Occurrence and environmental risks of contaminants of emerging concern across the River Athi Basin, Kenya, in dry and wet seasons.

Globally, the environmental occurrence of Contaminants of Emerging Concern (CECs) including pharmaceuticals (PhACs), personal care products (PCPs) and modern polar pesticides has raised ecological and human health awareness. However, as the developed world races against time to establish regulatory measures to mitigate their effects, developing nations including Kenya are lagging behind, partly due to unavailability of adequate data. In this work, a multi-residue analysis of 86 CECs was carried out on 198 surface water and 18 effluent samples collected at 24 sites across the River Athi basin area, Kenya, in both dry and rainy seasons. Overall, 57 CECs comprising 31 PhACs (0.4 ng L-1-142 µg L-1), 6 PCPs (0.7-570 ng L-1) and 20 pesticides (0.3 ng L-1-8.3 µg L-1) were detected. The maximum loads varied from 217 g day-1 (PCPs) to 46 kg day-1 (PhACs). Individually, carbamazepine, nevirapine, sulfamethoxazole and DEET were the most ubiquitous CECs, with detection frequencies (DF) higher than 80 %. The highest concentrations were observed at river sites that are heavily impacted by informal settlements, highlighting the critical role of slums in urban rivers pollution. At least 8 CECs including acetamiprid, alachlor, atrazine, diuron, nevirapine and paracetamol show potential risk to algae, Daphnia magna and fish, as exemplified by Risk Quotients (RQ) up to 174. Similarly, potential risk of antibiotic resistant bacteria development is evident (RQ up to 64), being driven by metronidazole, sulfamethoxazole and trimethoprim. Ultimately, further studies on the occurrence and distribution of antibiotic resistant bacteria within the basin and among the communities consuming untreated river water for drinking is merited.

Occurrence and point-of-use treatment of contaminants of emerging concern in groundwater of the Nzoia River basin, Kenya.

Groundwater constitutes a major source of fresh water globally. However, it faces serious quality challenges from both conventional pollutants and contaminants of emerging concern (CECs) such as pharmaceutically active compounds (PhACs), personal care products (PCPs) and pesticides. There exists a significant knowledge gap regarding the occurrence of CECs in groundwater, especially in Africa. This study presents unique data on the concentration of fourteen PhACs, five PCPs and nine pesticides in groundwater wells in Nzoia River basin, Kenya. Generally, PCPs were the most dominant class with concentrations up to 10 µg/L (methylparaben). Anti(retro)virals, being important in the treatment of HIV/AIDS, were more prevalent among the PhACs as compared to the developed world, with concentrations up to 700 ng/L (nevirapine). In contrast, pesticides were measured at lower concentrations, the maximum being 42 ng/L (metolachlor). A basic risk assessment shows that - among the detected CECs - carbamazepine may pose medium human health risk and requires further investigation among infants and children. Point-of-use (POU) technologies are being increasingly promoted especially in the developing nations to provide drinking water solutions at the household level, but very little data is available on their performance towards CECs removal. Therefore, besides measuring CECs in groundwater, we investigated ceramic filters and solar disinfection (SODIS) as possible POU treatment options. Both techniques show potential to treat CECs in groundwater, with removal efficiencies higher than 90% obtained for 41 and 22 compounds in ceramic filters and SODIS, respectively. Moreover, for the more recalcitrant compounds (e.g. sulfadoxin), the performance is improved by up to three orders of magnitude when using TiO2 as a photocatalyst in SODIS.

Occurrence and treatment of contaminants of emerging concern in the African aquatic environment: Literature review and a look ahead.

