磷(P)是农业肥料中的关键成分,但它也是一种稀缺资源,为什么它的回收已经被彻底调查,一个有前途的资源是污水污泥。由于在污泥处置方面有更严格的规定,热处理(如焚烧)已成为一个有吸引力的选择。焚烧过程改变了P的化学形态,有利于钙缔合(磷灰石,磷灰石磷(AP)物种,这对于P回收是优选的。为了实现质的转化,确定限制或促进因素很重要。这项研究报道了铁的影响,铝和钙对磷酸铁和磷酸铝(NAIP)向AP物种的转化,通过研究瑞典10个市政污水处理厂的污泥和灰分进行评估。还评估了在处理过程中添加的铁和铝的效果。获得的结果表明,高钙浓度有利于在污泥和灰烬中形成AP物种,而高浓度的铁和铝有利于在污泥中形成NAIP物种。从NAIP到AP物种的转变受到铝的阻碍,不管它的起源,而铁没有这样的相关性。因此,为了从污水污泥灰中高效回收磷,在处理过程中添加的铝的量,以及它在污水处理厂流入流中的浓度,必须是有限的。
Phosphorus (P) is a key component in agricultural fertilizers, but it is also a scarce resource, why its recycling has been thoroughly investigated and one promising resources is sewage sludge. Because of stricter regulations in terms of sludge disposal, thermal treatment (e.g. incineration) has become an attractive option. The incineration process alters the chemical speciation of P in favour to calcium-associated (apatite, apatite phosphorus (AP)) species, which is preferred for P recovery. In order to achieve qualitatively transformation, it is important to identify limiting or promoting factors. This study reports on the impact of iron,
aluminium and calcium on the transformation of iron- and
aluminium-phosphate (NAIP) to AP species, assessed by studying sludge and ash from 10 municipal wastewater treatment plants in Sweden. The effect of iron and
aluminium added in the treatment processes was also evaluated. The obtained results show that high calcium concentration favours formation of AP species in both sludge and ashes, whereas high concentration of iron and
aluminium favours formation of NAIP species in the sludge. The transformation from NAIP to AP species is hampered by
aluminium, irrespectively of its origin, whereas no such correlations could be seen for iron. Therefore, in order to enable efficient P recovery from sewage sludge ash, the amount of
aluminium added in the treatment process, as well as its concentration in influent streams to the treatment plants, must be limited.