Evaluation of flocculation and dissolved air flotation as an advanced wastewater treatment.
A bench scale study was carried out in order to evaluate the applicability of dissolved air flotation (DAF) as an advanced treatment for effluents from three different domestic wastewater treatment processes, namely: (i) a tertiary activated sludge plant; (ii) an upflow sludge blanket anaerobic reactor (UASB); and (iii) a high-rate stabilization pond.
DISSOLVED AIR FLOTATION (DAF) FOR PRIMARY AND TERTIARY TREATMENT OF MUNICIPAL WASTEWATERS
ABSTRACT Tertiary treatment of municipal wastewater by dissolved air flotation was studied on a pilot‐scale. The effects of coagulant dose, flocculation pattern, dispersion water recycle ratio and hydraulic surface load on process performance were evaluated. The treatment of primary effluents by dissolved air flotation was investigated to assess the suitability of this process for the treatment of heavily polluted effluents and wastewater treatment plant by‐passes. The tertiary dissolved air flotation process typically achieved 90–99 % reductions in the numbers of enteric microbes (total coliforms, enterococci and F‐RNA coliphages). The average reductions of total phosphorus and chemical oxygen demand were 55–81 % and 28–39 %, respectively. Increasing the polyaluminium chloride coagulant dose from 2 to 10 mgAl3+ l−1 and the dispersion water recycle ratio from 11 to 22 % improved the efficiency of the process. Changes in the flocculation conditions (range of G‐values 10–55 s−1; retention time 4–8 min) and hydraulic surface load (5 or 10 m h−1) did not clearly affect the process efficiency. The dissolved air flotation process decreased the numbers of enteric microbes and reduced total phosphorus, chemical oxygen demand and suspended solids from the primary treated wastewaters on average by 98–99.8%, 90 %, 47% and 77 %, respectively. The dissolved air flotation process was demonstrated to be a suitable method for efficient tertiary treatment of wastewaters, as well as for the elimination of peak pollution loads or by‐pass wastewaters during the treatment plant overloading situations.
The camel in Somali oral traditions
The relationship between the camel and the Somali people has traditionally been reflected in Somalia's oral literary forms: Poems, proverbs, work songs, metaphores and tales of wisdom. The author h ...