TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Process: The phthalic acid esters are comprised in sewage water, sludge, waste, refuse, or liquid or semi-liquid manure. At least one bacterial strain is comprised in an enriched or defined culture consisting of one or more isolated strains each capable of anaerobic degradation of phthalic acid esters as a pure isolate, where the defined culture comprises at least two isolated strains, particularly at least three isolated strains, more particularly at least four isolated strains. The enriched culture or the defined culture is supplied continuously or semi-continuously, where the enriched culture or the defined culture is grown aerobically prior to the addition. The enriched culture or the defined culture is added in an amount of at least 5-20% v/v and the added culture comprises from 102-109 bacteria/ml, more particularly 104-106 bacteria/ml. The bacterial isolates comprise bacteria selected from the genera Exiguobacterium or Bacillus, where the Exiguobacterium comprises E. gaetbuli strains and where the Bacillus comprises B. fusiformis or B. licheniformis strains. The E. gaetbuli strains are selected from DSMZ deposit number DSM 17351 or DSM deposit number DSM 17352. The B. fusiformis strain is DSM deposit number DSM 17353. The B. licheniformis strain is DSM deposit number DSM 17354. Isolating bacterial strains, which strains in pure form each are capable of anaerobic degradation of phthalic acid esters comprises enrichment for bacterial populations comprising bacterial strains capable of anaerobic degradation of phthalic acid esters as pure isolated strains, comprising cultivating natural bacterial isolates under anaerobic conditions in the presence of phthalic acid esters under CSTR conditions, and isolating single colonies on nutrient plates comprising phthalic acid esters. The natural isolates are provided from sewage water, sludge, waste, refuse, or liquid or semi-liquid manure. The CSTR is working under mesophilic anaerobic conditions for at least two hydraulic retention times. The phthalic acid esters comprises Di-Butyl-Phthalate (DBP), Di-Methyl-Phthalate (DMP), Di-EthylPhthalate (DEP), Di-Ethyl-Hexyl-Phthalate (DEHP), or Benzyl-Butyl-Phthalate (BBP) esters, where DBP is present in the range of 2-1000 mg/l in the reactor, particularly from 5-500 mg/l, more particularly from 10-300 mg/l, more particularly from 20-100 mg/l. Enrichment is performed for at least three hydraulic retention times, more particularly for at least four hydraulic retention times.Preferred Composition: The composition comprises at least one of the bacterial strains of (2).