Alan Howard

Modelling algal growth and transport in rivers: a comparison of time series analysis, dynamic mass balance and neural network techniques

Algae present considerable problems for river qualitymanagers and water suppliers and methods to predicttheir behaviour, growth and transport can assist inoperational management. Alternative techniques existfor predicting algal response and three approacheshave been compared and applied to data from six sitesalong the River Thames. These techniques include timeseries analysis, dynamic mass balance and growthequations and neural network approaches. It is shownthat neural network techniques offer a new approachrequiring less intuitive knowledge but predictivecapability is not improved greatly compared to otherapproaches. Neural networks enable models to bedeveloped along all six reaches of the RiverThames.

Effect of earthworm Eisenia fetida and wetland plants on nitrification and denitrification potentials in vertical flow constructed wetland

The response of nitrification potentials, denitrification potentials, and N removal efficiency to the introduction of earthworms and wetland plants in a vertical flow constructed wetland system was investigated. Addition of earthworms increased nitrification and denitrification potentials of substrate in non-vegetated constructed wetland by 236% and 8%, respectively; it increased nitrification and denitrification potentials in rhizosphere in vegetated constructed wetland (Phragmites austrail, Typha augustifolia and Canna indica), 105% and 5%, 187% and 12%, and 268% and 15% respectively. Denitrification potentials in rhizosphere of three wetland plants were not significantly different, but nitrification potentials in rhizosphere followed the order of C. indica>T. augustifolia>P. australis when addition of earthworms into constructed wetland. Addition of earthworms to the vegetated constructed significantly increased the total number of bacteria and fungi of substrates (P<0.05). The total number of bacteria was significantly correlated with nitrification potentials (r=913, P<0.01) and denitrification potentials (r=840, P<0.01), respectively. The N concentration of stems and leaves of C. indica were significantly higher in the constructed wetland with earthworms (P<0.05). Earthworms had greater impact on nitrification potentials than denitrification potentials. The removal efficiency of N was improved via stimulated nitrification potentials by earthworms and higher N uptake by wetland plants.

Statistical analysis of algal and water quality data

Data on cyanobacteria (blue-green algae) are generallycollected on a reactive basis, frequently in responseto bloom events. Such data presents a biased andincomplete snapshot of water quality. This paper looksat two typical data sets for UK waters showing thatwhile statistics may be used to describe the data theyare of limited use in forecasting. Suggestions ofappropriate tests for small and sparse data sets aremade.

Computer simulation modelling of buoyancy change in Microcystis

This paper reviews the development of the SCUM seriesof models and presents additional algorithms forcalculating surface radiation flux and growth. Thefirst SCUM models used data obtained by laboratoryinvestigation of Oscillatoria agardhii byKromkamp & Walsby (1990). However when applied toother species the models became unstable. More recentattempts have taken a different and more theoreticalapproach combining lake mixing and modellingcomponents of SCUM with a buoyancy routine (CYANARA)developed at the Institute of Freshwater Ecology.Model algorithms and sample model results are brieflydescribed. The growing importance of the World Wide Webin modelling is highlighted and explained.

Cyanobacterial (blue-green algal) blooms in the UK: a review of the current situation and potential management options

Nuisance cyanobacterial blooms are an important environmental problem. Toxins released by cyanobacteria can kill animals and cause illness in humans. The sustainable manage ment of toxic cyanobacteria would increase the conservation and amenity value of affected water bodies, and decrease on-site water treatment costs. Methods are available to kill or to prevent blooms but often the expense is prohibitive or the agent used is detrimental to desirable lake organisms. Different management strategies are therefore considered within the context of the current state of the UK water industry. Particular reference is made to the potential impact of the 1994 Ofwat-determined water-price increase limits on environmental policy and prioritization.

Simulating cyanobacterial growth in a lowland reservoir

MOTIVATION There has been a rise in the incidence of reported cyanobacterial bloom contamination, in England and Wales associated with freshwaters, over the past 10 years. These blooms can, under certain environmental conditions, produce toxins, which can be harmful to mammals. This paper presents a new model of cyanobacterial growth that incorporates the functionality of earlier buoyancy regulation models. The model includes algorithms allowing temperature-correction of the main process rates; loss of colonies; net chlorophyll-a production and changes in colony size. RESULTS The model was used to simulate cyanobacterial growth in a lowland impoundment in Southern England for 1994 and 1995. Predicted results were compared to observed data for the 2 consecutive years and the model results compare favourably with the observed data.

Purifying capability, enzyme activity, and nitrification potentials in December in integrated vertical flow constructed wetland with earthworms and different substrates

The response of purifying capability, enzyme activity, nitrification potentials, and total number of bacteria in the rhizosphere in December to wetland plants, substrates, and earthworms was investigated in integrated vertical flow constructed wetlands (IVFCW). The removal efficiency of total nitrogen (TN), NH4–N, chemical oxygen demand (COD), and total phosphorus (TP) was increased when earthworms were added into IVFCW. A significantly average removal efficiency of N in IVFCW that employed river sand as substrate and in IVFCW that employed a mixture of river sand and Qing sand as substrate was not found. However, the average removal efficiency of P was higher in IVFCW with a mixture of river sand and Qing sand as substrate than in IVFCW with river sand as substrate. Invertase activity in December was higher in IVFCW that used a mixture of river sand and Qing sand as substrate than in IVFCW which used only river sand as substrate. However, urease activity, nitrification potential, and total number of bacteria in December was higher in IVFCW that employed river sand as substrate than in IVFCW with a mixture of river sand and Qing sand as substrate. The addition of earthworms into the integrated vertical flow constructed wetland increased the above-ground biomass, enzyme activity (catalase, urease, and invertase), nitrification potentials, and total number of bacteria in December. The above-ground biomass of wetland plants was significantly positively correlated with urease and nitrification potentials (p < 0.01). The addition of earthworms into IVFCW increased enzyme activity and nitrification potentials in December, which resulted in improving purifying capability.