III. Heavy metal content of sewage effluent, sludge, soil, and pasture

Abstract

Surface irrigation of pasture with treated sewage effiuent at Templeton, Christchurch for up to 16 years, had little effect on the heavy metal composition of the soil or pasture. Slightlv higher levels of O.IN HC1-extractable Zn, Cu, Co, and Mn in the effiuent-treated soil did not increase levels of these elements in the pasture, and did not increase the Cd/Zn ratio. The ilb:ience of any marked changes in heavy metal content is attributed to the low levels of these elements in the raw sewage effiuent, which is of domestic origin. It is concluded that at the present effiuent application rate (840 mm/year) the scheme, without sludge disposal, has an essentially indefinite life span, in terms of heavy metal accumulation. If land application of the sludge is introduced, it would take at least 200 years for heavy metals to reach the recommended limit of 5% of the soil cation exchange capacity.

Agricultural use of treated sewage effluents: agronomic and environmental implications and perspectives for Brazil

“…Moreover, the study showed that in sandy soils the recovery percentage of N was higher at lower application rates (50 mm week -1 ), whereas at higher application rates (200 mm week -1 ) the efficiency of N recovery from the effluent was lower (≤ 50%) causing increased N concentrations in the groundwater. In a long term study (16 years) on ryegrass, Quin & Syers (1978) found no changes of Cu, Mn, Ni, Zn, Cd, Cr, Pb, cobalt (Co) and strontium (Sr) concentrations in leaves after TSE irrigation.…”

“…In other studies decreases in heavy metal availability were attributed to increasing pH after TSE irrigation (Falkiner & Smith, 1997), including studies on Ni (Johns & McConchie, 1994b), Cu, Mn, Zn (AlJaloud et al, 1995 and Pb (Paliwal et al, 1998). On the other hand, Quin & Syers (1978) verified in pasture soils irrigated with TSE over 16 years slight increases in available Cu, Mn and Zn concentrations (extracted with 0.1 mol L -1 HCl solution). Also Siebe (1995) found slight increases in Cd, Cu and Zn (extracted in aqua regia) in soils cropped with alfalfa and irrigated with TSE for more than 80 years.…”

Heavy Metals Contamination Through Industrial Effluent to Irrigation Water in Gadoon Amazai (Swabi) and Hayatabad (Peshawar) Pakistan

“…Regular use of water contaminated with heavy metals in cultivated fields leads to soil pollution and slowly make the soil enriched with heavy metals. It has been shown by different studies that the presence of heavy metals like Fe, Pb, Hg reduces the fertility of soil and agricultural output [12]. Certain heavy metals such as Cu, Fe, Mn, Ni and Zn in control concentration, act as micronutrients for plants and micro-organisms while others like Cd, Pb and Cr are harmful beyond a certain limits [13].…”

Disponibilidade de nitrogênio, alterações nas características químicas do solo e do milho pela aplicação de efluente de esgoto tratado.

“…Assim, vários experimentos têm mostrado a possibilidade de obtenção de alta produtividade e qualidade nas culturas de alfafa (Bole & Bell, 1978;Day et al, 1982;Darwish et al, 1999), aveia forrageira (Day & Tucker, 1959), azevém perene (Quin & Syers, 1978;Quin & Woods, 1978), capim de Rhodes (Feigin et al, 1978;Vaisman et al, 1981), capim napier (Jeyaraman, 1988), milho forrageiro (Overman & Nguy, 1975;Karlen et al, 1976;Overman, 1981) e trigo forrageiro (Day & Tucker, 1959;Day et al, 1974), mediante irrigação com água residuária. Porém, a cevada forrageira foi 22% menos produtiva quando irrigada somente com efluente (Day & T ucker, 1959) e tal fato, segundo os autores, foi atribuído à presença de detergentes e de alta concentração de sais solúveis na água residuária.…”

“…Todavia, as informações do presente estudo discordam com alguns dados obtidos por Quin & Syers (1978), Al-Jaloud et al (1995) e Al-Nashabandi et al (1997.…”