ALBERT

Notes: For many decades, anaerobic digestion has been the most important technique of sewage sludge treatment at larger sewage-treatment works. Also, the low running costs of the process make it attractive for the treatment of strong industrial effluents. This paper reviews these advantages and discusses some disadvantages of the anaerobic treatment of industrial effluent. Operating and cost data are presented from Europe and from a detailed UK case study which supports the conclusion that anaerobic treatment will be the most cost-effective method of treatment of strong industrial effluents such as those from food and paper processing.

Notes: Laboratory work to improve the performance of storm-water separators, to meet new Environment Agency and European standards, is described in this paper. Residence-time distribution testing, using particulate and dissolved tracers, was used to study the hydraulics of separation. Oil-separation efficiency and head-loss analysis was used to develop additional final coalescing filters to reduce oil concentrations in the discharge to less than 5 mg/l. Field tests found lower oil, but greater metal, concentrations in runoff compared with those previously reported. It is suggested that improved separators could provide part of a multi-barrier design to improve the sustainability of removal of priority pollutants in highway runoff.

Notes: : The stability in water of a novel new chloramine agent, 3-chloro-4, 4-dimethyl-2-oxazolidinone (agent I), which is an excellent water disinfectant, has been compared to the stabilities of several other water disinfectants. The agents tested in addition to agent I included N-chlorosuccinimide, 2, 4-dichloro-5, 5-dimethylhydantoin, tichloroisocyanuric acid, calcium hypochlorite, commercial grade HTH, and household bleach. The total chlorine content of a water solution of agent I in a demand free environment remains constant over a period of at least eight weeks, while that for all of the other agents declines markedly over that time period. An explanation for these observations will be offered. Prior work in these laboratories concerning use of agent I as a disinfectant for lake water in a laboratory scale treatment plant had shown that agent I has considerable potential for use as an alternative to chlorine gas for water disinfection.

Notes: : A new insoluble N-halamine polymeric disinfectant material has been tested in a water filter application to determine (1) its tendencies to leach undesirable decomposition products, (2) its range of potential applicability, and (3) its regenerability. In flowing water tests, poly-1,3-dichloro-5-methyl-5-(4‘-vinylphenyl)hydantoin (Poly-I) leached only small amounts of total organic carbon, free and total chlorine, anions, and volatile organics such as trihalomethanes. Furthermore, Poly-I provided bactericidal efficacy over the pH range 4.5 to 9.5 and at temperatures as high as 37°C. Poly-I is deactivated by reducing agents such as sodium thiosulfate and by ethanol; following deactivation, it can be regenerated by exposure to flowing aqueous free chlorine. Poly-I appears suitable for use as a biocidal filter for small potable and recreational waters, for it is effective over a wide pH and temperature range and is readily regenerable. It would not be useful, however, for disinfection of large bodies of water such as in city treatment plants because of its cost and the large amount of the material that would be necessary.

