Biodegradability enhancement of purified terephthalic acid wastewater by coagulation-flocculation process as pretreatment.
In this work, the coagulation-flocculation process was used as pretreatment for purified terephthalic acid (PTA) wastewater with the objective of improving its overall biodegradability. PTA production generates wastewaters with toxicants p-xylene [1,4-dimethyl-benzene (C8H10)], a major raw material used in the production process, along with some of the intermediates, viz., p-toluic acid, benzoic acid, 4-carboxybenzaldehyde, phthalic acid and terephthalic acid. These compounds affect the bio-oxidation process of wastewater treatment; hence removal of these constituents is necessary, prior to conventional aerobic treatment. This paper addresses the application of coagulation-flocculation process using chemical coagulants, viz., aluminium sulphate (alum), polyaluminium chloride (PAC), ferrous sulphate and ferric chloride in combination with anionic polyelectrolyte. Polyaluminium chloride (PAC) in conjunction with lime and polyelectrolyte removed about 63.1% chemical oxygen demand (COD) and 45.2% biochemical oxygen demand (BOD) from PTA wastewater. Coagulation-flocculation process coupled with aerobic bio-oxidation treatment of PTA wastewater achieved, COD & BOD removals of 97.4% and 99.4%, respectively. The biodegradability enhancement evaluated in terms of the BOD5/COD ratio, increased from 0.45 to 0.67 at the optimum conditions. The results obtained from these studies indicate that the coagulation-flocculation process could be a suitable pretreatment method in reducing toxicity of PTA wastewater whilst enhancing biodegradability for aerobic biological treatment scheme.
National Environmental Engineering Research Institute, Nehru Marg, Nagpur 440020, India. m_karthik@neeri.res.in
Manikavasagam
M
Karthik
Nishant
N
Dafale
Pradyumna
P
Pathe
Tapas
T
Nandy
D000534:Alum Compounds / Q000737:chemistry; D000536:Aluminum Hydroxide / Q000737:chemistry; D001673:Biodegradation, Environmental; D019149:Bioreactors; D017610:Calcium Compounds / Q000737:chemistry; D002712:Chlorides; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D005427:Flocculation; D007220:Industrial Waste; D010087:Oxides / Q000737:chemistry; D010795:Phthalic Acids; D012722:Sewage; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
D000534:Alum Compounds; D017610:Calcium Compounds; D002712:Chlorides; D005290:Ferric Compounds; D005296:Ferrous Compounds; D007220:Industrial Waste; D010087:Oxides; D010795:Phthalic Acids; D012722:Sewage; D014874:Water Pollutants, Chemical; C016213:aluminum oxychloride; C041524:aluminum sulfate; C020748:ferrous sulfate; D000536:Aluminum Hydroxide; C011363:terephthalic acid; C016538:lime; C024555:ferric chloride