J.E. Burgess

Developments in odour control and waste gas treatment biotechnology: a review

Waste and wastewater treatment processes produce odours, which can cause a nuisance to adjacent populations and contribute significantly to atmospheric pollution. Sulphurous compounds are responsible for acid rain and mist; many organic compounds of industrial origin contribute to airborne public health concerns, as well as environmental problems. Waste gases from industry have traditionally been treated using physicochemical processes, such as scrubbing, adsorption, condensation, and oxidation, however, biological treatment of waste gases has gained support as an effective and economical option in the past few decades. One emergent technique for biological waste gas treatment is the use of existing activated sludge plants as bioscrubbers, thus treating the foul air generated by other process units of the wastewater treatment system on site, with no requirement for additional units or for interruption of wastewater treatment. Limited data are available regarding the performance of activated sludge diffusion of odorous air in spite of numerous positive reports from full-scale applications in North America. This review argues that the information available is insufficient for precise process design and optimization, and simultaneous activated sludge treatment of wastewater and airborne odours could be adopted worldwide.

NUTRIENT ADDITION TO ENHANCE BIOLOGICAL TREATMENT OF GREYWATER

This study compares the chemical oxygen demand (COD) removal and respiration rates of a microbial population treating real and synthetic greywaters dosed with nutrient supplements. The nutrient composition of the real and synthetic greywaters was analysed and the dosing regime for nitrogen, phosphorus and a range of trace metals planned accordingly. The doses consisted of eight single additives (macronutrients and trace metals) to the control greywater and six trace metal additions to C: N : P balanced greywater. The COD removal for the control real and synthetic greywater in lab-scale activated sludge systems (0.038 and 0.286 kg COD kg MLSS(-1) d(-1), respectively) confirmed nutrient limitation and the poor degree of greywater treatment. Nutrient dosing increased the COD removal rate and oxygen uptake rate in many cases. The greatest stimulation of microbial activity was observed with zinc additions to C: N: P balanced real greywater (1.291 kg COD kg MLSS(-1) d(-1) over 30 times the control). Inhibitory effects to various extents were rare and limited mainly to the additions of metals to synthetic greywater. The dominance of chemicals effects was observed on addition of some micronutrients; notably iron and aluminium, metals on which many coagulants for use in biotreatment of other wastewaters are based. The data indicate that the impact of understanding microbial processes and the nutrients required for wastewater treatment can only serve to optimise process efficiency for the proposed treatment of greywater.

Treatment Methods for Wine-Related and Distillery Wastewaters: A Review

ABSTRACT A large and increasing volume of wastewater is produced globally by the winery and distillery industries. These wastewaters are generally acidic, high in chemical oxygen demand (COD) and color, and may contain phenolic compounds that can inhibit biological treatment systems. Treatment of distillery and phenolic compound–rich wastewaters by physicochemical, aerobic biological systems and hybrid treatment methods are discussed, as well as products derived from fungal treatment. White-rot fungi have been shown to exhibit unique biodegradation capabilities, primarily due to their production of extracellular and broad substrate range enzymes that are capable of mineralizing lignin, a recalcitrant biopolymer. One of these enzymes, laccase, catalyses the oxidation of various organic compounds with the subsequent reduction of molecular oxygen to water. Laccase synthesis, induction, and inhibition are discussed with the utilization of waste residues for laccase production and the enzymes potential industrial applications. Distillery wastewaters offer a unique, presterilized, potential growth substrate for the production of lignolytic enzymes such as laccase. Compounds may be utilized for enzyme and biomass production resulting in remediation by the growing fungus.

Role of micronutrients in activated sludge-based biotreatment of industrial effluents.

Industrial processes often produce wastewaters that resist biological treatment owing to the unfamiliarity of some components to biological systems. Availability of nutrients determines the community structure of the activated sludge and hence the efficiency of the degradation process. Micronutrients influence the bacteria involved in waste degradation and also the species diversity within the sludge. The requirements for and toxicity of different micronutrients vary according to the nature of the waste and the ecology of the sludge. Adding micronutrients to biological treatment processes is one possible approach to upgrading an existing facility in order to deal with increasing volumes and strengths of industrial wastewaters and the tightening discharge legislation.

Dinitrogen oxide production by a mixed culture of nitrifying bacteria during ammonia shock loading and aeration failure.

A number of experiments was conducted in order to establish if N2O in the exhaust gas from an aerobic consortium of nitrifiers could be used as an indicator for monitoring the nitrification process. Laboratory-scale experiments with an activated sludge system showed a strong correlation between ammonia shock loads and both the concentration of N2O and the rate of increase of N2O in the exhaust gas for shock loads less than 1.60 mg ammonical nitrogen (NH3-N) per g total suspended solids (TSS). For greater ammonia shock loads, correlation was found between build-up of nitrite in the aeration tank and the concentration of N2O in the exhaust gas from the tank. When subjecting the system to aeration failure, a similar pattern was seen, with a correlation between nitrite build-up in the aeration tank and increases in the concentration of N2O in the exhaust gas. The results from this work suggest that the changes in N2O concentration in the exhaust gas from a nitrifying process may be a useful parameter for monitoring such processes.

