Chemical rehabilitation of rapid sand filter at Klagshamn WWTP in Malmö / Kemisk rekonditionering av sandfilter på Klagshamn ARV i Malmö
At many wastewater treatment plants (WWTPs), rapid sand filters are used as polishing step before the wastewater is released to the recipient. Thus, after time, the media gets clogged and the filters are regularly backwashed. In case of poor backwashing, the next filtration cycle will begin with an inefficient filter. Agglomerates of media grains, flocculation chemicals, biosolids and fats can lead to appearance of “mud balls”. “Mud balls” can grow rapidly and form cracks, increasing the local filtration rates or causing increased head loss and, consequently, destroy the filter. In such cases, rehabilitation of filter media is needed. Replacing the old media is a costly and time consuming procedure. In this paper, different chemical cleaning methods are compared with the aim to find a procedure that can be applied in a full scale without negative impact on the recipient or on the main process. Ten percent solution of sodium hydroxide has shown good impact on media characteristics and can solve problems with “mud balls”. Applied in full scale, the method has four to five time lower cost compared to replacement of the filter media.
Utvärdering av filtermaterial för att avlägsna lösta organiska föroreningar i dagvatten / Evaluation of filter materials for the removal of organic contaminants in stormwater
Stormwater is frequently contaminated with organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), phthalates and alkylphenols emitted from traffic and building materials. Filters with adsorbing materials have the potential to remove dissolved, colloidal and particulate organic pollutants from stormwater. The aim of this research project is to investigate how effectively filter materials remove dissolved organic pollutants from stormwater. 11 materials were investigated in batch tests with synthetic stormwater: PAHs, phthalates and alkylphenols in concentrations ranging from 10 to 300 μg/L and dissolved organic matter were mixed with the materials for 10 min to 24 h, after which residual concentrations of compounds in the aqueous phase were analyzed. The materials chitosan, cellulose, zeolite, perlite and vermiculite exhibited limited adsorption of the investigated pollutants. However, pine bark and plastic fibers could remove most contaminants by ≥ 70 %. Untreated and treated pine bark from different manufacturers showed similar adsorption capacity; it is therefore not critical which pine bark product is used. A large proportion of the contaminants were adsorbed within 10 min of contact with the barks. Continued studies should focus on the practical application of the materials and optimization of filter facilities.
Vattnets roll i Tchads jordbruksproduktion – metoder för förbättrad analys av jordbruksförändring / The role of water in crop production in Chad – methods for improved analysis of agricultural change
Agriculture constitutes the largest economic sector and professional occupation in Chad, and is undergoing rapid changes due to processes of population increase, institutional reforms, conflicts in neighbouring countries, increasingly globalized trade networks, and environmental changes. But despite their importance for livelihoods and economic growth, the specific patterns and drivers of change in the agricultural sector are however poorly understood. This article summarizes the current state of knowledge about the processes of change in the agricultural sector in Chad and their drivers, as well as the research methods used to address them. It shows that a large part of the processes of change remain unexplained, which requires improved research- and data management methods. Finally, a framework is presented on how to realize such improvements.
Extreme value analysis of wave runup and dune erosion at Ängelholm beach, south Sweden / Extremvärdesanalys av våguppspolning och dynerosion vid Ängelholms strand
This study employs extreme value analysis to estimate 10-, 50-, and 100-year return levels of wave runup and annual dune erosion on the basis of 40 years simulated data from Angelholm Beach, Sweden. The offshore wave climate is computed with the SMB-formulations and propagated nearshore with the SWAN wave model. The runup is computed with a Hunt-type equation and the erosion with an impact formula. The results show that the dune crest elevation is in general higher than the most extreme runup. The volume of sediment in the dunes is sufficient to protect the developed hinterland in the short-term perspective; however, long-term effects due to sea level rise and gradients in longshore sediment transport are not considered and may change this conclusion.