With World Environment Day being celebrated on Thursday, the Yamuna river today projects a grim picture of increasing pollution levels. "The Biochemical Oxygen Demand (BOD) load, an important indicator of pollution levels, has increased by 13 per cent over last year,' Central Pollution Control Board (CPCB) has said in its latest report. This rise might be because of increase in generation of BOD load in the city or decrease in treatment efficiency of sewage treatment plants (STPs).