Off-line particle size analysis of digested sludge.

Particle size analysis was carried out on six samples of digested sludge using laser diffraction. The digested sludge was produced in laboratory-scale reactors under different feed regimes based on a mixture of primary and waste activated sludge (WAS). Laser diffraction proved capable of providing rapid, reproducible results of the particle size distribution of each sample, and highlighted differences between the different treatments. An increase in the level of WAS in the digester feed sludge led to a shift in the size distribution, with a decrease in the number of smaller sized particles.

Treatment of wine distillery wastewater: a review with emphasis on anaerobic membrane reactors.

This review summarises research efforts and case studies in the treatment of wine distillery wastewaters. Experiences in treating wine distillery wastewaters can contribute to the field of oenology, as many oenologists are concerned with the selection, efficiency and economy of their wastewaters. Characteristics of wastewaters from different distilleries and various methods for treating these wastes are discussed. Wine distillery wastewaters are strongly acidic, have a high chemical oxygen demand, high polyphenol content and are highly variable. Primary attention is focused on the sustainable biological treatment of wine distillery wastewaters, mainly by energyefficient anaerobic digestion in different reactor configurations from bench to pilot and full-scale treatment. Finally, areas where further research and attention are required are identified.

Fungal and enzymatic remediation of a wine lees and five wine-related distillery wastewaters

The aim of this work was to characterise wine-related wastewaters and ascertain the wastewater concentrations that were optimal for treatment by Trametes pubescens. Laccase production was also monitored. Crudely purified laccase was tested independently to determine its role in phenolic compounds degradation and colour change. The fungal treatment resulted in decreases in the wastewater chemical oxygen demand of up to 83+/-2.1%, phenolic compounds of 87+/-1.6% and colour of 88+/-4.7%. Although laccase treatment lowered total phenolics by up to 61+/-0.5%, the colour was increased by up to 160+/-5%, indicating the formation of colour-rich compounds. Trametes pubescens MB 89 greatly improved the quality of all six wastewaters tested, although two wastewaters had to be diluted to below 50% to allow for bioremediation by the submerged fungal culture. Laccase synthesis greater than 1500 U/l was obtained in all wastewaters, with a maximum of 8997 U/l. The complete fungal system was found to be superior to enzymatic treatment alone. Enzymatic treatment reduced the total phenols but did little to improve the colour of the wastewaters, and in the case of wine lees significantly increased the colour.

Developments in ecotoxicity testing

Effluent discharges from industrial facilitiesare complex, comprising of many differentcomponents and vary continuously in quantityand quality. Traditionally aquatic ecosystemshave been protected from anthropogenic impactsby controlling the input of wastewaters andother sources of pollution, which reducedissolved oxygen concentrations in receivingwaters. Recent attention has focused on thedirect effects that toxic pollutants can impacton biological systems. Consequently, the use ofwhole effluent testing has increased as arapidly and cost-effective means of evaluatingand controlling the environmental impact ofsuch emissions. However, unless the causes ofthe toxicity can be identified, the toxicity ofthe effluent cannot be effectively managed. Thetraditional way of identifying the toxicelements is to conduct a ToxicityIdentification Evaluation (TIE). However, thisprovides little information on the toxicity ofdefined mixtures of chemicals. This paperreviews the current status of aquatic toxicitytesting in relation to test species,methodology and media and compares the resultsof exposure of individual compounds to that ofchemical mixtures. It discusses the applicationof using mathematical models to predict thetoxicity of chemical mixtures in order toreduce the need to generate large amounts ofexperimental data. The different regulatoryapproaches between North America and Europe areintroduced for testing the toxicity ofdischarges to the aquatic environment as wellas the need for future research.

The Influence of Iron-Based Co-Precipitants on Activated Sludge Biomass

European Community legislation will increase the requirement for efficient phosphorus removal. The impact of chemical phosphorus removal by co-precipitation has only been considered from an effluent quality point of view. This paper considers the direct impact of two iron-based chemicals—iron (El) chloride and iron (II) sulphate—on an activated sludge pilot plant. Average chemical oxygen demand (COD) removals were 84.0% for iron (III) and 78.6% for iron (II). Nitrification appeared to be inhibited by the addition of high doses of iron (III). Ammonia removals of just 17.3% were observed compared with 88.7% for iron (II) addition. Suspended solids removal was poor (average removals = 69.5% for iron (II) and 48.0% for iron (III)) during the last few months of the trial due to problems with filamentous bacteria and denitrification in the sedimentation tanks. The oxygen uptake of the biomass dosed with iron (II) (0.0121 mg 02 mg biomass−1h−11) was on average 32.4% higher than that of iron (III); the latter averaged 0.0086mg 02 mg biomass−11 h−11. Species diversity index (ST) was similar for both chemicals; ST = 24.7 with iron (II) addition and ST = 22.1 with iron (III). There was a difference in the floe characteristics of the biomass. The floes produced with iron (II) were larger and more dense than those with iron (III).