Fate of pharmaceuticals and personal care products in wastewater treatment plants - Conception of a database and first results

We created a database in order to quantitatively assess the occurrence and removal efficiency of pharmaceuticals and personal care products (PPCPs) in wastewater treatment plants (WWTPs). From 117 scientific publications, we compiled 6641 data covering 184 PPCPs. Data included the concentrations of PPCPs in WWTP influents and effluents, their removal efficiency and their loads to the aquatic environment. The first outputs of our database allowed to identify the most investigated PPCPs in WWTPs and the most persistent ones, and to obtain reliable and quantitative values on their concentrations, frequency of detection and removal efficiency in WWTPs. We were also able to compare various processes and pointed out activated sludge with nitrogen treatment and membrane bioreactor as the most efficient ones.     

Characterization of aluminium-based water treatment residual for potential phosphorus removal in engineered wetlands

Aluminium-based water treatment residual (Al-WTR) is the most widely generated residual from water treatment facilities worldwide. It is regarded as a by-product of no reuse potential and landfilled. This study assessed Al-WTR as potential phosphate-removing substrate in engineered wetlands. Results indicate specific surface area ranged from 28.0 m² g⁻¹ to 41.4 m² g⁻¹. X-ray Diffraction, Fourier transform infrared and energy-dispersive X-ray spectroscopes all indicate Al-WTR is mainly composed of amorphous aluminium which influences its phosphorus (P) adsorption capacity. The pH and electrical conductivity ranged from 5.9 to 6.0 and 0.104 dS m⁻¹ to 0.140 dS m⁻¹ respectively, showing that it should support plant growth. Batch tests showed adsorption maxima of 31.9 mg P g⁻¹ and significant P removal was achieved in column tests. Overall, results showed that Al-WTR can be used for P removal in engineered wetlands and it carries the benefits of reuse of a by-product that promotes sustainability.     

Extraction of raw sewage sludge containing iron phosphate for phosphorus recovery

The objective of the present study was to establish an alkali extraction technology for FePO₄-containing sewage sludge obtained from a wastewater treatment system that includes phosphorous removal by iron electrolysis. By clarifying the extraction properties of phosphorous, organic matter, and inorganic matter, conditions for alkali extraction were optimized. As a result, it was suggested that unheated phosphorous extraction would be superior for FePO₄-containing sewage sludge. And, extraction methods and sewage sludge properties were also compared, and the noteworthy result that extraction of metals can be suppressed to extremely low amounts with alkali extraction as compared with acid extraction was obtained. A new insight was also gained that, as compared with the use of incinerated ash reported in previous studies, alkali extraction was more efficient when raw sewage sludge was used.     

The Effects of Magnesium and Ammonium Additions on Phosphate Recovery from Greenhouse Wastewater

Phosphorus recovery from greenhouse wastewater, using precipitation-crystallization, was conducted under three levels of calcium concentration, 304 mg/L (7.6 mmol/L), 384 mg/L (9.6 mmol/L), and 480 mg/L (12 mmol/L), and also with additions of ammonium and magnesium into the wastewater. Jar test results confirmed high phosphate removal, with more than 90% of the removal achieved with a pH as low as 7.7. Under the low calcium concentration, ammonium addition affected the chemical reactions at pH lower than 8.0, where struvite was produced; when the pH was raised to 8.8, other calcium compounds dominated the precipitation. Under the medium calcium concentration, ammonium and magnesium addition helped struvite precipitation in the low pH range. Hydroxyapatite (HAP) was the main product. Under the high calcium concentration, ammonium addition showed no effects on the precipitation.     

Phosphate Recovery from Greenhouse Wastewater

A study was conducted to investigate the suitability of phosphate recovery from greenhouse wastewaters by using precipitation/crystallization process. More than 90% of the phosphate could be removed from the greenhouse wastewater. Various calcium phosphate salts were obtained in the process; hydroxyapatite [Ca₅(PO₄)₃OH] could be the main product from the precipitates. Phosphate removal was affected by the presence of magnesium ion in wastewaters. An increase of magnesium concentrations in wastewaters decreased phosphate removal rates. The chemical contents of precipitates in terms of calcium, magnesium and phosphate were affected by calcium to magnesium molar ratio. Higher calcium contents were obtained at wastewaters with high calcium to magnesium molar ratio. An addition of magnesium did not affect the potassium contents in the precipitates. K‐struvite, MgKPO₄·6H₂O, was not the major product in the precipitate, even with addition of a large quantity of magnesium.     

