Fig. 1 Process of CASS wastewater treatment The emitter outflow was mainly affected by multiple fac- tors such as work pressure, manufacturing variability, aa aaa aaa ahaa "ical lala iailaaa allan a ine as “ane During the experiment, data of water quality character- istics are daily recorded by an online water quality moni- toring system, which is set around the water outlet in the plant. The monitoring system contains water quality auto- matic measuring instruments, automatic samplers, and a monitoring system, monitoring contents included COD (Chemical Oxygen Demand), SS (Suspended Solid), NH,*- N (Ammonium Nitrogen), TP (Total Phosphorus), pH and temperature in the certain time every day. The information of relative instruments is listed in Table 1. Water quality data are displayed in Fig. 2. The COD varied around 17.39 mg/L, with a maximum of 40.8 mg/L and a minimum of 1.2 mg/L. SS varied around 7.70 mg/L, the maximum was 42.9 mg/L and minimum was 0.3 mg/L. NH4‘-N changed between 12.1 and 0.136 mg/L, and the average value was 2.72 mg/L. TP was fluctuated around 0.80 mg/L, with maximum 3.4 mg/L and minimum 0.135 mg/L. pH was fluctuated slightly between 7.52 and 7.03, and the average value was 7.14. And the water temperature changed along with weather; in the first year, it rose from 24.5 to 27.9 °C and dropped to 16.3 °C, and the lowest temperature Table 1 Information of monitoring system instruments water temperature and clogging degree (Nakayama and Bucks 1991; Ravina et al. 1992; Provenzano and Pumo 2004). Field experiment could restore the real emitter work circumstance and comparatively accurately reflected the clogging behavior during field work. However, environ- ment would affect the field test, causing outflow deviation. In order to get the independent clogging influence value Aqc;,, it is necessary to correct the actual measured outflow to eliminate the influence of alternation in emitter work pressure as a neighboring clog and water temperature. The water temperature or tested emitter number will differ significantly after the field experiment lasts a long time. According to the relation between emitter outflow and pressure, the section; D (m) was the diameter of lateral; h,,, (m) was the head loss between two sections. The head loss of two adjacent sections was calculated by using the equation in microirrigation engineering standard. di = 920 + Age Table 2 Characteristic parameters of tested emitters During the experiment, the outflow of all emitters is tested for 3 min at the preliminary 492 h every 12 h and in every 24 h from 492 h to 540 h, and the recorded data were analyzed by taking the average of two repeated groups. In general, a single emitter was defined as unclogged if its outfl ow was higher than 95 % of the initial flow, while 80-95 % was defined as slightly clogged, 50-80 % was defined serious clogged as generally clogged, 20-50 % was defined as y clogged, and <20 % was defined as completely (Wu 2006). The changes in the distribution of different clogging degrees in a drip irrigation system were counted and tai in head part (No. 0-20), middle part (No. 21-40) 1 (No. 41-60) part of the lateral, respectively. Considering two repeated treatments, totally 120 emitters were included, and 40 in each part (head, middle and tail). The relative average discharge of drip irrigation emitters (Yan et al. 2011) was calculated in Eq. 13: Dra = Ki X t+ c, fis the total running time of the system, K, 9 is the average relative outflow linear variation fitting gradients of initiate linear period and accelerated linear period, c is the average relative outflow linear variation fitting parameter, as it has no real significance and is out of analysis. N means not significant, * means significant (p < 0.05), and ** means very significant (p < 0.01) Table 3 Average relative outflow variation parameters of 8 typeset of emitters reduced 4.1—13.1 % at the first year. But the linear starting times of initiate linear period were different between dif- ferent types of emitters, among which the pressure-com- pensating emitters started at 72-108 h, and the non- pressure-compensating started at 60-72 h. Dra varied generally in linear during the period of time, and t-check results of pressure-compensating emitters were not signif- icant except E;, but all those non-pressure-compensating ones breached linear significance level. k; varied from AS the system running, CU variation escalated to initiate linear period, where emitter clogging started showing its influences. The starting times were the same to Dra. As a whole, CU varied in linear (R* > 0.86), but the varying rate differed between emitters. Generally, CU variation gradi- ent of pressure-compensating emitters were higher than non-pressure-compensating emitters, k, varied from —0.037 to —0.112 for pressure-compensating emitters and from —0.042 to —0.094 for non-pressure-compensating Dra = K34 X t+ c, K3,4 is the irrigation uniformity linear variation fitting gradients of initiate linear period and accelerated linear period, other symbols mean the same as above Table 4 Irrigation uniformity variation parameters of 8 typeset of emitters Fig. 8 Dynamic changes of clogging distribution of different pressure-compensating emitters make linear fitting (Ravina et al. 1992). The difference might come from the influence of field test and the restarting in the 2nd year, as well as the correction of measured outflow data, which eliminated the immediate effect of temperature and pressure variation. The correc- tion was designed for making the emitter clogging status more reliable, but somehow enhanced the linear variation of Dra and CU. When the system runs to 540 h, Dra ranged from 29.3 to 61.3 %, and CU from 12.7 to 41.5 %, which were lower than that in fresh water or ground water system at the same time span. The results proved reclaimed water would aggravate emitter clogging again (Adin and Sacks 1991; Ravina et al. 1992, 1997; Capra and Scicolone 2004; Taylor et al. 1995; Li et al. 2009). period, initial linear period and accelerated linear period with different changing properties. The fluctuated balance period came first, Dra and CU fluctuated slightly, and emitters began to clogging. Followed was the initial linear period, in which Dra and CU variation of most emitters fitted in linear well, the number of generally clogged emitters increased gradually. In the accelerated linear period after restarting in the 2nd year, the absolute values of linear fitting gradients were larger, R* were above 0.91, seriously and completely clogged emitters began to appear and increased until the end of experiment. It can be also concluded from some results that Dra varied wavy in preliminary stage and then decreased in line, but the linear characteristics were not significant and the authors did not Fig. 9 Dynamic changes of clogging distribution of different non-pressure-compensating emitters (E5—Eg) In addition obvious linear , aS shown in Fig. 10, Dra and CU had relationship. The relationship between Dra and CU of pressure-compensating emitters was more concentrated t han non-pressure-compensating ones. Pres- sure-compensating emitters’ CU dropped when Dra decreased to a bout 95 % and showed a linear relationship with Dra. In comparison with the other group, pressure- compensating D. is smaller R*, ind emitters had a longer fluctuated period and icating that pressure-compensating emitters’ CU was less sensitive than Dra. Among all the emitters, E; and Es; had poor linear relationship when the experiment ended. They a so had larger Dra than the others. 216-252 hand 252-264 h, respectively, after restarting in the 2nd year. The result was different with Capra and Scicolone (2004), in whose experiment the completely clogging emittet appeared in 5 h and Li et al. (2009) that completely clogging emitter appeared after 804 h. The main reason was the wate quality, as the suspended particles were 5—25 mg/L in the water used in the experiment. The dimension was just between those in the water used by Capra and Scicolone (2004) and Liu and Huang (2009). But the difference was relatively small with Liu and Huang (2009), because restarting the system in the 2nd year advanced the emerging time of completely clogging emitters. Completely clogging emitters increased rapidly after appearing and fluctuating slightly in the process. There were some researchers found that a few completely clogging emitters sometimes recovered high outflow (Adin concentrated than non-pressure-compensating ones. Pres- Fig. 10 Relationship between Dra and CU
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