Study On The Combined Process Of SBR And Constructed Wetland For Domestic Wastewater Reclamation And Reuse

As water consumption increases sharply, many areas face water shortage now or in the near future. In order to overcome this crisis, a number of measures have been introduced for the effective use of this valuable natural resource. In this situation, wastewater could be considered as a water resource. However, the conventional treatment systems have focused on disposal rather than reuse. Thus the related issues of what kind of wastewater should be treated, how to treat and how to transport them should be studied.City sewage infrastructure of high input, high urban wastewater treatment plant operating costs, the net leakage cause secondary pollution and lack of water resources reuse of sewage in the demand, there is an urgent need for table operation, low power consumption sewage treatment process. In this study, SBR technology and artificial wetlands technology combination for domestic wastewater treatment in order to get the best working conditions of combination treatment domestic sewage and the optimal economic operating parameters to give full play for constructed wetland performance and SBR system to reduce energy consumption.In the composition process constructed wetlands is a natural process, we setting aeration natural trough in constructed wetland in order to improve the dissolved oxygen within constructed wetland so not need energy for this process. The Sequencing Batch Reactor (SBR) is the name given to a wastewater treatment system based on activated sludge and operated in a fill-and-draw cycle. The most important difference between SBR and the conventional activated sludge systems is that reaction and settle take place in the same reactor. Activated sludge in the SBR need dissolved oxygen and must maintain a certain level of activated sludge concentration, SBR system aeration intensity and aeration time have a big impact in the combination process and energy consumption.At ambient normal temperature conditions T≥15oC, the SBR system running three cycles per day, the volume of wastewater treating is equal to 1.5m3/day, constructed wetland and hydraulic retention time approximately is equal to one day. The SBR system is running four operation cyclic modes (first, second, third and fourth) and aeration time reduced from 5 to 2 hours, at the same time adopt restrictions aeration, SBR system will be controlled low dissolved oxygen state DO in the range (0.5-1) mg/L, in this condition we do (COD, Ammonia, TN and TP) tests in order to meet with "Urban Landscape Water Standards"(GB/T18921-2002).At ambient low temperature conditions T < 15oC, the SBR system running two cycles per day, the volume of wastewater treating is equal to 1m3/day, constructed wetland and hydraulic retention time approximately is equal to 1.5 day, in the condition of low temperature we do the same tests before as (COD, Ammonia, TN, TP) but the difference in this condition the standard adopted is "City of miscellaneous water standards" (GB/T18921-2002) which not required to meet with TN and TP effluents, also this condition specified by extended aeration time and cyclic modes her represented by fifth, sixth, seventh and eighth as selected operating modes.The experiment started in April 2006 to the end of March 2007, lasted one year. Test operation of the eight cycles, each cycle run 20-25 days. The primary objective of this investigation was to optimize eight operations cyclic modes of existing (SBR) to elevate the water quality of the treated sewage wastewater to the level meet with "landscape water standards" and "miscellaneous city water quality standards". Both SBR and constructed wetland treatment systems were employed for the experimental tests.As mentioned before we do optimization to chose best operation cyclic mode under normal and low temperature at low dissolved oxygen, so considered third cyclic mode as the best one satisfied"urban landscape water standards"for TN, TP, ammonia and COD removals by combination SBR with constructed wetland for domestic sewage treatment processes under normal temperature condition when T≥15°C, The results showed that the removal efficiency that has been achieved by combined SBR with constructed wetland systems were (79.78%+9.93%), (52.74%+39.84%), (43.02%+ 35.12%) and (30.14%+61.95%) for COD, Ammonia, TN and TP respectively, third cyclic mode characterized by follow: SBR characterized by one hour (fill), three hours (aeration), one hour (settle), one hour (discharge) and two hours (idle) while constructed wetland characterized by (Hydraulic Retention Time) is 24 hours, (Hydraulic Load Rate) is 16.1cm/d and sewage treatment is 1.5m3 per day. While considered eighth cyclic mode as the best one satisfied "City of miscellaneous water standards" just for ammonia and COD removals by combination SBR with constructed wetland for domestic sewage treatment processes under low temperature condition when T< 15°C, The results showed that the removal efficiency that has been achieved by combined SBR with constructed wetland systems were (68.33%+21.06%) and (92.51%+3.74%) for ammonia and COD respectively, eighth cyclic mode characterized by follow SBR characterized by one hour (fill), eight hours (aeration), one hour (settle), one hour (discharge) and one hours (idle) while constructed wetland characterized by (Hydraulic Retention Time) is 36 hours, (Hydraulic Load Rate) is 10.7cm/d and sewage treatment is 1 m~3 per day.In the constructed wetland, Cyperus alternifolius and aquatic Canna is a good wetland plant, plant root system, the long of Cyperus alternifolius roots more than 30 centimeters, in the two plants root system contain large attachment filler. In the plant root zone due to oxygen plant roots, provide an aerobic microbial environment, biofilm formation of dense structure, a brown flocculent.