Anaerobic co-digestion of sewage sludge and primary clarifier skimmings for increased biogas production.

The objective of the study was to identify the impact of co-digesting clarifier skimmings on the overall methane generation from the treatment plant and additional energy value of the increased methane production. Biogas production from co-digesting clarifier skimmings and sewage sludge in pilot-scale fed-batch mesophilic anaerobic digesters has been evaluated. The digester was fed with increasing quantities of clarifier skimmings loads: 1.5, 2.6, 3.5 and 7.0 g COD equivalent/(L·d) (COD: chemical oxygen demand). Average volatile solids reduction of 65% was achieved in the scum-fed digester, compared with 51% in the control digester. Average 69% COD removal was achieved at highest scum loading (7 g COD eq/(L·d)) with approximate methane yield of 250 L CH(4)/kg COD fed (4 ft(3)/lb COD fed). The results show that scum as co-substrate in anaerobic digestion systems improves biogas yields while a 29% increase in specific CH(4) yield could be achieved when scum load is 7 g COD eq/(L·d). Based on the pilot-scale study results and full-scale data from South East Water Pollution Control Plant and Northeast Water Pollution Control Plant the expected annual energy recovery would be approximately 1.7 billion BTUs or nearly 0.5 million kWh.

Acetoclastic methanogens in an anaerobic digester could be susceptible to trace metal supplementation.

The objective of this study was to investigate the effects of nutrient supplementation on anaerobic biomass. While many studies emphasized the importance of supplementing trace metals such as iron, cobalt, and nickel for maximum methanogenic activity, there is no evidence whether such supplements, even at relatively low concentration, could perturb anaerobic biomass. Effects of supplementing nutrients, including yeast extract, on anaerobic biomass from two full-scale mesophilic digesters, operating under different conditions, at the North East Water Pollution Control Plant in Philadelphia, Pennsylvania, USA, were assessed using biochemical methane potential tests. The results show that acetoclastic methanogens from a recently cleaned digester was not stimulated by nutrient supplementation at relatively low concentrations and a slight perturbation was observed when supplementation was at a relatively high concentration. Furthermore, greater degree of susceptibility to the trace metal supplementation was observed for biomass from another digester that had not been cleaned for over 10 years, thus it had reduced active volume due to grit accumulation. For instance, supplementation of 200 mg/L of iron as FeCl(2)·4H(2)O to the biomass from the reduced-active-volume digester caused 17% reduction in CH(4) production, as compared to a control which did not receive any supplements, while the same concentration had no effect on the biomass from full-active-volume digester. Results strongly suggest that acetoclastic methanogens stressed due to reduced hydraulic/solids retention time may be susceptible to trace metal addition. Therefore, trace metal supplementation for anaerobic digesters should be considered on a case by case basis.

Measurement of angular distributions of Drell-Yan dimuons in p+p interactions at 800 GeV/c.

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a hydrogen target. The polar and azimuthal angular distribution parameters have been extracted over the kinematic range 4.5

Measurement of Upsilon production for p + p and p + d interactions at 800 GeV/c.

We report a high statistics measurement of Upsilon production with an 800 GeV/c proton beam on hydrogen and deuterium targets. The dominance of the gluon-gluon fusion process for Upsilon production at this energy implies that the cross section ratio, sigma(p+d-->Upsilon)/2sigma(p+p-->Upsilon), is sensitive to the gluon content in the neutron relative to that in the proton. Over the kinematic region 0

Measurement of angular distributions of Drell-Yan dimuons in p+d interactions at 800 GeV/c.

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a deuterium target. The muon angular distributions in the dilepton rest frame have been measured over the kinematic range 4.5

J/psi polarization in 800-GeV p-Cu interactions.

We present measurements of the polarization of the J/psi produced in 800-GeV proton interactions with a copper target. Polarization of the J/psi is sensitive to the ccmacr; production and hadronization processes. A longitudinal polarization is observed at large x(F), while at small x(F) the state is produced essentially unpolarized or slightly transversely polarized. No significant variation of the polarization is observed versus p(T).

Observation of polarization in bottomonium production at square root of s = 38.8 GeV.

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.