Development of new pathogen surrogates and synthetic DNA tracers for water applications

<p>In recent years, we have conducted research into developing new pathogen surrogates and synthetic DNA tracers for water applications. Biomolecule-modified particles have been used to mimic <em>Cryptosporidium</em>, rotavirus and adenovirus with respect to their filtration removal and transport in porous media. Additionally, we have developed new DNA tracers as free DNA molecules or DNA-encapsulated biopolymer microparticles to track water contamination. DNA markers are also used to label some surrogates to facilitate their sensitive detection by using qPCR.</p><p>The surrogates have been validated in laboratory conditions alongside the actual pathogens. The <em>Cryptosporidium </em>surrogates have been satisfactorily validated in alluvial sand, in limestone sand, in coagulation and rapid sand filtration studies. The rotavirus surrogates have been successfully validated in coastal sand aquifer media, in unmodified and hydrophobically modified quartz sand, and in stony alluvial soils under on-site wastewater applications. The research findings have demonstrated that these new surrogates significantly outperform the most commonly used existing surrogates, namely, unmodified microspheres for <em>Cryptosporidium </em>oocysts and MS2 phage for viruses. Working with the water industry, we have applied the <em>Cryptosporidium </em>surrogate to pilot-scale rapid sand filters and point-of-use domestic filters and determined its removal efficiencies in water filtration systems commonly used in New Zealand. The artificial DNA tracers have been validated in surface water, groundwater and soils, and they were readily trackable in a surface stream for up to 1 km.</p><p>Our proof-of-concept studies suggest that the new pathogen surrogates and synthetic DNA tracers we have developed show great promise as new tools for water applications. The ‘micro mimics’ approach has opened up a new avenue for assessing pathogen removal and transport in water systems without the risk and expense that accompany work with actual pathogens. With further validation, the new surrogates could be used to study pathogen removal and transport in subsurface media after the disposal of effluent and biosolids to land, and to assess the performance of filtration processes in water and wastewater treatment. With future up-scaling validation of the new synthetic DNA tracers, these tracers could be useful for concurrently tracking multiple pollution sources and pathways in freshwater environments.</p>

USING CEMENT KILN DUST AS LOW PERMEABLE BARRIER FOR RESTRICTION THE PROPAGATION OF CADMIUM IONS TOWARDS THE WATER RESOURCES

This study was aimed to determine the interaction of cement kiln dust - aqueous solution contaminated with Cadmium ions was studied through set of batch tests with operational conditions of contact time ≤120 min, sorbent dosage from 0.05 to 1 g/100 mL and agitation speed ranged from 50 to 300 rpm for initial concentration of 50 mg/L with initial pH of 3 to simulate the acetogenic phase in the sanitary landfill. The best values of these conditions are 1 hr, 0.7 g/100 mL and 250 rpm respectively, To obtain maximum removal efficiencies of 97.6%. Freundlich and Langmuir models have a high ability in the representation of the sorption data with determination coefficient (R2) greater than 0.97 and the sorption capacity reached to 84.1 mg/g. This certifies that the physical sorption and chemisorption can occur together to remove Cadmium ions from the aqueous solutions. Tests elucidated that the average coefficient of the hydraulic conductivity is equal to 9.7×10-13 m/s and this is suitable for LPB. Finally, COMSOL Multiphysics 3.5a package was able to simulate the distribution of cadmium ions concentrations within two-dimensional physical model packed with sand aquifer and CKD LPB. A good matching between model predictions and experimental results are recognized at selected points up and down gradient of LPB.

Hydrostratigraphy and Hydraulic Characterisation of Shallow Coastal Aquifers, Niger Delta Basin: A Strategy for Groundwater Resource Management

