Many Issues' Research Of Sewage Treatment Plant's Water Used In Sewage Source Heat Pump System

In recent years, urban sewage processing capacity in China has grown rapidly. To the end of 2004, China's 661 cities have built 708 sewage treatment plants with total processing capacity of 49.12 million m3 per day and annual urban sewage handling capacity of 16.28 billion m3. Moreover many new sewage treatment plants have been completed gradually. The fact that water from the sewage treatment plant has several apparent merits, including larger water flux, higher water source concentration and better water quality has created good conditions for the application of urban sewage source heat pump. Urban secondary effluent from sewage treatment plants should be developed vigorously to build more urban sewage source heat pump systems, which not only exploits effectively valuable cooling and heating resource in sewage, but also brings enormous economic, environmental benefits for the enterprise and the community.Through participation in making the feasibility report of Qingdao Maidao district sewage source heat pump engineering, the author finds that since the sewage source heat pump system using effluent of sewage treatment plant is generally very large, there exist several aspects of problems which are worth exploring: water source capacity assessment of heating and cooling, water storage measures when inadequate, anti-pollution necessity of the front-end system, system transportation energy consumption, etc. By analysis, this paper holds that:(1) Although the sewage treatment plants own great resources, with the rapid development of the construction industry and the urgent need for reducing emissions and energy consumption, we always hope that the limited sewage resources can offer heating and air conditioning for as many construction areas as possible. To rationally plan sewage source heat pump system scale, it is necessary to assess the capacity of heating and air-conditioning of sewage resources. This article holds that it is too rough to convert simply the sewage minimum flux into served construction area in sewage resource evaluation. Therefore, the sewage flux, heating and air conditioning hourly load and simultaneity usage coefficient of the end users are presented in this paper to assess served construction area of sewage more accurately.(2) Under the condition of no water storage pools, the scale of system is based on the water flux in the period of relatively low load and high load. But in most cases it is very difficult to meet the actual demand. In order to make full use of sewage resource and expand the scale of heat pump system, we can install water storage pools for peak load shifting. The method of determining the volume of water storage pool is presented in this paper: continuous water shortage flux in the worst condition is the theoretic volume of water storage pool;(3) By the experiment in Qing river sewage farm in Beijing, we make sure that the water quality from the second-class sewage farm is not too good. With the change of uncertain elements, such as weather, sewage farms will suffer from some serious situations. It is necessary that we should design measures for anti-pollution and removing debris;From the result of comparison experiment of advanced filter equipment, we find that it's hard to satisfy the stability of system for intermittence filter equipment of anti-pollution and removing debris, especially in rainy days.(4) For the design feature of small temperature difference and large flux, we discuss the influence on energy consumption caused by distance of transporting and establish the related model; Under the condition of system energy consumption proportion and economic specific friction resistance, the judge computing formula for the biggest economic transporting distance of sewage heat pump system is shown in this paper, which provides the judging basis for the economical feasibility of actual engineering.