An investigation of agricultural use potential of dewatered sewage sludge

Background: One of the useful applications of Dewatered sludge (DWS) of municipal wastewater treatment plants (WWTPs) is its use as manure in agriculture; therefore, its quality characteristics should be specified. The aim of this research was to determine biological and physicochemical characteristics of DWS of Sari WWTP and compare them with standards, and also to investigate its potential use in agriculture. Methods: Sludge samples were taken from the sewage sludge of Sari WWTP. Sampling and analysis of samples parameters including fecal coliform, salmonella, helminth ova, carbon, nitrogen, C/N, phosphorus, organic matter, potassium, moisture, electrical conductivity, and PH, were performed during four seasons with three replications based on the standard method. Results: The fecal coliform, salmonella, and helminth ova of the DWS were 2.37×106 ± 1.06×106 MPN/1 g d.s weight, 47±12.92 MPN/4 g d.s weight, and 466±61.85 number/4 g d.s weight, respectively, therefore, the DWS of Sari WWTP was categorized in the class B of the EPA standard. The amounts of C/N, organic matter, carbon, nitrogen, phosphorus, potassium, moisture, electrical conductivity, and PH were obtained to be 12.7±1.15, 42.4±3.27%, 24.6±1.89%, 1.94±0.13%, 2.35±0.6%, 0.57±0.13%, 82±3.12%, 1.34±0.21 ds/m, and 7.41± 0.45, respectively. Conclusion: The DWS of Sari WWTP has a good fertility value but it cannot be safely used in agriculture and should be improved for class A by the Processes to Further Reduce Pathogens (PFRP), especially by composting. Keywords: Sewage sludge, Agricultural use, Fertilizer, Pollution control, Dewatered sludg

Inactivation of Coliforms in Sludge Through Cavitation Phenomena by Ultrasonic Waves

Background: One of the most challenging and critical processes in wastewater treatment is sludge treatment. This study aimed to investigate the effects of low frequency ultrasound and high level of energy on inactivation rate of total coliform of sludge and ascertain the optimal operating parameters of the ultrasound waves.Methods: In this research, the density of ultrasound (W/mL) and time (minutes) were investigated. The effect of these parameters on the inactivation of total coliform in sludge was also investigated.Results: The results revealed that the optimum operating time and ultrasound density were 30 minutes and 2.5 W/mL, respectively. Also, the frequency of 20 kHz of total coliform removal rate in these conditions was 99.44% .Conclusion: Ultrasound waves as well as micro and nano bubbles could remove total coliform and decontaminate the sludge, thereby incrementing the rate of treatment

Extracting minerals from desalination brine using innovative capacitive photo electrocatalytic desalination cells (cPEDC)

Limited freshwater supplies and increasing water demand prompt us to seek new advanced wastewater treatment and desalination technologies. Brine production and demanding energy limit the use of current desalination methods. However, this brine contains minerals that are valuable for extraction.In this study, a novel system, the capacitive photo electrocatalytic desalination cell (cPEDC), consists of a capacitive deionization (CDI) and a five-chamber photo electrocatalytic desalination cell, was designed and utilized for the first time. The cPEDC’ performance was evaluated based on TDS removal rate, magnesium, calcium, alkaline recovery from brine, membrane scaling reduction, and phenol removal from industrial saline wastewater.The results show a removal rate of 54.81 and 41.16% for magnesium and calcium from the brine. Recovering 76.8% of the removed magnesium as Mg(OH)2 precipitation was accomplished inside the chemical production chamber (CPC). In addition, 64.82% of the removed Ca was extracted via the desorption step of the CDI module. Meanwhile, the cPEDC can produce 31.45 mV power alongside achieving TDS and phenol removal efficiency and desalination rate (DR) of 50.77%, 58.78%, and 927.5 mg/h after 20 h, respectively.The cPEDC can be considered a “green” technology to desalinate brine, treat wastewater, produce power and extract minerals

