Activated Sludge Process Design & Simulation of a Domestic Wastewater Influenced by Wine Production

Abstract

Urban wastewater can have different characteristics depending on its origin and the industrial component. When focusing on wastewater influenced by wine industry, these characteristics are very significant for the design of a Wastewater Treatment Plant. This wastewater gathers a high quantity of organic matter during the harvest of the grapes season (vintage). In this study are evaluated and solved the main difficulties in the design of an Activated Sludge (AS) process from an urban WWTP in a winery region in Aragón, Spain. After a research, it has been concluded that the main challenges for the water treatment of urban winery regions like this are the high flowrate and high organic matter load, especially in the shape of readily biodegradable organic matter (mainly organic acids, sugars and alcohols). Another difficulty found has been the lack of nutrients needed for the microorganisms to biologically treat the organic matter in this wastewater. After the research has been done, the peaks of organic matter have been solved by designing the AS process with the influent parameters from the month of October as a worst-case scenario. Designing the plant to meet parameters in this scenario ensures that the system will overcome the increase of organic load provoked during vintage period. The AS process will also perform properly during the rest of the year. Secondly, through the influent analysis, the nitrogen scarcity challenge has been analyzed. It has been concluded that the minimum BOD5 ratio of BOD5:TKN:TP = 100:5:1 has not been achieved during some parts of the year. Because of this, the minimum nitrogen and phosphorous ratio in the Activated Sludge process has been increased into BOD5:TKN:TP = 100:7:1.2 to calculate the ammonia and orthophosphates addition that is needed in every month of the year. Then, a preliminary design of the AS process has been performed according the ASM1 model and using the worst-case scenario influent. This model can give an idea of the dimensions of the system, which is adjusted and checked later through simulation. However, this model requires a COD fractioning, and, in this case, it hugely varies from a standard one because the readily biodegradable COD fraction (like organic acids, sugars and alcohols) takes a high percentage. COD fractioning from Beck and collaborators work (2005 (1)) has been used as a reference, since it is also devoted to urban wastewater from a winery region. This fractioning suits better because it lowers the recalcitrant fraction of the COD in the influent and increases the biodegradable one.After the ASM1 calculation, the design volume of the aerobic reactor has been set at 248.8 m3 and its Solid Retention Time has been stablished at 5 days. The design inlet flowrate has been 1.5 times higher than the flowrate of the worst-case scenario influent. In the last part of the report, LynxASM1 software has been used to perform the simulation of the AS system and it takes the ASM1 values obtained in the preliminary design. A worst-case scenario and a yearly simulation have been made to assure that the effluent meets the legislation standards of a WWTP with no nitrogen release limitations.