Optimization of leachate treatment using persulfate/H2O2 based advanced oxidation process: case study: Deir El-Balah Landfill Site, Gaza Strip, Palestine.

The objective of this study was to investigate the performance of employing H2O2 reagent in persulfate activation to treat stabilized landfill leachate. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as persulfate and H2O2 dosages, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following two responses proved to be significant with very low probabilities (<0.0001): chemical oxygen demand (COD) and NH3-N removal. The obtained optimum conditions included a reaction time of 116 min, 4.97 g S2O8(2-), 7.29 g H2O2 dosage and pH 11. The experimental results were corresponding well with predicted models (COD and NH3-N removal rates of 81% and 83%, respectively). The results obtained in the stabilized leachate treatment were compared with those from other treatment processes, such as persulfate only and H2O2 only, to evaluate its effectiveness. The combined method (i.e., /S2O8(2-)/H2O2) achieved higher removal efficiencies for COD and NH3-N compared with other studied applications.

Performance of combined sodium persulfate/H2O2 based advanced oxidation process in stabilized landfill leachate treatment.

A combination of persulfate and hydrogen peroxide (S2O8(2-)/H2O2) was used to oxidizelandfill leachate. The reaction was performed under varying S2O8(2-)/H2O2 ratio (g/g), S2O8(2-)/H2O2 dosages (g/g), pH, and reaction time (minutes), so as to determine the optimum operational conditions. Results indicated that under optimum operational conditions (i.e. 120 min of oxidation using a S2O8(2-)/H2O2 ratio of 1 g/1.47 g at a persulfate and hydrogen peroxide dosage of 5.88 g/50 ml and8.63 g/50 ml respectively, at pH 11) removal of 81% COD and 83% NH3-N was achieved. In addition, the biodegradability (BOD5/COD ratio) of the leachate was improved from 0.09 to 0.17. The results obtained from the combined use of (S2O8(2-)/H2O2) were compared with those obtained with sodium persulfate only, hydrogen peroxide only and sodium persulfate followed by hydrogen peroxide. The combined method (S2O8(2-)/H2O2) achieved higher removal efficiencies for COD and NH3-N compared with the other methods using a single oxidizing agent. Additionally, the study has proved that the combination of S2O8(2-)/H2O2 is more efficient than the sequential use of sodium persulfate followed by hydrogen peroxide in advanced oxidation processes aiming at treatingstabilizedlandfill leachate.

Effect of persulfate and persulfate/H2O2 on biodegradability of an anaerobic stabilized landfill leachate.

The current study investigated the effects of S2O8(2-) and S2O8(2-)/H2O2 oxidation processes on the biodegradable characteristics of an anaerobic stabilized leachate. Total COD removal efficiency was found to be 46% after S2O8(2-) oxidation (using 4.2 g S2O8(2-)/1g COD0, at pH 7, for 60 min reaction time and at 350 rpm shaking speed), and improved to 81% following S2O8(2-)/H2O2 oxidation process (using 5.88 g S2O8(2-) dosage, 8.63 g H2O2 dosage, at pH 11 and for 120 min reaction time at 350 rpm). Biodegradability in terms of BOD5/COD ratio of the leachate enhanced from 0.09 to 0.1 and to 0.17 following S2O8(2-) and S2O8(2-)/H2O2 oxidation processes, respectively. The fractions of COD were determined before and after each oxidation processes (S2O8(2-) and S2O8(2-)/H2O2). The fraction of biodegradable COD(bi) increased from 36% in raw leachate to 57% and 68% after applying S2O8(2-) and S2O8(2-)/H2O2 oxidation, respectively. As for soluble COD(s), its removal efficiency was 39% and 78% following S2O8(2-) and S2O8(2-)/H2O2 oxidation, respectively. The maximum removal for particulate COD was 94% and was obtained after 120 min of S2O8(2-)/H2O2 oxidation. As a conclusion, S2O8(2-)/H2O2 oxidation could be an efficient method for improving the biodegradability of anaerobic stabilized leachate.

Assessment of the waste stabilization pond performance, New Borg El-Arab City.