Photo-dissociation of dimethylamine by KrBr excilamp

A study of dimethylamine photo-dissociation in the gas phase has been conducted using UV radiation delivered from a KrBr^* excilamp, driven by a sinusoidal electronic control gear with maximum emission at wavelength of 207 nm. The electrical input power and radiant power of the lamp were measured to determine their effects on the degradation. The influence of flow velocity and initial concentration of dimethylamine were also examined. In order to evaluate the photo-dissociation process comprehensively, several parameters were investigated, including removal efficiency, energy yield, carbon balance and CO₂ selectivity. It is shown that the removal efficiency increases with enhanced input power and decreased gas flow rate. A high removal efficiency of 68% is achieved for lamp power 102 W and flow velocity 15 m³ h⁻¹. The optimum dimethylamine initial concentration is around 3520 mg m⁻³, for which the energy yield reaches up to 442 g kW h⁻¹ when the input power is 65 W. In addition, two chain compounds (1,3-bis-dimethylamino-2-propanol; 3-penten-2-one, 4-amino) and three ring organic matters (1-azetidinecarboxaldehyde, 2,2,4,4-tetramethyl; N-m-tolyl-succinamic acid; p-acetoacetanisidide), were identified by GC–MS as secondary products, in order to demonstrate the pathways of the dimethylamine degradation.     

Responses of alkaline phosphatase activity to wind-driven waves in a large, shallow lake: Implications for phosphorus availability and algal blooms

Phosphorus is a vital nutrient for algal growth, thus, a better understanding of phosphorus availability is essential to mitigate harmful algal blooms in lakes. Wind waves are a ubiquitous characteristic of lake ecosystems. However, its effects on the cycling of organic phosphorus and its usage by phytoplankton remain poorly elucidated in shallow eutrophic lakes. A mesocosm experiment was carried out to investigate the responses of alkaline phosphatase activity fractions to wind waves in large, shallow, eutrophic Lake Taihu. Results showed that wind-driven waves induced the release of alkaline phosphatase and phosphorus from the sediment, and dramatically enhanced phytoplanktonic alkaline phosphatase activity. However, compared to the calm conditions, bacterial and dissolved alkaline phosphatase activity decreased in wind-wave conditions. Consistently, the gene copies of Microcystis phoX increased but bacterial phoX decreased under wind-wave conditions. The ecological effects of these waves on phosphorus and phytoplankton likely accelerated the biogeochemical cycling of phosphorus and promoted phytoplankton production in Lake Taihu. This study provides an improved current understanding of phosphorus availability and the phosphorus strategies of plankton in shallow, eutrophic lakes.     

Prediction of Pb speciation in concentrated and dilute nutrient solutions

Despite the presence of numerous studies in the literature examining the phytotoxicity of Pb, there is a lack of precise quantitative data on limiting concentrations of Pb for plant growth. Using the PhreeqcI chemical equilibrium model, simulations were conducted to examine the speciation of Pb in concentrated and dilute nutrient solutions. Due to the higher P concentration of Hoagland's solution (1000microM), precipitation of chloropyromorphite (Pb5(PO4)3Cl) was predicted to occur at lower pH values, and at lower Pb concentrations, than for a dilute nutrient solution (2microM P). Although nutrient solutions prepared in the glasshouse were supersaturated (and Pb concentrations were substantially higher than predicted by modeling), they confirmed the importance of the P concentration in influencing the precipitation of Pb. Given the low solubility of Pb-phosphates, nutrient solutions with low P concentrations should be utilized, and plant growth should be related to measured Pb concentrations rather than to the quantity of Pb initially added.     

Spatial variability of arsenic concentration in soils and plants, and its relationship with iron, manganese and phosphorus

Spatial distribution of arsenic (As) concentrations of irrigation water, soil and plant (rice) in a shallow tube-well (STW) command area (8 ha), and their relationship with Fe, Mn and P were studied. Arsenic concentrations of water in the 110 m long irrigation channel clearly decreased with distance from the STW point, the range being 68-136 μg L⁻¹. Such decreasing trend was also noticed with Fe and P concentrations, but the trend for Mn concentrations was not remarkable. Concerning soil As, the concentration showed a decreasing tendency with distance from the pump. The NH₄-oxalate extractable As contributed 36% of total As and this amount of As was associated with poorly crystalline Fe-oxides. Furthermore only 22% of total As was phosphate extractable so that most of the As was tightly retained by soil constituents and was not readily exchangeable by phosphate. Soil As (both total and extractable As) was significantly and positively correlated with rice grain As (0.296 ± 0.063 μg g⁻¹, n = 56). Next to drinking water, rice could be a potential source of As exposure of the people living in the As affected areas of Bangladesh.