With water scarcity as a pressing issue in Saudi Arabia and other Middle Eastern countries, the treatment and reuse of municipal wastewater is increasingly being used as an alternative water source to supplement country water needs. Standards are in place to ensure a safe treated wastewater quality, however they do not regulate pathogenic bacteria and emerging contaminants. Information is lacking on the levels of risk to public health associated with these factors, the efficiency of conventional treatment strategies in removing them, and on wastewater treatment in Saudi Arabia in general. In this study, a municipal wastewater treatment plant in Saudi Arabia is investigated to assess the efficiency of conventional treatment in meeting regulations and removing pathogens and emerging contaminants. The study found pathogenic bacterial genera, antibiotic resistance genes and antibiotic resistant bacteria, many of which were multi-resistant in plant discharges. It was found that although the treatments are able to meet traditional quality guidelines, there remains a risk from the discussed contaminants with wastewater reuse. A deeper understanding of this risk, and suggestions for more thorough guidelines and monitoring are needed.

Pretreatment of waste activated sludge (WAS) and the subsequent near-critical water gasification (NCWG) is a potential avenue to convert WAS into value added products. Part one of the research investigated thermal and thermochemical pretreatments. No difference was observed in the percentage of sludge liquefied beyond 10min between 200°C to 300°C. It was found that pretreated activated sludge supernatant (PASS) doubled the gas yield compared to untreated sludge when gasified. The order of effectiveness for sludge treatment was thermo-alkali > thermal > thermo-acid for hydrogen production in NCWG. Part two investigated NCWG parameters to identify optimal conditions. High gasification yields were obtained using a commercial catalyst (Raney nickel), with hydrogen content of 65-75% of the gas phase products. Thermo-alkali treated PASS was found to perform well at subcritical temperatures with 25% higher yields than thermally treated PASS. Increased catalyst loading had little additional effect on gas yields above 0.075g.

The application of municipal sewage biosolids to agricultural land is a common practice worldwide. Increasing attention is being directed at the presence of organic contaminants bound to the organic phase during wastewater treatment, which end up in the biosolids. The goal of this study was to investigate the decomposition of an alkaline-stabilized biosolid being used as an agricultural soil amendment containing unknown organic contaminants. A two year field trial and a 120 day laboratory soil incubation using increasing rates (0, 7, 14, 28, and 42 Mg ha-1) of an alkaline-stabilized biosolid (ASB) were set up to monitor biosolid decomposition and concentrations of selected contaminants over time. The seven contaminants selected for monitoring (p-cresol, indole, 4-t-octylphenol, phenanthrene, triclosan, carbamazepine, and benzo[a]pyrene) represent a wide range of physico-chemical properties and fall under several different chemical classes. The decomposition of ASB in soil was examined in the incubation study. Almost half of the CO2-C evolved from ASB amended soils occurred within the first 6 days, indicating that a relatively labile pool of carbon remains in ASB following the sewage treatment process. By day 121, between 71 to 78% of the total carbon added to soil had been evolved as CO2-C. A new model developed during this study to describe carbon mineralization, a first order plus logistic function (FLOG), performed better than other commonly used models. The method chosen to analyze organic contaminants in soil was only able to determine four out of seven compounds reliably, with recoveries greater than 50% for 4-t-octylphenol, phenanthrene, triclosan, and benzo[a]pyrene. In treated soils, only triclosan was able to be detected and quantified. Average triclosan concentration in the incubation study ranged from a high of 143 ng g-1 on day 3 to a low of 26 ng g-1 by day 121, representing an 81% decrease over a roughly 4 month period under idealized conditions. In the field, triclosan concentrations following a Fall biosolids application in Oct. 2008 increased to detectable levels (29 to 47 ng g-1) in all three plots measured in Nov. 2008, which remained elevated (29 to 66 ng g-1) over the winter period in two out of three plots when sampled in May 2009. Following the Spring application in June 2009, measured triclosan concentrations in July 2009 samples from these same two plots were lower than predicted (33 to 48 ng g-1) and eventually decreased to levels below the detection limit by the Oct. 2009 sampling.