EFFECT OF ULTRASOUND TECHNOLOGY ON WASTEWATER TREATMENT EMPHASIZING ON HEALTH ISSUE

Background: Wastewater and sludge have huge pathogenic substances. So far, various physical and chemical processes have been used for disinfection, including chlorination, ozone and ultraviolet radiation. The use of this type of disinfectants is currently decreasing due to the hazards that they pose such as byproducts of disinfection, including carcinogenic Trihalomethanes. Nowadays, researchers have begun to use other processes that create less risks such as ultrasound technology. Ultrasoundwaves by breaking the cell wall causes reducing pathogenic populations and eliminating the risk of disinfection byproducts and are one of the newest methods for disinfection in water and wastewater treatment plants. For physical, chemical and biological effects of ultrasound waves on plants, ultrasound radiation results in the rotational movement of the protoplasm in individual cells and affects the growth rate of plants. In humans, the hypothesis is that exposure to ultrasound causes subsequent electrolytic balance changes in the nerve tissue and increases blood glucose levels. Ultrasound waves cause bacterial colony damage and thinning of the cell wall and the release of the cytoplasmic membrane. Mechanical effects of ultrasound waves can be used for water and wastewater disinfection. Methods: This research is a descriptive-analytic study that was carried out in a batch experiment. The goal of this research is to investigate the effect of ultrasonic waves on disinfection in South Tehran wastewater treatment plant.  Results: The results showed that by increasing the time and density of the ultrasound, the rate of removal of E.coli increased. Also, the optimal sonification time was 30 minutes and the optimal ultrasound density was 2.5 watts per milliliter at a frequency of 20 kHz. E.coli removal rate in these conditions was more than 99%.   Conclusion: According to the results of this study, the use of ultrasound waves has a significant effect on the elimination capacity of Escherichia coli and can be used as an appropriate alternative for stabilization and disinfection in wastewater treatment plants. Keywords: Ultrasound, Health, Wastewater, Treatment, Cavitatio

Effects of Sludge Holding Tank on the Effluent Quality and Sludge Settling Potential in Conventional Activated Sludge

Excess sludge treatment and disposal is a major challenge for wastewater treatment plants worldwide. In this study, sludge reduction was evaluated using pilot scale sequencing batch reactors (SBRs). Two SBRs were operated alongside each other over a period of 12 months during which time measurements were performed to determine COD, MLSS, MLVSS, pH, DO, SV1, SOUR, and ORP. The results showed that among the different SRT durations (5, 10, 15, 20, 25 days), the 10-day sludge retention time yielded maximum COD removal efficiency (90%) without any bulking or foaming problems. Prior to any reactions taking place in the reactor, the sludge was exposed to various oxidation reduction potentials for 1 to 8 hours in order to determine the effects of uncoupling metabolism on biomass production under different anoxic and anaerobic conditions. COD was observed to decrease from 600 to 33 mg/l while MLSS increased from 1350 to 1500 mg/l over a retention time of 7 hours and for an ORP value of -238 mv. The effluent COD obtained as a result of operating this process was below the limits set by environmental regulations for surface waters and reuse in agriculture. For an ORP value of -238mv, SOUR and SVI were measured to be 22 mgO2/h.gVSS and 40 ml/g, respectively

Removal of lead and cadmium with an optimized composite of expanded graphite/g-C3N4/phenylenediamine