Notes: A study to determine the effects of four stocking densities on growth and feed utilization of wild-caught black sea bass Centropristis striata was conducted in a pilot-scale recirculating tank system. The outdoor system consisted of 12 insulated fiberglass tanks (dia. = 1.85 m; vol. = 2.17 m3) supported by biological filters, UV sterilizers, and heat pumps. Subadults (N= 525; ×± SD = 249 ± 16.8 g) were stocked at densities of 4.6 fish/m3 (1.18 kg/m3), 16 fish/ m3 (3.91 kg/m3), 25.3 fish/m3 (6.83 kg/m3), and 36 fish/m3 (7.95 kg1m3), with three replicate tanks per treatment. Fish were grown under 35 ppt salinity, 21-25 C, and under ambient photoperiod conditions. A commercial flounder diet containing 50% protein and 12% lipid was hand-fed twice daily to satiation for 201 d.Mean (range) total ammonia-nitrogen, 0.61 (0-2.1) mg/L, nitrite-nitrogen, 0.77 (0.04-3.6) mg/L, and nitrate-nitrogen 40.1 (0-306) mg/L were significantly higher (P 〈 0.0001) in the 25.3 and 36 fish/m3 treatments than in the 4.6 and 16 fish/m3 treatments [0.19 (0.05-0.5), 0.1 (0.24-0.63), and 11.9 (1.3-82.2) mg/L, respectively]. However, there were no significant differences (P 〉 0.05) in growth (RGR = 196.8-243.1%; DWG = 2.55-2.83 g/d; and SGR = 0.55-0.61%/d), coefficient of variation of body weight (CwtV., = 0.24-0.25), condition factor (K = 2.2-2.4), feed consumption (FC = 1.45-1.65%/d), and feed conversion ratio (FCR = 1.45-1.52) among stocking densities. Final biomass densities on day 201 reached 3.48, 12.0, 21.1, and 27.2 kg/m3 at stocking densities of 4.6, 16, 25.3, and 36 fish/m3, respectively. Survival (83.8-99.1%) did not differ among treatments. Apparent net protein retention (ANPR) was significantly higher (P 〈 0.005) for fish stocked at the lower densities of 4.6 and 16 fish/m3 (22.5-23.7%) than for those stocked at 25.3 and 36 fish/m3 (21-20.1%). There were no significant differences (P 〉 0.05) in apparent net energy retention (ANER = 55.9-59.1 %) among stocking densities. Final whole body protein (15.3-16.3%) and lipid (23.1-26.4%) levels did not differ significantly (P 〉 0.05) among treatments.The results demonstrated that growth, survival, and feed utilization were not impaired under stocking densities ranging from 4.6-36 fish/m3 (3.48-27.2 kg/m3), despite a slight reduction in water quality at the higher densities. In addition, growth variation and final whole body protein and lipid levels were not influenced by these densities. The results suggest that black sea bass are tolerant of crowding and moderate variations in water quality during intensive culture in recirculating tank systems and that higher stocking densities are possible.

Notes: Abstract. This paper presents a critical survey of theories of migration, their welfare and policy implications and their empirical relevance. We also develop some extensions to the theory beginning with the Harris and Todaro (HT) model. In particular, the HT model is extended to examine risk averse behaviour within families where the migration of members of families serves to diversify risk. The welfare implications of the individual migration decision and government intervention in the form of employment subsidies are examined. Recent evidence on international migration is presented. It is shown that migration does not flow automatically in response to wage differentials. Characteristics of migrants and the process of self-selection are found to be important determinants of the rate of migration.

Notes: Direct water recycling has become an important part of water conservation in the dry areas of the world and is now being seriously considered for the UK. This paper reviews current demands in large buildings and balances these against non-potable re-use. Work is also described on the development of a sustainable low running cost treatment unit. Results are presented from a 751/day prototype biological process operated with a synthetic sewage, which achieved a near potable standard at a cost of 25 p/m3. The design, performance and costings of a 40 ‘population equivalent’demonstration unit are also given.

Notes: We characterised the spatial structure of soil microbial communities in an unimproved grazed upland grassland in the Scottish Borders. A range of soil chemical parameters, cultivable microbes, protozoa, nematodes, phospholipid fatty acid (PLFA) profiles, community-level physiological profiles (CLPP), intra-radical arbuscular mycorrhizal community structure, and eubacterial, actinomycete, pseudomonad and ammonia-oxidiser 16S rRNA gene profiles, assessed by denaturing gradient gel electrophoresis (DGGE) were quantified. The botanical composition of the vegetation associated with each soil sample was also determined. Geostatistical analysis of the data revealed a gamut of spatial dependency with diverse semivariograms being apparent, ranging from pure nugget, linear and non-linear forms. Spatial autocorrelation generally accounted for 40–60% of the total variance of those properties where such autocorrelation was apparent, but accounted for 97% in the case of nitrate-N. Geostatistical ranges extending from approximately 0.6–6 m were detected, dispersed throughout both chemical and biological properties. CLPP data tended to be associated with ranges greater than 4.5 m. There was no relationship between physical distance in the field and genetic similarity based on DGGE profiles. However, analysis of samples taken as close as 1 cm apart within a subset of cores suggested some spatial dependency in community DNA-DGGE parameters below an 8 cm scale. Spatial correlation between the properties was generally weak, with some exceptions such as between microbial biomass C and total N and C. There was evidence for scale-dependence in the relationships between properties. PLFA and CLPP profiling showed some association with vegetation composition, but DGGE profiling did not. There was considerably stronger association between notional sheep urine patches, denoted by soil nutrient status, and many of the properties. These data demonstrate extreme spatial variation in community-level microbiological properties in upland grasslands, and that despite considerable numeric ranges in the majority of properties, overarching controlling factors were not apparent.