Immobilization of Lead and Zinc Leached from Mining Residual Materials in Kabwe, Zambia: Possibility of Chemical Immobilization by Dolomite, Calcined Dolomite, and Magnesium Oxide

Massive amount of highly contaminated mining residual materials (MRM) has been left unattended and has leached heavy metals, particularly lead (Pb) and zinc (Zn) to the surrounding environments. Thus, the performance of three immobilizers, raw dolomite (RD), calcined dolomite (CD), and magnesium oxide (MO), was evaluated using batch experiments to determine their ability to immobilize Pb and Zn, leached from MRM. The addition of immobilizers increased the leachate pH and decreased the amounts of dissolved Pb and Zn to different extents. The performance of immobilizers to immobilize Pb and Zn followed the following trend: MO > CD > RD. pH played an important role in immobilizing Pb and Zn. Dolomite in RD could slightly raise the pH of the MRM leachate. Therefore, the addition of RD immobilized Pb and Zn via adsorption and co-precipitation, and up to 10% of RD addition did not reduce the concentrations of Pb and Zn to be lower than the effluent standards in Zambia. In contrast, the presence of magnesia in CD and MO significantly contributed to the rise of leachate pH to the value where it was sufficient to precipitate hydroxides of Pb and Zn and decrease their leaching concentrations below the regulated values. Even though MO outperformed CD, by considering the local availability of RD to produce CD, CD could be a potential immobilizer to be implemented in Zambia.

Quantifying the energy consumption and greenhouse gas emissions of changing wastewater quality standards

Regulations to ensure adequate wastewater treatment are becoming more stringent as the negative effects of different pollutants on human health and the environment are understood. However, treatment of wastewater to remove pollutants is energy intensive, so has added significantly to the operation costs of wastewater treatment plants. Analysis from six of the largest wastewater treatment works in South East England reveals that the energy consumption of these treatment works has doubled in the last five years due to expansions to meet increasingly stringent effluent standards and population growth. This study quantifies the relationship between energy use for wastewater treatment and four measures of pollution in effluents from UK wastewater treatment works (biochemical oxygen demand, ammoniacal nitrogen, chemical oxygen demand and suspended solids). The linear regression results show that indicators of these pollutants in effluents, together with the extension of plants to improve wastewater treatment, can predict over 95% of energy consumption. Secondly, using scenarios, the energy consumption and greenhouse gas emissions of effluent quality standards are estimated. The study finds that tightening effluent standards to increase water quality could result in a doubling of electricity consumption and an increase of between 1.29 and 2.30 additional MTCO2 per year from treating wastewater in large works in the UK.

Landfill leachate treatment - towards an integrated approach

Full-scale results during two years operation in a controlled activated sludge system withnitrogen removal show that nitrification can be managed around the year, even long periods atlow temperature ( 4 - 5 °C), which is a new feature in landfill leachate management. The totalnitrogen removal was 46 - 57 % as annual averages and was limited seasonally by the lowcarbon content of leachate, Addition of external carbon was also tested. The removal ofheavy metals was reasonable (45 - 90 %), but organohalogen compounds was removed onlypartially (around 20 %). The biological step suits for the first phase of local treatment andrather low costs can be achieved. If more stringent effluent standards are required, a posttreatment system can be added - some of the most suitable alternatives and their costs arediscussed. From environmental point of view more comprehensive alternatives should beconsidered, which means the integration of processes inside the landfill body to the wholetreatment system.

ESTIMATION OF COASTAL ASIMILATION CAPACITY BASED ON STANDARD EFFLUENT WASTE NITROGEN AND PHOSFORUS OF SHRIMP CULTIVATION

This research was conducted in May 2018 in the coastal area of ​​Banyuputih Subdistrict, Situbondo Regency, East Java with the aim of estimating the volume of seawater available in coastal waters and the capacity of coastal waters in assimilating N and P waste load based on N and P effluent standards for cultivation shrimp. The results showed that the coastal waters of Banyuputih had a volume of water available for dilution of N and P wastes of 43,198,298 m3. The maximum N and P waste load that can be assimilated by water according to the standard effluent of N waste for shrimp farming is 172, 8 tons and for the P waste load is 17.28 tons. The results of this study can be used as a reference in determining the environmental carrying capacity of coastal waters in the development of intensive shrimp ponds in the study area.

Separating grey- and blackwater in urban water cycles – sensible in the view of misconnections?

The infrastructure approach SEMIZENTRAL has been developed for fast growing cities, to meet their challenges regarding water supply as well as biowaste and wastewater treatment. The world's first full-scale SEMIZENTRAL Resource Recovery Center (RRC) has been implemented in Qingdao (PR China). Greywater (GW) and blackwater (BW) are collected and treated separately. Measurement of influent concentrations differ significantly from the design values. Thus, the operation strategy for the RRC had to be adapted. Amongst other reasons, the changed influent characteristic was caused by misconnections of GW and BW sewers. Already a misconnection rate of 6–8% requires an extension of the GW treatment process for nitrification/denitrification to fulfill effluent standards. Hence, measures should be taken to avoid or reduce misconnections. Nonetheless, in a semi-centralized scale (>10,000 inhabitants) a 100% avoidance might not be possible. Thus, consequences from misconnections should be considered during the design of source-oriented infrastructure systems.