Awareness about the rising detection and reported (eco)toxicological effects of contaminants of emerging concern (CECs, e.g. pharmaceuticals and personal care products - PPCPs - and modern pesticides) in the aquatic environment is growing. CECs are increasingly reported in the African aquatic environment, although the amount of data available is still limited. In this work, a comprehensive review is presented on the occurrence of CECs in wastewater, sludge, surface water, sediment, groundwater and drinking water of Africa. Further attention is given to the performance of wastewater stabilization ponds (WSPs) and trickling filters (TF) with respect to CECs removal. For the first time, we also look at the state of knowledge on the performance of point-of-use technologies (POUs) regarding the removal of CECs in drinking water. Generally, CECs in Africa occur at the same order of magnitude as in the Western world. However, for particular groups of compounds and at specific locations such as informal settlements, clearly higher concentrations are reported in Africa. Whereas antiretroviral and antimalarial drugs are rarely detected in the Western world, occurrence patterns in Africa reveal concentrations up to >100 µg L-1. Removal efficiencies of WSPs and TFs focus mainly on PPCPs and vary significantly, ranging from no removal (e.g. carbamazepine) to better than 99.9% (e.g. paracetamol). Despite the rising adoption of POUs, limited but promising information is available on their performance regarding CECs treatment in drinking water, particularly for the low-cost devices (e.g. ceramic filters and solar disinfection - SODIS) being adopted in Africa and other developing countries.

Occurrence, fate and removal of pharmaceuticals, personal care products and pesticides in wastewater stabilization ponds and receiving rivers in the Nzoia Basin, Kenya.

Although there is increased global environmental concern about emerging organic micropollutants (EOMPs) such as pharmaceuticals, personal care products (PPCPs) and polar pesticides, limited information is available on their occurrence in Africa. This study presents unique data on concentrations and loads of 31 PPCPs and 10 pesticides in four wastewater stabilization ponds (WSPs) and receiving rivers (flowing through urban centres) in Kenya. The WSPs indicate a high potential to remove pharmaceutically active compounds (PhACs) with removals by up to >4 orders of magnitude (>99.99% removal), mainly occurring at the facultative stage. However, there are large differences in removal among the different classes, and a shift in the relative PhACs occurrence is observed during wastewater treatment. Whereas the influent is dominated by high-consumption PhACs like anti-inflammatory drugs (e.g. paracetamol and ibuprofen, up to 1000 µg L-1), the most recalcitrant PhACs including mainly antibiotics (e.g. sulfadoxin and sulfamethoxazole) and antiretrovirals (e.g. lamivudine and nevirapine) are largely abundant (up to 100 µg L-1) in treated effluent. Overall, concentrations of EOMPs in the Nzoia Basin rivers are the highest in dry season (except pesticides) and in small tributaries. They are of the same order of magnitude as those measured in the western world, but clearly lower than what we recently measured in the Ngong River, Nairobi region. Based on the specific consumption patterns and recalcitrant behavior, high concentrations (>1000 ng L-1) are observed in the rivers for PPCPs like lamivudine, zidovudine, sulfamethoxazole and methylparaben. Concentration levels of pesticides are in general one order of magnitude lower (<250 ng L-1). Our data suggest a continuous input of EOMPs to the rivers from both point (WSPs) and diffuse (urban centres) sources. To better understand and manage the impact of both sources, EOMP removal mechanisms in WSPs and their attenuation in rivers merit further research.

2-Amino-ethanaminium iodide.

The title salt, [NH(3)CH(2)CH(2)NH(2)](+)·I(-), has an array structure based on strong inter-molecular N-H⋯N hydrogen bonding formed between the ammonium and amine groups of adjacent cations. This inter-action gives a helical chain of cations that runs parallel to the b axis. The four remaining NH group H atoms all form hydrogen bonds to the iodide anion, and these iodide anions lie in channels parallel to the cation-cation chains.

catena-Poly[[(nitrito-κO,O')silver(I)]-µ-1,2-bis-[1-(pyridin-4-yl)ethyl-idene]hydrazine-κN:N'].

