The main objective of this paper was to examine the effect of the increase of organic loading rates (OLRs) (by reducing solid retention time, SRT, from 20 d to 5 d) in single-phase mesophilic anaerobic co-digestion of the sewage sludge with glycerine (1% v/v). Experimentally, it was confirmed that anaerobic co-digestion of these biowastes in steady-state conditions can achieve 85±5% of volatile fatty acid (VFA) reduction at SRTs between 20 and 9 d, with a methane production around 0.8 l CH4/l/d. Decreases in the SRT not only allow maintaining the sludge stability and the biogas production, but it also implies an increase in the waste that could be treated and lower cost. Therefore, mesophilic anaerobic co-digestion of sewage sludge and glycerin at SRT lower than 20 d is possible and preferable, due to it is more economical and environmental friendly.
Overactivity of phosphoribosylpyrophosphate synthetase (PRS) is an X chromosome-linked disorder of purine metabolism that is characterized by gout with uric acid overproduction and, in some families, neurodevelopmental impairment. We present the case of a 24-year-old Spanish woman with renal colic and hyperuricemia, which first manifested at age 11 years. Results of enzymatic and genetic studies supported the view that accelerated purine nucleotide and uric acid production in this woman resulted from defective allosteric regulation of PRS activity, which is, in turn, a consequence of a mutation in one of the patient's PRPS1 genes: an A-to-T substitution at nucleotide 578, encoding leucine for histidine at amino acid residue 192 of the mature PRS1 isoform. A previous example of disordered regulation of PRS1 activity in a family with a different substitution at the same amino acid residue strengthens this proposed mechanism. This is the first reported instance of PRS overactivity in which the propositus and sole affected family member is a woman.
The aim of this research is to enhance the mesophilic anaerobic digestion of municipal sludge from Cadiz-San Fernando (Spain) wastewater treatment plant at 20days hydraulic retention time (HRT). Two different strategies were tested to improve the process: co-digestion with the addition of soluble organic matter (1% v/v); and alkali sludge pre-treatment (NaOH) prior to co-digestion with glycerine (1% v/v). Methane production (MP) was substantially enhanced (from 0.36±0.09 L CH l/d to 0.85±0.16 L CH l/d), as was specific methane production (SMP) (from 0.20±0.05 L CH/g VS to 0.49±0.09 L CH/g VS) when glycerine was added. The addition of glycerine does not seem to affect sludge stability, the quality of the effluent in terms of pH and organic matter content, i.e. volatile fatty acids (VFA), soluble organic matter and total volatile solid, or process stability (VFA/Alkalinity ratio<0.4). Alkali pre-treatment prior to co-digestion resulted in a high increase in soluble organic loading rates (more than 20%) and acidification yield (more than 50%). At 20days HRT, however, it led to overload of the system and total destabilization of the mesophilic anaerobic co-digestion of sewage sludge and glycerine.
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