The groundwater from shallow coastal aquifers in Nigeria has been reported to be under intense stress resulting from both natural and anthropogenic impacts ranging from saltwater intrusion, effluent-related contamination and pollution to oil spillage, gas flaring, municipal, industries and agriculture. Here we characterised the hydrostratigraphy and hydraulic characteristics of the shallow coastal aquifers of the Niger Delta basin and assessed the resilience of groundwater to both natural and anthropogenic impacts. Fifty-two borehole logs were analysed from which lithological sections were used to generate cross-sections along with four profiles. The system was more complex than previously reported: a unit of silty sand was observed in the western part of the basin that thins out leaving the eastern part of the basin as an unconfined aquifer underlain by multiple thin beds of the sand aquifer. A layered sand aquifer occurs in the northern parts of the basin, which holds freshwater in this area, and is interbedded by clay layers which serve as aquitards. The relatively higher hydraulic conductivity of the Benin Formation units compared to those of the Deltaic Formation leave it with weaker climate change resilience and more vulnerable to pollution and contamination. While groundwater remains the dominant source of fresh water in the northern part of the basin, a strategic approach is needed to access potable water from the southern part where contaminated surface water appears to directly interact with groundwater of the uppermost unconfined aquifer. Management of waste and effluent related to oil spillage, municipal, industries and agricultural in this area should be engineered to protect the groundwater resources of this aquifer.

Dissolved Inorganic Geogenic Phosphorus Load to a Groundwater-Fed Lake: Implications of Terrestrial Phosphorus Cycling by Groundwater

The general perception has long been that lake eutrophication is driven by anthropogenic sources of phosphorus (P) and that P is immobile in the subsurface and in aquifers. Combined investigation of the current water and P budgets of a 70 ha lake (Nørresø, Fyn, Denmark) in a clayey till-dominated landscape and of the lake’s Holocene trophic history demonstrates a potential significance of geogenic (natural) groundwater-borne P. Nørresø receives water from nine streams, a groundwater-fed spring located on a small island, and precipitation. The lake loses water by evaporation and via a single outlet. Monthly measurements of stream, spring, and outlet discharge, and of tracers in the form of temperature, δ18O and δ2H of water, and water chemistry were conducted. The tracers indicated that the lake receives groundwater from an underlying regional confined glaciofluvial sand aquifer via the spring and one of the streams. In addition, the lake receives a direct groundwater input (estimated as the water balance residual) via the lake bed, as supported by the artesian conditions of underlying strata observed in piezometers installed along the lake shore and in wells tapping the regional confined aquifer. The groundwater in the regional confined aquifer was anoxic, ferrous, and contained 4–5 µmol/L dissolved inorganic orthophosphate (DIP). Altogether, the data indicated that groundwater contributes from 64% of the water-borne external DIP loading to the lake, and up to 90% if the DIP concentration of the spring, as representative for the average DIP of the regional confined aquifer, is assigned to the estimated groundwater input. In support, paleolimnological data retrieved from sediment cores indicated that Nørresø was never P-poor, even before the introduction of agriculture at 6000 years before present. Accordingly, groundwater-borne geogenic phosphorus can have an important influence on the trophic state of recipient surface water ecosystems, and groundwater-borne P can be a potentially important component of the terrestrial P cycle.

Clogging of Infiltration Basin and Its Impact on Suspended Particles Transport in Unconfined Sand Aquifer: Insights from a Laboratory Study

A laboratory study was undertaken to investigate the physical clogging of a sand medium by injecting suspended particles (SP), with diameters ranging from 0.03 to 63.41 μm, into an infiltration basin, which was installed in a sand tank under the condition of constant head. The hydraulic conductivity (K) of the saturated porous medium was found to have decreased by 27% because of re-arrangement over the seven days of self-filtration. A clogging layer was observed on the infiltration basin bottom, probably due to straining over the stormwater infiltration stage. Particle-size analyses also indicate that retention of bigger SP led to faster straining of smaller SP, despite the small fraction of bigger SP. The clogging layer weakened the hydraulic connection between the water level in the basin and the water table of the unconfined aquifer until nearly no water could infiltrate into the aquifer. The deposition of finer SP that entered into the aquifer are governed by the hydrodynamic forces. These finer SP caused non-uniform permeability reduction of the porous medium, with an estimated 35% of permeability reduction occurring beneath the infiltration basin. However, the reduction appears to be reversible, as the fine SP deposited on the pore surfaces of the porous medium can be released or detached by the continuous horizontal hydraulic gradient. Extended tailing of the outlet breakthrough curve (BTC) also strongly supported the detachment of SP. This study focused on the effects of particles’ polydispersity and hydrodynamic forces on the hydraulic characteristics of the porous medium.