MBR-Combined Constructed Wetland Process Experimental Study On Treatment Of Bathing Wastewater

In recent years, water quality was deteriorated due to the increasing pollution to thewater environment. It is difficult for a single wastewater treatment process to adapt tothe complicated wastewater quality conditions. Therefore, the combination oftechnologies and optimization of conventional processes are considered as the trend tosolve this problem.Membrane Bioreactor (MBR) has small footprint area, high removal ratio, andeasy operation, which is widely used for wastewater with high concentration and lowbiodegradable rate. The MBR is efficient for organics and suspended solids removal,but the effluent has relative high nitrogen and pHospHorus level. Constructed Wetlandtechnology has low operation cost, high N and P removal rate, easy management, andmany relative environmental benefits. The constructed wetland also has thedisadvantages of large footprint, seasonal sensitive, and easily affected by temperature.This research takes landscape water body as an example. The selected water bodyis located in a university campus, which is heavily polluted without regular influent. Itis proposed to build a MBR for bathwater collected from campus, and recycledbathwater will be used as a source for the landscape water body. At the same time, theapplication of constructed wetland is also studied for water purification to the landscapewater body. The objective is to meet the landscape water quality requirement.This research compared several conditions of MBR by changing the operationparameters in experiments, and suggested an optimum working condition. The treatmentefficiency of constructed wetland under three different packing materials was alsostudied, in order to improve the landscape water quality. Detailed results are showing asfollow:1） The recycled bathwater after MBR treatment can reach the standard oflandscape water. MBR has acceptable nitrogen and pHospHorus removal, goodquality in effluent, ability to balance shock load, easy operation, automatedcontrol, and land area saving. The COD removal is high under3000mg/L~4000mg/L sludge concentration, and the membrane flux can be sustained.2） Optimum working condition for this MBR:Membrane Flux:13~15L/(m~2h);Suction/Suspended Time: water-pumping12min, suspended3min;Aeration Rate:450~550L/m~2h; Anoxic Hydraulic Retention Time:1.3~1.5h;Aerobic Hydraulic Retention Time:3~4h;Sludge Retention Time of60~80d;Sludge Concentration:3000mg/L~4000mg/L.Three packing materials were used in this research: gravel (G), Pebble (P), andShale (S). Six combinations (G, P, S, G/P, P/S, G/S) were for the same wastewatersamples. The results showed that: under1.5mg/L loading, the Total Nitrogen (TN)removal is low in P packing (36.5%removed), but can be increased by mix with Gpacking (G/P has8%higher TN removal than P); S has higher TN removal (45.1%).When hydraulics loading is set at10.0mg/L, TN removal for G packing is54.7%, butG/P efficiency decreased to44.5%, which concludes that smaller packing porosity andlonger contacting time will result a better TN removal.The S packing and G/P combination has relative high efficiency for TotalPHospHorus (TP) removal.