Land disposal of treated human and animal effluent through pumice sand soils is a common practice around Rotorua, in the central North Island of New Zealand. There is increasing concern about the possibility of contamination of shallow pumice sand aquifers associated with this practice. In this study, we investigated the transport and attenuation of F-RNA bacteriophages and Escherichia coli in saturated pumice sand aquifer media using a field tracing experiment, and laboratory batch and column studies. The influence of dissolved organic carbon on microbial transport was also investigated by conditioning the 18 cm-long column with ultrafiltered sewage. The CXTFIT curve-fitting program was used to model the experimental data and to determine transport and attenuation parameters. Batch studies showed more than 90% adsorption of both microbial indicators onto pumice sand. High mass removal of microbial indicators was shown in the field (>99% for phage MS2 and E. coli at 2 m down gradient of the injection well; not detected at 6 m) and in the 'clean sand' column (65% for phage MS2 and 90% or E. coli). These results suggest that uncontaminated pumice is an effective sorbent capable of retaining microbial contaminants due to high surface area and porosity. However, in the column, with additional dissolved organic carbon, phages showed a progressive reduction in mass removal and retardation between experiments (93%, 75%, and 63% removal; retardation factor: 3.5, 2.5 and 1.2). This suggests that the organic matter competed with phages for the sorption sites, thus promoting phage transport. As a result, viral transport rates may be significantly greater in contaminated compared with uncontaminated pumice sand aquifers.

The effect of aeration rate on nutrient removal from slaughterhouse wastewater was examined in two 10-L laboratory-scale sequencing batch reactors (SBRs--SBR1 and SBR2) operated at ambient temperature. The contaminants in the slaughterhouse wastewater had average concentrations of 4,000 mg chemical oxygen demand (COD) L⁻¹, 350 mg total nitrogen (TN) L⁻¹ and 26 mg total phosphorus (TP) L⁻¹. The duration of a complete SBR operation cycle was 8 h and comprised four operational phases: fill (7 min), react (393 min), settle (30 min) and draw/idle (50 min). During the react phase, the reactors were intermittently aerated four times at 50-min intervals, 50 min each time. DO, pH and oxidation-reduction potential (ORP) in the reactors were real-time monitored. Four aeration rates--0.2 L air min⁻¹ in SBR1 for 70 days, 0.4 L air min⁻¹ in SBR1 for 50 days, 0.8 L air min⁻¹ in SBR2 for 120 days and 1.2 L air min⁻¹ in SBR1 for 110 days--were tested. When the aeration rate was 0.2 L air min⁻¹, the SBR was continuously anaerobic. When the aeration rate was 0.4 L air min⁻¹, COD and TP removals were 90% but TN removal was only 34%. When the aeration rates were 0.8 and 1.2 L air min⁻¹, average effluent concentrations were 115 mg COD L⁻¹, 19 mg TN L⁻¹ and 0.7 mg TP L⁻¹, giving COD, TN and TP removals of 97%, 95% and 97%, respectively. It was found that partial nitrification followed by denitrification occurred in the intermittently aerated SBR systems.

In the daily and final landfill cover barrier system, the hydraulic properties of compacted soil liners and the strength of soil can be adversely affected by desiccation cracking, resulting in the loss of effectiveness and integrity of the containment system as a barrier. Recently, there is an interest of using fiber additive to overcome the desiccation cracking problem. In this study, the desiccation crack test was conducted to investigate the effect of fiber additive on suppressing desiccation cracks in compacted Akaboku soils. Polypropylene (C₃H₆) fiber was used as an additive material for soil sample. The percentages of fiber used were varied as 0.0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0% and 1.2% (by dry weight of samples). The soil specimens were compacted under the conditions of maximum dry density and optimum water content. The surficial cracking area was measured to determine the crack intensity factor (CIF) of the soil samples. The desiccation crack test results indicated that the percentage of volume change of the compacted soil specimen decreased with addition of fiber. The change in the soil surface area decreased with increasing in the fiber content (FC), and consequently, the volumetric shrinkage strain decreased. The CIF for the soil without fiber (FC = 0.0%) were significantly higher than the soil with fiber additive. The CIF of soil at FC = 0.0% decreased from 2.75% to 0.6% for the soil at FC = 0.2%. It was also found that the maximum crack depth reaches almost 50% of the thickness of the soil without fiber additive. This study suggests the potential application of the fiber additives to soils as an available method to suppress desiccation cracks encountered in landfill cover barriers.

