Low-temperature post-treatment of anaerobically treated-sewage in anaerobic filter with cationic-polymer addition.

The post-treatment of domestic sewage pretreated in a 6 m3 UASB was investigated in two high-rate anaerobic filter (AF) reactors operated in parallel. The difference between the two AF reactors was only the addition of cationic polymer to the second reactor (AF + P). The reactors were operated at low temperatures, ranged between 13 and 20 degrees C. The media in each AF reactor consisted of vertical sheets of reticulated-polyurethane foam (RPF) with knobs. The results demonstrated that the AF + P reactor (HRT = 3 h) with cationic polymer addition (2 mg/L) was an efficient system for post-treatment. The removal efficiencies for total, suspended, colloidal and dissolved COD were, respectively, 41, 86 and 76 and 12% in the AF + P reactor and they were, respectively, 80, 97, 77 and 66% in the UASB + (AF + P) system. The removal of total, suspended and colloidal COD in the UASB + (AF + P) system were significantly higher than those achieved in the UASB + AF system. As hardly any nutrient was removed in the UASB + (AF + P) system, the effluent after pathogen removal is a valuable product for irrigation and fertilisation to close the water and nutrients cycle.     

Model studies of erosion of natural barriers by a wave flow occurring as a result of landslides

Conclusion On the basis of data of model tests it can be stated that substantial deformation of the Usoi landslide will not be observed as a result of a surge overtopping it with the proposed parameters.Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 8, pp. 38–40, August, 1993.     

Optimal immigration, education and growth in the long run

The paper extends Manning's model on education and balanced growth to include labour immigration. Each immigration unit is assumed to consist of one skilled worker and some unskilled members. The optimal immigration policy which maximizes the per capita steady-state consumption of the host country is derived. We show that optimal immigration policy can reduce the steady-state skilled labour ratio. More interesting still, contrary to the widespread belief that immigration of skilled workers hurts local skilled workers, it is the unskilled local workers whose interests are threatened by optimal immigration policy.     

The Post-Issue Operating Performance of IPO Firms

This article investigates the change in operating performance of firms as they make the transition from private to public ownership. A significant decline in operating performance subsequent to the initial public offering (IPO) is found. Additionally, there is a significant positive relation between post-IPO operating performance and equity retention by the original entrepreneurs, but no relation between post-IPO operating performance and the level of initial underpricing. Post-issue declines in the market-to-book ratio, price/earnings ratio, and earnings per share are also documented.     

The distributional impact of unification and the 1992–93 recession on West German households

The 1992–93 recession in the western states of Germany has been attributed, in substantial measure, to the macroeconomic consequences of policies to finance unification. Studies of the costs of unification have not attempted to measure the burden of the recession. We estimate a dynamic, panel model of household incomes using data from the German Socio-Economic Panel (GSOEP) and use it to forecast what these incomes would have been in 1992–94 without a recession. Using a ratio of actual to forecast incomes, we compare the relative burden of the recession across households. Our findings suggest that western households below the median income bore the brunt of the combined impact of unification and the recession of 1992–93.
JEL classification: P3, D3, E3.     

Changes in Lake Ontario Total Phosphorus Concentrations 1976–1978

An apparent decrease in total phosphorus concentrations of approximately 4.l μgP/L has been reported recently for the spring values of 1977 and 1978 in Lake Ontario. Investigation of the loading reduction for this period independent of sedimentation factors can account for only 10% of the change. The results indicate that changes in the sedimentation rate of total phosphorus during this period offer an explanation for the majority of the change in concentration.