In light of rising costs in fossil fuels and petroleum, as well as the strain on this largely non-renewable resource, the conversion of biomass, in this case waste biomass, to value-added products is becoming more attractive. In this study, municipal sewage sludge and biosolids were used to determine their potential for glucose recovery. This research focused on three pretreatment processes including drying/grinding, as well as acid and alkaline pretreatments, followed by acid hydrolysis on primary sludge, activated sludge and biosolids. After each pretreatment under specified conditions, the residues remaining from the sludges and biosolids underwent a 2 % H2SO4 acid hydrolysis at 120oC for 1 hr. Compared with activated sludge and biosolids, primary sludge was found to demonstrate the highest potential for glucose recovery in this study. Primary sludge with 1.0 N HCl pretreatment over a 24 hour contact period yielded the highest glucose conversion result as 5.67±0.24%. The best KOH pretreatment condition for primary sludge was a 0.5 N KOH concentration for a 0.5 hour contact period. However, no consistent glucose recovery trend as a function of reagent concentration or contact time was identified for any of the sludges or biosolids in this study. Drying and grinding were also found to efficiently improve the acid hydrolysis results. Fibre content analysis was also performed on the sludge and biomass feedstocks and their residues following pretreatment and acid hydrolysis during this study, to better understand the conversion of these waste biomass feedstock. The Van Soest methods for neutral-detergent, acid-detergent and acid insoluble lignin analysis and the Weende crude fibre analysis were applied to the sewage sludge and biosolids samples prior to and after acid hydrolysis to determine the fibre content including cellulose, hemicellulose and lignin. A modification to the Weende crude fibre analysis was introduced, where a centrifuge step was added prior to the second filtration after the alkaline digestion of the procedure to reduce filter clogging problems. The centrifuge modification effectively reduced the filtering time from one day to 30 minutes; however, there was an average loss of 46% in crude fibre with the addition of this centrifugation step. It was found that most of cellulose content in the feedstock samples was hydrolyzed to glucose after the acid hydrolysis process and most hemicellulose content was likely to have been solubilized and washed away during acid and alkaline pretreatments and acid hydrolysis. The lignin content did not appear to be affected by the pretreatments applied nor the acid hydrolysis. / Thesis (Master, Civil Engineering) -- Queen's University, 2008-07-25 16:10:42.518

The purpose of this study is to investigate the possibility of using the Bleached Kraft wastewater sludges as a sealant to a permeable soil structure which could contain these liquids. The sludges used are either self-contained in wastewater, produced from treatment processes, or from the addition of chemical coagulant to the wastewater. / The mechanisms of the sludge sealing phenomena which were investigated individually are divided into physical, physico-chemical, biophysical and bio-physico-chemical types of seals. Coarse sand #24 was found suitable for this sealing study as a particle size cut. Among the types of sealings studied, the bio-physical type of seals is the most effective. The physico-chemical type of seals is effective in the initial stage of sealing. The coefficient of the permeability is reduced from an average of 6.4 x 10('-2) cm/sec to 1.0 x 10('-6) cm/sec in a period of 24 hours, with a risk of leakage of less than 1% of the total effluent. / A long-term stability of using sludges as a liner to the wastewater pond has become a substantial issue. Alum was originally chosen as an effective coagulant for forming a layer of sludge for physico-chemical types of sealing. However, after the stability analyses, one finds that alum sludge is not a stable material under commonly-found hydrostatic pressures and high pH ranges. The results of the research shows that one of the alumino-silicate sludges is much more stable than that of alum sludge. The relatively stable alumino-silicate sludge was obtained from one of the coprecipitations of sodium-silicate and sodium aluminate in a BKME solution. / The economic impact of using alumino-silicate sludge is significant. The cost comparison study shows a cost ratio in the range of up to 1:10 as compared to conventional lining material. The results can be used for the implementation of field work in sludge sealing practice. In addition, this investigation could form an excellent foundation for further studies on other effluents with different parameters.