The biodegradation of different peat types was studied with a manometric respirometric test. Compaction peat and sphagnum peat samples were analysed, and the effect of peat pH on biodegradation behaviour was evaluated. Only minor (BOD/ThOD < 0.4%) biodegradation was observed with compaction peat samples, and the stable state, in which biodegradation stopped, was achieved during a two month period. As expected, sphagnum peat samples with a lower decomposition rate degraded more than compaction peat samples. Alkalinity (pH between ca. 4-9) of the peat was noticed to reduce the degree of biodegradation and accelerate the achievement of the stable state.

Agrichemical spills and discharges to soil can cause point-source contamination of surface and ground waters. When high contaminant concentrations inhibit natural attenuation in soils, chemical treatments can be used to promote degradation and allow application of treated soils to agricultural lands. This approach was used to remediate soil containing >650 mg atrazine, >170 mg metolachlor and >18,000 mg nitrate kg⁻¹. Results indicated a decrease in metolachlor concentration to <1 mg kg⁻¹ within 95 days of chemical treatment with zerovalent iron (Fe⁰, 5% w/w) and aluminum sulfate (Al₂(SO₄)₃, 2% w/w) but after one year >150 mg atrazine and >7000 mg nitrate kg⁻¹ remained. Laboratory experiments confirmed that subsequent additions of sucrose (table sugar) to the chemically pretreated soil promoted further reductions in atrazine and nitrate concentrations. Field-scale results showed that adding 5% (w/w) sucrose to windrowed and pretreated soil significantly reduced atrazine (<38 mg kg⁻¹) and nitrate (<2,100 mg kg⁻¹) concentrations and allowed for land application of the treated soil. These results provide evidence that zerovalent iron in combination with Al₂(SO₄)₃ and sucrose can be used for on-site, field-scale treatment of pesticide- and nitrate-contaminated soil.

Intensive cultivation of fen peat soils (Eutric Histosols) for agricultural purposes, started in Europe about 250 years ago, resulting in decreased soil fertility, increased oxidation of peat and corresponding CO₂-emissions to the atmosphere, nutrient transfer to aquatic ecosystems and losses in the total area of the former native wetlands. To prevent these negative environmental effects set-aside programs and rewetting measures were promoted in recent years. Literature results and practical experiences showed that large scale rewetting of intensively used agricultural Histosols may result in the mobilisation of phosphorus (P), its transport to adjacent surface waters and an accelerated eutrophication risk. The paper summarises results from an international European Community sponsored research project and demonstrates how results obtained at different scales and from different scientific disciplines were compiled to derive a strategy to carry out rewetting measures. A decision support system (DSS) for a hydrologically sensitive area in the Droemling catchment in north-eastern Germany was developed and is presented as a tool to regulate rewetting in order to control P release. It is demonstrated that additional laboratory experiments to identify essential processes of P release during rewetting and the site-specific management of the water table, the involvement of specific knowledge and experience of the stakeholders are necessary to develop an applicable DSS. The presented DSS is practically used to prevent freshwater resources from diffuse P pollution.

Urban stormwater can be treated by infiltration at the source using systems like permeable paving. A critical component of such a system is the filtration media. Laboratory experiments were conducted using columns and boxes to evaluate the sediment retention efficiencies of different filtration media--crushed Greywacke, Greywacke mixed with 10% sand, and layered Greywacke and sand-Greywacke mix. Sediments of 0.001-6 mm were applied at concentrations of 460-4,200 mg/l along with water at flow rates of 100-900 ml/min. All columns showed between 96 and 91% sediment retention efficiency for single dry sediment applications, with lowered sediment retentions at higher flow rates. Decreasing the sediment loading, applying particles of <38 μm size, and suspending the particles in inflow as opposed to directly applying sediments to the column surface gave lower sediment retention efficiencies of 55 to 89%. Sediment retention primarily occurred in the top 20 mm of all columns and the 50th percentile value of retained sediments was 100-300 μm. The box tests showed little effect of flow and sediment loading on particle retention, with the tests showing an average retention of 93%. Similar to the column tests, the box tests showed lower sediment retention (84 to 88%) for <38 μm sediments and greater retention (approximately 95%) for larger sediments.

