Allium test has already been used to determine cytotoxicity of waste drilling fluids. In the present work the cytotoxicity of four pure chemicals (Defoamex, Idthin 400, Magco Thin and Slick Pipe) was investigated. Those chemicals are components of drilling fluids, therefore, they are usually constituents of oil and gas industry waste waters. The tested chemicals were prepared in 1:9 dilution and cytotoxic effects on root-tip meristem ofAllium ascalonicum were analysed after 24-, 48- and 72-hour-treatments. All samples showed cytotoxicity which was proved by cytogenetic parameters such as inhibition of mitotic activity and increase of mitotic abnormalities and chromosomal aberrations in comparison with the control. Almost all mitotic abnormalities induced by four chemicals tested were the result of disturbed spindle mechanisms accompanied with stickiness. Slick Pipe revealed the most prominent mitodepressive effect and induced a high number of abnormalities. It caused a significant decrease of mitotic activity and increase of mitotic abnormalities after all three treatment durations, while chemicals Defoamex and Magco Thin showed a significant decrease of mitotic activity only after 72-hour-treatment. Chemicals Defoamex, Idthin 400 and Magco Thin revealed a significant increase of mitotic abnormalities after 48- and 72-hour-treatments.

A greenhouse experiment using soil was conducted to investigate the effects of the addition of different forms of either nickel or lead, together with an acidifying agent, on the distribution of Ni, Pb, Zn, Cu and Mn in wheat plants, and on the post-harvest extractability of these elements in the soil. Two treatments consisting of soil alone or soil mixed with sewage sludge at a rate of 200 Mg ha⁻¹ were used as controls. Nickel (400 mg kg⁻¹) or lead (1600 mg kg⁻¹) was added to the soil as an inorganic salt or mixed previously with sewage sludge. Six further treatments including an acidifying agent (wastewater from olive oil processing: alpechin) were also prepared. Wheat (Triticum aestivum L. var. Mesa) plants were harvested 75 d after germination. Dry matter yield of wheat was increased by the addition of sewage sludge. No reductions in yield were observed after the addition of nickel or lead. Nickel concentration and uptake by wheat, and extractability from soil, were higher when the sewage sludge enriched in nickel was added to soil. This effect was enhanced when the acidifying agent was also added. In contrast, lead availability was higher after the addition of inorganic Pb to soil. The addition of both forms of Ni enhanced Zn, Cu and Mn uptake by the plant, whereas the addition of lead increased Zn and Cu. After harvesting, increases in extractable Zn and Cu in the soil were observed only in treatments with sewage sludge, and not after the addition of Ni or Pb, or after the addition of the acidifying agent. Decreasing the pH of the soil with the acidifying agent tended to increase Mn uptake by wheat, and Mn extractability from the soil after harvesting.

A study on the factors influencing nitrogen removal in waste water stabilization ponds was undertaken in an eight-pond series in Werribee, Australia. Nitrogen species including Kjeldahl nitrogen, total ammonia nitrogen, nitrite and nitrate were monitored monthly from March 1993 to January 1994. At the same time, pH, temperature, chlorophylla content and dissolved oxygen were also recorded. Highest nitrogen removal occurred during the period with highest levels of chlorophylla content and dissolved oxygen, but the rate of nitrogen removal was not related to temperature and pH. Enhanced photosynthetic activities resulting from an increased phytoplankton abundance due to prolonged detention time caused an increase in dissolved oxygen, and created an optimum condition for nitrification to occur. In this process, ammonia was oxidized to nitrite and nitrate which were subsequently reduced to elemental nitrogen. Apart from nitrification-denitrification which was the major nitrogen removal pathway in the study system, algal uptake of ammonium, nitrate and nitrite as nutrient sources also contributed to the nitrogen removal. The role of phytoplankton and zooplankton in the treatment process in waste stabilization ponds was discussed.

In the late 1980s, citrus plantations in the area of Villarreal (Spain) showed injuries similar to those previously reported for boron and fluorine toxicity. The area was affected by the disposal of industrial wastewater, mainly from ceramic industries. Conjunctive uses of surface water, groundwater and wastewater for irrigation had taken place. A survey was conducted at 25 orchards to assess leaves and soil for their boron, fluorine, lead, nickel and zinc contents. Wastewater and groundwater were also analyzed to corroborate the presence of these pollutants. The results showed that both boron and fluorine contents were greater than those reported as excess at the most part of the orchards included in the study. Heavy metals toxicity effects were not confirmed. Boron pollution was attributed to industrial wastewater spills and fluorine contamination from atmospheric pollution.

Groundwater in the Rio de las Avenidas sub-basin corresponds to the bicarbonate-sodium and bicarbonate-calcium hydrochemical facies, which result from the mineralization of water passing through alkaline rocks (andesites) which prevail in this basin. However, the presence of high concentrations of Na⁺ and K⁺ reveals the existence of an external inflow of these elements: the registered mean values are respectively 94.3 and 19.0 ppm, with the Tèllez and Tizayuca areas standing out with reported values of up to 142 ppm. As for the concentration of soluble water cations, we find in decreasing order: Na⁺, Ca²⁺, Mg²⁺, K⁺, along with the anions HCO₃ ⁻, Cl⁻, SO₄ ²⁻, CO₃ ⁻, which combine to form the NaHCO₃, NaCl, Ca(HCO₃)₂, MgSO₄ and KCl salts. The presence of biological contaminants, P and detergents in the groundwater indicates that it may have been contaminated by waste water. In addition to the contaminants mentioned above, large quantities of Pb, B, Zn, Fe, Mn, Cr, Co were detected and although Fe, Pb, Zn, B, and Mn are closely related to the local lithology, the high concentrations of these elements along with the occurrence of Co, Cr, Cd, and Ni confirm the gradual degradation of the aquifers in the sub-basin. The water temperature indicates the existence of low temperature thermal processes in the area.