An essential step in producing "drinking" water is to precipitate the suspended and dissolved colloids through the addition of flocculents such as lime, ferric chloride, aluminium sulphate and/or poly-electrolytes. The by-product of this process is termed water treatment sludge (WTS) and contains mainly silt, clay and some organic matter. Previously this material was disposed of in landfill but more recently, alternative methods for its disposal are being evaluated. A potential disposal option is land treatment. In this system of waste disposal the inherent properties of the soil are used to assimilate the waste. Although the effect of the land disposal of WTS on soil chemical quality is gaining increasing research attention, few studies have investigated the effects on soil physical quality. This study was originally commissioned by a local water utility to evaluate the effects of the land disposal of sludge produced at their works, on soil quality. At this plant organic polymers are used to both flocculate the material and to thicken the sludge in the water recovery process. Fresh sludge has a consistence approaching that of slurry but dries to angular shaped aggregates of extremely high strength. Nevertheless, sludge aggregates comprise a network of micro-pores and channels and are therefore porous. Because of these properties, the potential use of WTS as a soil conditioner was considered.. Since lime, gypsum and polyacrylamide are wellrecognised soil conditioners, these were included as reference treatments in the study. Two field trials (Brookdale and Ukulinga) and laboratory experiments were designed to investigate the influence of WTS on soil in terms of water retention, hydraulic conductivity, evaporation, aeration, aggregation and strength. Seven rates of WTS are represented at the . Brookdale trial but research efforts were concentrated on the 0, 80, 320 and 1280 Mg ha' treatments. WTS was also applied as a mulch (without incorporation into the soil) at the 320, 640 and 1280 Mg ha" level. Gypsum was applied at rates of 5 and 10 Mg ha", lime at 2 and 10 Mg ha' and anionic polyacrylamide at 15 and 30 kg ha'. At the Ukulinga trial, WTS was mixed with the upper 0.2 m of the soil at rates of 0, 80, 320 and 1280 Mgha'. Only the high rates of gypsum, lime and anionic polyacrylamide being tested at the Brookdale trial are represented at the Ukulinga trial. All treatments in this study were maintained fallow. The laboratory study features an additional two soils to those from the field experiments, chosen to produce a range in clay contents. WTS influenced several soil physical properties. Soil bulk density decreased following the addition of sludge to soil. This caused an increase in porosity (particularly macro-porosity) and therefore water retained at saturation, but only of statistical significance at the 1280 Mg ha" level. Equally an increase in water retention at the wilting point (-1500 kPa matric potential) also occurred, owing to the high microporosity of sludge aggregates. Despite these effects very little change in both the plant available and readily available water content occurred. Neither, gypsum nor lime caused any significant change in water retention. Aslight improvement was noted on the polyacrylamide treatment at the Brookdale site but this effect did not persist for very long after the trial was established. Although in situ field measurements were influenced strongly by natural spatial variability, WTScaused a marked increase in the saturated hydraulic conductivity (Ks). The reasons for this relate to the higher porosity and the inherently stable nature of the sludge aggregates, which imparts a more open structure to the soil and reduces the extent of pore blockage. This finding was corroborated in a laboratory study in which strong positive correlations between sludge content and Ks was found. The water retention curve and saturated hydraulic conductivity was used to predict the unsaturated hydraulic conductivity function (Kw)using the RETe computer model of van Genuchten et al., 1991. The results showed a decrease in Kw on the sludgeamended treatments the extent of which increased with sludge content. This finding was tested in an evaporation study conducted under controlled environmental conditions. More water was conserved on the sludge-amended treatments than the control, because of its lower Kw. The application of the sludge as a mulch was more effective in conserving water than incorporating the sludge with soil. The air-filled porosity at field capacity (-10 kPa matric potential) of the sludge-amended soil remained within a favourable aeration range of 10-15%, which suggests that aeration should not be a limiting factor for plant growth. Air-permeability nevertheless improved substantially. Attempts at using the size distribution of dry soil aggregates to evaluate the influence of the sludge on aggregation proved unsuccessful. Saturated soil paste extracts for selected soil depths beneath the mulch layers at the Brookdale trial, nevertheless, showed significant increases in Ca2+ and Mt+ concentrations, which is encouraging from a soil stability perspective. Due to the inherently strongly aggregated nature of this soil, no meaningful change in aggregate stability, however, was measured. Significant improvements in soil stability were, nevertheless, found when fresh sludge was mixed with soil. If the sludge is not allowed to dry fully beforehand the polymer that it contains remains active and available for bonding of the soil particles together. Upon drying, these polymers become irreversibly attached to the soil substrate and win not become reactivated even upon re-wetting of the soil. This also explains why sludge aggregates found below only a few centimetres of the soil surface maintained their strongly aggregated nature. This suggests that although WTS consists of mainly silt and clay, the risk of this constituent fraction becoming released and clogging water conductive soil pores are, at present, low. Despite the high strength of the sludge aggregates the penetrometer soil . strength (PSS)within the tilled layer was non-significantly different from the control treatment. Below the tilled layer, however, the PSS on the sludge-amended treatments were lower owing mainly to wetter soil conditions. The research completed to date suggests that land treatment as an environmentally acceptable disposal option for water treatment sludge shows promise since soil conditions tend to be improved. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2001

Pretreatment of waste activated sludge (WAS) and the subsequent near-critical water gasification (NCWG) is a potential avenue to convert WAS into value added products. Part one of the research investigated thermal and thermochemical pretreatments. No difference was observed in the percentage of sludge liquefied beyond 10min between 200°C to 300°C. It was found that pretreated activated sludge supernatant (PASS) doubled the gas yield compared to untreated sludge when gasified. The order of effectiveness for sludge treatment was thermo-alkali > thermal > thermo-acid for hydrogen production in NCWG. Part two investigated NCWG parameters to identify optimal conditions. High gasification yields were obtained using a commercial catalyst (Raney nickel), with hydrogen content of 65-75% of the gas phase products. Thermo-alkali treated PASS was found to perform well at subcritical temperatures with 25% higher yields than thermally treated PASS. Increased catalyst loading had little additional effect on gas yields above 0.075g.

No description available.