Urban rainfall-runoff residuals contain metals such as Cr, Zn, Cu, As, Pb and Cd and are thus reasonable candidates for treatment using Portland cement-based solidification-stabilization (S/S). This research is a study of S/S of urban storm water runoff solid residuals in Portland cement with quicklime and sodium bentonite additives. The solidified residuals were analyzed after 28 days of hydration time using X-ray powder diffraction (XRD) and solid-state ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. X-ray diffraction (XRD) results indicate that the main cement hydration products are ettringite, calcium hydroxide and hydrated calcium silicates. Zinc hydroxide and lead and zinc silicates are also present due to the reactions of the waste compounds with the cement and its hydration products. ²⁹Si NMR analysis shows that the coarse fraction of the waste apparently does not interfere with cement hydration, but the fine fraction retards silica polymerization.

The use of three inorganic materials as potential immobilizers of metals in soils has been studied by monitoring metal availability by EDTA extraction, the Simple Bioaccessibility Extraction Test (SBET) and extraction with a mixture of organic acids (OA). The SBET test was the most suitable for risk assessment in soils of recreational areas. The materials were a 4A-type zeolite, tri-calcium phosphate and 'slovakite', a synthetic sorbent developed for remediation of metal-polluted soils. Adsorption/desorption experiments of metals by the isolated materials showed that all materials caused a strong retention of metals from solutions, with negligible release by dilution. When added to soils of three parks, zeolite and, to a much lesser extent, slovakite caused some increase in soil pH. Despite this increase of pH, zeolite is often the least effective amendment for decreasing metal availability estimated by any method, and even sometimes seems to cause some increase, as well as an increase of soil electrical conductivity. In contrast, slovakite causes a decrease of available metals as estimated by EDTA and SBET, but by SBET the effect seems to be steadily reduced after the first samplings, so that after 300 days the metals extracted by this method are very similar to the data for the blanks. Despite the differences in pseudo-total metal contents, few differences are noticeable among parks. In general, these amendments are scarcely efficient in the case of neutral urban soils like those studied here. Other techniques are needed for controlling and, eventually, decreasing metal pollution hazard in soils of recreational areas.

This paper deals with field measurements and hydraulic, oxygen transport and geochemical speciation modeling undertaken to evaluate the performance of a sand-bentonite test cover overlying a 20% sloping waste rock platform. A pit run (gravelly sand) layer protected the sand-bentonite layer. The study site was the Whistle Mine near Capreol, Ontario, Canada. The purpose of the study was to evaluate a number of test covers and select a final cover for the decommissioning of 7 million tonnes of acid-generating waste rock at the site. The sand-bentonite test plot and a control plot consisting of waste rock without cover were monitored over 3 years for water content, suction, soil temperature, gaseous oxygen concentrations, and water percolation. Air temperature, rainfall, snow pack and potential evaporation were also monitored. Finite element modeling showed very good agreement between modeled and measured cumulative precipitation, daily potential evaporation and cumulative evaporation, and to a lesser extent, the cumulative water percolation through the test cover. Due to construction difficulties in the field, the back of the waste rock platform was not covered with the test cover. This resulted in oxygen ingress from the back side of the waste rock. Oxygen transport modeling showed that if the entire waste rock pile had been covered, the daily oxygen flux would have been reduced by 90% to only 0.003 g/m²/day. Such low oxygen flux would minimize sulphide oxidation and hence acid generation in the waste rock. Aqueous equilibrium speciation modeling suggested that the concentrations of sulphate [graphic removed] , iron (Fe), and aluminum (Al) in percolate water in contact with waste rock were controlled by secondary minerals such as gypsum, alunite, and ferrihydrite.