The asymmetric unit of the title compound, [Ag(NO(2))(C(14)H(14)N(4))](n), contains half of the repeating formula unit (Z' = 1/2). The Ag(I) ion lies on a twofold rotation axis. The primary structure consists of a one-dimensional coordination polymer formed by the Ag(I) ions and the bipyridyl azine ligand in which there is an inversion center at the mid-point of the N-N bond. The nitrite anion inter-acts with the Ag(I) ion through a chelating µ(2) inter-action involving both O atoms. In the crystal, the coordination chains are parallel and inter-act through Ag⋯π [3.220 (2) Å] and π-π [3.489 (3) Å] inter-actions.

5,7,7,12,14,14-Hexamethyl-4,8-diaza-1,11-diazo-niocyclotetra-deca-4,11-diene diiodide dihydrate.

The asymmetric unit of the title compound, C(16)H(34)N(4) (2+)·2I(-)·2H(2)O, contains one half-cation, one iodide anion and one water mol-ecule. The cation has crystallographically imposed centrosymmetric symmetry. Despite some differences in the unit-cell dimensions, packing analysis on a cluster of 15 cations and a comparison of the hydrogen bonding suggests that this compound is isostructural with its bromide analogue. Inter-molecular hydrogen bonding forms eight-membered [H-O-H⋯I](2) and [H-N-H⋯I](2) rings and creates a sheet structure.

The cobalt(II) salt of the azo dye Orange G.

Crystallizing the cobalt(II) salt of the azo dye Orange G from water was found to give the solvent-separated ion-pair species hexa-aqua-cobalt(II) 7-oxo-8-(2-phenyl-hydrazin-1-ylidene)-7,8-dihydro-naphthalene-1,3-disulfonate tetra-hydrate, [Co(H(2)O)(6)](C(16)H(10)N(2)O(7)S(2))·4H(2)O. The asymmetric unit of the cobalt(II) salt contains three independent octa-hedral [Co(OH(2))(6)](2+) cations, three azo anions, all with similar configurations, and 12 uncoordinated water mol-ecules. The structure is closely related to that of one of the known magnesium analogues. Both structures have Z' = 3, feature nearly planar azo anions [maximum displacement of azo-N atoms from the plane of the phenyl ring = 0.058 (7) Å] in their hydrazone tautomeric form, form layer structures with hydro-philic and hydro-phobic layers alternating along the b-axis direction, and are stabilized by an extensive network of hydrogen bonds..

4-(Benz-yloxy)benzaldehyde.

The title compound, C(14)H(12)O(2), has an essentially planar conformation with the two aromatic rings forming a dihedral angle of 5.23 (9)° and the aldehyde group lying in the plane of its aromatic group [maximum deviation = 0.204 (3) Å]. Weak inter-molecular C-H⋯O contacts are found to be shortest between the aldehyde O-atom acceptor and the H atoms of the methyl-ene group.

1-Benz-yloxy-4-(2-nitro-ethen-yl)benzene.

The title compound, C(15)H(13)NO(3), crystallizes with three independent mol-ecules per asymmetric unit (Z' = 3). One of these mol-ecules is found to have a configuration with a greater twist between its two aromatic rings than the other two [compare 70.26 (13) and 72.31 (12)° with 84.22 (12)°]. There are also differences in the number and nature of the weak inter-molecular C-H⋯O contacts formed by each of the three mol-ecules.

Cephalexin: a channel hydrate.

The antibiotic cephalexin [systematic name: D-7-(2-amino-2-phenylacetamido)-3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid] forms a range of isomorphic solvates, with the maximum hydration state of two water molecules formed only at high relative humidities. The water content of the structure reported here (C(16)H(17)N(3)O(4)S.1.9H(2)O) falls just short of this configuration, having three independent cephalexin molecules, one of which is disordered, and 5.72 observed water molecules in the asymmetric unit. The facile nature of the cephalexin solvation/desolvation process is found to be facilitated by a complex channel structure, which allows free movement of solvent in the crystallographic a and b directions.