This work investigated the effect of floc microstructure (size and fractal structure) and shear forces on dewatering processes, which are crucial for environmental and economical aspects in many industries. Due to limitations inherent In experimental investigations, a numerical code using the discrete element method and including some novel force models (polymer bridging force, elastic bending moment and a modified concept of rolling friction torque) was developed to simulate the consolidation behavior of flocculated systems. The code showed good agreement with experimental results. The elastic behavior of aggregates is known to depend on the backbone structure (stress bearing structure of the aggregate). However, there is little known about backbone structure. It was found that backbone represents a fractal structure with a fractal dimension value close to 1 and increasing with increase of aggregate mass fractal dimension. The dewatering process was characterized by compressive and hindered settling behavior. The numerical study of compressive rheology with different aggregate microstructure showed that the compaction results from a reduction of the correlation length rather than increase in fractal dimension. The compressive behavior is consistent with theoretical models at higher compressive stresses but is not well described at low compressive stresses. A semi- empirical model is presented describing the compressive rheology in both regions via a correction factor derived using dimensional analysis. The hindered settling behavior was in good agreement with the theoretical model based on the assumption of self similar structure. The investigation revealed that shear effect is not due entirely to hydrodynamics and can arise from the particle bonding mechanism alone. The study showed that low shear increases compressibility but high shear is detrimental. At low shear, bond bending at local voids results in solid densification. High shear increases kinetic energy and kinetic repulsion of the particles. The effect of shear is analogous to the anomalous behavior of the water density- temperature function. At low temperature bond breakage increases the density and at high temperature thermal expansion decreases the density. The investigation showed that shear increases the permeability due to bending of the structure in the shear direction, resulting in large pores.

This thesis investigated the final products from the current effluent treatment system for woolscouring (wool washing) plants, namely, (i) sludge produced from the chemical flocculation of solids in the wastewater from the wash bowls, and (ii) concentrated suint (sheep sweat) produced from evaporation of the liquid phase separated from the sludge. In addition, fibrous wastes from the woolscouring process were studied. The aims of the study were to (i) investigate whether suint could be applied in a sustainable way to arable land as a potassium fertiliser, and (ii) assess the conditions under which the sludge could be composted for use as a soil conditioner to return organic matter to soil. Experiments involving suint were performed at both laboratory and glasshouse scales, while experiments involving the solid woolscour wastes were based both in the laboratory and using a small-scale (4.5 m3 total capacity) in-vessel composting unit established at a New Zealand woolscour. Decomposition was measured using net-nitrogen mineralisation and weight loss methods. Suint, the water-soluble contaminants on the fleece, contained high levels of potassium (20% on a dry weight basis) and also appreciable quantities of sulphur, sodium, and chlorine. Biological treatment before evaporation stabilised the resulting suint and improved the consistency of its composition. Suint did not affect the soil processes examined, in that it partly decomposed in soil, did not inhibit the turnover of model organic compounds, did not affect soil properties such as pH and electrical conductivity, and did not lead to increased leaching of mineral nitrogen. Suint was either neutral or positive towards plant performance when applied to soil at a rate of 100 kg potassium per hectare. Suint was therefore judged to be suitable for application to land and could be targeted to soils known to be deficient in potassium or to areas where crops with a high potassium demand are grown. Sludge, composed of dirt (soil particles, faecal matter, and skin and fibre debris) and wool grease, was highly variable in terms of its rate of decomposition, ranging from 0.8 to 27.8% of the initial total nitrogen mineralised over 30 days at 37℃. Fibrous wastes, such as opener (fibre and contaminants removed from the wool by agitation prior to scouring) and scoured wool cleaner (wool fibre and dust removed from scoured and dried wool) wastes, also showed variability in decomposition rates. Sludge decomposition was improved by as much as threefold when co-incubated with fibrous wastes. Although it was shown that the polyacrylamide and pesticide content of sludge did not inhibit its decomposition, the effect of the grease content was not fully understood. Chemical properties of woolscour sludge, such as the carbon to nitrogen ratio, suggested that sludge was a substrate of good resource quality. From a biological perspective, however, the data suggested that woolscour sludge was limited in available nutrients; sludge nitrogen was derived principally from keratin, which decomposed at a low rate resulting in the slow release of mineral nitrogen and low levels of microbial activity. Thus, sludge appeared a poor substrate for composting. However, the results from composting trials indicated that the sludge could be successfully processed after blending with a bulking agent such as sawdust. The blended material showed a 90% reduction in wool grease over 21 days of composting when the moisture content of the composting mass was kept optimal. Compost temperature exceeded 55℃ when wool fibre was added to the blend. Initial results from a case study involving the commercial composting of the entire sludge production (16 tonnes per day) from a New Zealand woolscour indicated that a saleable compost could be produced from a material that would otherwise go to landfill, and served to illustrate the commercial significance of these research results.