits, the sludge had a high ecological risk level. Therefore, the accumulation and transfer of sludge must be carried out under the provisions of the Basel Convention and environmental considerations.
Narges Arab Ameri, Hatam Godini, Mansur Zarrabi, Mohammad Darvishmotevalli,
Volume 17, Issue 4 (3-2025)
Abstract
Background and Objective: Wastewater produced in industrial estates is crucial to address due to the wide range of pollutants it contains. The objective of the present study was to investigate the performance of the Chamshahr Industrial Estate Wastewater Treatment Plant for effluent and sludge reuse.
Materials and Methods: In this descriptive and comparative study, the quality of raw industrial wastewater, effluent, and sludge from the wastewater treatment plant of the Chamshahr Industrial Estate was investigated over three periods at monthly intervals. Additionally, archival quality data for wastewater, effluent, and sludge from 1402 to 1403 were analyzed. The results were compared with the standards and guidelines of Iran, WHO, FAO, USEPA, and others. The wastewater treatment method employed a combination of chemical sedimentation and aerated lagoons with return sludge.
Results: The volume of wastewater produced in this industrial estate was 15,000 m³/day, primarily originating from leather and tanning industries (6,100 m³/day), which exhibit high pollution intensity. The treatment plant's efficiency in removing BOD, COD, and TSS was 62±24%, 72±19%, and 84±13%, respectively. However, due to the concentration of heavy metals, such as chromium in the wastewater (0.28 mg/L) and sludge (353.5 mg/L), the treatment method was unable to meet existing standards and guidelines. Furthermore, the salt content in the effluent (43,300 mg/L) and sludge (202,000 mg/L) was excessively high, rendering it unsuitable for disposal or reuse without further treatment.
Conclusion: The performance of the wastewater treatment plant fails to meet the standards and guidelines for environmental discharge and the reuse of effluent and sludge. Therefore, the final effluent and sludge require additional treatment to enable reuse and prevent environmental pollution.
Maryam Ghani, Masoomeh Askari, Babak Mahmoudi, Nejat Mousavipour, Reza Barati Rashvanlou, Shahrokh Nazmara,
Volume 18, Issue 1 (5-2025)
Abstract
Background and Objective: Sewage sludge, a byproduct of wastewater treatment plants, is rich in organic matter and nutrients. With appropriate treatment, sludge can be utilized as a fertilizer for agriculture and soil amendment. This study aimed to evaluate the microbial quality of wastewater treatment plants in Tehran.
Materials and Methods: This study was conducted during the winter of 2018. A total of 25 samples were collected from the dewatering tank and sludge storage areas. Fecal coliform counts were determined using EPA Method 1681, while Salmonella and parasite egg counts were assessed using EPA Methods 1682 and 1992, respectively.
Results: In the dewatered sludge, fecal coliform levels ranged from a minimum of 67 MPN/g.TS on the first day to a maximum of 18,518 MPN/g.TS on the third day. Salmonella levels measured on the fifth, eighth, and tenth days were 0.55, 0.32, and 0.66 MPN/4g.TS, respectively. Parasite egg counts recorded on the second, ninth, and tenth days were 4 OVA/4g.TS. In the stored sludge, regardless of depth or geographic location of the disposal land, fecal coliform counts during retention times of 2, 3, 4, 5, 6, 7, 8, and 9 years were 10, 186, 480, 30, 27, 29032, 2, and 11 MPN/g.TS, respectively. Salmonella and parasite eggs were not detected in the stored sludge.
Conclusion: The findings indicate that, in the sludge storage unit compared to the sludge dewatering unit, achieving Class A standards for sludge is feasible through continuous quality monitoring.
Mohammad Aqanaghad, Amir Sheikhmohammadi, Esrafil Asgari, Hamidreza Tajfar,
Volume 18, Issue 3 (12-2025)
Abstract
Background and Objective: This study aimed to assess the chemical and microbial quality of sludge generated at the Khoy wastewater treatment plant using an SBR process, and to compare the results with established agricultural standards.
Materials and Methods: In this study, monthly sludge samples were collected and analyzed using standard EPA methods, including the 15-tube technique for coliforms, flotation for Ascaris eggs, and acid digestion for heavy metals. Data were analyzed using SPSS v.25 and statistical analyses included Pearson correlation tests.
Results: The analyzed sludge exhibited an acceptable pH (7.14) and a high organic carbon content (27.32%). However, its elevated salinity (9891 µS/m) and low C/N ratio (6.38) indicated biological instability and limitations for direct agricultural application. The concentrations of heavy metals—including arsenic (10.27 mg/kg), copper (134.86 mg/kg), and zinc (530.93 mg/kg)— exceeded Iran’s national standards. Heat-map analysis confirmed a significant correlation between salinity, and the levels of chloride (Cl-), and sulfate (SO42-). Despite its nutritional value, the sludge is not recommended for direct agricultural use without prior treatments such as stabilization, salinity reduction, and pathogen removal.
Conclusion: Despite the substantial nutrient content of the sludge, including nitrogen, phosphorus, and organic carbon, its direct application in agriculture faces serious limitations due to high salinity, an imbalanced C/N ratio, severe microbial contamination (e.g., nematode eggs), and the exceedance of permissible levels for several heavy metals. Safe utilization of this sludge requires corrective treatments such as stabilization, disinfection, desalination, and regular monitoring of heavy metal concentrations.
