HUR TILLFRISKNADE SJÖARNA? / Research on Recovery of Polluted Lakes
In order to evaluate the effects of advanced wastewater treatment plants for phosphorus removal, the National Swedish Environment Protection Board during 1971 started a program for analysing the conditions in a number of recipient lakes. Some lakes from which sewage effluent was completely diverted were included.
Of 23 lakes possible to evaluate, 15 responded positively with lowered concentrations of total phosphorus. Lowered chlorophyll a values were recorded in seven lakes and a significant increase of transparency could be noted in six lakes. Nitrogen increased in a number of lakes. In many shallow lakes no improvements could be observed due to internal loading from the sediments. In these lakes considerable amounts of phosphorus were released from the sediments stimulating algal growth, the phosphorus was then recycled back to the sediments. “Complete abstract not presented.”