CO COMPOSTING OF FATS FROM THE DAIRY INDUSTRY

C.A: MARTÍN; LOVATO MARÍA; FIASCONARO, MARÍA LAURA

S. Margherita di Pula, Cagliari

Simposio; XV International Waste Management Symposium; 2015

International Waste Management

The State of Santa Fe produces almost 50 % of the milk of Argentina. Dairy industries are involved in the manufacturing of several products such as fluid milk, cheese, cream, etc. Dairy industries produce nearly thousands of liters of wastewater per day and represent an important pollution problem in the region. Dairy wastewater is characterized by high biological-oxygen demand (BOD) and chemical oxygen demand (COD) concentrations, and generally contains fats, nutrients, lactose, as well as detergents and sanitizing agents. Dairy wastewaters are generally treated using biological methods such as activated sludge processes, aerated lagoons, trickling filters, sequencing batch reactors (SBR), anaerobic sludge blanket (UASB) reactors, anaerobic filters, etc. (1). Common techniques for treating dairy industry wastewaters include grease traps, oil water separators for separation of floatable solids, equalization of flow, and clarifiers to remove SS. Over the last ten years, there has been an increasing interest on the use of dissolved air flotation equipments (DAF) for clarifying solids from biological systems in lieu of traditional gravity clarifiers (2). DAF is a relatively simple technology that uses fine air bubbles to separate liquid particles and light suspended solids (mostly fats) from wastewater. These particles and solids are floated via the bubbles to the surface of a flotation cell for removal from a wastewater stream. The main objective of this work was to study the viability of the composting of DAFW with different co substrates and determine the effect of different proportions of DAFW on composting efficiency and final compost quality. These results would contribute to optimize composting performance and the production of compost with different characteristics and end use.Different amount of DAFW (70, 60, 50, 30, 0 % w/w) from a local dairy industry were added to a mixture of wood chips and green grass as bulking agent and C/N source. The composting process was performed in open air windrows (100 L ca.) with periodical turnovers. Laboratory analyses included moisture, temperature, particle size, electrical conductivity and pH Nitrogen (Kjeldahl), heavy metals, K, P, Mg, Ca, Na (Atomic Absorption Spectrometry), ash, organic matter and grease Furthermore, phytotoxicity of the compost was studied using germination test (relative seed germination, RSG) and seed bioassay (Capsicum annum L) during the compost stabilization along 240 days. An additional blank run without DAFW was made to determine the intrinsic effect of the addition of the co substrate. From the analysis of the whole data is possible to conclude the feasibility of the DAFW valuation using composting process and the improvement of quality of the obtained final product.