New Borg Al-Arab city includes 9 residential areas and 4 industrial zones. The four industrial zones are occupied by 266 running factories belonging to different industrial sectors. All the domestic sewage as well as the industrial wastewater is treated at an oxidation pond treatment plant and the plant effluent is used in irrigation of silviculture areas. The plant consists of 2 pond complexes. Each complex comprises 9 facultative ponds, arranged in 3 parallel series. Raw wastewater is pre-treated through screens and grit removal before entering the primary ponds. The study aims at assessment of the performance of the waste stabilization ponds. The results revealed that pre-treatment units were not functioning properly. The retention time was calculated to be 6 days in each pond of the first complex and 3 days in each pond of the second complex. The mean BOD surface loading rate was calculated to be 676 kg/ha/d for the first complex and 1584 kg/ha/d for the second. The plant was hydraulically and organically overloaded. The percentage removal of BOD, COD, SS, and NH3-N had an annual mean of 57%, 56%, 44%, and 39%, respectively for the first complex and 21%, 42%, 39%, and 25%, respectively for the second. Faecal coliforms were reduced by about 1 log10 unit in both complexes. The final pond effluent was not complying with the Egyptian law for reuse in irrigation. The study proposed some recommendations which can improve the efficiency of the plant as well as the effluent quality.

Water treatment plants assessment at Talkha power plant.

Talkha power plant is the only power plant located in El-Mansoura. It generates electricity using two different methods by steam turbine and gas turbine. Both plants drew water from River Nile (208 m3 /h). The Nile raw water passes through different treatment processes to be suitable for drinking and operational uses. At Talkha power plant, there are two purification plants used for drinking water supply (100 m3/h) and for water demineralization supply (108 m3/h). This study aimed at studying the efficiency of the water purification plants. For drinking water purification plant, the annual River Nile water characterized by slightly alkaline pH (7.4-8), high annual mean values of turbidity (10.06 NTU), Standard Plate Count (SPC) (313.3 CFU/1 ml), total coliform (2717/100 ml), fecal coliform (0-2400/100 ml), and total algae (3 x 10(4) org/I). The dominant group of algae all over the study period was green algae. The blue green algae was abundant in Summer and Autumn seasons. The pH range, and the annual mean values of turbidity, TDS, total hardness, sulfates, chlorides, nitrates, nitrites, fluoride, and residual chlorine for purified water were in compliance with Egyptian drinking water standards. All the SPC recorded values with an annual mean value of 10.13 CFU/1 ml indicated that chlorine dose and contact time were not enough to kill the bacteria. However, they were in compliance with Egyptian decree (should not exceed 50 CFU/1 ml). Although the removal efficiency of the plant for total coliform and blue green algae was high (98.5% and 99.2%, respectively), the limits of the obtained results with an annual mean values of 40/100 ml and 15.6 org/l were not in compliance with the Egyptian decree (should be free from total coliform, fecal coliform and blue green algae). For water demineralization treatment plant, the raw water was characterized by slightly alkaline pH. The annual mean values of conductivity, turbidity, and TDS were 354.6 microS/cm, 10.84 NTU, and 214.6 mg/I, respectively. There was an increase in the results of conductivity, turbidity, total hardness, and TDS in carbon filter effluent which was attributed to the desorption of adsorbed ions on the carbon media. The removal efficiencies of turbidity, total hardness, and TDS indicated the high efficiency of the cationic filter. The annual removal efficiencies of conductivity, turbidity, chloride, and TDS proved the efficiency of the anionic filter for removing the dissolved and suspended ions. All of the recorded values of the pH, conductivity, turbidity, chlorides, hardness, and TDS of the mixed bed effluent indicated that the water at this stage was of high quality for boiler feed. The study recommended adjustment of coagulant and residual chlorine doses as well as contact time, and continuous monitoring and maintenance of the different units.

Quality monitoring of composting processes of wastewater sludge in Alexandria.

There are two wastewater primary treatment plants in Alexandria (west and east). The produced primary sludge is mechanically dewatered and transported to sludge disposal site 9N where composting is carried out. However, prior to 1970, composting played a very minor role in sludge or solid wastes treatment because of greatly unfavorable balance between its economics and those of the principal competing option, namely landfill disposal. This study aims at monitoring and evaluating the composting process of demitted sludge produced from Alexandria wastewater treatment plants. Ten batches of sludge were composted. During the composting process the batches were been investigated and followed up to 3 months. Representative samples (10 for each batch) were taken from these batches at the start of windrowing and after each turning (4-15 days) and were analyzed for physical; chemical; bacteriological; and parasitological characteristics, heavy metals, and plant nutrients. Results revealed that C/N ratio of the final compost product comply with the decree of the Minister of Agriculture No. 100 11967, while moisture, C%, and TKN did not. Heavy metals, faecal coliforms, and helminthes complied with the decree No. 222/2002 for the Minister of Housing, Utilities, and Urban Communities. Moisture had positive correlation with both C and VS and negative correlation with pH. Temperature had negative correlation with TKN. Both total and faecal coliforms had negative correlation with temperature and positive correlation with C, N, and VS. It is recommended to optimize the quality of the produced sludge compost by use bulking agent rich in carbon and nitrogen as Hay or Rice straw, instead of the matured sludge compost.