J.N. Lester

Nonylphenol in the environment : A critical review on occurrence, fate, toxicity and treatment in wastewaters

Nonylphenol is a toxic xenobiotic compound classified as an endocrine disrupter capable of interfering with the hormonal system of numerous organisms. It originates principally from the degradation of nonylphenol ethoxylates which are widely used as industrial surfactants. Nonylphenol ethoxylates reach sewage treatment works in substantial quantities where they biodegrade into several by-products including nonylphenol. Due to its physical-chemical characteristics, such as low solubility and high hydrophobicity, nonylphenol accumulates in environmental compartments that are characterised by high organic content, typically sewage sludge and river sediments, where it persists. The occurrence of nonylphenol in the environment is clearly correlated with anthropogenic activities such as wastewater treatment, landfilling and sewage sludge recycling. Nonylphenol is found often in matrices such as sewage sludge, effluents from sewage treatment works, river water and sediments, soil and groundwater. The impacts of nonylphenol in the environment include feminization of aquatic organisms, decrease in male fertility and the survival of juveniles at concentrations as low as 8.2 microg/l. Due to the harmful effects of the degradation products of nonylphenol ethoxylates in the environment, the use and production of such compounds have been banned in EU countries and strictly monitored in many other countries such as Canada and Japan. Although it has been shown that the concentration of nonylphenol in the environment is decreasing, it is still found at concentrations of 4.1 microg/l in river waters and 1 mg/kg in sediments. Nonylphenol has been referred to in the list of priority substances in the Water Frame Directive and in the 3rd draft Working Document on Sludge of the EU. Consequently there is currently a concern within some industries about the possibility of future regulations that may impose the removal of trace contaminants from contaminated effluents. The significance of upgrading sewage treatment works with advanced treatment technologies for removal of trace contaminants is discussed.

A review of atmospheric polycyclic aromatic hydrocarbons: Sources, fate and behavior

A review has been written to assess the sources, fate and behavior of polycyclic aromatic hydrocarbons (PAH) in the atmosphere. PAH are formed mainly by anthropogenic processes, especially the combustion of organic fuels. PAH concentration in air will reflect the location of source emitters, with high concentrations corresponding with urban and industrial areas. PAH are however ubiquitous contaminants of the environment having been detected in remote areas of the world. This is thought to be due to long term transport in the atmosphere. PAH can also be subjected to chemical and/ or photochemical change whilst resident in the atmosphere prior to their removal by either wet or dry deposition.

Aquatic environmental assessment of the top 25 English prescription pharmaceuticals

An environmental assessment is presented for the 25 most used pharmaceuticals in the National Health Service (NHS) in England in 2000. Predicted environmental concentrations (PECs) for the aquatic environment were calculated using conservative assumptions and all PECs exceeded 1 ng 1 (-1). The calculation of predicted no-effect concentration (PNEC) based on aquatic toxicity data from the literature was possible for eleven of the pharmaceuticals. PNECs were predicted with ECOSAR for 12 of the remaining 14 but no data was available for two of the compounds. The PEC/ PNEC ratio exceeded one for Paracetamol, Amoxycillin, Oxytetracycline and Mefenamic acid. Comparisons of the predicted concentrations of the compounds in sewage sludge based on either calculated sludge-water coefficients (Kd), octanol water coefficients (K(ow)), acid base constants (pKa) or environmental modelling revealed large variations. No toxicity data was available for the terrestrial environment and no assessment was made.

Polybrominated diphenyl ether (PBDE) flame retardants.

Polybrominated diphenyl ether, PBDE, flame retardants are now a world-wide pollution problem reaching even remote areas. They have been found to bioaccumulate and there are concerns over the health effects of exposure to PBDEs, they also have potential endocrine disrupting properties. They are lipophilic compounds so are easily removed from the aqueous environment and are predicted to sorb onto sediments and particulate matter or to fatty tissue, aiding their distribution throughout the environment. PBDEs are structurally similar to PCBs and DDT and, therefore, their chemical properties, persistence and distribution in the environment follow similar patterns. Concentrations of PBDEs found in environmental samples are now higher than those of PCBs. Evidence to date demonstrates that PBDEs are a growing problem in the environment and concern over their fate and effects is warranted. The manufacture of reactive and additive flame retardants is briefly discussed and their fate and behaviour in the environment is assessed. PBDE toxicology is reviewed and methods of analysis are evaluated.

