Performance Evaluation of Eichhornia Crassipes for Kitchen Wastewater Treatment

Abstract

Kitchen wastewater (KWW) is a type of grey wastewater that has garnered significant attention due to the presence of organic pollutants and oil and grease. Eutrophication in water bodies and chocking of sewer lines are common hazardous impacts due to KWW. Stagnant KWW invites serious diseases such as malaria, filarial, and dengue. The present water crisis demands the reuse of KWW for non-potable purposes. In this study, the potential reusability of KWW in irrigation was analyzed to reduce the present freshwater demand. An initiative has been taken to collect the KWW samples from an educational institute in India to check its suitability for irrigation. The samples were characterized by their physical, chemical, and bacteriological properties. The characterized data were compared with the standard limit for irrigation Food and Agriculture Organization (FAO 1994) and the United States Salinity Laboratory (USSL 1954). Apart from the irrigation standards, the characterized data were also compared with sodium adsorption ratio (SAR), residual sodium carbonate (RSC), sodium percentage (Na%), magnesium hazard (MH), Kelly’s ratio (KR), and permeability index (PI) to get better clarity. Characterized data showed the absence of carbonate, fluoride, chromium, and Escherichia coli in KWW. Parameters like pH, chloride, iron, copper, magnesium, lead, nickel, sodium, calcium, zinc, aluminum, and sodium adsorption ratio were within the permissible limit, whereas bicarbonate, total dissolved solids, electrical conductivity, sulphate, and potassium exceeded the limit as per FAO (1994) standard. The result obtained from the USSL (1954) classification system suggested that 30.77% of KWW samples were safe for irrigation. Moreover, its quality was found to be safe for irrigation based on SAR, Na%, KR, and MH. The study showed that for RSC and PI indices, the KWW needs to be treated for sustainable reuse. For better decision making of KWW reuse in irrigation, the output of Mamdani fuzzy inference system (MFIS) was compared with the USSL (1954) classification system. Overall agreement between USSL (1954) and MFIS was found to be 55.6% for KWW. Hence, there is a need for raw KWW treatment. In this study, the phytoremediation method using Eichhornia crassipes (EC) was used for KWW treatment because of its low-cost. For performance evaluation of EC, field experiments were conducted for both raw and decomposed KWW. From treatment analysis of raw KWW with EC for 21 days (monitored at 3 days of an interval), it was observed that nitrate nitrogen and ammonium nitrogen concentrations reduced to 98.57% and 81.82%, respectively, within 15 days, whereas pH value increased towards neutral range from 4.35 to 6.48. It was also found that EC showed good reduction efficiency for BOD5 (77.62%), ammonium nitrogen (81.82%), total organic carbon (38.33%), and total suspended solids (95.97%) as compared to control (KWW sample without EC). Phytoremediation using EC reduced potassium concentration to 75.51%. An increase of 47.01% biomass of EC was observed for 21 days of the experiment. Further, efficiency of EC was evaluated for the decomposed KWW sample. Physical and chemical parameters were monitored for 28 days (monitored at 7 days of an interval). Initially, control (raw KWW sample without EC) and raw KWW+EC were kept for two weeks, and then in control (decomposed KWW sample), EC was added and kept for the next two weeks. In the initial sample, the concentration of electrical conductivity, total dissolved solids, nitrate nitrogen, ammonium nitrogen, phosphate phosphorus, and potassium were found to be exceeded the standard limit of irrigation water quality. However, after 28 days for raw KWW+EC, the concentrations of these parameters were reduced to 63.71%, 63.71%, 99.01%, 94.36%, 98.05%, and 83.30%, respectively, and found within the limit. An increase of 51.73% and 117.34% biomass (fresh weight) were observed for raw KWW+EC and decomposed KWW+EC, respectively. Higher value of bioconcentration factor (BCF) was found for iron (8,363.40) in raw KWW+EC, whereas for decomposed KWW+EC higher BCF value was found for iron (1,481.33), nickel (1,497.3), zinc (5,225.4) and mercury (1,286.9). It was also observed that calcium, copper, magnesium, sodium, lead, and potassium showed translocation factor (TF) >1 in raw KWW+ EC, and for decomposed KWW+EC, calcium, magnesium, sodium, and mercury showed TF > 1. Apart from the field experiment, cost-benefit analysis of KWW treatment project was carried out using the Net Present Value method. Both the lower and upper bound of the selling price of treated KWW and discount rates were estimated in order to have a profitable KWW treatment project. The effect of soil and crop selection on the revenue generation during the reuse of treated KWW was also studied. The possible solution to reduce present water stress over different cities of India was also highlighted. This study can be beneficial for reducing the wastewater handling problem and solving the demand for freshwater.