Computer simulation of the coagulation of suspended solids — The applicability of the Müller–Smoluchowski theory

The results of studies carried out using a computer programme simulating the coagulation of suspensions containing spherical sol particles and spherical coagulant particles are reported.The influence of the degree of dispersion of the system on the coagulation reaction kinetics was investigated. The obtained results of kinetic studies were tested in the light of classical Müller–Smoluchowski equations. The influence of the physical properties of the coagulant,such as size, density and mass, on the coagulation rate was tested. It was found that within the range described in this paper, the rate of the simulated coagulation process fulfils both the kinetic equation of a first-order reaction, and the kinetic equation of a second-order reaction.Within the tested range, a significant influence of the mass and size of the coagulant on the coagulation rate was ascertained. The kinetic Müller–Smoluchowski dependence is fulfilled in a broader range of the degree of dispersion, when the coagulant particle mass and the sol particle mass are equal. When the particle mass increases with an increase in the particle radius, the coagulation rate increases faster that it would result from the Müller's dependence.     

PSII activity and pigment dynamics of Symbiodinium in two Indo-Pacific corals exposed to short-term high-light stress

This study examined the capacity for photoprotection and repair of photo-inactivated photosystem II in the same Symbiodinium clade associated with two coexisting coral species during high-light stress in order to test for the modulation of the symbiont’s photobiological response by the coral host. After 4 days exposure to in situ irradiance, symbionts of the bleaching-sensitive Pocillopora damicornis showed rapid synthesis of photoprotective pigments (by 44 %) and strongly enhanced rates of xanthophyll cycling (by 446 %) while being insufficient to prevent photoinhibition (sustained loss in F _v/F _m at night) and loss of symbionts after 4 days. By contrast, Pavona decussata showed no significant changes in F _v/F _m, symbiont density or xanthophyll cycling. Given the association with the same Symbiodinium clade in both coral species, our findings suggest that symbionts in the two species examined may experience different in hospite light conditions as a result of different biometric properties of the coral host.     

Evaluation of Solvita compost stability and maturity tests for assessment of quality of end-products from mixed latrine style compost toilets

It is challenging and expensive to monitor and test decentralized composting toilet systems, yet critical to prevent the mismanagement of potentially harmful and pathogenic end-product. Recent studies indicate that mixed latrine composting toilets can be inhibited by high ammonia content, a product of urea hydrolysis. Urine-diverting vermicomposting toilets are better able to accomplish the goals of remote site human waste management by facilitating the consumption of fecal matter by earthworms, which are highly sensitive to ammonia. The reliability of Solvita® compost stability and maturity tests were evaluated as a means of determining feedstock suitability for vermicomposting (ammonia) and end-product stability/completeness (carbon dioxide). A significant linear regression between Solvita® ammonia and free ammonia gas was found. Solvita® ranking of maturity did not correspond to ranking assigned by ammonium:nitrate standards. Solvita® ammonia values 4 and 5 contained ammonia levels below earthworm toxicity limits in 80% and 100% of samples respectively indicative of their use in evaluating feedstock suitability for vermicomposting. Solvita® stability tests did not correlate with carbon dioxide evolution tests nor ranking of stability by the same test, presumably due to in situ inhibition of decomposition and microbial respiration by ammonia which were reported by the Solvita® CO₂ test as having high stability values.     

On‐target deposition of aerially applied deltamethrin

Abstract

The mean amount of deltamethrin deposited on natural substrates (i.e., soil and vegetation) in three experiments was 63, 73, and 76% of applied. Composite samples taken from 16 sites/replicate gave representative and repeatable measures of deposition. The use of Teflon discs as artificial targets to measure aerial deposition was investigated. The discs had only 34–71% mean trapping efficiency for the spray droplets. Deposition was quite variable among different sampling sites within a field (CV=73–83%). Much of this variation was caused by irregular overlapping of spray swaths.     

An integrated appraisal of energy recovery options in the United Kingdom using solid recovered fuel derived from municipal solid waste

This paper reports an integrated appraisal of options for utilising solid recovered fuels (SRF) (derived from municipal solid waste, MSW) in energy intensive industries within the United Kingdom (UK). Four potential co-combustion scenarios have been identified following discussions with industry stakeholders. These scenarios have been evaluated using (a) an existing energy and mass flow framework model, (b) a semi-quantitative risk analysis, (c) an environmental assessment and (d) a financial assessment. A summary of results from these evaluations for the four different scenarios is presented. For the given ranges of assumptions; SRF co-combustion with coal in cement kilns was found to be the optimal scenario followed by co-combustion of SRF in coal-fired power plants. The biogenic fraction in SRF (ca. 70%) reduces greenhouse gas (GHG) emissions significantly (～2500 g CO₂ eqvt./kg DS SRF in co-fired cement kilns and ～1500 g CO₂ eqvt./kg DS SRF in co-fired power plants). Potential reductions in electricity or heat production occurred through using a lower calorific value (CV) fuel. This could be compensated for by savings in fuel costs (from SRF having a gate fee) and grants aimed at reducing GHG emission to encourage the use of fuels with high biomass fractions. Total revenues generated from coal-fired power plants appear to be the highest (£95/t SRF) from the four scenarios. However overall, cement kilns appear to be the best option due to the low technological risks, environmental emissions and fuel cost. Additionally, cement kiln operators have good experience of handling waste derived fuels. The scenarios involving co-combustion of SRF with MSW and biomass were less favourable due to higher environmental risks and technical issues.     

A mechanism for horizontal zooplankton transport by vertical migration in tidal currents

A mechanism is proposed by which net horizontal transport can be induced in an organism which migrates vertically in a purely oscillatory, vertically sheared tidal current. The mechanism contains two elements. First, for all reasonable tidal current profiles, net horizontal transport is induced in any organism which migrates vertically with a period which is an exact multiple of the tidal period. (This is the basis for the widelyknown process of selective tidal stream transport where the migration period and the tidal period are exactly equal.) The second element in the new mechanism is the observation that diel migration, the most common form of vertical migration, has a period of 24 h and is therefore an exact multiple of the principal solar semi-diurnal tidal constituent (S2) which has a period of 12 h. This relation between the S2 and diel migration periods stems from the fact that both phenomena are independently locked to the solar cycle. Diel vertical migration can therefore interact with the S2 tidal current constituent to induce longterm horizontal transport in migrating organisms. For reasonable tidal current and vertical migration parameters it is found that horizontal transport rates of 4 km d^–1 are possible. The direction of net transport depends upon the phase of the S2 tidal current relative to local noon. The hypothesis is therefore proposed that geographical variation in S2 phase is a factor responsible for creating regions which are either retention-favorable or otherwise for diel-migrating marine organisms.