SummaryIn recent years considerable effort has been made in the Netherlands toward the development of a more sophisticated anaerobic treatment process, suitable for treating low strength wastes and for applications at liquid detention times of 3-4 hr. The efforts have resulted in a new type of upflow anaerobic sludge blanket (UASB) process, which in recent 6 m3 pilot-plant experiments has shown to be capable of handling organic space loads of 15-40 kg chemical oxygen demand (COD).m-Yday at 3-8 hr liquid detention times. In the first 200 m3 full-scale plant of the UASB concept, organic space loadings of up to 16 kg COD.~n-~/day could be treated satisfactorily at a detention time of 4 hr, using sugar beet waste as a feed. The main results obtained with the process in the laboratory as well as in 6 m3 pilot plant and 200 m3 full-scale experiments are presented and evaluated in this paper. Special attention is given to the main operating characteristics of the UASB reactor concept. Moreover, some preliminary results are presented of laboratory experiments concerning the use of the USB reactor concept for denitrification as well as for the acid formation step in anaerobic treatment. For both purposes the process looks feasible because very satisfactory results with respect to denitrification and acid formation can be achieved at very high hydraulic loads (12 day-') and high organic loading rates, i.e., 20 kg COD.~n-~/day in the denitrification and 60-80 kg C O D~r~/ d a y in the acid formation experiments.

No abstract

Smit Nymegen Magnetic Water treatment Systems (MWS), a business group of Smit Transformatoren BV, has recently developed a very efficient magnet for wastewater treatment. The magnet is the core element of a complete system to eliminate phosphates, heavy metals and other pollutants from wastewater. The system is based on the attachment of wastewater pollutants to a magnetic carrier material (magnetite) and a subsequent magnetic separation of the magnetite-pollutant conglomerates. After separation, the magnetite is recovered and re-used in the process. Main advantages of the magnetic separation process are:▸high elimination performance▸low power input for magnet operation▸compact process▸low space requirements▸no clogging because of open matrix structure. The development of the magnetic system has been focused on the phosphate-removal from effluents of sewage treatment plants. Being a tertiary treatment, magnetic phosphate removal can be applied after any type of sewage treatment and it does not interfere with the biological process. Pilot plant tests at various sewage works showed that magnetic separation reduces the total-phosphate concentration to values as low as 0.1-0.5 mg/l. The system will be demonstrated in two full-scale plants with a capacity of 300 m3/h and 600 m3/h, respectively. The costs of magnetic phosphate removal (Dfl. 12,- to 18,-) are competitive with those of other phosphate removal techniques. The development of the magnetic phosphate removal system is granted by the Dutch Ministries of Housing, Physical Planning and Environment, Economic Affairs and Transport and Public Works.

The influence of the manure concentration -in the range of 50 to 112.5 g total solids (TS)/litre -and the detention time -in the range of 40 to 10 days -upon the anaerobic digestion of piggery waste was investigated in laboratory experiments (1.5 -6 litres) and in pilot plant experiments (240 litres). In spite of high ammonia nitrogen concentrations a stable digestion could be achieved and maintained at all manure concentrations and all detention times applied, except when 112.5 g TS/ litre manure was added at a 10-day detention time (space load 8.1 kg volatile solids (VS) per m : ' per day.Although a stable digestion could be maintained up to a space load of 5.4 kg VS m~3 day-1 , the maximum space load at which a satisfactory reduction of ob jectionable manure odour was attained appeared to be about 3.6 kg VS m-3 day-1 .