ASSESSMENT OF TREATMENT EFFICIENCY BY NON-ENERGY CONSUMING AERATION SYSTEM FOR FAECAL SLUDGE MANAGEMENT IN AN EMERGENCY HUMAN SETTLEMENT IN BANGLADESH
Rohingya issue is the world’s fastest growing force displacement crisis. Around 8,99,349 Rohingya people have been driven to seek sanctuary in Bangladesh. In this high densely populated emergency settlement, management of faecal sludge is now-a-days becoming a great challenge with the limited resources and space. Wastewater treatment is an indispensable part of faecal sludge management. This study was carried out to identify the wastewater treatment efficiency of the up-flow filtration system with constructed wetland. 15 samples in total were collected from the treatment plant. Total five sample collection points that were raw wastewater, the outlet point of 1st, 2nd and 3rd filter chamber, the outlet point of constructed wetland of the treatment plant. Samples were collected from each point in three consecutive days. Nine parameters of each samples were analyzed in the laboratory. With the help of the literature review, those parameters were selected. For the characterization of FS as well as wastewater, parameters include inorganic, solids concentration, biological constitutes, nutrients and pathogens should be considered (Henze & Comeau, 2008; Niwagaba et al., 2014; Tchobanoglous et al., 2000). Total suspended and dissolved solid as solids concentration; Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Nitrogen (TN), Ammonia (NH3), Nitrate (NO3-), Total Kjeldahl Nitrogen (TKN), Total Phosphorus (TP) and Phosphate (PO43+) as nutrients are mentioned as important for the characterization of domestic wastewater (Negwamba & Dinka, 2019; Dawood et al. 2017; Hegazy and Gawad, 2016; Kulkarni et al. 2018). From the background study, BOD, COD, pH, EC, nitrate, ammonia, phosphate, TDS and TSS were measured in this study for the assessment of the performance of the treatment plants. The treatment plant was found good at the removal of excess nutrients though NH3 concentration was not within the standard limit. However, the nutrient removal percentages were high in comparison with other parameters. BOD5 concentration of the final treated water were high that is almost twice than the DoE permissible limit. It is due to that no complete biological unit was present in the treatment process Though the BOD5/COD value of raw wastewater was good enough for treatment. A very partial anaerobic process might happen both in the filtration chamber and constructed wetland. Conventional biological process consumes energy and costs to maintain and operate which is not sustainable in the context of Rohingya emergency settlement. In this study, considering the crisis of energy, a non-energy consuming aeration system has been recommended to incorporate into the existing treatment process. This aeration system has been analyzed theoretically and found efficient to improve the water quality.
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APHA Method 5210B was followed to measure BOD 5 . Multimeter, model number HACH 125 was used to determine the DO of each sample. In this case, 5 mL of the samples and 295 mL of distilled water was mixed so that the dilution factor (D.F) would be 60 for each sample. For determining the chemical oxygen demand of each sample, dilution factor was used in titration method. Dilution Factor (DF) 50 (1 mL of the sample and 49 mL of distilled water) was used for all samples. 2.5 mL were taken from the diluted samples. 1.5 mL Potassium dichromate (K2 Cr2 O7 ) and 3.5 mL sulfuric acid (H2 SO4 ) were mixed with the sample. Then the total solution was kept in a digester at 150°C temperature for two hours. After that the solution was cooled to the room temperature. Then the COD of the samples were measured by colorimetric method by HACH DR 2500 Spectrophotometer. At first, calibration curve was made from five standard solution of potassium hydrogen phthalate by following APHA standard Method 5220C. pH is determined by following APHA Method 4500 H. Multimeter model number HACH 125 was used as electrometric measurement. Electric Conductivity was also determined by following APHA Method 2510 and using multimeter. APHA Method 4500-P was followed to determine the phosphate concentration of the samples. The amount of phosphate in each sample was determined by spectrophotometer model number HACH DR 2500. Phosver 3 reagent was used for the determination of PO 4 3+ . Dilution factor was used for all samples. 1 mL of sample was diluted with 9 mL distilled water i.e. the dilution factor was 10. In the procedure, each sample was divided into 10 mL of direct sample and 10 mL of sample mixing with phosver 3. The amount of phosphate in each sample was determined by following APHA Method 4500-NO3 and using spectrophotometer model number HACH DR 2500. Nitrover 5 reagent was used. Dilution factor was used for all samples. 1 mL of sample was diluted with 9 mL distilled water i.e. the dilution factor was 10. To find out the concentration of Ammonia of the samples, APHA Method 4500-NH 3 was followed. 1 mL of sample was diluted with 29 mL distilled water i.e. the dilution factor was 30. APHA Method 2510 and 2540D were followed for TDS and TSS testing of the samples. For each sample, two beaker was washed and kept them into oven for 10 minutes to be dried fast. The two beaker were then weighted. After that 100 mL of each sample was taken into one beaker and another beaker was kept beneath the filter media (figure 12). 100 mL of sample was also passed through the Hoffmann filter paper and suspended particles were retained. Then the two beakers of each samples were kept into the oven for 24 hours at 105°C. After 24 hours, the two beakers were weighted again. From the difference between the weight after and before oven dried, TS, SS and DS were measured.