In this study, an optimized composite of expanded graphite /g-C3N4 /phenylenediamine was synthesized and characterized by SEM, FESEM, EDS, XRD, and BET methods.The composite was prepared with an optimized combination using response surface methodology (RSM) as a proper adsorbent for eliminating heavy metals from water samples. The evaluation of the final adsorbent was accomplished by removing metal ions like Pb2+ and Cd2+. Under the optimum adsorption conditions for Pb2+ and Cd2+ (pH:5, adsorbent dosage:2 g/L, and Time:60 min), elimination efficiencies were 78.4% for Cd2+ and 71.35% for Pb2+. pH was the most important factor that influenced the adsorption rate. A short contact time for maximum removal efficiency was reported because of the porous structure of the constructed composite. As a result of the absorptive construction, the equilibrium showed a satisfactory agreement with the Freundlich model. The kinetic evaluations showed that the adsorption process of both heavy metals fitted the pseudo-second-order model. Furthermore, the results of thermodynamic studies indicated that the adsorption was an endothermic and spontaneous process. A series of regeneration experiments (5 cycles) was directed to evaluate the adsorbent reusability. The results presented that it was a suitable adsorbent for heavy metal uptake from aquatic solutions

Application of Ultrasonic Wave Irradiation for Hydrolysis and Amortization of Ability of Biological Analysis of Organic Substances in Dairy Wastewater; Case Study: Tehran Pegah Dairy Complex

In dairy industries large amount of water is utilized and major parts disposed as wastewater. The concentration of organic substance in this wastewater is relatively high. For example in Tehran Pegah Dairy Complex (TPDC) as the biggest Iranian  a dairy producer, around 3500 cube meter of wastewater generated for processing of 1000 tons milk, per day. The concentration of chemical oxygen demand (COD) and 5-days biological wastewater demand (BOD5) is about 3000, 1000 mg/L respectively. In this paper the effects of applying ultrasonic wave irradiation on hydrolysis of chemical oxygen demand in TPDC with 20 kHz operational frequency was investigated. The Samples were taken during one working day from 8 a.m. to 4 p.m. Samples were taken every two hour using composite sampling with constant volume from the outlet of equalization tank. Analysis of experimental data showed that it is possible to transfer some part of insoluble COD and BOD5 to soluble form by applying ultrasonic wave. The maximum of this conversion was about 52% which observed at 480s contact time and output power 300 W. For 300 and 600 W output power with extending contact time in the range of 60 to 480s, hydrolysis of organic matter showed ascending trend, but at 900w output powers find out different behavior. Therefore, when hydrolysis of organic matter consider, it is recommended to use low output power and long contact time. And it is important to considering that by this conversion, achievement the high level of treatment become more feasible and a reduction in the cost of treatment obtained consequently

Removal capability of 4-Nonylphenol using new nano-adsorbents produced in sand filters of water treatment plants

Sand filters are a physical treatment unit in water treatment plants that have considerable potential for removing large suspended matter. However, these filters are somewhat inefficient in removing micro-pollutants. In this study, using waste leachate, carbon nanoparticles were coated on the silica particles to increase the surface adsorption capacity on silica substrates of rapid sand filters. The surface properties of nano-adsorbents produced by scanning electron microscopy, Raman spectroscopy and EDS test were investigated. Furthermore, the adsorption capacity of 4-Nonylphenol was examined using a new nanocomposite under different operational conditions (contact time, temperature and initial concentration) and after obtaining pHzpc, the effect of pH, total dissolved solids (TDS) and total organic carbon (TOC) on the efficacy of 4-Nonylphenol removal was tested. The adsorption isotherms in three temperature amounts of 15, 25, and 50 °C were also studied and Langmuir isotherm well fit the experimental data. To evaluate the thermal effect on the adsorption process, the thermodynamic study was also conducted. The results demonstrated that this reaction is spontaneous, endothermic and thermodynamically desirable. The experimental data also showed that the new engineered material is a good reusable adsorbent in water treatment

Phytoremediation of hydrocarbon-contaminated soils with emphasis on the effect of petroleum hydrocarbons on the growth of plant species

