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The environmental effects of the urban agglomeration planning policy (UAPP) are an exploration by rapidly developing China and a concern for countries seeking development and urban reform around the world. This paper takes the three regional urban agglomerations in the Yellow River Basin (YRB) as the research object and collects the panel data of 106 prefecture-level cities from 2006 to 2019 to study the reduction effects of UAPP on the industrial wastewater discharge (IWD). The empirical results from Difference-in-Differences models indicate that UAPP can significantly inhibit IWD. UAPP reduces IWD by promoting green innovation, and the development of service industries can strengthen this effect. UAPP shows a stronger IWD reduction effect in the northeast YRB than that in the southwest region. Compared to urban agglomerations with a single provincial jurisdiction, UAPP exerts stronger IWD reduction effects on urban agglomerations with multiple jurisdictions. Moreover, there exist spatial spillover effects of UAPP on IWD. These findings provide support and references for urban reform and the development of green cities in countries around the world, especially in developing countries. • Urban agglomeration planning policies can reduce industrial wastewater discharge. • Green innovation is the main intermediary factor. • Service industry development strengthens the discharge reduction effects. • The discharge reduction effects are stronger with multiple jurisdictions. • There exist spatial spillover effects of the discharge reduction effects. [ABSTRACT FROM AUTHOR]

The amount of industrial pollution entering the environment and its impact on living organisms is an ongoing concern. At the same time, due to an increasing awareness, new methods of wastewater treatment are being explored that are not only effective but also environmentally acceptable. Meeting environmental standards for permitted concentrations is a necessity, but investigating the effects of wastewater on living organisms is also an important issue. In this paper, the influence of metal ions (Fe(III), Cr(III), Ni(II), Cu(II)) in industrial wastewater from electropolishing of stainless steel on Daphnia magna has been investigated. Daphnids have been exposed to wastewater both before and after treatment (Ca(OH) 2 precipitation, sorption with peat). Immobilisation in a 48-h acute toxicity test and EC 50 has been determined. In the case of studied industrial wastewater, the organic content (expressed as total organic carbon) of the effluent has a positive impact in terms of the survival of D. magna and increases the range of heavy metal concentrations tolerated by them. The application of a two-stage process with Ca(OH) 2 neutralisation followed by sorption with peat allows for the removal of almost 100% of metal ions from the wastewater. The reduction obtained ensured a limited impact on D. magna and a decrease in immobilisation to less than 10%. Proper execution of the wastewater treatment process ensures a reduction of its negative impact on living organisms. • Influence of industrial electropolishing wastewater on D. magna has been investigated. • Ca(OH)2 treatment and sorption with peat from a health resort in Poland were used. • Two-stage treatment removed almost 100% of Fe, Cr, Ni and Cu ions from wastewater. • The reduction in concentration resulted in a decrease in D.magna immobilisation to <10%. • Reduced toxicity has mitigated the environmental impact of wastewater. [ABSTRACT FROM AUTHOR]