Nutrient Loading in the River Systems Around Major Cities in Bangladesh: A Quantitative Estimate with Consequences and Potential Recycling Options

Biological organisms including humans require mineral nutrients for their growth and development. A significant amount of these nutrients remain unused in the left over materials, known as waste, causing environmental degradation. These nutrients could potentially be a resource for agriculture if recycled and reused. Therefore, a critical examination of nutrient loading from waste such as from human excretion and biowaste it required. Here, we estimated the nutrient loading from municipal organic waste (MOW) and human excreta using linear modelling, explored the potential consequences to ecosystem services and proposed several management strategies. Waste and human excreta generation were calculated from the per capita generation rate while nutrient concentrations were considered as the average of literature values. The daily carbon (C), nitrogen (N), phosphorus (P) and potassium (K) loading from MOW, urine and faeces to water bodies around the major cities in Bangladesh were estimated at 2158, 112, 58 and 91 t, respectively. The nutrient loading to water bodies reduces several ecosystem service with estimated cost of BDT. 42.93 million for reduction in fish production and half of property rent. Combined pyrolysis and composting of municipal organic waste can reduce the volume of organic waste. Similarly, pyrolysis of faeces and then sorption of nutrients using the produced biochar could recycle 440 t C, 71 t N, 113 t P and 73 t K day−1. Combing the nutrient recycling through pyrolysis-composting of MOW and faeces pyrolysis-sorption of nutrients from urine, the estimated nutrient recycling was 39% C, 11% N, 68% P and 11% K of the intrinsic nutrients in waste. Altogether, our study provides a comprehensive understanding of nutrient loading, its consequences and potential recycling options that may help to attain environmental sustainability.