To date, many developing countries such as Iran have almost completely abandoned the idea of decontaminating oil-polluted soils due to the high costs of conventional (physical/chemical) soil remediation methods. Phytoremediation is an emerging green technology that can become a promising solution to the problem of decontaminating hydrocarbon-polluted soils. Screening the capacity of native tolerant plant species to grow on aged, petroleum hydrocarbon-contaminated soils is a key factor for successful phytoremediation. This study investigated the effect of hydrocarbon pollution with an initial concentration of 40 000 ppm on growth characteristics of sorghum (Sorghum bicolor) and common flax (Linum usitatissumum). At the end of the experiment, soil samples in which plant species had grown well were analyzed for total petroleum hydrocarbons (TPHs) removal by GC-FID. Common flax was used for the first time in the history of phytoremediation of oil-contaminated soil. Both species showed promising remediation efficiency in highly contaminated soil; however, petroleum hydrocarbon contamination reduced the growth of the surveyed plants significantly. Sorghum and common flax reduced TPHs concentration by 9500 and 18500 mg kg‑1, respectively, compared with the control treatment.À ce jour, plusieurs pays en voie de développement, comme l’Iran, ont presque complètement abandonné l’idée de décontaminer les sols pollués par le pétrole à cause des coûts élevés reliés aux méthodes conventionnelles (physiques/chimiques) de décontamination des sols. La phytoremédiation est une nouvelle technologie verte qui peut s’avérer une solution prometteuse au problème posé par la décontamination des sols pollués par des hydrocarbures. Évaluer la capacité d’espèces indigènes tolérantes à croître sur des sols âgés et pollués par des hydrocarbures de pétrole représente l’une des étapes clé de la phytoremédiation. Au cours de la présente étude, l’effet de la pollution aux hydrocarbures sur les caractéristiques de croissance du sorgho (Sorghum bicolor) et du lin cultivé (Linum usitatissumum) a été évalué à partir d’une concentration initiale de 40 000 ppm. À la fin de d’étude, des échantillons de sols dans lesquels des plantes avaient obtenu un bon taux de croissance ont été analysés à l’aide d’un appareil CG-DIF afin de déterminer les taux d’hydrocarbures pétroliers (THP) totaux enrayés des sols. Le lin cultivé a été utilisé pour la première fois dans l’histoire de la phytoremédiation de sols contaminés par le pétrole. Les deux espèces ont fait preuve d’une efficacité prometteuse dans les sols fortement pollués. Cependant, la pollution par les hydrocarbures de pétrole a réduit de façon significative la croissance des plantes à l’étude. Le sorgho et le lin cultivé ont réduit la concentration en THP de 9 500 et 18 500 mg kg‑1, respectivement, comparativement au traitement témoin

Performance of the Subsurface Flow Wetland in Batch Flow for Municipal Wastewater Treatment

Subsurface flow wetlands are one of the natural treatment methods used for municipal and industrial wastewater treatment that are economical in terms of energy consumption and cost-effectiveness. Much research has been conducted on wetland operation with continuous flow but not enough information is available on batch flow. This study investigates wetland efficiency in batch flow. For the purposes of this research, two pretreatment units of the anaerobic pond type with digestion pits and two subsurface flow wetlands with a 2-day detention time were built on the pilot scale. The cells were charged with sand of 5 mm effective size, uniformity coefficient of 1.5, and a porosity of 35%. One wetland cell and one pretreatment unit were used as control. The municipal wastewater selected to be monitored for the one-year study period had a flow rate of 26 m3/day and average BOD5 of 250mg/l, TSS of 320mg/l, TKN of 35mg/l, TP of 12mg/l and TC of 2×108 MPN/100ml from Sabzevar Wastewater Treatment Plant. The average removal efficiencies of BOD5,TSS,TKN,TP, and TC in the continuous flow for the combined control pretreatment and wetland cell were 77.2%, 92%, 91%, 89%, 96.5% while the same values for the batch flow for the combined experimental pretreatment and wetland cell were 92%, 97%, 97.5%, 97%, and 99.75%, respectively. The removal efficiency in the subsurface flow wetlands in the batch flow was higher than that of the continuous flow. Thus, for wastewaters with a high pollution level, the batch flow can be used in cell operation in cases where there is not enough land for spreading the wetland cell