Low-strength wastewater treatment by a multistage anaerobic filter packed with waste tyre rubber

A laboratory-scale fixed bed reactor of five stages running serially, with free working volume of 61, and up- and down-flow successively, was used for treating low-strength wastewater. With this design was sought a greater pa ssage of the liquid over the support of the biofilm, constituted of waste t yre rubber (disposable material). The objective was to demonstrate the effi ciency of this system to purify domestic wastewaters of 1000 mg COD/1 of hi gh microbiological load. Different hydraulic retention times (HRTs), 4, 2 a nd 1 days, and 12 and 8 h, were studied. For HRTs from 4 to 1 days, the eff iciency of organic matter removal in the first stage reached the maximum va lue, and was maintained after passing the liquid through the rest of the st ages. For 12 and 8 h, a greater variation of the removal efficiency was obs erved among all the stages; fundamentally, in the first three. BOD removal efficiencies greater than 60% were achieved: acceptable values for this pri mary treatment. The variations during the process in GOD, total and suspend ed solids, minerals and volatiles, volatile fatty acids, alkalinity, ammoni a nitrogen and phosphorus, and faecal coliforms were determined. Good resul ts were achieved for short HRTs, therefore, it would be possible to try a g reater wastewater flow. The total and faecal coliform removal efficiencies varied from 99% for 4 days to 70% for 8 h HRT. This was considered acceptab le taking into account the high microorganisms concentration of the wastewa ter used (1.4 x 10(10) MPN/100 ml). (C) 1999 Elsevier Science Ltd. All righ ts reserved.