Undersökning av utökade användningsområden för Lotsbroverkets slam
Lotsbroverket is the largest wastewater treatment plant on the Aland Islands and it isdesigned for handling wastewater from approximately 30 000 persons. In 2011,Lotsbroverket produced about 2800 m3 of dewatered sludge. The sewage sludge that isproduced is transported to a contractor where it is processed to eventually be used e.g.in the construction of green space. This study aims to investigate available applicationoptions in terms of the sewage sludge that is produced in Lotsbroverket. The main aimis to study the feasibility of using the produced sewage sludge as a fertilizer in theagriculture of the Aland Islands.The sludge already fulfills limit values for heavy metals in accordance with the Act"The Aland Government´s directive on the use of sewage sludge in agriculture." Inorder to clarify the sludge content of pharmaceutical and organic substances it isrequired that the substances are identified and a risk assessment is performed. In theliterature it is found that the risk of human exposure to these substances is low if thesludge is treated appropriately. Suggested appropriate treatment of the plant's sludge isthermophilic digestion whereby also pathogens are killed.The soil of the Aland Islands has a high content of phosphorus. Since 1995 there is anenvironmental program to which currently 95% of the island's farmers are connected.The program controls the use of fertilizers i.e. by setting maximum permitted levels ofphosphorus. Since sewage sludge contains relatively much phosphorus it may be alimitation of the use of sewage sludge on agricultural land of the Aland Island. That iswhy it would be suitable to use the sludge with a different fertilizer in order to obtainthe proper fertilizing properties.In Europe, the use of sewage sludge in agriculture is relatively widespread. Severalcountries have less strict laws regarding the sludge content than the Aland Islands.Because large amounts of fruits and vegetables annually are imported into the island,there is reason to believe that the population already consumes products grown onsludge treated soils. Several of the farmers on the Aland Islands are currently scepticalin terms of using sewage sludge in agriculture, mainly due to uncertainties in the sludgecontent. Regarding the certification of Lotsbroverket in accordance with the Swedishcertification system REVAQ no barriers have been found. To ensure that a certificationis possible, however, further investigations are required.