M. A. Connor

Multivariate data analysis of key pollutants in sewage samples: a case study

Waste water treatment plants often need detailed information about the sources and levels of pollutants in sewage in order to maintain stable process conditions and to achieve permitted levels for hazardous compounds in their effluents. A high content of pollutants is usually traceable to industrial inputs. In this study the main objective was to study the factors affecting the composition of sewage of domestic origin. Sixty-five domestic sewage samples collected during 9 months at eight different sites in Melbourne, Australia, were analyzed for 83 chemical variables. The data set also included two samples of combined domestic/industrial wastewaters, seven samples from waste water treatment plant influent streams and five domestic water supply samples. The data was studied with multivariate data analysis methods; principal component analysis (PCA) and partial least squares (PLS). With multivariate methods, effects of lifestyle of residents, day of the week and sampling time or weather on the pollutant levels could be determined.

Nitrogen removal from wastewater treatment lagoons

In an attempt to gain a better understanding of ammonia and nitrogen removal processes in multi-pond wastewater treatment lagoons, an analysis was carried out of data obtained during regular monitoring of Lagoon 115E at the Western Treatment Plant in Melbourne. To do this, a contour plot approach was developed that enables the data to be displayed as a function of pond number and date. Superimposition of contour plots for different parameters enabled the dependence of ammonia and nitrogen removal rates on various lagoon characteristics to be readily assessed. The importance of nitrification as an ammonia removal mechanism was confirmed. Temperature, dissolved oxygen concentration and algal concentration all had a significant influence on whether or not sizeable nitrifier populations developed and persisted in lagoon waters. The analysis made it evident that a better understanding of microbial, chemical and physical processes in lagoons is needed before their nitrogen removal capabilities can be predicted with confidence.

Water treatment design for site remediation at Casey Station, Antarctica: site characterisation and particle separation

Abstract Antarctica is commonly regarded as a pristine environment, but more than a century of human activity has left an extensive legacy of abandoned waste. The Australian Antarctic Division (AAD) has identified the Thala Valley Tip near Casey Station as a high priority site for remediation. However, there are difficulties with regards to contaminant dispersal by melt-water during extraction of wastes and contaminated sediments. Characterisation of contaminants and other site-specific conditions is crucial when designing appropriate water treatment technologies. Analysis of contaminants in Tip waters has found that heavy metals are predominantly associated with particles, although there are substantial concentrations of dissolved metals as well. The combined chemical and physical analyses indicate that the main heavy metals transport mechanism as adsorption to the surface of particles, which are then carried by surface and sub-surface runoff. To remove heavy metals from contaminated water during the proposed clean-up of Thala Valley a multistage treatment process will be required. The first stage is one of particle removal. A plant has been designed that uses coagulation and flocculation chemicals to produce a fast settling, flocculated suspension. The flocculated particles will settle out in an inclined settler, producing a clarified effluent and a concentrated sludge. The clarified water will then be passed through a 1-μm filter to remove any residual particles prior to dissolved heavy metals removal either by ion exchange or distillation. Future research will focus on optimisation of the water treatment system, especially coagulation and flocculation processes and the impact of pH, turbidity, low temperature and water chemistry on flocculation efficiency.

Wastewater treatment in Antarctica

Since the exploration of Antarctica began, procedures for dealing with human wastes have changed considerably. The establishment of research stations made it necessary to provide for sewage disposal. However, the introduction of advanced wastewater treatment processes has been driven largely by an intensifying concern to protect the Antarctic environment. A key step was the adoption by Antarctic Treaty nations of the so-called Madrid Protocol, in which minimum standards for sewage treatment and disposal are prescribed. The provisions of this protocol are not particularly onerous and some countries have elected to go beyond them, and to treat Antarctic research station wastewater as they would at home. Transferring treatment technologies to Antarctica is not simple because the remoteness, isolation, weather and other local conditions impose a variety of unusual constraints on plant design. The evolution of advanced treatment plant designs is examined. Most countries have opted for biofilm-based processes, with Rotating Biological Contactors (RBC) favoured initially while more recently contact aeration systems have been preferred. Sludges are now generally repatriated, with a diversity of sludge dewatering techniques being used. The evolution of treatment process designs is expected to continue, with growing use, especially at inland stations, of sophisticated processes such as membrane technologies and thermally efficient evaporative techniques.

A method of comparing the performance of air classifiers

Abstract An experimental and theoretical comparison is made between a “zig-zag” air classifier and a straight-duct type. Equations are presented, based on a model already published, for the effective diffusivity of spherical particles in a turbulent air stream. The diffusivity reflects the tendency of particle species to diffuse the “wrong” way, that is to be lost. The lower the value of the effective diffusivity, the more efficient is the classifier. It is shown that the effective diffusivities are lower in the “zig-zag” classifier than in the straight-duct type especially for the “light” species. It is also shown that the effective diffusivities of “light” and “heavy” species are similar in value, indicating the mid-point as the optimum feed location. It is also shown that, at high values of the air/solids ratio, the effective diffusivities can be easily estimated by using mixtures of regular particles, or simply by feeding a single species of spherical particles. The effective diffusivities were found to be independent of the number of stages in the “zig-zag” classifier, and took values similar to freestream diffusion values. The method described represents a very simple test which could be applied to proposed designs of air classifier to enable a comparison of effectiveness to be made.

Effect of recirculation rate on methane production and SEBAR system performance using active stage digester

A project was undertaken to examine the feasibility of treating organic wastes from Thai fruit and vegetable markets using the sequential batch anaerobic digester (SEBAR) approach. A key feature of the SEBAR system is the regular interchanging, or recirculation, of portions of leachate between each freshly filled digester and a support digester to which it is coupled until it is ready to operate independently. Leachate transfer from this support digester to the fresh waste digester provides additional alkalinity to help counteract the effects of early high acid release rates; it also helps build a balanced microbial population in the fresh waste digester. To optimize the leachate recirculation process, the effect of varying the quantities of leachate interchanged between freshly filled waste digesters and the still highly active support digesters to which they were coupled was studied. It was found that increasing the recirculation rate accelerated the onset of both waste degradation and methane production. The increasing of recirculation rate from 10% to 20% and 10% to 30% could reduce the SEBAR cycle period by approximately 7% and 22% without significant reduction in the amount of methane obtained from the systems. The methane yields were 0.0063, 0.0068 and 0.0077 l g—1 VS added in the NEW digester per day using leachate recirculation rates of 10%, 20% and 30%, respectively. This finding has potentially important practical and economic implications for those using the SEBAR system to add value to market waste.

INTEGRATING CONSERVATION AND WASTEWATER TREATMENT

Abstract The continuing growth of the Earths human population is causing serious problems for both people and wildlife. Among the more important of the problems facing human communities are lack of access to fresh water supplies and inadequate sanitation. For wildlife the increasing pressures caused by expanding human populations are threatening increasing numbers of animal and plant species. At present those responsible for meeting the water supply and wastewater treatment needs of human communities appear unaware of the potentially important role that appropriately designed treatment plants can play in promoting wildlife and plant conservation. The types of modifications that can be made to treatment plants, and how these benefit wildlife are reviewed and the obstacles to their introduction are discussed. It is shown that treatment plants designed to incorporate conservation measures can lead to both direct financial rewards for local communities as well as less tangible benefits .