ABSTRACT
To lower energy consumption at a sewage treatment plant (STP), primary settling could be enhanced to direct more chemical oxygen demand (COD) to anaerobic digestion (AD) for increased biogas production and decreased aeration. Primary settling can be chemically enhanced by applying flocculation aids (FAs). FAs are refractory compounds that may affect all sludge treatment facilities. In this study the consequences are investigated of the application of FAs for chemically enhanced primary treatment (CEPT) on AD and subsequent dewatering of digested sludge in a conventional STP. It was found that FAs maintain their effect throughout all sludge processing facilities. With CEPT, more readily degradable solids were removed, resulting in a higher bio methane potential of the primary sludge. In AD, FAs lowered the viscosity; meanwhile an increased hydrolysis rate was observed. But FAs also partially irreversibly bound substrate in such way that it is not available for biological degradation anymore. In subsequent dewatering of digested sludge, a higher dry solids concentration was observed with CEPT. A computer simulation showed that in a conventional STP, CEPT would not be economically feasible. However, several benefits were discussed that can make CEPT an interesting option for future low COD/N-tolerant STPs with, for example, Anammox processes for N removal.
Subject(s)
Models, Theoretical , Sewage/chemistry , Waste Disposal, Fluid/methods , Water/chemistry , Anaerobiosis , Biofuels , Biological Oxygen Demand Analysis , Computer Simulation , Flocculation , Hydrolysis , Methane/metabolismABSTRACT
OBJECTIVE: To determine the effect of an antiprotozoic treatment on children with persistent abdominal pain and infection with Dientamoeba fragilis. DESIGN: Retrospective. METHOD: A total of 43 children with D. fragilis infection and persistent gastrointestinal complaints were included in the study. Of these 27 were treated with clioquinol and 16 with a nitroimidazole drug: metronidazole or tinidazole. The parasitological and clinical effects of the treatment were assessed. RESULTS: In 33 of the 43 (77%) children, no parasites were detected during follow-up with a triple faeces test: 22/27 following treatment with clioquinol and 11/16 following treatment with a nitroimidazole drug. In 27 of the 33 (82%) children with a negative follow-up result, gastrointestinal complaints were considerably less or had completely disappeared. In 2 of the 10 (20%) children in which D. fragilis had not disappeared in the follow-up period, the complaints were less or had disappeared. CONCLUSION: Effective treatment of D. fragilis infection in children with longstanding gastrointestinal complaints often resulted in a reduction or disappearance of the complaints.