No abstract

The efficiency of copper removal from an aqueous solution was investigated in a continuous flow activated sludge system. Two identical biological reactors made of acrylic were used to carry out the research. Reactor one (R1) was used as control and contained only biomass. Reactor two (R2) contained biomass and microwave incinerated rice husk ash (MIRHA). Different concentrations of copper dosages in the range of 0.5 mg/L, 1 mg/L, 2 mg/L, 5 mg/L, 10 mg/L and 15 mg/L were used. Activated sludge was allowed an acclimatization time of 15 days in both reactors. Microwave incinerated rice husk ash (MIRHA) was then added to reactor two (R2) from day 16. It was allowed to acclimatize with the activated sludge until day 25. The reactors were subsequently fed with an aqueous solution containing copper of various doses from day 26 onwards. The results show that the effluents from both reactor one (R1) and reactor two (R2) have a minimum removal efficiency of about 86% for all the copper doses investigated. The maximum average copper removal efficiency for reactor one (R1) and reactor two (R2) is 93% and 97% respectively. Reactor two (R2) had higher copper removal efficiency for all the concentrations investigated. The mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS) of reactor two (R2) significantly increased from phase 2 to phase 6 whereas in reactor one (R1), mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS) stabilized from phase 2 to phase 4. This implies that using microwave incinerated rice husk ash (MIRHA) as an adsorbent in an activated sludge system can increase the reactor performance.

Two support materials, microwave incinerated rice husk ash (MIRHA) and groundwater treatment plant sludge (GWTPS), were used as support materials for biomass in the removal of copper from aqueous solution during a continuous flow study. A third reactor containing biomass alone without the addition of support material (RB) was used as a control to monitor the performance of the support materials. All reactors were given 15 days for the acclimatization of biomass. The reactors containing MIRHA and GWTPS were given an additional 10 days for acclimation after the addition of the support materials on day 15. All reactors were identically designed with a size of 8.5 L and operated at a flowrate of 7 L/d and SRT of 30 days across 8 different phases. Different concentrations of Cu(II) ranging from 0.5 mg/L to 15 mg/L were applied to the reactors at different phases. Results obtained from each phase of the experiments showed that GWTPS and MIRHA improved copper toxicity resistance in their respective reactors. For the control reactor (RB), copper toxicity was significant and violated the DOE Malaysia copper effluent standard at phase 5 (influent concentration 2 mg/L) whereas MIRHA and GWTPS reactors violated the DOE Malaysia copper effluent standard at phase 7 (influent concentration 10 mg/L) respectively. However, GWTPS containing reactor showed slightly better support for toxicity resistance than reactor MIRHA. The toxicity of copper on the three reactors was observed in the reduction of mixed liquor volatile suspended solids (MLVSS) within each reactor. For the control, MLVSS rapidly decreased from phase 3 to phase 8 whereas MIRHA and GWTPS reactors increased from phase 3 to phase 6 and decreased from phase 7 to phase 8. These results have shown that MIRHA and GWTPS have the potential of improving biomass resistance to toxicity of heavy metals.

Copper removal from synthetic wastewater by biomass assisted adsorbents was evaluated in this study. Three different biological reactors of the same size (8.5 L) were aerobically operated at solid retention time (SRT) of 30 days and hydraulic retention time (HRT) of 0.8 day. The first reactor was operated with biomass alone as the control reactor. The second reactor consist of biomass and ground water treatment plant sludge (GWTPS) whilst the third reactor consist of biomass and hybrid adsorbent (HA), which comprises 50% of microwaved incinerated rice husk ash (MIRHA) and 50% of GWTPS. The reactors were operated in eight different phases (Phase 1 – 8). Phases 1 – 2 were operated as acclimation period during which the biomass were allowed to stabilize within the reactor without copper addition. From phase 3 – phase 8, copper was added to the influent of the reactors at various concentrations and the reactor performance was monitored every two days. Results revealed that copper removal with the control reactor (RC) was markedly inferior compared with the reactors supported with GWTPS and HA adsorbents. The copper removal in the control reactor was in the range 0.47 – 2.62 mg/L from phase 5 to phase 8. Copper removal in the GWTPS reactor was in the range 0.19 – 0.83 mg/L from phase 5 to phase 8 whereas copper removal in the HA reactor was in the range 0.27 – 1.09 mg/L at the same conditions. Percentage removal of copper was 85 %, 94 % and 95 % for the control, GWTPS and HA reactors, respectively. The adsorbents, GWTPS and HA reactors removed copper effectively. This study demonstrates that solid waste materials such as GWTPS and HA can be beneficially utilized to improve biomass tolerance towards heavy metal toxicity and yields a significant removal of copper.

The performance of a biological system was evaluated for copper removal with and without the addition of an adsorbent to the aeration compartment. Three different reactors were employed in this study. The first reactor consist of biomass alone and was used as a control reactor (CR). The second reactor consist of biomass and microwave incinerated rice husk ash (MIRHA) whereas the third reactor consist of biomass and hybrid adsorbent (HA), which is a mixture of MIRHA and groundwater treatment plant sludge (GWTPS). The reactors were operated at solid retention time (SRT) of 30 days and hydraulic retention time (HRT) of 19.8 hours. The experiment was conducted in 8 different phases consisting of various copper concentrations coming from the influent source. The first and second phase were acclimation period during which copper was not added to the influent wastewater. From the third to the eight phase, copper was fed to the reactors at different concentrations. Reactor performance was monitored every two days. Results show that copper toxicity was significant for the control reactor from phase from phase 5 to phase 8 with effluent concentration between 0.34 – 2.62 mg/L. Copper removal was significant for both MIRHA and HA reactor. Effluent copper concentration in the MIRHA reactor was 2.04 mg/L and 1.09 mg/L for HA reactor at phase 8 (copper concentration 15 mg/L). Addition of the adsorbents (MIRHA and HA) enhanced the biomass tolerance towards copper toxicity at high concentration and improved copper removal efficiency. This study, therefore demonstrates that low cost non-conventional adsorbents could be utilized as support materials to enhance biomass tolerance towards heavy metal toxicity.