Review: Phosphorus removal and recovery technologies

A review has been undertaken of technologies to remove and recover phosphorus from wastewater and their potential to facilitate the recycling of phosphorus and its sustainability. A wide range of technologies were identified, including chemical precipitation, biological phosphorus removal, crystallisation, novel chemical precipitation approaches and a number of wastewater and sludge-based methods. Phosphorus in wastewater represents a significant renewable resource and there is no environmental or technical reason why phosphorus cannot be recycled. Indeed, there are many potential environmental benefits from reducing reliance on phosphate rock and associated impurities, a practice which is ultimately unsustainable. Co-operation and leadership by government is required to progress phosphorus towards sustainability.

Human Pharmaceuticals in the Aquatic Environment a Review

There has been increasing concern in recent years about the occurrence, fate and toxicity of pharmaceutical products in the aquatic environment. Many of the more commonly used drug groups (for example antibiotics) are used in quantities similar to those of pesticides and other organic micropollutants, but they are not required to undergo the same level of testing for possible environmental effects. The full extent and consequences of the presence of these compounds in the environment are therefore largely unknown and the issue as a whole is ill-defined. Although these compounds have been detected in a wide variety of environmental samples including sewage effluent, surface waters, groundwater and drinking water, their concentrations generally range from the low ppt to ppb levels. It is therefore often thought to be unlikely that pharmaceuticals will have a detrimental effect on the environment. However, the lack of validated analytical methods, limited monitoring data and the lack of information about the fate and toxicity of these compounds and/or their metabolites in the aquatic environment makes accurate risk assessments difficult.

Metal removal in activated sludge: the role of bacterial extracellular polymers

Abstract A combination of flocculation and settling is the mechanism by which metal removal is achieved in activated sludge. Bacterial extracellular polymers appear to play an important role in flocculation; metal cations may also be involved in this process. Extracellular polymers in activated sludge are mainly of a polysaccharide nature, although protein and nucleic acid from autolysis are constituents of the polymer matrix. Precipitated metals may be removed either by independent settling or by physical trapping in the sludge floc matrix. Metals present in the ionic form may be removed from solution by adsorption to sites on bacterial extracellular polymers. Metal ions may also be accumulated in the cytoplasm of a bacterial cell, or adsorbed on to the cell wall. If activated sludge plants are overloaded with metals, toxic effects on bacteria and other microorganisms may severely inhibit the treatment process, resulting in poor quality effluents. Acclimated bacterial cultures can tolerate much higher metal concentrations than non-acclimated cultures; these are advantageous in the treatment of metal-laden wastes.

Human Pharmaceuticals in Wastewater Treatment Processes

The presence of human pharmaceutical compounds in surface waters is an emerging issue in environmental science. In this study the occurrence and behavior of human pharmaceuticals in a variety of wastewater treatment processes is reviewed. Although some groups are not affected by sewage treatment processes others are amenable to degradation, albeit incomplete. While water purification techniques such as granular activated carbon could potentially remove these pollutants from wastewater streams, the high cost involved suggests that more attention should be given to the potential for the optimization of current treatment processes, and reduction at source in order to reduce environmental contamination.

Conditions influencing the precipitation of magnesium ammonium phosphate.

Struvite precipitation in wastewater treatment works has caused substantial operational problems since the early 1960s. Struvite, magnesium ammonium phosphate hexahydrate (MgNH4PO4 6H2O), is a white inorganic crystalline mineral that precipitates in places with increased turbulence such as pumps, aerators and pipe bends. Batch experiments were conducted to examine the influence of a number of physical and chemical parameters on struvite crystallisation. This was undertaken by dosing a medium of de-ionised water with varying concentrations of Mg2+, NH4+ and PO4(3-) ions. Preliminary experiments found that struvite could be precipitated out of solution at pH 10 and increasing the ion concentration stoichiometrically could increase crystal yield. Increasing the NH4+ concentration increased purity of the precipitate. As reaction time was increased from 1 to 180 min, crystal size was found to increase from 0.1 to 3mm.

Leaching of chromated copper arsenate wood preservatives: a review

Recent studies have generated conflicting data regarding the bioaccumulation and toxicity of leachates from preservative-treated wood. Due to the scale of the wood preserving industry, timber treated with the most common preservative, chromated copper arsenate (CCA), may form a significant source of metals in the aquatic environment. The existing literature on leaching of CCA is reviewed, and the numerous factors affecting leaching rates, including pH, salinity, treatment and leaching test protocols are discussed. It is concluded from the literature that insufficient data exists regarding these effects to allow accurate quantification of leaching rates, and also highlights the need for standardised leaching protocols.