ABSTRACT
The alkaline solubilization of excess mixed sludge was investigated and subsequently the released phosphorus was recovered as magnesium ammonium phosphate (MAP). Considerable and rapid release of glycogen and protein was encountered after alkaline addition into the sludge. Only 45.0% of sludge cells were destructed after 240â¯min treatment in R1 while the corresponding ratio was 96.1% in R3 according to the release of DNA. Non-apatite inorganic phosphorus (NAIP) in the alkaline treated sludge decreased due to the dissolution of Al(OH)3 and AlPO4, which was the dominant reason for phosphorus release. Soluble orthophosphate (SOP) in the supernatant of alkaline treated sludge could be recovered quickly with the recovery efficiency of 84.6% within 5â¯min and about 53-55% of P participated in MAP reaction, producing large amounts of acicular crystals.
Subject(s)
Sewage , Struvite , Phosphates , PhosphorusABSTRACT
Taking a pumped storage reservoir located in southern China as the research object, the paper established a three-dimensional hydrodynamic and eutrophication model of the reservoir employing EFDC (environmental fluid dynamics code) model, calibrated and verified the model using long-term hydraulic and water quality data. Based on the model results, the effects of nitrogen and phosphorus concentrations on the algae growth were analyzed, and the response of algae to nitrogen and phosphorus concentration and quantity of pumping water was also calculated. The results showed that the nitrogen and phosphorus concentrations had little limit on algae growth rate in the reservoir. In the nutrients reduction scenarios, reducing phosphorus would gain greater algae biomass reduction than reducing nitrogen. When reducing 60 percent of nitrogen, the algae biomass did not decrease, while 12.4 percent of algae biomass reduction could be gained with the same reduction ratio of phosphorus. When the reduction ratio went to 90 percent, the algae biomass decreased by 17.9 percent and 35.1 percent for nitrogen and phosphorus reduction, respectively. In the pumping water quantity regulation scenarios, the algae biomass decreased with the increasing pumping water quantity when the pumping water quantity was greater than 20 percent of the current value; when it was less than 20 percent, the algae biomass increased with the increasing pumping water quantity. The algae biomass decreased by 25.7 percent when the pumping water quantity was doubled, and increased by 38.8 percent when it decreased to 20 percent. The study could play an important role in supporting eutrophication controlling in water source area.
