Alternatives for Soil Disposal of Excess Activated Sludge from the Industrial Waste Treatment Plant at Companhia Alcoolquímica Nacional

Abstract

The industrial wastewater treatment plant at Companhia Alcoolquímica Nacional in Cabo, PE, with operation start-up expected in the second semester of 1986, is composed of: hydraulic and organic load equalization, pH correction and an extended aeration activated sludge plant. For the purpose of disposing of 995 kg solids/day (dry solids) excess biological sludge, a study was undertaken with the intention of using land disposal, after preliminary comparison with other conventional methods. For the disposal of this sludge, which was thickened to 4% suspended solids by dissolved air flotation, two alternatives were proposed:Land disposal by subsurface injection (10 t dry solids per hectare per pass every 60 days).Land disposal by the trench fill system, in an available area of 3 ha. In the case of subsurface injection, grass would be used for the vegetation cover. In the case of the trench fill system, corn and/or manioc tillages would be used. The crops obtained from these tillages may be used for animal feed. After analysing several factors, such as available area, implementation and operating costs, handling facilities and climatic conditions, the trench fill disposal system was chosen. This has the following features:(a)Trenches with 50 cm base, distance from one trench to the next of 100 cm, (i.e., 10 trenches per 15 m), 35 cm depth;(b)0.3% trench slopes;(c)Conveyance of thickened sludge through a main chute with 0.1% slope;(d)120 t dry solids/ha/yr application, on a 3 ha total area;(e)Addition accomplished at a rate of 1/5 ha/day (5 days per week), the whole cycle being completed every three weeks.

Tratamento anaeróbio de vinhaça em reator UASB operado em temperatura na faixa termofílica (55ºC) e submetido ao aumento progressivo de carga orgânica

“…Dois condutos de vidro foram introduzidos na parte superior do gasômetro; um permitiu o deslocamento da solução para o exterior à medida que ocorria a produção de gás que foi coletado em um recipiente graduado; outro condutor, que não tinha contato com a solução, conduzia o gás produzido a este recipiente e armazenado no headspace do reator, similar ao descrito por FERNANDES Jr. (1995). A tabela 07 a seguir demonstra a separação das fases no tratamento da vinhaça relacionando concentrações, cargas orgânicas volumétricas, TDH, problemas operacionais ou instabilidades.…”