Factors affecting pH change in alkaline waste water treatment - II: Carbon dioxide production

The carbon dioxide produced during biological oxidation of wastewater has a pronounced influence upon the pH that is attained in the activated sludge process. The quantity produced is proportional to the COD removed, its degree of oxidation and depends also on the oxidation level of the substrate. A discussion of metabolism is given with emphasis on the description of the oxygen consumption. The theory is compared with experimental results. A mass balance for the metabolism of model compounds is presented. This model is based on a thermodynamic consideration of the metabolic process and offers a basis for calculation of R. Q. values. Experimental evidence for the applicability of this model is presented. Experimental results for a sewage are applied in pH calculations

Trace analysis of phosphates in small aqueous volumes

The indirect determination of trace amounts of phosphate through estimation of the molybdenum in the phosphomolybdic acid complex has been improved. The lower limit of spectrophotometric determination is about 0.10 μg

Eutrophication: the role of sediments

Sediments of eutrophic lakes and ponds are rich in nutrients. A part of these accumulated nutrients is a potential source for the primary production in the water body. Before radical and expensive management measures are taken for the reduction of eutrophication, the contribution of the internal nutrient source to the sustainment of algal growth should be considered. This presentation aims at contributing to the insight with respect to phosphate because in The Netherlands a phosphate reduction program is under consideration. Successively the quantities and chemical characteristics of sediment phosphates, the magnitude and mechanisms of sediment release and the effects of reduction programs will be discussed. Part of the information presented has been acquired in a joint research program with the Environmental Section, Delta Service, Rijkswaterstaat

Biological assessment of effects of combined sewer overflows and storm water discharges.

The biological effects of discharges from combined or separated sewer systems are difficult to assess or to predict due to variahilities in concentrations, environmental conditions, morphometry, susceptibility of organisms, seasonality and other factors. A general discussion of the problem results in an outline of two approaches. The first approach is to generalize field experiences and some examples of results are presented and explained. Notably site-specific conditions are shown to overshadow effects of discharges for many of the biological components in the ecosystem. The secend approach is to perform toxicity tests which account for the temporal and spatial scales encountered in the field and for the relevant concentratien levels

Onderzoek naar de fosfaat uitwisseling tussen water en bodem in het Veluwemeer/Drontermeer

De Veluwerandmeren worden 's winters doorgespoeld met algen- en fosfaatarm polderwater. Dit resulteert in slechts een halvering van de vrij hoge algenconcentratie. Een belangrijke oorzaak hiervan is de nalevering van nutrienten vanuit het sediment. Via een vijfjarig onderzoek tracht men een beter inzicht te krijgen in de nalevering van fosfaa

Eutrofiering in Nederland.

Een derde onderzoek is uitgevoerd naar de eutrofieringstoestand in de (semi-) stagnante zoete oppervlaktewateren in ons land. Van 121 plassen en meren werden min of meer volledige gegevens ontvangen betreffende de fysische, chemische en biologische kenmerke